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Bulletin No. 20. v. P. P.-72. 

U. S. DEPARTMENT OF AGRICULTURE. 

DIVIBIOH OF VEGETABLE PHYSIOLOGY AND PATHOLOGY. 
B. T. GALLOWAY, Chief. 



PEACH LEAF CURL: 



ITS NATURE AND TREATMENT 




NEW^TOlSr B. PIKRCE, 

In Oharge of Pacifio Coast Laboratory, Santa Ana, Oalifomia. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1900. 



.'/ 






V^- 



o 



DIVISION OF VEGETABLE PHTSIOLOQY AND PATHOLOGY. 

SCIENTIKK^ STAFF. 

B. T. Galloway, Chirf of Divmon. 
- Albert F. Woods, Asdstani Chief. 

ASBSOCIATES. 

Erwin F. Smith, P. II. Dorsett, 

Merton B. Waite, Oscar I^)kw, 

Newton B. Pierce, Wm. A. Orton, 

Herbert J. Webber, Ernst A. Bes^sey, 

M. A. Carleton, Flora W. Patterson, 

Marci's L. Floyd.* 

IN charge of laboratories. 

Albert F. Woods, Plant Physiology. 

Erwin F. Smith, Plmii Patholofjj/. 

Newton B. Pierce, Pacific Chant Lafxtratory. 

Herbert J. Webber, PkifU BreaUiiy. 

Oscar LoEw,t Plant Nutrilion and Fennerttation. 

♦Dctailwl JIN toljacco expert, Division of Soils. 

Hn charge of tobacco fermentation invesstigatiouH, Divi.sion of Hoils. 



LETTER OF TRANSMITFAL 



U. S. Department of Agriculture, 
Division of Vegetable Physiology and Pathology, 

WashingUm, D. C, F^mai^ W, 1900. 
8ik: I respectfully transmit herewith a report on peach leaf curl, 
prepared by Mr. Newton B. Pierce, who has charge of the work of 
this Division on the Pacific coast, and recommend that it be published 
as Bulletin No. 20 of the Division. The report embodies the results 
of investigations and experiments carried on for a number of years, 
and shows conclusively that peach leaf curl can be controlled by com- 
paratively simple and inexpensive treatment. 
Respectfully, 

B. T. Gali^way, 
Chiif of iJlvh'ion . 
Hon. James Wilson, 

Secretury of Aijrtculture. 

3 



LETfER OF SUBMITTAL. 



Pacific Coast Ijaboratory, 
Sa7ita Aiia^ CaL, Deciinhei* 15^ 1899, 
Sir: I herewith submit a report of investigations on the nature and 
treatment of peach leaf curl. The experiments described were con- 
ducted under the most varied conditions of soil, climate, etc., in all the 
leading peach centers of the United States, and it is believed that the 
recommendations for treatment here given are equally applicable 
wherever peaches are grown. 

Respectfulh^, Newton B. Pierce, 

hi Charge of Paeijie Cornet Lahoratm^y, 
Mr. B. T. Galloway, 

Chli'f Divimoii <tf VeijetaUe PhyHwhHjy and Pathology. 

5 



LIHTER OF SUBMITTAL 



Pacific Coast Laboratory, 
Smita A7ia, CaL, Dramhei' 15, 1809. 
Sir: I herewith submit a report of investigations on the nature and 
treatment of peach leaf curl. The experiments de^scribed were con- 
ducted under the most varied conditions of soil, climate, etc., in all the 
leading peach centers of the United States, and it is believed that the 
recommendations for treatment here given are ecjually applicable 
wherever peaches are grown. 

Respectfully, Newton B. Pierce, 

hi Charge of PiWijic ( ^fHint LahmiUrry. 
Mr. B. T. Galloway, 

Clui'f DimHion of Vcgeinhle PhyHiohHjy and PatlHthnjij, 

5 



8 (M)NTENT8. 

Page. 

Chapter VIII. — Preparation, Composition, and General Characters op 

THE Sprays Uhed 146 

Preparation of the copper sprays 146 

Copper sulphate solution 147 

Bordeaux mixture 149 

Eau celeste 152 

Modified eau celeste W^i 

Aninioniaciil copper carlx)nate l^'^i 

Preparation of the sulphur sprays 154 

Prej)aration of conibineti c()i)iK'r an<l sulphur sprays and n<)ti»s on other 

sprays tested lt>l 

Bordeaux mixture and sulphur sprays combine<l 161 

Miscellaneous sprays 161 

General characters of the sprays testeil 162 

The enduring qualities of the sjirays 162 

The corrosive at'tion of the sprays 164 

Advantages of discernible and indiscernible sprays I(i5 

Sprays adapteil to use in wet and in dry localities 166 

Chapter IX. — The Application of Sprays 167 

General accessories for winter spraying 167 

Nozzles suited to winter work 167 

Hose and extension pijKJs .• 169 

Protection of the sprayer 170 

Pumps for various sized orc-hards 171 

Spraying tanks 1 75 

Applying winter sprays for curl 175 

The time for winter spraying 1 76 

The manner of applying winter sprays 1 76 

Spraying where other diseases are present with curl 177 

Prune rust on the i)eax*h (I^tcrinia p-nml Pers. ) 1 77 

Mildew of the \yetwh ( Podoaphtera oryaamthiv I)e B.) 178 

Brown rot of the peach (Moiiilia fniciigena Pers.) 1 78 

Black sj)ot of the jK^ach (('UuloRjyoAnm car^jf)philmn Thiini.) 1 78 

Winter blight of the jHiach and other spot and shot-hole diseases, sucli 

as PhyUoMida nrcnmarma Berk., (WcoRfMmt ci rcumsriiata Sacr., etc.. 179 

Sooty mold of the i)eax»h 1 79 

Animal i)arasites of the pc»ach tree 180 

Chapter X. — Nature and SoriuE of the Sprayincj Materials Used 181 

Copper sulphate 181 

Copj)er carbonate ia*i 

Ammonia 185 

Sodium carbonate 187 

Sulphur 190 

Chapter XI. — Peach Variktiks and Nursery Stck'K in Relation to CVrl.. 194 

Comparison of peach varieties 194 

Treatment of nursery stock 200 

Summary 202 



ILLUSTRATIONS. 



PLATES. 

Page. 

Plate I. Curl-infested peach shoot from Biggs, Cal 11 

II. Mycelium of Exomcus deforman — the fungus causing j^each leaf curl . 35 

III. Fruiting stages of Exoftscus deforrnaua 36 

I V. Germination of the ascospores of Krodsnitt dejormmm 38 

V. Terminal peach twigs infestetl with peach leaf curl 42 

VI. Sprayed and unsprayed peach branches 42 

VII. Sprayed and unsprayed Crawfords Late trees, Live Oak, (-al 77 

VIII. Unsprayed trees in Lovell orchard, Biggs, Cal 89 

IX. Lovell trees sprayed with Bordeaux mixture. Biggs, Cal 89 

X. Fruit produced by row 15, experiment block, Biggs, Cal 107 

XI. Lovell trees sprayed with sulphur, lime, and salt, Biggs, Cal 112 

XII. lovell trees sprayed with sulphur and lime. Biggs, Cal 112 

XIII. Lovell trees sprayed with Bordeaux mixture. Biggs, Cal 115 

XIV. Lovell trees sprayed with eau celeste. Biggs, Cal 115 

XV. Lovell trees sprayed with modified eau celeste. Biggs, Cal 115 

^yj TFig. 1, Manner of spraying trees on one side. Biggs, Cal 1 .oq 

iFig. 2, Action of curl on trees sprayed on one side, Biggs, Cal/ 

XVII. Condition of trees sprayed on one side at maturity of fruit 124 

XVIII. Fruit gathered from sprayed and unsprayed halves of tree 124 

XIX. Showing fruitfulness of sprayed half of tree 124 

XX. Sprayed and unsprayed Crawfords Late trees. Live Oak, Cal 142 

XXI. Steam spray -cooking appliances for small orchards 158 

XXII. Steam spray-cooking appliances for large orchards 161 

XXIII. Appearance of orchard at close of spray work. Biggs, Cal 176 

XXIV. Unpruned trees, too late for spraying ■... 176 

XXV. An orchard properly pruned, but too late for spraying 176 

XXVI. An outfit for spraying small orchards : 204 

XXVII. An outfit for spraying medium-sized orchards 204 

XXVIII. Spraying eight trees at a time, Rio Bonito orchard, Biggs, ('al 204 

XXIX. A power sprayer in use at Santa Barbara, Cal 204 

XXX. A power sprayer, San Diego, Cal 204 

FIGURES. 

Fi(i. 1. Cyclone nozzle, with direct discharge and dogorger 168 

2. Cyclone nozzle, with lateral discharge, for thin sprays 168 

3. Heavy cyclone nozzle, with oblique discharge, for thick sprays 168 

4. Wire-extended suction hose 169 

5. Bamboo extension pipe 169 

6. Spray pump for use on barrel or tank 171 

7. Spray pump for use on barrel or tank 172 

8. Spray pump for general orchard work, upright lever 173 

9. Spray pump for general orchard work, upright lever 174 

10. Pneumatic pump for general spraying 175 

9 




\ B F /. ,. ..^V 



Bull. 20, Div. Veg. Ph/s. m. Path., U. S. Dept. Agriculture. 




DESCKIPTION OF PLATE I. 

Curl-infeeted peach shoot from Biggs, Cal. Leaves of this character are baclly 
infested with Exoaticus deformans. The greatly broadened and distorted leaves, which 
are characteristic of this diseafie^ are shown, and the whitened, spore-covered surface 
of some of the more elevated portions of the upper surface may be distinguished. 
The petioles of the affected leaves are greatly enlarged, the branch is much bent and 
distorted, and the internodes of the diseased portion of the branch are greatly 
Hhortene<l. A branch thus l)adly diseased is apt to die during the year unless con- 
ditions for growth are very favorable. It is in shoots of this character that the 
mycelium occurs in greatest abundance, but the hyphaj have l)een seen to spread 
only a short distance beyond the parts showing the hypertrophy. (Compare with 
Pis. V and VI.) 



12 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

GENERAL CHARACTERISTICS OF THE DISEASE. 

The disease of peach trees here considered is variously known in 
different regions and languages. In the United States it is commonly 
know as peach leaf curl, or curl leaf of the peach; in England and 
all British possessions, as leaf blister, leaf curl, or curly leaf; in 
Fmnce, as cloque du pScher; in Germany, as Krftuselkrankheit; in 
Italy, as Fillorissema, etc. 

Peach leaf curl is a disease which seriously affects the leaves, flowers, 
tender shoots, and fruit of the peach. Its action is most severe in the 
spring of the year, shortly after the leafing of the trees, and the greatest 
injuries are caused in wet seasons and in humid localities. The leaves 
become enlarged, thickened, much curled, and distorted. As the dis- 
ease progresses the healthful green of the foliage is changed to a 3'el- 
lowish, sickly appeamnce. The leaves soon fall, and the newly formed 
fruit ceases to grow, yellows, wilts, and likewise falls. The total loss 
of foliage and crop is common in seasons favorable to the disease. A 
second growth of leaves develops more or less rapidly, according to 
the severity of the disease and the favorable or unfavorable soil and 
atmospheric conditions prevailing at the time. If the soil and atmos- 
phere are dry and the temperature high, new foliage may appear slowly 
and much of the terminal growth may die throughout the orchard. In 
severe attacks young tree.s are frequently killed. The second crop of 
loaves, appearing on affected trees after the spring defoliation, usually 
remains comparatively free from curl for the rest of the season. The 
amount of disease which will appear upon this later crop of foliage 
depends largely upon the humidity or dryness of the atmosphere, 
excessive moisture favoring a continuance of the trouble. The action 
of the disease upon spring branches causes them to enlarge, become 
curved and distorted in various ways, and often to dry up and die. 

GEOGRAPHIC DISTRIBUTION. 

Peach leaf curl exists in most peach-growing countries. Its distri- 
bution in the United States extends from the Gulf of Mexico to Can- 
ada and from the Atlantic to the Pacific. The centers of greatest 
prevalence, and where the greatest losses are sustained from this cause, 
are in the leading peach-growing districts bordering the Great Lakes, 
especially in Michigan and western New York; in the central, north- 
ei'n, and coast regions of California; and west of the Cascade Moun- 
tains in Oregon and Washington. The disease is less serious, or is of 
minor importance, in those peach-growing counties of New York 
most distant from the lakes, in Pennsylvania, Ohio, Indiana, Illinois, 
and in southern California. Still less injury is repoi-ted from New 
Jersey, Delaware, Connecticut, Rhode Island, Massachusetts, Mary- 



GEOGBAPHIC DI8TBIBUTI0N. 13 

land, Virginia, West Virginia, Kentucky, Tennessee, North Carolina 
South Carolina, Arkansas, Oklahoma, Louisiana, Mississippi, Ala- 
bama, and Florida, but in most of these regions occasional serious 
outbreaks are reported in seasons favorable to curl or in particular 
localities. It prevails rather more seriously in portions of Geor- 
gia, Kansas, and Missouri. In Texas, New Mexico, Arizona, and 
Colorado it has occasioned but little loss and is not widely known. 
Rcp)ort8 from Utah and Nevada are meager, but it is probable that the 
disease prevails to a limited extent in both States. The more northern 
States not mentioned here have either failed to report the prevalence of 
the disease or are properly included within that portion of the United 
States unsuited, by rigor of climate, to successful peach culture. 

In Canada both Ontario and British Columbia, which are the leading 
peach -growing provinces, are favorably situated for the serious devel- 
opment of peach leaf curl in wet seasons. Mr. John Craig, horticul- 
turist of the Central Experimental Farm, Ottawa, writes that the 
disease "obtains in Canada in all the peach -growing districts, including 
British Columbia and the Province of Nova Scotia." It is known to 
cause considerable losses of fruit in some sections.^ 

Peach leaf curl exists also in some if not all the peach-growing coun- 
tries of South America. In Chile the peach is widely grown, })eing 
planted from the snow line of the Andes to the Pacific Ocean, and from 
Copiapo south as far as Valdivia, a distance of 800 miles. Mr. C. T. 
Ward, Jr.,' of the Hacienda Loreto, Department of Limache, says that 
the parasite of peach leaf curl "exists all over the country where the 
peach grows," but that no satisfactory method of control is yet 
pi-acticed there. 

In Europe Dr. R. Sadebeck' records the disease from Denmark, Ger- 
many, Austria, Switzerland, and Italy. He states that in central Ger- 
many it prevails more extensively than in the vicinity of Hani))urg.* 
Among the many German scientists who have written upon this 

' Mr. L. Woolverton, secretary of the Fruit Growers' Association of Ontario, Haid, 
in 1890, in a paper entitled, Points on Peach Growing in the Niagara District, piib- 
lii?he<l in the Annual Rejjort of the Society for that year, pp. 56 and 57: " The pca<'h 
hai* its share of enemies and diseases, chief among which are the curl, curculio, the 
lK)rer, and the yellows. For the curl I know no remedy. It is not often severe, but 
i^oiiietimes with the diseased leaves the fruit also drops.'' Mr. John C-raig, in writing 
from Ottawa under date of October 7, 1897, says, relative to the (liHca.se in Ontario: 
** It is only severely injurious here during years of unusually luiavy rainfall. This 
year it was very bad." 

* Letter of March 22, 1896, to Mr. J. M. Dobbs, U. 8. Consul at Valparaiso, (-hile. 

'Sadebeck, Dr. R., Die parasitischen Exoasceen. Eine Monographic, Haml)urg, 
1893, p. 94. 

*Sadebeck, Dr. R., Untersuch. iiber die Pilzgattmig Exoascua, Hamburg, 1884, p. 
115. 



14 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

disease and its cause are Sadebeck/ Winter,* De Bary,' von Tavel,* 
Ha tig,* Zopf/ Tubeuf,' Ludwig,* Sorauer/ Frank,'" Kirchner,^^ 
Fuckel,*'* and others. Winter says (1. c.) that the fungus of thij? 
malady causes great damage by early defoliation of the trees, and that 
it even kills the diseased trees by its repeated occurrence. 

In Great Britain peach leaf curl has been common for a great many 
years. In 1821 it was accurately described by an English gardener 
under the name of ''blight." He says:" *' Under this denomination 
[blight] are frequently confounded two varieties of disease materially 
different in their appearance, and which I shall distinguish by the 
appellation of hlister and curl. The foniier is generally confined to 
such pe>ach trees as have glandular leaves, which are mostly asubject 
to it in the months of April and May, and when attacked it is not 
until the latter part of the season, if at all, that they become healthy. 
The leaves so attacked are crisp, and a^ssume a swollen, crumpled, and 
succulent appearance; the shoots themselves are affected by it in the 
same manner, and never produce either good blossom or healthy w(X)d.'' 
Berkeley ** has described the fungus causing this disease, and it has 
been mentioned by Bennett and Murray*** and many other English 
writers. (Consult a popular article on Peach Blister, by W. G. Smith, 
GanhnerH^ Chnmich^ Vol. IV, pp. 36, 37.) 

*Sadebeck, Dr. R., see locations cited; also Einige neue Beobat^h^ungen unci krit- 
ische Bemerkungen iiber die Exoascaceie, Hot. Ges., 1895, Band XIII, Heft (>. 

* Winter, Dr. Georg, Die diircb Pilze veruraachten Krankheiten der Kultuf^e- 
wachse, Leipzig, 1878, p. 47; also Rab. Krypt. Flora, 1885, II, p. 6. 

*De Bary, Prof. A., Comparative Morphology and Biology of the Fungi, Mj-ceto- 
zoa, and Bacteria, English edition, Oxford, 1887, p. 265; see also in the same volmiie 
various other references to the arrangement and position of the Exoastnis group. 

* Tavel, Dr. F. von, Vergleichende Morphologic der Pilze, Jena, 1892, pp. 55, 5(). 
^Ilartig, Dr. Rol:>ert, Lehrbuch der Baumkrankheiten, Berlin, 1889, p. 118; also 

the English edition, Text-book of the Diseases of Trees, London, 1894, p. 182. 

®Zopf, Dr. Wilhelm, Die Pilze in morphologischer, phyeiologischer, biologischcr, 
und systematischer Beziehung, Breslau, 1890, pp. 236, 282. 

"Tul)eiif, Dr. Karl Freiheer von, Pflanzenkrankheiten durch kryptogame Para- 
siUm verursacht, Berlin, 1895, pp. 167-188. 

*Ludwig, Dr. Friedrich, Lehrbuch der Niederen Kryptogamen, Stuttgart, 1892, 
p. 205. 

•Sorauer, Dr. Paul, Hand buch der Pflanzenkrankheiten, Zweiter Theil, Die pani- 
sitaren Krankheiten, Berlin, 1886, p. 278. 

*<* Frank, Dr. A. B., Die Krankheiten der Pflanzen, Band II, Die Pilzparasitan»n 
Krankheiten, Breslau, 1896, pp. 249, 250. Edition of 1880-81, Vol. II, p, 526. 

"Kirchner, Dr. Oskar, Die Krankheiten und Beschadigungen unserer landwirt- 
schaftlichen Kulturpflanzen, Stuttgart, 1890, i)p. 324, 407. 

^'^Fuckel, L., SymboUe mycologic^e, 1869, p. 252. 

•' Sec (luotation in Rei)ort of Michigan Pomological Society for 1873, pp. 16, 17. 

'* Berkeley, M. J., Introduction to Cryptogam ic Botany, 1857, p. 284, and Outline}^ 
of Briti^^h Fungology, I/Ondon, 1860, pp. 376, 444, tab. 1, fig. 6. 

^* Bennett, A. W., and Murray, (ieorge, A Handbo(3k of Cryptogamic Botany, 
London, 1889, p. 379. 



GEOGRAPHIC DISTRIBUTION. 15 

Tulasne/ Prillieux,* and others (Cours completo d'agriculture, T. 
XV, p. 255, art. Pecher) have studied this disease more or less care- 
fully in France, where it often develops in a serious form. In June, 
181)0, the writer saw the peach trees near the Mediterranean, particu- 
larly about Montpellier, in anything but a healthy condition. On the 
Hd of June leaf cuxl was bad, and the ends of branches were seen to 
ho dying in some cases. In Italy Briosi and Cavara,' Berlese,* and 
Comers ^ are among those who have described this malady. The dis- 
ease varies in its prevalence through Italy in accordance with its 
habits elsewhere. The trees of northern Italy appeared more health- 
ful than in the south of France during the visit of the writer in 1890, 
but considerable gummosis, perhaps due to the same caiLsc, was 
observed in both regions. In western Sicily, near Palermo, leaf curl 
was again encountered in severe form. The situation in Spain and 
Portugal is not known, but in the more humid coast regions it should 
not be materially different from the condition found in Italy. In 
Greece, as stated by Prof. P. Genardius,* the disease rarely causas 
any damage of importance, because of the dryness of the climate, and 
for ihis reason, he states, no treatment has been tried. In Austria- 
Hungan^ the situation respecting leaf curl is much the same as in 
Italy. Dr. Johann Bolle, director of the Institute of Experimental 
Agricultural Chemistry, at Gorizia, writing from the island of Cherso, 
under date of October 25, 1897, states that in rainy weather 
the disease appeal's some years with great intensity and causes great 
damage. In Roumania the situation is much the same. Prof. Wilhelm 
Knechtel, of the Agricultural School of Herestrau, states in a letter 
dated Bucharest, October 17, 1897, that in that country leaf curl of the 
peach is also a troublesome and destructive disease to which the trees 
are subject in many years. He states that Roumania has in the region 
of the lower Danube almost a steppe climate — in summer very hot 
and dry, in winter cold, with very abrupt temperature changes, so 
that the variations of temperature within twenty -four hours not infre- 
quently amount to from 10° to 15^ R. (22.50° to 33.75° F.). When 
such changes of temperature occur in the spring at the time of leaf 
development the disease is certain to appear. The growth of the 
vegetation, which has been favored through the preceding warm days, 
is checked during succeeding days of lowered temperature, when 

'Tulasne, L. R., Ann. d. Sci. Nat., 1866, ser. 5, T. V, p. 128. 

'PriUieux, Ed., Bull, de la Soc. Bot. de France, 1872, T. XIX, pp. 227-230; Compt, 
Rend. 3; also Maladies des Plantes Agricoles, Paris, 1895, T. I, pp. 394-400. 

'Briosi, G., and Gavara, F., Fungi Parassiti d. Piante Coltiv. od Utili, essice., delin. 
e descr., 1891, fasc. 5, No. 104. 

* Berlese, A. N., I Parassiti Vegetali d. Piante Coltiv. o Utili, Milano, 1895, pp. 
124-126. 

*Comes, O., Crittogamia Agraria, Napoli, 1891, pp. 163, 165-167, 549. 

* Utter dated Athens, Sept. 12, 1895. 



16 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

the development of the fungus begins, so that in June all loaves at the 
ends of the young branches are curled and deformed and perhaps all 
the blossom buds fall oflf. If the more developed leaves at the base of 
the young shoots prove more resistant to the fungous action, then fresh 
shoots are formed in June, even if not in normal condition, but yet 
somewhat healthy, so that the tree remains intact.^ In the more pro- 
tected hill regions of the vineyards, at the foothills of the Carpathian 
Mountains, this disease is also troublesome,, but less intense than in 
other parts of the country. 

Peach leaf curl exists in South Africa, and probably also throughout 
Algeria and other peach-growing portions of the continent. Professor 
MacOwan, of the department of agriculture of Cape Colony, has 
written of the disease in South Africa, giving his views as to the 
proper manner of treating the same. ^ He also writes that it is ''a 
great plague at the Cape."* 

A peach grower of Drysdale, Frere, Natal, in writing to the Cape 
Colony agricultural department under date of October 31, 1893, says 
that he has a good many peach trees of the yellow, white, and St. 
Helena varieties, and that they are all affected with the discolored and 
curled-up leaves characteristic of this disease; that several of his neigh- 
bors are complaining that their peach trees are suffering like his; and 
that the disea.se seems to be spreading. The young trees were simi- 
larly affected. ' 

Perhaps no foreign country has suffered more from peach h^af curl 
than New Zealand. Mr. W. M. Maskell, of Wellington, writes as 
follows : * " The curly blight has been for many years prevalent in this 
country— so nuich so that whereas in the early days pea<*hes were exceed- 
ingly luxuriant and fine, they have dwindled to comparatively very 
small and poor trees and in many parts of the colony almost died out. 
In the last two or throe years the people have been advised to employ 
remedi(»s, and have done so to some extent, so that there is a marked 
improvement in the peach orchards. » * * j ^^n myself recollect, 
early in the sixties, when the most splendid peaches used to grow 
wild in the warm northern districts, where now scarcely a tree is 
seen; and the curly l)light has been a dreadful curse all over the colony." 

Australians report peach leaf curl among their serious plant dis- 
eases. In South Australia it "hius been known quite twenty years/'* 
and prol)ably longer, and occasions considerable losses in seasons 
favoring it. The situation is nmch the same in New South Wales. 

^MacOwan, Prof. P., Agricultural Journal, publishe<l by the department of 
agriculture of Cape Colony, li^»2, Vol. V, pp. 252, 258. 

MA^tter dated Cape Town, Oct. 26, 1895. 

''Agricultural Journal, Cai)e Colony, Vol. VI, No. 23, p. 451. 

* Utter dated Wellington, New Zealand, Deceml)er 24, 1895. 

^ Olwiervations of Mr. A. Molineux, general secretary for the agricultural bun»au 
of South Australia, letter dated Adelaide, February 11, 1895. 



GEOGRAPHIC DISTRIBUTION. 17 

Prof. N. A. Cobb,* pathologist for the agricultural department of that 
colony, has described the malady quite fully, and although ho fails to 
specify particular localities, it is probable that his descriptions are 
drawn from observations made in the colony for which he writes. He 
says that in the most severe cases of the disease " the fruit falls about 
three weeks after setting, and not a peach is left to ripen. This occurs 
on trees on which the disease is chronic and severe. * * * Such 
trees are worthless, nay, worse than worthless; they are a constant 
menace to the peach trees in the neighborhood. The sooner they are 
cut down and burned, and thus utterly destroyed, the better it will be 
for the peach industry. * * * I have now described the disease in 
its worst form, a form in which it is not common. The milder forms 
of the disease are much more frequent." 

Peach leaf curl also prevails in Victoria, where it has been placed, 
according to Mr. D. McAlpine,** pathologist for Victoria, among the 
specified diseases in the vegetable diseases bill, recently passed in that 
colony. Mr. McAlpine also says that according to Mr. George Neilson, 
chief inspector under the vegetation diseases act, it has been known 
in Victoria since 1856, and affected peach trees were just as bad 
then as now. Mr. McAlpine adds: ''The disease is distributed all 
over the colony. In the cooler districts it is genemlly more severe 
than in the northern and warmer districts, and it is genemlly more 
prevalent in a moist and cool spring than in a dry, warm one." 

The situation in Japan has been learned through the obliging and 
careful inquiries of Prof. K. Miyabe,* of the Sapporo Agricultural 
College. He writes that Exoascm deforjiians is at present a serious 
pest to the peach trees at Sapporo, north island, and states that his 
attention was first called to its presence in that place some three or 
four years since, but that there is no doubt of its existence from the 
time of the first introduction of American peach trees, about twenty- 
three years ago. The Japanese flowering (double red) peach trees and 
nectarines were introduced at Sapporo by a florist about six or seven 
years ago from Echigo Province in the northern part of the main 
island or Honsiu. These varieties were found to bo attacked to some 
extent during these few years. American varieties arc now most seriously 
affected, and many persons have been obliged to cut down their trees 
on account of the disease. Respecting the distribution throughout 
Japan, Professor Miyabe says: '^As to the rest of Hokkaido [the 
northern island] I found the fungus in 181)0 at Mombetsu, a fanning 
village on Volcano Bay, settled about twenty-seven years ago by the 
people from Sendai. I could not tell whether the peach trees culti- 
vated there were of American or Japanese origin. In Honsiu, or 

*Cobb, Prof. N. A., paper in the Agricultural Gazette, 1892, Vol. Ill, pp. 1001-1004. 
'Letters dated Melbourne, Australia, July 14, 1896, and Oct. 12, 1897. 
• liCtter dated Sapporo, Hokkaido, Jai)an, Nov. 22, 1897. 
19093— No. 20 2 • 



18 PEACH LEAF CURL! ITR NATURE AND TREATMENT. 

Main Lsland, the peach curl seemn to be prevalent only in the northern 
provinces. » * » j sent letters of inquiry relating to this question 
to the graduates of our college, who studied especially about the 
parasitic fungi in our laboratory, and whose opinions I can trust. 
From Mr. Y. Takahashi, at Morioka, in Rikuchu Province, I received 
the following answer: 'Peach curl is very prevalent in this town. 
Almost every tree is more or less attacked by the fungus. I saw some 
trees entirely attacked. At the end of summer [spring?] all the dis- 
eased leaves fell to the ground and new leaves were produced."- In 
the southern island, Kumamoto, a correspondent reported to Professor 
Miyabe that the disease had not been seen there by him. From Tokyo 
Professor Shirai, of the College of Agriculture, reports that he has 
not yet found the disease in that section of the main island. 

In China, as the writer is informed, peach leaf curl prevails to a 
very large extent, and the losses are probably considerable from this 
cause.* 

ORIGIN OF THE DISEASE. 

The country of origin of peach leaf curl is not positively known. 
It was hoped that the inquiry as to distribution would develop posi- 
tive information respecting this point, but such has not been the case. 
That seedling peaches are remarkably susceptible to the disease, and 
that the Chinese Saucer peach is among those most subject to it, 
appears to indicate that the home of the peach is the source of the 
disease, and that the two may have come to us together from a com- 
mon point of origin. Recent studies have been constantly tending 
to reduce the number of species of plants once thought to be subject 
to curl. At present it is believed that it is confined almost wholly to 
the peach or its derivatives, as the nectarine and peach-almond. The 
exceptions to this, where the disease has been noted on the plum, 
almond, etc., are rare, and not sufficiently numerous or general to mate- 
rially aflFect the evidence that the peach is the natural host of the fungus. 
Thus far, however, it has been impossible to learn if the peach in the 
interior of China, its supposed home, is affected by this trouble, though 
in the coast regions it is said to prevail extensively. Such information 
as has been obtained from Japan indicates the recent introduction of 
the disease in that country, and that the United States is probably its 
source rather than the near-by continental coast. In Austialia, how- 
ever, this may properly be questioned, for, as already mentioned^ Mr. 

* Ijetter f roin Augustus White, Esq., forwarded April 3, 189(5, through the klndnesa 
of Mr. Rufus S. Eastlack, then U. S. Deputy Consul-General at Shanghai, China. 
Mr. White says, in concluding his statement**, that the Chinese, ignorant of tlie use 
of the knife in pruning, trust solely to an annual inspection of the trees at the time 
the blossoms set, when they carefully pick off all excess of fniit, and with it all 
diseased leaves, et<\, but allow these to fall to the ground and remain under the 
trees to rot or reproduce the plague, as nature thinks best. 



LOSSES FROM THE DISEASE. 19 

George Neilson, chief inspector under the vegetation diseases act of 
that colony, states that peach leaf curl has been known in Victoria since 
1856. This dates the presence of the disease in Australia back to a 
time when its importation from America to that country 'would be 
doubtful. Its European origin, however, may not be improbable. 

The severity of the disease in the gardens of China and the fact that 
the peach probably reached Europe and America from the East make 
it still desirable to learn if the trouble is prevalent among the wild or 
escaped peach trees in the interior of the Chinese Empire. 

It may be pertinent to state, in view of the fact that Darwin holds 
the peach to be derived from the almond, that none of the many widely 
cultivated varieties of the almond in California, either of local or for- 
eign origin, arc subject to peach leaf curl, even when growing beside 
peach orchards denuded by it. Trees which are apparently the result 
of almond and peach crosses are somewhat aflFected, however, and sev- 
eral of the nectarines, which are derived from the peach, are quite 
subject to it. Seedling peaches, as stated, are very commonly attacked, 
but of some forty to fifty varieties of seedling almonds examined by 
the writer none has thus far shown the disease. 

LOSSES FROM THE DISEASE. 

The direct annual losses to the peach interests of the United States 
from peach leaf curl are very large, and are usually much greater 
than is suspected by the growei*s themselves, as the nature and action 
of the disease are misunderstood by them, and its effects frequently 
attributed to other causes. In case an orchard is so affected that it 
fails to hold the crop, or sets but a partial crop, the grower has but 
little ground for an opinion as to what the yield would have been had 
curl not prevailed, hence the estimates of losses made by growers are 
frequently very unsatisfactory. In case curl occurs after a severe 
cold spell in spring, as is quite conmionly the case, the orchardist is 
apt to charge the loss of fruit to the low temperature rather than to 
the disease. The preventive spray work conducted by the Depart- 
ment has shown, also, that the loss estimates are nearly always too 
low. 

By preventing the disease upon a portion of the trees of an orch- 
ard the amount of injury sustained by the untreated trees has been 
determined most accumtely by direct comparison. Such comparative 
work has now been conducted for sevei-al years in many of the leiiding 
peach-growing centers of the country, and these tests enable the 
writer to state that the losses sustained by the peach industry are 
probably not overdrawn in the following estimates: Of a- large num- 
ber of peach growers who replied to a circular letter sent them in 
1893, there were 261, living in 35 peach-growing States and Terri- 
tories, who stated whether or not their orchards were affected by curl. 



20 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

Sixty -three per cent of these (158 growers) reported that their 
orchards were affected, and 37 per cent (93 growers) reported that 
their trees had not been troubled by it. Of the 158 whose trees 
were affected, 66 per cent (104 growers), or about 42 per cent of the 
251 orchardists reporting on this disease, reported more or less loss. 
The growers who reported loss were residents of 21 States, and were 
scattered from the Atlantic to the Pacific. The losses sustained varied 
from a small amount of fruit to the entire crop, and in some instances 
many of the young trees were killed. Of the entire number of reports 
received as to the presence or absence of curl in the orchard of the 
grower, 93 came from States or sections of the country where little 
leaf curl prevails, as Texas, Delaware, Florida, Kansas, etc., so that 
the data should be strictly representative of the peach-growing coun- 
try as a whole. The replies received were from Alabama, Arizona, 
Arkansas, California, Colorado, Connecticut, Delaware, Florida, Geor- 
gia, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Marj^land, 
Massachusetts, Michigan, Mississippi, Missouri, Nebraska, New Jer- 
sey, New Mexico, New York, North Carolina, Tennessee, Texas, 
Virginia, Washington, and West Virginia. 

The amount of loss siLstained by the 42 per cent of the growers 
reporting losses is given in the replies in various ways. Some 
growers have reduced their loss to dollars and cents; others have indi- 
cated the loss in percentage of crop; while still others have used some 
tenn, such as "slight" loss, ''small" loss, etc., as a reply to the 
inquiry. In estimating the true loss sustained by these growers a 
uniform system has been adopted. Where the loss has been stated in 
dollars the amount has been recorded as given. Where the loss is given 
in percentage of crop the cash loss has been deteiinined from the basis 
used by the United States Census Bureau in determining the value of 
peach crops for the Eleventh Census. A full peach crop was valued 
at $150 per acre, and all portions of a crop at the same rate. Where 
the report of the grower was indefinite, the stat-ement being that the 
loss was small, it has been placed at $2.50 per acre, which amounts to 
about 2i cents per tree as usualW planted. It is probable that this 
is nmch below the average loss in such cases, as a loss so small as 
this would usually escape notice. In all the calculacions in these esti- 
mates an effort is made not to overmtc the loss. These calculations 
gave a loss to the growers avei-aging $10.95 per acre for the acreage 
reported as suffering from the disease, or 42 per cent of the f uU area. 
This IS equivalent to about $4.60 per acre for the entire acreage, or 
about 4 cents per tree. At first thought this may seem high, but this 
is more apparent than real. If one 10-acre orchard loses its crop from 
curl, valued at $150 per acre, the loss amounts to $1,500. There ma\' 
be 32 other orchards of 10 acres each all about this orchard where not 
a peach is lost, yet the average for such a district is the same as that 
stated. This is perhaps a clearer manner of putting the matter than 



LOSSES FROM THE DISEASE. 21 

by placing an average loss for all orchards. The loss may be viewed 
in still another manner. If an orchardist has grown peaches for 32 
years and lost only one crop during that time from leaf curl his loss 
for the third of a century will avemge as high as here calculated. 

There are large sections of the country where curl is scarcely known, 
as in portions of Texas. For such regions the preceding estimates may 
appear high. On the other hand, there are other prominent sections 
of the country devoted to peach culture where these estimated losses 
will certainly be far too low. 

If the preceding calculations and statements are accepted as fairly 
representing the situation throughout the country, the annual losses 
from curl .in the United States may be approximated. The Eleventh 
Census reports the orchards of peach trees in the United States at 
that time (1889-90) as 507,736 acres, and from replies to our circular 
we are led to believe that curl was present in 63 per cent of these 
orchards and that 42 per cent sustained some loss from the disease. 

Most of the orchards included in the 42 per cent sustained only a 
slight loss, but a very small percentage sustained a heavy loss, some- 
times amounting to the entire crop. The average loss for the 42 per 
cent of the orchards is found to amount to $10.95 per acre, or about 
10 cents per tree, averaging the trees at 108 per acre. The total 
acreage of the country being 507,736, the loss should be calculated 
upon 42 per cent of this, or 213,249 acres, which gives a total esti- 
mated annual loss from peach leaf curl of $2,335,076. In this estimate 
no account has been taken of the great injuiy to the growth of trees, 
the injury to nursery stock, the death of young orchard trees, nor the 
loss to succeeding crops from the reduced number or quality of f mit 
buds on affected trees. There is also the loss arising from the culti- 
vation and pruning of unproductive orchards, which, if it could be 
determined, would probably bring the entire annual loss to the 
country up to $3,000,000 or more. 

Since 1893, when the investigation of this disease was undertaken 
by the writer, a veiy large amount of correspondence has been con- 
ducted with peach growers in all parts of the Union who have sus- 
tained losses from curl, and this correspondence has resulted in the 
accumulation . of a large number of facts respecting these losses. 
These data, however, have not been drawn upon in the above esti- 
mates, as it might be claimed that they were from growers only who 
have suffered from the disease, and consequently would not fairly 
represent the industry as a whole — a claim which can not be made 
against the circular letter, the basis of the estimates, which wjus 
addressed to peach growers in general in all parts of the United 
States. In fact there appears to have been a larger percentage of 
replies received from sections of the' country where curl is scarce 
than from the more affected portions. 



CHAPTER 11. 

NATURE OF PEACH LEAF CURL. 

The study of the nature of plant diseases is intimately linked with 
the study of plant physiology, and the true science of vegetable 
pathology is largely, as Ward has defined it, the study of. abnormal 
physiology. (Introduction to Hartig's Text-book of the Diseases of 
Trees.) These facts become evident when studying the etiology of 
peach leaf curl and the conditions attendant upon its widespread 
development. The direct cause of peach leaf curl has long been 
known as a parasitic fungus, Exoascus deformmin (Berk.) Fuckel, 
but it is evident from a careful study of the disease that the injurious 
development of the fungus is distinctly correlated with special physi- 
ological phenomena of the peach tree itself. These conditions of the 
tree are in turn dependent upon such external influences as tem- 
perature, the humidity of the soil and atmosphere, and others. Such 
facts were foreshadowed by the theories advanced by peach growers 
as to the cause of the disease. Many growers have considered peach 
leaf curl as the direct result of exce&sive moisture and low tem- 
perature or sudden changes, and as these physical conditions cer- 
tainly have an important bearing upon the injurious development of 
the disease, they are considered together with the direct relations of 
the parasite to its host. However, too much stress can not be placed 
upon the fact that the fungus alone is responsible for the injury to the 
tree. Without the parasite not a leaf would curl nor a peach fall on 
account of this malady — in fact, no such disease would exist. This is 
shown by the work hereafter detailed. It is fortunate that the direct 
cause of peach leaf curl is a parasitic fungus rather than unfavorable 
atmospheric conditions, for the latter could not be controlled, while 
the control of the fungus has been found practicable, simple, and inex- 
pensive. 

PHYSICAL CONDITIONS INFT.UENCING THK DISEASE. 

The influences of temperature, humidity, situation, soil, etc. , upon leaf 
curl are often so well marked that they have frequently and in fact quite 
generally been mistaken for the active cause of the disease. Indeed a 
very large percentage of peach growers have maintained, to within the 
past ten or fifteen years, that sudden changes of tempemture occurring 
in conjunction with wet weather are the sole cause of the curling and 
22 



PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 23 

loss of foliage. Notwithstanding the number of known facts to. the 
contrary, there are even now many growers who retain this idea to the 
utter and needless loss of their crops. The writer has met men who so 
finiily believe that leaf curl is due to uncontrollable climatic influences 
that they would not consider other explanations, being unwilling to 
visit the orchard, though the crop was being lost through curl and 
by so doing future crops might have been saved. 

To gather the experience of peach growers in general 4*especting the 
conditions under which leaf curl develops most severely, a circular of 
inquiry was addressed to several hundred orchardists in November, 
1893. The replies to some of the questions are presented. Among 
the inquiries the growers were requested to state if they had observed 
the disease to be more prevalent after a cold spell in the spring. To 
this question 97 replies were received, 89 affirmative, 6 negative, and 
2 growers said they had observed no diflference, which shows that the 
orchardists are almost unanimous in holding that a cold spell in the 
spring favors the development of curl. 

To the second question, as to whether the trees were most affected by 
curl in a wet or dry season, there were 104 replies. Of these, 78 
stated that peach trees were most affected in wet seasons, 8 that they 
were most affected in dry seasons, and 18 that there was no difference. 
Here again is seen a marked agreement in the replies, a great majority 
of the growei-s recognizing that wet years favor the disease. 

The above-considered conditions — a cold spell in the spring and wet 
weather — may be explained by stating that such conditions favor, on 
the one hand, the serious development of the fungus causing the dis- 
ease, and, on the other, they result in a much greater susceptibility of 
the tissues of the peach leaves to the attacks of the parasite. Where 
both cold and rain occur together in the spring, about the time the 
leaves are pushing, the disease is liable to develop seriously and few 
varieties can then resist it. The action of wet, cold weather upon the 
tissues of the peach, making them much more subject to curl than they 
otherwise would be, has been considered in relation to other plants in 
a paper by Prof. H. Marshall Ward,' who says that when thecomhtned 
effects of tlie physical ewinronment are unfavorable to the hont^ hut notso 
firare evefii fa/oorahle to the paras^ite^ u^efind the dlseai<e a^'imunlng a more 
or less pronounced epidemic character. He is not here speaking of curl, 
but the statement holds perfectly true for that disease. A cold, wet 
spell succeeding warm spring weather, has a tendency to saturate and 
soften the tissues of the peach, as in the case of other plants. The 
sudden checking of active ti'anspiration, due to lowered temperature 
and saturated atmosphere, soon results in the tissues of th(* plant being 
suffused with water. ''The stomata," as Ward puts it, Vare nearly 

'Wani, Prof. II. Marshall, The Relations between Host and Paiw^ite in Certain 
Dii«eaBes of Plants, Croonian liccture, Pr(x\ lioy. Soe., Vol. XLVII, No. 290. 



24 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

closed, the cell walls bounding the intercellular passages and the air 
in the passages themselves are thoroughly saturated with water and 
aqueous vapor, respectively, and the movements of gases must be 
retarded accordingly; turgescence is promoted, and the water contents 
accumulate to a maximum, owing to the disturbance of equilibrium 
between the amounts absorbed by the active roots in the relatively 
warm soil and those passing off into the cold, damp air; much more 
water is absorbed by the roots in the relatively warm soil than passes 
off as vapor in equal periods of time." Further than this, Ward states 
that "the low temperature, feeble light, and partially blocked ven- 
tilation system have for a consequence a depression of respiratory 
activity and the absorption of oxygen genemlly." This must give a 
lowered vitality and an accumulation of organic acids. The reduced 
light also leads to a decided reduction in the assimilative power of the 
leaver. ''The turgid condition of the cells, and the diminished inten 
sity of the light," Ward says, *'will favor growth." If this takes 
place, ''the tendency will be for the very watery cell walls to l>ec>ome 
relatively thinner than usual, as well as watery, because the ill-nourished 
protoplasm does not add to the substance of the walls in proportion. 
This being so, we have the case of thinner, more watery cell walls 
acting as the only mechanical protection between a possible fungus and 
the cell contents." 

It is generally known that the conditions of moisture and shade, 
which are above shown as making the tissues of a host plant more 
tender and watery (more subject to fungous attacks), are also the 
conditions most favorable to the development of fungi. This holds 
equally as good for Exoascus deformans as for other forms. In speak- 
ing of these conditions in relation to a fungus known as Botryth^ Pro- 
fessor Ward gives some generalizations equally applicable to Eroascus 
def(yrmans in its relation to curl. He says that just those external 
climatic conditions which are disturbing the well-being of the green 
host plant are either favorable to the fungi considered or, at any rate, 
not in the least inimical to their development. "Thus," he says, " the 
oxygen respiration of the fungus goes on at all temperatures from 0^ C. 
to 30^ C. and higher, and although we still want information as to 
details, experiments have shown that the mycclia flourish at tempera- 
tures considerably below the optimum for higher plants. Moreover, 
light, so indispensable for the carbon assimilation of the green host, 
is absolutely unnecessary for the development of the fungus. Then, 
again, the dull, damp weather and saturated atmosphere, so injurious 
to higher vegetation, if prolonged, because they entail interference 
with the nonual performance of various correlated functions, aa we 
have seen, and render the plant tender in all respects, are distinctly 
favorable to the development of these fungi; consequently the very 
set of external circumstances which make the host plant least able to 



PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 25 

withstand the entry and devastation of a parasitic fungus like Botryth^ 
at the same time favor the development of the fungus itself." 

The writer thinks, as the result of observations in the field, that 
EeoasGus deformans is favored in both its entrance and spread within 
its host by the conditions which hav>3 just been considered. It is a 
widely observed fact that leaf curl usually develops sparingly in a 
unifonnly warm and dry spring, and it is also noticed that where 
infection has occurred a return of warm, dry weather, or even the 
occurrence of a hot, dry wind, will check the development of the 
fungus within the tissues. An infected leaf may fail to develop 
the spores of the fungus under such circumstances. The thin, satu- 
rated cell walls and the moist intercellular spac^es thus appear to be 
closely correlated with the active vegetation of the fungus. The 
growth and consequent tenderness of the tissues is also important in 
this connection. Where soil, elevation of orchard, and atmospheric 
conditions are unfavorable to a saturated condition of the plant paren- 
chyma, the disease is not likely to run more than a short and feeble 
course. Soil and elevation are here considered with atmospheric con- 
ditions, for it is found that on the same fanii a difference of elevation 
or soil moisture may determine the degree of vimlence of the disease. 
The influence of elevation may be of only secondary nature — that of 
maintaining a higher temperature — but its action on the disease is fre- 
quently well marked. Of 92 orchardists who expressed their views 
as to whether trees are affected by curl most on high or on low land, 
48 say that trees suffer most on low land, 14 on high land, and 30 
think there Ls no difference. While the majority claiming that trees 
on low land are most affected is not as large as some of the majorities 
obtained in replies to other questions, it represents over one-half 
the replies received to the question under consideration and is more 
than three times as great as the number who believe trees to l)e most 
affected on high land, hence is sufficient to establish confidence in its 
reliability, even if it were not indorsed by many published statements 
to the same effect. 

Mr. Thomas A. Sharpe, superintendent of the experiment farm at 
Agassiz, British Columbia, has made several comparative reports on 
the action of peach leaf curl on trees planted in the valle}' and upon 
the more elevated bench lands of the farm. A few brief statements 
from these reports i^hould be of value in connection with the above 
statements.^ In 1892, Mr. Shai'pe says, the peju»h trees suffered from 
a severe attack of leaf curl. '' Only 5 varieties of those planted in 
the valley escaped" the disease. ''The trees planted on the bench 
lands did not suffer so much, and appeared to recover much more 
rapidly than those in the valley" (1. c, p. 278). In 1893, it is said, 



^ See reporte of experimental farms, Ottawa, Canada, for tlie years indicated. 



26 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

the curl leaf in the peach and nectarine trees was worse than it had 
ever been tefore, the Malta being the only variety that was entirely 
healthy on level land. The varieties received from England and 
planted on the level land were just as badly aflfected as the others. 
The first and second bench orchards suffered alike with those on the 
level ground, but the orchard highest up, at an elevation of 800 feet, 
had no curl in any case, and the trees appeared to have suffered less 
from cold than those lower down (1. c, p. 342). Mr. Sharpe says 
that in 1896, ''as heretofore, the trees on the upper benches, both 
nectarine and peach, escaped the curl leaf entirely" (1. c, p. 44:9). 
Again, it is said that "the peach crop on the level land this year [in 
1898] was almost an entire failure. The curl leaf was very prevalent, 
nearly every tree being seriously affected by it." Relating to the 
orchard on the bench lands, it is stated that "curl leaf did not affect 
the foliage there; in fact, it has never injured the foliage on either 
peach or nectarine trees on the benches over .300 feet above the 
valley" (1. c, p. 403). These facts have an especial interest and 
value in that they were recorded by a single observer on one farm 
and during successive years and epidemics of curl, and they are in 
perfect hannony with the experience of a majority of the growers 
whose views are presented above. 

The soil may exert its influence by abundantly or feebly supplying 
the transpiration stream, in accordance with the degree of accessibility 
of the moisture it contains, to the root hairs of the tree. It may be 
said, however, that as leaf curl commonly develops at the beginning 
of spring growth or at the close of the winter's rains, the soil will 
rarely be found so deficient in moisture as to greatly retard the devel- 
opment of the disease where other conditions are favorable. It is prob- 
ably equally true that the excess of water usually found in the soil 
in the spring is favorable to the special development of the disease at 
that season in its worst form. 

Besides the influence of tempoi^ar^^ excessive humidity of the atmos- 
phere upon leaf curl, which has already been considered, there are 
other atmospheric influencas and relations of importance, which depend 
upon the local or general geographic, topographic, and climatic fea- 
tures of country. Some of these more prominent atmospheric 
influences may here be briefly considered, together with their most 
probable causes. 

Proximity to large bodies of water, whether salt or fresh, greatly 
favors the development of curl. The cause for this clearly rests in the 
resulting greater humidity and lower temperature of the atmosphere. 
Plants growing in a constantly humid atmosphere have normally more 
succulent and tender tissues than those growing in a drier region. The 
reasons for this have already been alluded to for special cases of 
extreme atmospheric humidity and lowered temperature. Near large 



PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 27 

• 

bodies of water spring £og8 commonly occur, and these lead to the 
increase of the atmospheric humidity at a time when the foliage is 
tender and growing rapidly, thus stimulating a development of curl 
almost annually and over wide stretches of country. Independent of 
fogs, the atmosphere about large bodies of water is also much more 
humid than in an inland region. Instances of the iniSuence of large 
bodies of water on the general prevalence and frequent occurrence of 
curl in a region are found in western New York, near the shore of Lake 
Ontario; in Ontario, Canada, near Lakes Erie and Ontario; in Michi- 
gan along the shore of Lake Michigan; in California about the bay of 
San Francisco and at other points along the Pacific coast; in Washing- 
ton and British Columbia about Puget Sound; and in many similar 
situations in all portions of the world where the peach is grown. The 
writer believes, however, that the influence of large bodies of water 
upon the development of curl depends in part upon the normal spring 
temperature of the region, and likewise upon the source of the prevail- 
ing winds. Where the prevailing spring winds are from a dry, inland 
region instead of from the water, the atmosphere does not feel the 
influences of the latter. Moreover, where the spring tempeiuture is 
high, transpiration may proceed normally even in the neighborhood of 
large bodies of water, and curl may not conmionly prevail. 

In contrast to the influences of large bodies of water are those of 
neighboring dry and arid plains or desert regions. In the midst of 
such influences peach leaf curl can rarely attain to an epiphytotic 
development, and then only under special favoring seasonal condi- 
tions. The atmosphere is normally too dry in such situations to exert 
a predisposing action upon the host, and it certainly does not favor 
the serious development of the parasite. Exemplifying these condi- 
tions are large areas in Arizona, New Mexico, Nevada, Utah, Colorado, 
Texas, Kansas, and California. Little or no curl is reported from the 
more arid portions of these sections of the country, its absence being 
due, at least in part, to the influences here considered. 

Another of the broader influences affecting the general and perma- 
nent prevalence of curl over extensive regions is the normal annual 
mnfall. Comparisons of this kind must be made, however, between 
regions of approximately similar tempemture. Under such condi- 
tions it may be said that the general annual prevalence of leaf curl 
increases with the increase of normal annual precipitation. Compari- 
sons of this kind can hardly be justly drawn in the Mississippi Valley 
or on the Atlantic coast^ as the tempemture conditions vary too 
greatly in those regions from north to south. On the Pacific coast, 
however, owing to the modifying influence of the Pacific Ocean,, the 
temperature prevailing from Lower California to British Columbia, 
a distance of about one thousand three hundred miles, presents no 
such great variations as are found in a like distance from south to 



28 PEACH LEAF OUBL: ITS NATUBE AND TBBATMENT. 

• 

north on the Atlantic coast, so that the relations of annual minfall to 
the constant prevalence of curl may be more fairly decided. 

In the following remarks on this subject I have left out of consid- 
omtion the temporary influence of exceptional seasons and, as far &s 
possible, the special influence of local features. The subject should 
be viewed from the broad field above pointed out. In southern Cali- 
fornia loiif curl is not recognized as a generally prevalent and serious 
trouble, but there is evidence which shows that its prevalence increase8 
from San Diego northward to the San Bernardino Mountains. The 
average annual rainfall varies from about 10 inches at the former place 
to 10 inches at Ijos Angeles, which is not far from the mountains. In 
the San Joaquin Valley the prevalence of curl increases as a whole from 
the south central portion toward Sacramento and the north. The 
average annual rainfall, which is 7 inches at Tulare, 9 inches at Fresno, 
11 inches at Merced, and 14 inches at Stockton, reaches 20 inches at 
Sa(^ramento, about which center curl is quite prevalent. The average 
minfall at Oakland is 23 inches, and curl is quite troublesome there. 
In the Sacramento Valley curl is frequently quite prevalent, and the 
rainfall varies from 20 inches at Sacramento and Chico to 34 inches at 
Redding. About Ashland, in southern Oregon, the rainfall is 23 
inches, and the disease is about as in the Sacramento Valley. Farther 
north in Oregon curl l)ecomes decidedly more prevalent and injurious 
at the west of the Cascade Mountains, and increases as Portland is 
approached. The rainfall is 35 inches at Roseburg, 46 inches at 
AlUmy, and 49 inches at Portland. From Albany to Portland the 
pea(*h industry has been greatly injured by curl, and on its ac<*ount 
many growers in this region have considered peach culture a failure. 

Curl, it seems, was introduced into the central part of the Willamette 
Valley, Marion County, nearly half a century ago. Prior to that 
time the peach was successfully grown in that region in spite of the ' 
humidity of the climate. In the Patent Oflice Report for 1855, p. 
298, there is a statement of the situation in Polk and Marion counties 
from 1852 to 1855. This statement was from Mr. Amos Harry, of 
Farm Valley, Polk C/Ounty, Oreg., and is of spex;ial interest in this 
connection. Mr. Harry says: "The pe4U^h in this county has l)een 
affected with a disease known as the 'curled leaf,' which threatens to 
destroy the trees. It made its appearance at Mill Creek, in Marion 
County, in 1852, and extended considerably on that side of the river 
(Willamette River) in 1858, but had reiiched most parts of the valley 
in 1854-55. Some trees seem to escape it much more than othei^s, but 
if the n)alady increases for two years to come as it has for two post, I 
fear we shall come entirely short of this delicious fruit. Some think 
it is owing to cold, wet weather, and recommend shortening all the 
limbs as a remedy, and some experiments seem to favor this idea- 
Others think it is produced by an insect, and that no remedy will save 
the trees unless it can be appli<Hl to tht^ wliole surface of the leaves.'- 



PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 29 

The rainfall at Portland, as already said, is 49 inches, and curl is com- 
monly prevalent and severe. At Unaatilla, east of the Cascade Moun- 
tains, but a)>out the same distance north as Portland, the rainfall is 
only 10 inches, while on that side of the mountains the peach industry 
is extensive and everywhere prosperous, leaf curl being much less 
prevalent and of secondary importance. This shows that it is not the 
distance north and the consequent lower temperature which makes curl 
more severe at Portland than at Los Angeles for instance, but that it is 
the excess of i-ainfall, for at the eiist of the mountains, near Umatilla, 
the temperature goes equally as low or lower than at Portland, and 
curl is of little importance there. In the Puget Sound region peach 
culture has never developed extensively, thegenei'al prevalence of curl 
and its injurious action being one of the chief reasons. The i-ainfall 
is 50 inches at Seattle and 56 inches at Olympia. It is only 7 inches 
at Kennewick and 9 inches at Ellensburg, on the east side of the Cas- 
cade Range. The peach orchards of North Yakima and neighboring 
sections on the east side of the Cascjules and near Ellensburg, wh(*re 
this rainfall is taken, are noted for their extent, thrift, and gencml 
hesilth, and curl is not a serious trouble. This case is pamllel with 
that of Portland, already considered. The rainfall at the west of the 
mountains is 50 to 56 inches or more, while at the east it is only 7 to 
9 inches. In the former region peach growing is not listed by the 
Washington Board of Horticulture as one of the horticultuml indus- 
tries, but in the latter region the peach is a leading fruit, l)eing 
extensively and successfully grown. The winter temperature east of 
the mountains should range fully as low where the peaches are grown 
as at the west of the range. The contrast in peach culture in the two 
situations results from the difference of rainfall, and the heavy rain- 
fall at the west of the Cascades results in a development of curl almost 
prohibitive to peach growing.* 

In replying to a circular letter sent to the peach growers of Mary- 
land, November, 1893, Mr. T. C. Stayton, of Queen Anne, makes some 
statements which bear directly on the matter here considered and are 
of much interest as resulting from personal observation. After speak- 
ing of the conditions in Maryland, Mr. Sbiyton says: ''I was in 
Wiishington State during the months of April, May, June, etc., this 
year, and I find they can not grow peach trees west of the C'ascade 
Mountains or in western Washington, as that part of the State is 
called, as that is a very wet part of our country.-' He adds that this 
was especially true in 1893, and continues: *'About all the young trees 
that had been planted in that part of the State died from curl leaf, or 
so nearly so that they were worthless, but over in eastern Washington 
I did not notice any curl leaf, the climate being dr}-." 

' For a full and accurate account of the rainfall conditions prevailing on the 
Pacific coaijt, see lieport of the Rainfall on the Pacific Slope for from Two to Forty 
Years, Washington, 1889; also other report*? of the Weather Bureau. 



30 PKACH LEAF CURL: ITS NATURE AND TREATMENT. 

Peai^h leaf curl appears to be more prevalent in late than in early 
springs. This is probably due to the lower temperature and greater 
rainfall usually accompanying the former. Of 80 growers who gave 
their experience in relation to this matter, 43 stated that curl affects 
trees most in late springs, 23 believed it affects them most in early 
springs, and 14 had noticed no difference. 

The quejstion as to whether peach leaf curl affects trees most after a 
cold or warm winter was submitted to the growers, and of the 67 who 
replied, 27 stated that trees were most affected after a cold winter, 21 
that they were most affected after a warm winter, and 19 growers had 
observed no difference. 

The question of the influence of heavy dews on curl was also sub- 
mitted to the orchardists, and the views expressed in their replies 
exhibit a remarkable agreement, 47 out of the 58 expressions of 
opinion received stating that the disease is no worse after a series of 
heavy dews. To the writer it appears probable that these answers are 
in perfect accord with the facts. Heavy dews can exert but slight 
influence upon the tissues of the peach, as they occur at night, when 
transpiration from the leaf is largely checked by the reduced light and 
lowered temperature of the atmosphere, resulting in the stomata being 
nearly closed. With the return of light and warmth the dew evapo- 
rates with the resumption of transpiration, and can have but little 
influence upon the tissues of the leaf. It might seem that dew would 
have a direct action on the germination of the spores of the fungus 
and in that way lead to a serious development of the disease after one 
or more heavy dews. This view, however, is not supported by observa- 
tions either in the field or in the laboratory. In regions having little 
cloudy weather, with exceptionally clear sky, as in many portions of 
the Southwest, the heat of the soil radiates rapidly after sunset. In 
such sections of the country the days are hot and the nights cool or 
cold in comparison, the i-ange of temperature l>etween night and day 
being often considerable. In such regions dew is common and often 
heavy, but it is here that least curl occurs. 

Relative to the action of dew on the germination of the spores of 
Exvmem deformans^ it may be said that something more than dew is 
required for such genni nation. The writer has tested this matter 
most thoroughly, not only with dew, but with many forms of culture 
mcHlia at various temperatures and with varying supplies of oxygen. 
Brefeld has also shown that moisture alone is not suflScicnt for germi- 
nation, behaving utterly failed to induce germination in a single instance 
after months of work with culture media in liquid form. Budding of 
the spores is easy to obtain in all liquids, and is mo^e abundant and 
continuous in suitable nourishing cultures than in dew or rain water. 
Fifty-eight growers replied to an inquiry on this subject, 47 stating 
that the disease is no worse after a series of heavy dews, 7 that it 
is worse, and 4 that no difference was observed. 



THE DIRECT CAUSE OF PEACH LEAF CURL. 31 

THE FUNGUS CAUSING THE DISEASE. 

The fungus causing peach leaf curl, now known as Exoii^cus defonnans 
(Berk.) Fuckel, is a member of the subfamily of fungi known as 
Erm^cece, The ExodscetE are low or simple Aaconiycetes^ or fungi bear- 
ing their spores in cases or asci. 

The classification of the Ewdscem which now lays greatest claim to 
scientific permanence is that outlined in the recent writings of Sade- 
beck, who has given careful study to these forms. ^ 

Of the five genera which he recognizes, only the last directly concerns 
us at this time, as it is to this genus {Exoasciis) that the peach curl 
fungus belongs, as well as numerous other species injurious to horti- 
culture. In considering this genus Sadebeck * has grouped thirt}'^ of 
its species according to certain characters of development. He recog- 
nizes the following characters of the genus: 

ExoAscus Fuckel. 

A. The mycelium is perennial in the inner tiesues of the axial organs. 

a. The development of the hymenium occurs only in the floral leaves of the 
host plant. Eight species. 

/;. The development of the hymenium occurs only in the foliage leaves of the 
host plant. Seven species, including E. d^formam^ 

c. The development of the hymenium occurs upon the leaves as well as upon the 
fruits. One species. 

B. The mycelium is perennial in the buds of the host plant and develops only 
subcuticularly in the leaves. 



* Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, p. 43. 
Smlebeck recognizes five genera in the Exoascae^ which he arranges and character- 

izoH in the following manner: 
EXOASCEjE: Ascomycetes whose asci are not united in a fruit body. 

A. The asci arise as swellings at the end of the branches of the mycelial 
threads. 

1. Endomyces Tulasne. Four-spored asci, no conidia within the same; the sterile 
threads develop chlamydoepores and oidia. 

2. MagnutdeUa Sadebeck. Parasitic. Asci with more than four spores; usually 
wnidia formations in the ascus. Oi'dia and chlamydospores wanting. 

B. The asci take their origin from a more or less loose hymenium. 

3. Ascocorticium Bref. Saprophytic on hark. The ascus layers are arrange<l in a 
U)08e hymenium upon the mycelium. 

4. Taphrina Fries. Parasitic. Without perennial mycelium. In the formation 
of the aseogenous cells differentiations of material occur. Forming leaf spots. 

5. Exodscus Fuckel. Parasitic. With perennial mycelium. In the formation of 
the asci no differentiations of material appear. The subcuticular mycelimn changes 
directly to aseogenous cells. Causing sprout deformations. 

* Sadebeck, Dr. R., Einige neue Beobachtungen und kritische Bemerkungen iiber 
die Exoascaceae, pp. 277,278, reprint from den Ber. d. deutsch. hot. Ges., 1895, 
Ikl. XIII. 

'Dr. von Derschau has described the occasional fruiting of Exomnis deformans in 
the blossoms of the peach. The figures given by this author do not show the nor- 
mal development of aseogenous cells in the blossoms which are so common in the 
leaf blade of the peach. His figures show the asci as arising from lateral branches 
of a <x)ntinuous mycelial hypha, and this mycelium is situated l)eneath the epidermal 
cells instead of between the cuticle and epidermis (Landw. Jahrb., BerUn, 1897, pp. 
897-901, and Table XLI). 



32 PEACH LEAF CURL: ITS NATUBE AND TEEA'HfCENT. 

n. The (level* )pnient of the hymenium occurs only in the floral l^avefi of the host 
plant. Thnn; PiK^ciee. 

h. The development of the hymenium occurs only upon the foliage leaves. Ten 
species, 

c. The noting mycelium extends intercellularly in the deformations of the leavis. 
One specicH. 

It may be seen under A i of this arrangement that Exoiucus defor- 
mmiH is said to possess perennial mycelium, inhabiting the inner tivS- 
sues of the axial organs, and that the development of the hymenimn 
occurs only in the foliage leaves of the host plant. As will be seen in 
another part of this bulletin, it is perhaps a perennial nature of the 
mycelium of E, di^fonnans which make« it difficult to thoroughly rid 
an orchard of curl by means of spray treatment, but this matter 
requires further careful consideration. 

The synonymy of Exfjosciis deformans (Berk.) Fuckel has l>een 
given by numerous writers. Sadcbeck* gives it as follows: 

Asi'omyceH deformans Berk. Intro, to Cryptogamic Botany, 1857, p. 284. 

Ancos])onum deformans Berk. Outlines, 1860, p. 449. 

Taphrina d(formam Tul. Ann. Sci. Nat., 1866, V. Ser., t. 5., p. 128. 

Kvoascas deformann Y\iQkfd\. (a) Persicic Fuck. Symbolic Micolog., 1869, p. 2.52. 

This fungus has been very commonly observed and frequently 
described by botanists since Berkeley called attention to it in 1857. 
It has thus been known as the cause of curl for a little less than half 
a century. The peculiar behavior of peach foliage under its ac*tion 
has been observed l)y horticulturists, however, for a much longer 
time. The disease was well described in England in the early part of 
the present century. 

In spite of the very common appearance of Kcoascus deformnnfi 
upon peach foliage in peach-growing countries, the descriptive litera- 
ture relating to its life history is not free from conflicting statement.^. 
Several species of ExoaHctcv have been confounded with this species 
in some instances, and subsequent writers have . perpetuated the 
confusion. 

Some earlier writers believed this species inhabits a considerable 
number of host plants, thus resulting in the description and distribu- 
tion of several distinct species as E^coiwcus deformans. To avoid such 
confusion it would be best to confine remarks upon this species to tlie 
fungus as it develops upon the peach {Pnmus ^>ersica L.), which if 
not its only host, is certainly its most common one. 

At least two modes of infection of the peach tree by Exo((^^^tfj< 
drfornaiihH are said to exist — (1) by means of perennial mycelium, 
and (2) by means of the spores of the fungus. 

Sadcbeck^ is authority for the statement that the mycelium winters 
over ill the youngest portions of the one-year-old branches of the host 



'Sa<lelH'C'k, Dr. 11., Die xmnusitistrhen Kxoawi'een, Hamburg, 1893, p. 53. 
'' Idem, 1. c. 



THE INFECTION OF THE HOST. 33 

plant, and may be seen in the primary cortex, in the medulla, and in 
the meduUaiy rays of the first shoots of each period of vegetation, 
but has not been observed in the soft bast. With the beginning of 
the new season of growth the mycelium, according to Sadebeck, 
extends into the leaves of the young shoots, penetrates first the inner 
tissue of the leaves, and finally progresses to the development of the 
subcuticular hymenium. From what foundation of experimentation 
Sadebeck has arrived at these views respecting this particular species, 
I am unable to state, but he has given the outlines of his investigations 
upon other species.^ 

The facts given by De Bary * can not be c^ted here, for this work 
was done upon the Exoascus infesting the cherry tree, and which is 
now considered to be distinct from E. deformans. 

The general acceptance of the view that spring infection of the peach 
foliage is largely due to the extension of the internal perennial myce- 
lium into the new shoots and leaves from the shoots of the previous 
summer, has probably considerably retarded the progress of prevent- 
ive treatment. Pathologists have thought it improbable that any 
considerable amount of disease could be prevented after a tree was 
once generally affected, as the perennial mycelium, being internal, 
could not be readily reached by external sprays. Prillieux,* writing 
in 1872, advises the gathering of the diseased leaves and the cutting 
away and burning of the diseased branches. Frank* has made like 
recommendations in both editions of his work on plant diseases. 
Assuming the mycelium to be perennial, he saN's that the curing of the 
disease might be aimed at through cutting back of the diseased branches 
and the prevention through quick removal of the diseased leaves. 
Winter* suggests a somewhat similar line of treatment, with the 
additional recommendation that the trees be protected from rain 
during the unfolding of the leaves. Dr. Cobb,* as late as 1892, after 
speaking of the perennial mycelium of this fungus, discusses pre- 
ventive and curative measures, such as the destruction of diseased 
leaves, prunings, etc., while in the more severe cases he says the 
sooner the trees are cut down and burned the better it will be for the 
peach industry. 

* Sadebeck, Dr. R, Die parasitischen Exoast-een, Hamburg, 1898, pp. 24-28. — Daa 
perennirende My eel der Exoascus- Arteii. 

*DeBary, A., Com. Mor. and Biol, of the Fungi, Mycetozoa, and Bacteria, Eng- 
lish edition, 1887, p. 266. 

» l*rillieux, Ed,, Bui. de la soc. hot. de France, 1872, T. XIX, p. 280. 

♦Frank, Dr. A. B., Die Krankheiten der Pflanzen, Breslau, 1881, Part II, p. 526; 
gewmd edition, 1896, Vol. II, p. 250. 

* Winter, Dr. Georg, Die durch Pilze verursac^hten Krankhi*itiMi der Kultnrge- 
wachse, Leipzig, 1878, p. 47. 

•Cobb, Dr. N. A., The Agricultural Gazette, Sydney, New South Walc^, 1H1)2, Vol, 
III, pp. 1001-1004. 

11K)93— No. %) 3 



84 PEACH LEAF OUBL'. ITS NATURE AND TBEATMENT. 

Relative tx) the use of fungicides the same writer says: *' These 
treatments are of doubtful value as far as the curl is concerned, and 
were it not that they are useful in other ways I would not mention 
them." It is evident that these views are the result of Dr. Cobb's 
belief that the perennial mycelium is responsible for the major portion 
of the spring infection of the tree. The writings of others to the 
sanae effect could be cited, but the views of the workers already named 
are sufficient to show that their recommendations for treatment have 
been based upon the hypothesis that the spring infection could not be 
prevented, by treatment with fungicides, as it arose mainly from in- 
ternal mycelium rather than from the germination of external spores. 
That this view has held back the preventive treatment of the disease, 
as already claimed, can not be doubted, and that a perennial mycelium 
is not responsible for more than a very small percentage of the spring 
infections seems evident from the results of the present experi- 
ments; in fact it may even be questioned if such infection takes plac« 
except under exceptionally favorable conditions. Our experiments 
have demonstrated that as high as 98 per cent of infections may be 
prevented by a single thorough application of a suitable fungicide. 
This is as high a percentage of control as is often obtained in the 
treatment of fungous diseases where no perennial mycelium exists, 
and it seems probable that the infections by this means may not com- 
monly exceed 5 per cent of each spring's infections. Were this not 
the case we would be forced to assume that the spray has a direct 
effect upon the hibernating mycelium, which certainly would be 
unusual and scarcely to be expected. 

The second mode of spring infection — that by means of spores — is 
probably much more general and important in this disease than has 
been supposed. That 90 to 98 per cent of the infections of the tree 
are prevented by a single spraying suggests that at least such percent- 
age of the infections is by means of spores. 

The mycelium of Exodscus defornumn as found in the peac*h, shows 
great differences in the form and appearance of its hypha?. These 
differences depend upon the stage of development of the fungus and 
the various functions of the mycelium. The writer recognizes three • 
types of hyphae, which may be termed vegetative, distributive, and 
fruiting. 

The vegetative hypha? are found most commonly in the leaf paren- 
chyma, but are also met with in the leaf stalk and cortical parenchyma 
of Vmdly diseased and distorted bmnches. These hypha* may be most 
distinctly seen, and are most highly developed, in infested leaves which 
have not yet formed the hymenium of ascogenous cells, but in which 
the parasite has been present a sufficient time to entirely alter the 
chamcter of the palisade tissue and cause the loss of the chlorophyll. 
In the leaf blade the palisade tissue first shows the serious action of 



BULL. 20. DIV. VEa PHY8, ft PATH^ U. S. OEPT. AQRIOULTURE. 




MYOCLIUM OF EXOA80U8 DEFORMANS, THE FUNGUS OAUSINQ REACH LEAF OURL. 



DESCRIPTION OF PLATE II. 

Mycelium of Exoascus deformans (600/1) . Figs. 1 and 2, normal vegetative hyphse, 
as found in the leaf parenchyma, showing characteristic septation, modes of branch- 
ing, etc. ; figs. 3, 4, and 5, usual t)rpe of distributive hyphae found in swollen branches 
iu the cortical parenchyma and medulla; figs. 6, 7, 8, and 9, fruiting hyphse, show- 
ing successive stages in the development of ascogenous cells from the subcuticular 
mycelium (6) to the half-formed ascogenous cells (9) . (See PI. Ill for further stages 
in the development of the ascogenous cells and asci.) 



THE MYCELIUM OF THE FUNGUS. 85 

the vegetative hyphae, which are usually found somewhat later among 
the cells of the spongy parenchyma, below the vascular network. The 
loss of chlorophyll from the two classes of leaf parenchyma commonly 
preserves the order here given. The form of the vegetative hyphae is 
very irregular, and their elements, or cell members, are often of dif- 
ferent size, length, and shape. The cells vary greatly in diameter 
from one end to the other, are frequently much curved and twisted, 
and oftentimes appear triangular in cross section. The branches 
may arise from greatly enlarged triangular bifurcations, or in other 
instances directly from the sides of the cells. These vegetative hyphce 
are all intercellular so far as observed, but are commonly found adher- 
ing closely to the cell walls of the host, frequently wrapping about the 
parenchyma cells. The walls of the hyphae are semitransparent but 
firm, commonly having a slight yellowish cast. The septa present 
peculiar characters. Two adjoining cells of a hypha have the appear- 
ance of being separately closed at the end and united with each other 
by means of an intervening plate, which if it should be dissolved or 
lost would leave the cells separated but closed. These peculiar septa are 
remarkably refractive and characteristic. They are well shown in the 
drawings of Sadebeck (Die parasitischen Exoasceen, Hamburg, 1893, 
Tab. II, figs. 7, 8). The predominating characters of the vegetative 
hyphce are shown in PI. II, figs. 1 and 2, of this bulletin. The hyphee 
there shown were carefully separated from the leaf parenchyma and 
drawn under the camera. The vegetative hyphee of the branch are 
much like those of the leaf, and have been seen most commonly among 
the looser parenchyma cells of the cortex just exterior to the bast fiber 
bundles. Thus far they have never been found by the writer in the 
cambial tissues. Sadebeck states that the mycelium has been found in 
the pith and medullary rays. 

The distributive hyphse are shown in PI. II, figs. 3, 4, and 5. 
They have been found by the writer in the tissue lying close beneath 
the epidermal cells of diseased peach twigs, and in great abundance in 
the pith. They are occasionally found in groups of several hyphas but 
slightly separated from each other and following a course parallel to 
the longitudinal axis of the shoot. The cells composing these hyphae 
are much longer than either the vegetative or the fruiting forms, while 
they are nearly straight and of more uniform diameter. The septa 
are characteristic of those found in the other forms of the mycelium 
of this fungus. Such distributive hyphae have been followed for some 
little distance in the swollen pprtions of the peach twig, and the name 
has been given them from their apparent function of spreading the 
fungus in the branch. Such hyphae branch by bifurcation, the branches 
conoimonly assuming a course parallel to the parent hypha and the 
direction of the peach limb. 



36 PEAOH LEAF OUBL: ITS NATUBB AND TREATMENT. 

The fruiting hyphee have been seen to arise in JExoaseus deffyrmwis 
from the vegetative hyphw after the latter have become well developed 
in the parenchyma of the leaf. Large, well-nourished vegetative 
hyphee conmionly develop just below the epidermal cells of the upper 
leaf surface/ From these hyphee arise blanches which penetrate 
between the cells of the epidermis, and press themselves between the 
epidermis and the cuticle. Such hyphse may be seen both in section 
and surface view. These subcuticular hyphee now branch f reeh% and 
follow with more or less regularity the triangular space formed by the 
juncture of two adjoining and somewhat rounded epidermal cells with 
the cuticle. This is presumably the line of least resistance to the 
advance of the hyphee. By opening and following these channels the 
mycelium assumes the outlines of a quite uniform network beneath the 
cuticle. While this manner of following the line of juncture of adjoin- 
ing epidermal cells with the cuticle is common, it is not invariably the 
practice of the fungus, cases occurring, where apparently no such 
agreement exists. Series of straight and parallel hyphse, at regular 
distances apart, are sometimes met with beneath the cuticle as the 
precursors of the hymenial layer. These send off lateral branches on 
either side, which by enlarging, branching, and curving eventually 
occupy most of the surface of the epidermis between the main hyphee. 
It is probable that the path followed by the fii-st subcuticular hy-phw 
depends largely upon the firmness with which the cuticle is attached 
to the epidermal cells, and which may largely depend upon the amount 
of water in the tissues and upon the age and rapidity of their growth. 
With the leaf tissues full of water and making a rapid growth, the 
h^j'phee could naturally pursue a more direct course beneath the cuti- 
cle than under contrary conditions. After the establishment of a 
much-branched filamentous network of subcuticular hyphee, the cells 
of which are usually slender, of medium length, thin-walled, and of 
comparatively uniform diameter (PI. II, fig. 6), these cells begin to 
distend, and are shortened by the formation of new transverse septa 
(PI. II, fig. 7, and PI. Ill, fig. 22). About this time all septa become 
much more distinct. At a later stage the cells become still more 
distended and subspherical (PI. II, fig. 8). As these enlarged cells 

» Miss E. L. Knowles (Bot. Gaz., Vol. XII, No. 9, p. 217) has called atten- 
tion to the fact that Winter^e statement that **the asci break through the lower 
side of the leaf" does not hold good for the peach (Kryp. Flora, Asco., p. 6, and 
Krank. Kultur-Gewachse, Leipzig, 1878, p. 47) . Winter is not alone in stating* that ^ 
the ascu of E. deformans arise on the under surface of the leaves. Robinson says: * * The 
asci are borne on both sides of the leaf, but in greater numbers upon the lower sur- 
face" (Robinson, B. L., Notes on the Genus Taphrina, Ann. Bot., Nov., 1887, Vol. I, 
No. 11, p. 168) . Atkinson also says: *' The asci are developed on both surfaces of the 
leaf" (Atkinson, Geo. F., Leaf Curl and Plum Pockets, Cornell Agr. Exp. Sta. Bull. 
No. 78, 1894, p. 325) . These and other like statements have probably arisen from a 
study of other foliage than that of the peach, and of other 8X)ecies of ExoascuSj and 
qave been perpetuated through insufficient reference to nature. 



DEiSORIPTION OF PLATE III. 

Fruiting stajrw of Kv^xiseus deformans. Figs. 1 to 13 (600/1), varioiiB stages and 
conditions of the asc'i and ascoepores of the fungus. Fig. 14, section of peach leaf, 
showing sul)epidernial and sulxiuticular mycelium, the latter already imrtially dif- 
ferentiated into ascogenous cells. Fig. 15, section of peach leaf showing three suc- 
cessive stages in the formation of the asci from the ascogenous cells: a, the pushing 
of the ascogenous cells; fe, the asc;us nearly full-formed, but with the contents still 
connected with the ascogenous cell; r, the asci separated by a septum from the ascog- 
enous cell, which now forms the stalk cell of the ascus. Figs. 16 to 20 (600/1) , the 
first stages in the formation of the asci from the ascogenous cells, the latter being 
ruptured alx)ve and the asci pushing upwanl. Fig. 21, the pushing of a forming 
ascus through the leaf cuticle (600/1). Figs. 22 t6 27 (600/1), various stages in the 
formation of ascogenous cells from sulxjuticular mycelium. (For several early stages 
in this process see PI. II, figs. 6 to 9). Figs. 28 to 30 (600/1) show fully developed 
ascogenous cells as seen from above. 



BULL. 20. DIV. VEa PHY8. ft PATH^ U. 8. DEPT. AQRIOULTURE. 









a^#» ,% 









t:^..^, W^ f-:^ 



'-yf-V^ ^^.'.v.v,- (2?.;-^ ^r- 



96 (V••:•^ >..,.--. 1/ 




rp') &: m ^''^' fP^'^'^- 






Bi 






.V«-w»rni 11. Iht-rc-. .xl.n.it dpi 




FRUITINQ STAGES OF EXOASOUS DEFORMANS. 



A Mo.-r. A- r...LtO.. »»li 






V 



•^'iiii'>"ORNi^ 



THE FRUITING HABITS OF THE FUNGUS. 37 

spread out between the epidermal cells of the leaf and the cuti- 
cle they are much distorted, curved, and lobed, the branches and 
lobe^ eventually filling, in a quite uniform and continuous manner, the 
entire space between the elevated cuticle and epidermis, so that a 
more or less perfect and continuous hymenial layer of ascogenous 
ceUs is formed (PL II, fig. 9; PI. Ill, figs. 23, 24, 25, 26, and 27). At 
this time the cells become well rounded and heavy-walled, and they 
may or may not become loosened and separated from each other 
(PL III, figs. 28-30). These ar^ now the fully developed ascoge- 
nous cells of the hymenium, and they are fully stored with nutritive 
materials for the development of the asci. In their compact, continu- 
ous, and rounded condition they resemble, when viewed from the sur- 
face, the stones in the pavement of an old Roman highway. 

The various phases of the development of the hymenium of ascog- 
enous cells may often be observed at one time in a single infected 
leaf. The center of a swollen spot frequently shows the fully devel- 
oped hymenium, while at the margin of the spot the first filamentous 
hj^phre are just spreading beneath the cuticle. In such instances 
nearly all stages in the development of the ascogenous cells may be 
studied in a single well-prepared specimen. The development of a 
subcuticular hymenium has been observed in the petiole as well as. in 
the blade of the leaf. 

The formation of the asci from the fully developed ascogenous cells 
has been carefully followed in the study of a large number of prepara- 
tions. Thus far no sexual phenomena have been observed in connec- 
tion with the formation of the ascogenous cells or with the develop- 
ment of the asci. As already said, the walls of the ascogenous cells 
are heavy. The early steps in the development of the asci from these 
cells (the development of a papilla-like elevation on the upper surface 
of the cells) cause the rupture or dissolution of the heavy wall where 
the elevation occurs. The phenomenon is that of the germination of 
a heavy-walled spore, or, perhaps, more properly, the outgrowth or 
prolongation of an endospore through the rupture of the epispore 
(PI. Ill, figs. 17, 18, etc.). The fact to be noted is the perfect rest- 
ing condition into which the ascogenous cells may pass before the 
development of the ascus, as shown by the marked delimitation between 
the thin wall of the forming ascus and the heavy wall of the ascogenous 
c*elL The entire isolation of single ascogenous cells or groups of cells 
from all sources of vegetative supply indicates that the ascus is 
entirely dependent for its nourishment upon the stored materials of 
the cell from which it arises. The pushing of the ascus after the com- 
plete development of the ascogenous cell instead of in direct con- 
tinuation of the development of the latter, also points to a probable 
cessation and renewal of the reproductive activity of the ascogenous 
ceU. 



38 PEACH LEAF CUBL: ITS NATURE AND TREATMENT. 

In view of those facts, it sooins possible that the ascogenous cells 
may be capable of enduring, under especially favorable conditions, a 
resting period of considerable time. Such resting ascogenous cells 
have been sought for upon the swollen branches of the peach, how- 
ever, without success. Further research along this line is desirable. 
As the fungus is already known to fruit upon the blade and petiole 
of the leaf and upon the blossom, and a vegetative mycelium Ls found 
growing thriftily in the swollen branches, there seems to be no good 
reason why the parasite may not fruit upon the infected twigs. 

The perpendicular growth of the developing asci in the leaf soon rup- 
tures or pierces the cuticle, and where large numbers of asci develop 
at the same time the cuticle is lifted, torn, and lost, the asci forming 
a more or less continuous plush-like surface growth. Isolated asci 
press through the cuticle so as to form separate perforations (PI. Ill, 
tig. 21). The contents of the forming ascus are finely granular, and 
as the ascus elongates these contents crowd into the upper portion and 
a septum is formed across the basal part in such a manner as to cut off 
the now emptied ascogenous cell as a stalk cell for the ascus (PI. Ill, 
fig. 15). When fully developed the asci are usually broader at the top 
than at the base, and of ten somewhat clavate in form. A series of a^ci 
measured varied in length from 34: to 44 A'? the average being 38 ^ ; the 
width of the asci ranged from 10 to 12 //, and the height of the stalk 
cells varied from 8 to 13 /^, the average being slightly over 10 /* (PI. 
Ill, figs. 1-13). 

The formation of the ascospore-s in Exoascus deformans has not l>een 
carefully studied by the writer. Sadebeck has shown, however, for K. 
turgldm^ that mitotic nuclear division oc<*urs in the ascus in connec- 
tion with spore formation (Untersuch. uber die Pilzgattung Exoas- 
cus, Hamburg, 1884, PI. Ill, fig. 20). The ascospores developed in 
the asci of E, defortaans vary in number from 3 to 8, the latter being 
the full and typiciil number. When mature they are surrounded by a 
moderately firm cellulose wall, which is rather inconspicuous, owing 
to its transparency. The spores are usually somewhat oval in form, 
being longer than broad, but occasionally some are seen which appear 
nearly or quite spherical. Fresh ascospores sometimes show distinct 
nuclear phenomena. This has been observed with spores still within 
the as(»us, as well as in many which have escaped. The nucleated 
appearance seems less common in budding or germinating ascospores 
than in those in a resting condition (PL IV, figs. 1, 2, 3, 4, and 10). 
The avel-age length of the ascospores measured was 7^^ /*? th® length 
varying from 6 to 9 //, and the average width was 6fV A'? varying from 
5 to 7 /^. The ascospores escape from the ascus through an apical rup- 
ture of the latter. 

Germination of the avscospores has been observed by the writer to 
proceed in two ways: (1) By means of budding or conidia formation: 
(2) by means of stocky germ tubes, often one branched and resembling 
promycelia. 



^RAi 



XTNIVEHEISITY' 



IcauFOH^^^ 



DESCRIPTION OF PLATE IV. 

Germination of the ascospores and conidia of Exoascus deformans. Figs. 1 to 12 
(about 800/1), ascospores, of which five show nuclear phenomena and several are 
budding. Figs. 13 to 21 (800/1), thin-walled conidia, several of which are producing 
buds; the remaining spores, unnumbered, show various modes of promycelium 
fonuation or mycelial germination. 



BUUL. fiO. DIV. VEa PHY8. ft PATH«, U. 6, OEPT. AQRIOULTURE. 



'•LATE IV. 




QERMINATION OF THE 8PORE8 OF EXOA8GU8 DEFORMANS. 






<.• 



GEBSONATION OF THE SPOBES. . 39 

Budding of the ascospore^s occurs either before or after the escape 
of the spores from the aseus. In the formation of the bud conidia the 
process may take place from the ascospore direct, one conidium after 
another being produced, or the contents of the ascospore may pass into 
a thin-walled conidium nearly or quite equal in size to the ascospore, 
this large conidium then assuming the function of bud production. 
Ordinarily the ascospore buds at one point only, but bud formation at 
two points has been seen. Budding occurs most commonly at one end 
of the ascospore, but occasionally lateral buds are observed. In the 
early stages of budding the ascospore sometimes shows a nipple-like 
swelling at one end, reminding one of the germinating end of the 
sporangium in the PeronosporecB. The successive primary conidia bud- 
ding from an ascospore may become loosened and turned to one side 
by the following conidium, which swells from the same germ pore of 
the ascospore. In other cases several conidia may remain united with 
each other, but when this condition is observed it is frequently the 
result of the secondary or tertiary budding of the primary conidium, 
several orders or generations of buds remaining united. When the 
process pi primary conidial budding can no longer take place the empty 
ascospore may or may not become separated from the last primary 
conidium. With the exception of the case above referred to, the dif- 
ferent orders or series of conidia (primary, secondary, tertiary, etc.) 
when grown in pure water, are each smaller than the preceding, and 
the conidia are considerably elongated in form, sometimes almost 
cylindrical. The walls of the conidia are more delicate than those of 
the j^rent spore. In a suitable nourishing fluid, as the extract of malt, 
the conidia take up nourishment and increase in size, thus enabling 
them to continue the budding process for considerable periods of time, 
as in the yeasts (Saccharomyces). Whether the conidia of Exodscm 
deformang are able to induce an alcoholic fermentation through their 
growth in saccharine culture media is not known, but Sadebeck states 
that the conidia of other species of this genus certainly possess this 
fermenting power. 

The second method of germination of the ascospore of HAcoascm 
deformaris.^ that is, the pushing of germ tubes, is rarely met with 
except upon the host plant itself. Such mode of germination is shown 
in PI. IV. The germ tube produced from the ascospore is usually 
much swollen near the spore and tapers considerably toward the 
extremity, though not infrequently considerable constrictions occur 
at one or more points in its course. It seems probable that this tube is 
in many cases capable of directly infecting the host, probably through 
a stoma, as observed by Sadebeck in Exoascus toaquinetiiy and that its 
function is not wholly the abjointing of sporidia. Such separation of 
sporidia, in fact, has not thus far been observed. The germ tube, 
or promycelium, is connected with the spore b}'^ a very narrow and 
short tube, with straight and i)arallel walls. The same mode of con- 
nection is also observable in the formation of the bud conidia, and 



40 PEACH. LEAF CURL: ITS NATURE AND TREATKENT. 

reniinds one of the sterigmata Iwaring the .spomngia of PhyUtphthmi 
nifentanH, 

Thus far efforts to induce filamentous germination of the bud conidia 
or of the ascospores of Exommw defo^'imins in culture media have 
proved unsuccessful. Brefeld has worked with this problem for 
months, and the writer has frequently attempted to obtain this fonn 
of germination.' Budding occurs, as alread}'^ indicated, quite readily 
in various nutrient solutions, and short promycelia from the ascospores 
have been found in some cultures. In nearly if not all cases, however, 
the ascospores showing promycelia or short mycelial germination have 
shown that this germination occurred under natuml conditions upon 
the peach leaf, the germinated spores being transferred from the leaf 
to the culture in preparing the latter. It may be added here that the 
bud conidia are also formed in vast immbers upon the surface of the 
infested leaf after the maturing of the ascospores. It is largely these 
conidia which give the infested leaf the marked white appearance 
commonly observed at the height of the disease. The leaf appears iis 
if covered with flour or a heavy white bloom. 

RELATIONS OF THE FUNGUS TO THE HOST. 

Under a previous heading in this chapter the physical conditions 
which influence the serious development of peach leaf curl have been 
considered in accordance with the light which we now have relative to 
such influences, and thert* remain to be taken up at this time the more 
intimate and direct relations of the host and parasite. These relations 
include the action of the fungus upon the cell contents, the cell walls, 
and the cellular tissues of the host; the probable mode of infex»tion and 
the spread of the parasite within the tissues; the wintering of the 
fungus upon the tree; etc. 

'A very considerable minil)er of (cultural experiments have been tried. The cul- 
tureH (»f aKCospores and conidia have been subjected to temperatures much below the 
freezing point and to various decrees of heat in the thermostat. Sudden changes of 
temperature have been tried. Increased and diminished amounts of oxygen, as con- 
trasted with that of the normal atmosphere, have been teste<l. Even a chamber filled . 
with nearly jmre oxygen has produced no apparent effect. Water from various 
Fource.^, such as rain water, dew, ice water, distilled water, tap water, etc., has been 
tested. Solutions of the various sugars, malt extract, sterilized beer, plum extract, 
etc., were tried. Hanging drop cultures of various nutrient media and plate cultures 
of ix)tato-peptone-HUgar gelatin have not shown germination. Drops of variou- 
nutrient solutions placed upon newly forming leaves dissei^ted from unopened peach 
buds and these held in moist chambers have given only negative results. The same 
is tnie for peach pits brought ne^r to germination and the cotyledons treated with a 
weak solution of diastase, the sjwre^s placed between them and held at various tem- 
peratures in moist chambers. Sections of such cotyledons with 8jx)res placed upon 
them were also i)repared in moist chambers. A brief treatment of the spores with 
ether was tested without bringing about germination. 

Prillieux states that attemi)t8 to artificially infect the U^ves or shoots have not 
thus far succeeded (Mai. d. Plantes Agr., Vol. I, p. 399), 



RELATIONS OF THE FUNGUS TO THE HOST. 41 

Ah already indicated, the writer's work with sprays seemed to show that 
not more than a small percentage of each year's infections ordinarily 
arise from a perennial mycelium. In the Lovell orchard, where the 
personally conducted work was carried out, it would appear that not 
to exceed 2 to 3 per cent of the infections could have arisen from that 
cause. On the other hand it would seem that at least 95 per cent of 
the infections arose from spores, for, as already stated, 95 to 98 per 
cent of the spring infections could be prevented by a single spraying, 
and this was actually accomplished where the spraying wa>s done with 
sufficient thoroughnCvSS. It is believed by the writer, however, that 
these percentages will vary within moderate limits in different locali- 
ties, with different varieties, and in different seasons. The following 
observations will explain these views. 

The mycelium of diseased leaves is found to be connected through 
the leaf petiole with the mycelium of the infected limb. From the 
writings of Sadebeck and many others it might be supposed that the 
leaves were infected from the perennial mycelium in a majority of 
causes, and that the mycelium met with in the petiole of the leaf origi- 
nated from the perennial mycelium of the. branch. That such spring 
infection reall}' occurs from the wintering mycelium of the branch 
should perhaps be admitted, but that such is the common mode of 
infection of the leaves is certainly doubtful. The writer's studies have 
shown that the mycelium in the branch close to a cluster of infected 
leaves diminishes in amount as it passes upward or downward in the 
branch from such leaves. This fact is as obvious from microscopic 
studies of the infested tissues as from the external hypertrophies 
observable to the eye. A macroscopic examination of diseased and 
swollen branches will show that the enlarged parts may extend upward 
or downward along the branch from the base of the petioles of the 
leaves, which seem to represent the center of infection. In a majority 
of cases these swollen ridges terminate before reaching another leaf 
bud, though in some instances they are seen to extend along the branch 
throughout the entire length of one or more internodes, and in such 
cases it is fair to suppose that the mycelium may have infected the 
young leaves of a second or third bud in its course. It should be 
remembered, however, that this m^'^celium, in a great majority of 
instances, indicates no connection with a previous year's mycelial 
growth, but has evidently just entered the branch from one or more 
infected leaves. The microscopic evidence supports these conclusions, 
which are, to some extent, in harmony with Bonton's observations, to 
be hereinafter considered, but the writer is scarceh^ prepared to admit 
the large percentage of spring infections arising from new mycelium 
entering the branch which the observations of that writer seem to 
imply.* The microscope shows that the hyphje which pass away from 

» Pacific Rural Press, Aug. 2, 1890, p. 88. 



42 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

the base of the leaf petiole gradually de<Tea.se in numbers as they 
recede from the leaves, and they app^'^ar to be whoHy lost at a short 
distance from the point of entrance into the shoot. As a inile, little or 
no mycelium has been found extending more than 1 or 2 inches beyond 
a iK)int where external macroscopic evidence of disease exists. 

The preceding facts lead to the belief that where mycelial infection 
of foliage takes plac^e from the branch it is usually done in the spring 
from hyphaj arising from spore- infected leaves of the same season, 
and that this occurs only in comparatively few instances or in bad 
cases of disease. They also indicate that living perennial mycelium 
which succeeds in accomplishing spring infection, is comparatively 
rare. Badly infested and swollen branches are apt to die and dry out, 
thus affording no living tissue for the support of the infesting myce- 
lium. Such branches, even if living until the following spring, are 
not apt to produce much growth, and frequently produce none what- 
ever. Furthermore, the badly swollen mycelium-infested branches 
are comparatively few, and it is believed that the infested winter buds 
of these branches very rarely exceed 2 to 3 per cent of the total num- 
ber of buds upon the tree. Most branches appear to suifer from the 
disease only in an indirect manner, that is, by the fall of affected 
foliage. It seems probable to the writer, therefore, that the swollen 
branches, in which the swelling is apparent to the eye, constitut>e the 
true and almost exclusive home of the perennial mycelium, and there- 
fore supply the only possible source of spring infection by the win- 
tering hyphaj, and consequently the only source of infection not 
controllable by sprays. This is in harmony with the results of w^ide- 
spread orchard treatment. All but 2 to 3 per cent of infections have 
been prevented by a single spraying. (See the results of work on 
half-spra3'^ed trees.) That such spraying did not prevent the spread 
of the mycelium in the inner tissues of the host is shown by the fact 
that when it is delayed until the leaves have fairly started and have 
become infested, the tieatment is ineffective and the disease will con- 
tinue to develop and both foliage and crop may be lost. It is not the 
checking of the spread of the mA^celium from the branch to the new 
leaves, therefore, that results from spraying, but the prevention of the 
early spore infections from without; and as all but 2 to 3 per cent of 
the year's infections may be thus prevented, all of such infection- 
must be considered as arising from spores. 

The limitation of the perennial mycelium of Exoascua deforman-H to 
the swollen branches or branch parts, as here held, is in harmon^'^ with 
observed facts respecting other species of Kv(Hi^ce<e, It is not under- 
stood, for instance, that trees developing witches' brooms are infested 
in all their branches, but that the branch-infesting mycelium is limited 
in its distribution to those centers which develop the abnormal multi- 
plication of shoots, the swellings and other external manifestations 
of disease. (See Pis. 1, V, and VI, and descriptions, in connection with 



J 



DESCRIPTION OF PLATE V. 

Terminal peach twigs badly affected by curl. The mycelium of the fungus has 
entered the growing end of these shoots, and the conditions being favorable, it has 
developed to such an extent as to prevent further elongation of the twig, thus form- 
ing a compact head, with greatly shortened intemodes. It is in shoots of this char- 
acter that the mycelium is found, and its extent is nearly coincident, so far a^ 
observed, with the swollen portions of the branch. Such swollen branches consti- 
tute a striking feature of the disease, but rarely involve more than 2 to 3 per cent of 
the buds of a tree. Specimens were collected at Santa Ana in the spring of 1899 and 
photographed natural size. (Compare with Pis. I and VI.) 



Bull 20, Div Veg. Phy». 8c Path., U. S. Dept of Agriculture. 



Plate V. 




Peach Twigs and Leaves Affected by Curl. 

The flLstributive mycelium «>f the fungus is found in such swollen branches. 






^ ■:; . 



DESCRIPTION OF PLATE VI. 

Sprayed and uneprayed branches of Lovell peach trees in the experiment block at 
Biggs, as they appeared in 1895. The sprayed branches at the left show the large 
amount of fruit and healthy foliage on the sprayed trees; the unsprayed branches 
at the right have lost most of their foliage and all the fruit from curl. These 
unsprayed branches show the typical and common effects of curl. Hypertrophy of 
the branch is not shown, and it is prol)able that these branches carry little if any 
perennial mycelium. Thorough winter treatment of such branches with proper 
fungicides will prevent 98 per cent of the spring infections and conduce to the 
development of foliage and fruit, as shown on the branches at the left. All these 
trees were ecjually infe(;ted by the fungus in 1893, when the orchard suffered severely 
from curl, and had the branches at the left not been sprayed before the leaf buds 
opened in the spring of 1895, they would have been in the same condition as those 
at the right of the j)late. (ComjMire with Pis. I, V, and VII.) 



Bull. 20. Div. Veg. Phy». & Path., U. S. Dept. of Agriculture. 



Plate VI. 




CONCLUSIONS REGARDING SPRING INFECTIONS. 43 

the present remarks on infested and noninfested branches.) It seems 
probable, therefore, (1) that most of the spring infections of the peach 
occur from spores which have wintered on the tree and about the newly 
foi-med buds; (2) that most of the infected leaves fall oflf without 
infecting the branch which bears them; (3) that the mycelium of badly 
diseased leaves sometimes infects the branch through the leaf petiole; 
(4) that such myceliuin after entering the branch may pass upward 
or downward, and in some instances may follow the branch for the 
length of one or at most a few internodes, and possibly infect one 
or two adjoining buds; (5) that badly infested branches usually die 
during the year, while in comparatively few instances they may sup- 
port a living mycelium capable of inducing spring infection of opening 
buds; (6) that most infected branches show by external hypertrophy 
the presence of the parasite, which may commonly be removed by 
pruning off the hypertrophied parts at a point a few inches below 
the swelling; (7) that seasons, atmospheric conditions, localities, and 
varieties may have a limited bearing on the extension of the mycelium 
in the branch and upon the amount of mycelium wintering in an 
active state, although the results of spraying in many parta of the 
country, continued for several years, have shown the variation in 
these respects to be confined within comparatively narrow limits. 

The direct infection of the i)each leaf by means of the spores of 
Exoasem deformans has not been seen. The efforts made to observe 
the germination and penetration of the fungus have already been 
touched upon. One thing seems certain, viz, that under ordinary 
conditions this form of infection occurs at a very early period in the 
development of the leaf, but evidently not before the opening of the 
leaf buds. Very young leaves are found to be already infected, but 
spraying just before the buds expand will prevent this infection, i. e., 
infection may be prevented by the treatment of closed buds, which 
would scarcely be true if a perennial mycelium were within. If we 
may judge by analogy, the germ tube of the fungus enters the leaf 
through a stoma. Sadebeck reports that such was his observation in 
Keodscus tosquinetii^ in which species the genn tube creeps for a short 
distance on the leaf surface, and then enters a stoma, much as in the 
germination of the conidium of Phytophthora omnwora. 

The major portion of the spring infection of foliage occurs while 
the latter is young and tender, but it is observed that new infections 
may take place for a considerable time if the various influencing con- 
ditions continue favorable to the fungus. These conditions act chiefly 
in suddenly retarding the transpiration of the host, and some of them 
have already been discussed. On the other hand, a short period of 
spore infection may be expected when external influences are such 
that transpiration Ls rapid and normal. The longer or shorter course 
of the disease in spring may be said to depend largely, therefore, upon 
the greater or less susceptibility of the tissues of the host, mostly 



CHAPTER III. 

HISTORY OF THE TREATMENT OF PEACH LEAF CURL. 
THE EUROPEAN SITUATION. 

That the present outline of the gradual development of methods for 
the treatment of peach leaf curl in the United States may be properly 
appreciated, it is desirable to first show the conditions prevailing in 
Europe as presented by some of the leading European writers on plant 
diseases. Prillieux, in an interesting paper on peach leaf curl, pre- 
pared in 1872, describes the fungus Etoasoits deformans and its action 
on the tissues of its host.^ He states that the fruiting fungus should 
be looked upon as the center of infection, and that it is desirable to 
remove the diseased leaves as thoroughly as possible and to destroy 
them. He also states that this work should be supplemented by the 
cutting oflF and burning of diseased branches. In 1878 Winter* stated 
that the only way to prevent this disease is to destroy the fungus by 
carefully removing the aflFected leaves, and by protecting the trees from 
rain during the unfolding of the leaves, as rain favors the spread of the 
parasite. The same year Felix von Thumen wrote of Exoasciis pruni^ 
the fungus causing plum pockets and closely related to Exoasciis defor- 
mans of the peach,* but made no recommendations for its treatment. In 
1885, however, he again spoke of the plum pocket disease and pointed 
out that it can not be removed except by severe cutting back of the 
new and old wood of the aflfected trees.* In 1880-81 Frank, in the 
second volume of the fii*st edition of his work on plant diseases, rec- 
ommends the cutting back of the twigs as a cure for leaf curl, and the 
quick removal of the diseased leaves for prevention.* 

In 1886 the well-known work of Sorauer on plant diseases* appeared. 
The treatment recommended by this author is somewhat similar to 
that recommended by Frank. He says, in speaking in a general way 

> Prillieux, Ed., Bull, de la Soc. Bot. de France, 1872, T. XIX, pp. 227-230. 

2 Winter, Dr, (Tcorg, Krankheiten der Kulturgewiichse, Leipeig, 1878, p. 47. 

'Thiimen, Felix von. Die Pilze und Pocken auf Wein und Obst, Berlin, 1878, III, 
Fungi Pomicoli, pp. 88, 89. 

^Thumen, Felix von, Die bekiimpfungder Pilzkrankheiten unsererKulturgewachse, 
Vienna, 1886, p. 71. 

"Frank, Dr. A. B., Pie Krankheiten der Pflanzen, Breelau, 1880-81, Theil II, 
p. 526. 

* Sorauer, Dr. Paul, Handbuch der Pflanzenkrankheiten, second edition, Theil II, 
p. 281. 

46 



HISTORY OF TREATMENT. 47 

of the Eacodf^cem^ that it has been proved that the mycelium winters 
over in the youngest parts of the shoots and in the buds, and he 
recommends the removal of isolated slightly diseased leaves soon after 
the first appearance of the blister-like swellings. When through the 
attack of a majority of the leaves of a branch it is shown that the 
mycelium is already present in the axial organs, it is advised that all 
of the young wood of the affected branches be cut off. Hartig de- 
scribed peach leaf curl in 1889,* and again in the English edition of 
his work published in 1894,* but he leaves the subject without making 
any suggestions as to treatment. In 1890 Dr. Kirchner published 
a work on plant diseases,^ in which he recommends the cutting oflf of 
diseased branches for the control of the disease. In 1891, Dr. Comes, 
in writing of this disease, states that no direct means for combating 
the parasite exists. He discusses the gathering and burning of dis- 
eased and fallen leaves, the cutting back of infected branches, and the 
application of cultural methods in their influence on the disease.* A 
most excellent work on plant diseases by Dr. Tubeuf appeared in 
1895.* This writer groups the diseases caused by the E^poascecp among 
those maladies which should be combated by the removal of the 
diseased living plants and plant parts (pp. 86, 87). The second edition 
of Frank's work on plant diseases appeared in 1896, fifteen years 
after the publication of the first edition, but the same recommenda- 
tions for the treatment of curl are again made, word for word.* In 
all the preceding works there is no recognition of the methods of treat- 
ment being adopted and discussed in the United States and in Aus- 
tralia. The recommendations for cutting away the diseased branches 
so generally presented are the same as advanced by Ehrenfels nearly 
a century before for the control of mildew of the peach.* 

It is hardly necessary to say here what most orchardists have learned 
by experience, that is, that it is impossible to eliminate the disease by 
ordinary cutting back of the branches, and that in the orchard it is 
equally impracticable to prevent the disease by the early removal of 
the diseased leaves. 

About this time the work being done on this disease appears to have 
attracted the attention of Europeans. In 1894, in his work on vege- 
table parasites, Berlese recommends for this disease in Italy the use 

* Hartig, Dr. Robert, Lehrbuch der Baumkrankheiten, Berlin, 1889, pp. 118,119. 

* Idem, The Biseafies of Trees, London, 1894, pp. 132, 133. 

* Kirchner, Dr. Oscar, Die Krankheiten und Beschiidij^ungen unserer lan<lwirt- 
Hchaftlichen Kulturpflanzen, Stuttgart, 1890, p. 324. 

♦Comes, Dr. O., Crittogamia Agraria, Naples, 1891, Vol. I, i)p. 167, 168. 

* Tubeuf, Dr. Karl Freiherr von, Pflanzenkrankheiten durch kryptoganu' Para- 
Fiten verureacht, Berlin, 1895, pp. 86, 87, and 184. 

•Frank, Dr. A. B., Die Krankheiten der Pflanzen, second edition, Breslau, 
1896, Bd. II, pp. 249, 250. 

^Ehrenfels, J. M. Ritter von, Veber die Krankheiten und Verletzimgen der 
Frucht- Oder Gartenbaume, Breslau, 1795, p. 225. 



48 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

of Bordeaux mixture in the spring, although he adds, as if doubting 
its utility, that the uiyceiium of the parasite winters over under the 
cortex of the branches.* 

In France, in 1895, Priliieux published the first volume of a work 
on plant disea8e8, devoting several pages to the consideration of peach 
leaf curl.* In this work the recommendations for treatment appear- 
ing in his paper in 1872 are not given, but instead it is stated that 
treatments with the salts of copper seem sometimes to produce good 
results in preventing the multiplication by spores; but, as in the case 
of Berlese, he adds, as if in doubt of the value of such treatments, 
that they ai'e without effect upon the perennial mycelium hidden in the 
tissues. 

By the year 1898 the true idea of the preventive treatment of curl 
had been gi'asped in Germany. Professor Weisz, in his paper on 
plant diseases,* published that year, cites the present method of con- 
trolling curl. After renewing the older recommendations to cut off 
and burn the affected twigs, he says that the trees should be sprayed 
with copper-soda or copper-lime solution (eau celest-e or Bordeaux 
mixture), the first time hefore the buds open. That these recom- 
mendations are not the results of work done by Weisz, however, 
appears probable, for his description of the disease is evidently quoted, 
as he falls into the error of Winter, Frank, Kirchner, and other 
writers in stating that the bloom produced by the fruiting of the 
fungus appears upon the under surface of the leaves. Had he worked 
upon this disease in the field he would not have been apt to follow 
the al)ove authors in their erroneous description of the fruiting habits 
of the parasite. 

DEVELOPMENT OF THE PRESENT METHODS OF TREATMENT. 

The successful treatment of peach leaf curl dates from the time 
when fungicides were first applied to dormant peach trees. So far as 
learned, this treatment was first practiced in California, being intro- 
duced by the winter application of sprays for the destruction of the 
San Jos6 scale {Asjrtdiotiis penilciomis). This insect was first discov- 
ered in the Santa Clara Valley about 1870, but some time had elapsed 
between the date of its introduction and the use of the stronger winter 
sprays for its control. 

Caustic soda and potash were early tested against this insect, and 
afterwards sulphur was added, the sulphides of potassium and sodium 
being used by many growers. Somewhat later whale oil soap andsul- 

^Berlene, A. N., I Parassiti Vegetal! delle Piante Coltivate o Utili, preface dat^ 
1894, pp. 124-126. 

-^ Priliieux, Ed., Mai. d. Plantes Agr., Paris, 1895-97, pp. 394-400. 

'Weisz, J. E., Die Hchiidlichsten Krankheiten unserer Feld-, Obst-, Gemuse- und 
Garten-Gewachse, Miinchen, 1898, p. 45. 



HISTORY OF TREATMENT. 49 

phur were combined by boiling, and still later a c^uHtic spray contain- 
ing lime was tested. All the above chemicalH, even the milk of lime, 
were applied to dormant trees, and they are all known to possess suffi- 
cient fungicidal action to control peach leaf curl to a large extent if 
applied to the trees shortly before they bloom. 

While many growers were using these caustic and sulphide sprays, 
another spray containing much larger quantities of sulphur was being 
used, and proved of much greater power, both as a fungicide and insecti- 
cide. This was a spray containing sulphur and lime, or a sulphide of 
calcium, and the history of its introduction is of special interest and is 
inseparable from the early histpry of the treatment of curl. Mr. Alex- 
ander Craw, quarantine officer of the California State Board of Horti- 
culture, has published an account of the Introduction of this spray in a 
recent number of the Pacific Rural Press,* but the following facts 
were gleaned from those who were the first to use and introduce the 
spray.* Mr. A. T. Covell, who first applied this spray to dormant 
peach trees, near Fresno, Cal., does not supply exact dates relative 
to the work, but Mr. N. W. Motheral, of Hanford, and Mr. I. H. 
Thoma^s, of Visalia, agree in placing its first use as a spray in the year 
1880 or 1881. The writer is infonned by Mr. Motheral that the lime, 
sulphur, and salt solution was originally used as a sheep dip in Aus- 
tralia, where it was known as the ''Victoria lime-and-sulphur-dip" for 
scab. He states that it was recommended by a Dr. Rowe, and offi- 
cially indorsed for a sheep dip in that country. This dip, it is also said, 
was introduced in California by Mr. Charles Hobler, of Hanford, and 
Mr. Hobler claims to have first recommended it to Mr. Covell, then 
living near Fresno, for the treatment of his infested peach trees. Mr. 
Covell disputes this claim, but holds that he (Covell) first used this 
solution as a spray upon his trees with success in the control of the 
San Jos^ scale. As soon as this spray was found to be a practical suc- 
cess, Mr. Covell, Mr. Thomas, and Mr. Motheral worked for its gen- 
eral adoption in the treatment of scale. Mr. Thomas states that he 
sprayed his own orchard the winter after seeing the action of the spray 
on Mr. CovelPs trees, and about this time the facts were given to the 
press. Mr. Thomas writes that this spray was in general use in and 
about Visalia as early as 1883, 1884, and 1885, and in Mr. Motheral's 
section, near Hanford, at the same time. It may here be stated, 
however, that lime and sulphur had been united by boiling in water 
and used as early as 1852, at least in hothouses, for controlling the dis- 
t'ases of plants. (See Revue Horticole, 1852, p. 1(>8, and Gardeners' 
Chronicle, 1852, p. 419.) 

'Pai-ific Rural Press, July 29, 1899, p. 68. 

'Letters from I. H. Thomas, Visalia, Cal., Sept. (5, 1899; N. W. Motheral, Han- 
ford, Cal, Sept 6, 1899; and A. T. Covell, Woodbridge, Cal., 0(tt. 13, 1899. 
19093— No. 20 4 



50 PEACH LEAF OURL: ITS NATURE AND TREATMENT. 

It will be seen by the preceding outline that strong fungicidal sprays 
were in general winter use upon peach trees throughout much of Cali- 
fornia in the years 1880 to 1885, during which time the peach or- 
chards of many portions of the State were badly affected by cui-l. In a 
report by Mr. W. G. Klee, who inspected the orchards in many counties 
of California from July to September, 1886, it is stated that in Alamed:; 
County the cultivation of peaches must be confined to such varieties avS 
are very little subject to leaf curl; in Santa Cruz County, that "peaches, 
of course, are subject to curly leaf, and can not, as a general thing, be 
considered profitable;" and that in the Santa Rosa Valley the peach is 
*'of course subject to cui'ly leaf."^ 

As peach leaf curl was quite prevalent throughput California in 
1880-86, and as a large number of peach growers treated their dor- 
mant trees with iungicidal sprays during that period, it is not strange 
that they soon learned that the winter sprays prevented curl. Mr. I. H. 
Thomas, of Visalia, informed the writer* that it was about the year 
1886 that he noticed that the orchards sprayed with the lime, sulphur, 
and salt solution were entirely free from leaf curl, while orchards con- 
tiguous were affected so badly that all the foliage fell off. 

In 1886 Mr. W. G. Klee said,^ when speaking of an inspection he 
made of the orchard of Mr. A. Block, of Santa Clara, CaL: '*A treat- 
ment of peaches affected with curly leaf attracted my attention. Tree^j 
not subjected to this treatment were in very poor condition, while the 
others, favored with it, were in fine, healthy bearing." Mr. Block says 
respecting this work* that he was making experiments for the destruc- 
tion of scale insects when he detected a perceptible difference in the 
amount of curl on the treated and the untreated trees. He thinks 
this was one or two years before Mr. Klee had seen his trees in 1886. 
After having noticed the action of the sprays applied for scale in the 
prevention of curl, he went to work to ascertain what particular 
ingredient caused the prevention of the fungous disease. These direct 
experiments, Mr. Block states, were carried out on a row of 23 ti*ees 
in his orchard. Among the chemicals tested were caustic soda, caustic 
potash, carbolic acid, tobacco, and sal soda, all more or less combined 
with whale oil. Among the numerous sprays used, Mr. Block thinks 
that a strong solution of caustic soda gave the best results. All these 
sprays were applied while the trees were dormant.* The stronger 

* Klee, W. G., Reports and Papers by the Inspector of Fruit Pests, read at Sacra- 
mento, November, 1886, Kept. Cal. State Bd. Hort., 1885-86, pp. 344, 347, 349, 350, 

'Letter dated Visalia, Cal., Sept. 6, 1899. 
»L. c, p. 347. 

* Letters dated Santa Clara, CaL, Sept. 1 and 10, 1899. 

* It may be noted that whale oil soap was thus used by Mr. Block with success 
against curl in 1885 and 1886. Prof. L. R. Taft, in a letter dated Agricultural GoU^e, 
Mich., Aug. 31, 1899, says that he had good results in the treatment of curl with 
limewater, lye, and whale oil soap. (See also records of experiments by the writer 
with milk of lime, etc.) Mr. F. M. Webster reports satisfactory results with whale 



HISTORY OF TREATMENT. 51 

caustic spray recommended by Mr. Block consisted of 1 pound of 98 
per cent caustic soda to 6 or 7 gallons of water. The same year, 1886, 
Mr. Sol. Runyon, of Courtland, Cal., reported that he had met with 
success in controlling a "blight" of peach trees, the name of the dis- 
ease not being known to him. This blight had previously caused all 
the leaves to fall from every tree he had, especially the young ones. 
He used a caustic spray on the dormant tree, as did Mr. Block, and 
states that the trees which he treated were not affected by the blight 
at all, while the untreated trees, right beside the treated ones, were 
badly affected.^ There is little doubt that Mr. Runyon was treating 
curl, as it is a very serious trouble in that section of the State. After 
the leaves had fallen in the autumn of 1886 and during the winter of 
1886-87, Mr. Runyon sprayed many of his peach trees with a spraj'^ 
composed of 2 gallons fish oil, 10 pounds' of caustic soda (98 per cent), 
and 5 pounds of copper sulphate to 100 gallons of water. This spray, 
a^ applied, was certainly a preventive of curl, and as a portion of his 
peach trees were left untreated the contrast should have been marked. 
Unfortunately, however, 1 have been unable to get further details of 
this early work with copper sulphate, as Mr. Runyon is no longer 
living.' 

In November, 1888, Mr. W. G. Klee stated at the Chico meeting of 
the California State Board of Horticulture, that an experienced and suc- 
cessful fruit grower in San Jos4 had used successfully for the purpose 
of killing scale insects, the so-called sal soda and whale oil wash, and 
that he maintained that ever fdnce he had been using that wash he had 
been free from leaf curl in his orchard.^ Mr. Joseph Hale, of Stock- 
ton, Cal. , reports * that he sprayed his peach trees, while dormant, in the 
years 1888, 1889, and 1890, as well as in subsequent years, and that as 
a result he sustained no loss from curl during these years. He used 
the lime, sulphur, and salt spray. Mr. G. W. Ramsey, of Lotus, 
Cal., states that he began spraying his orchard with lime, sulphur, 
and salt in 1890 or possibly in 1891. In 1895, in writing of his past 
spray work, he states that his trees had not been affected in the least 
by leaf curl since he had been using the above wash. He says: "It 
completely exterminated the scale the first two years I used it, but I 
continue to apply it to my trees once a year to prevent leaf curl." He 
further states that this wash must be applied when the buds are dor- 
mant, and that it is generally applied in February in his section. 

oil soap (South Aufltralian Journal of Agriculture, March, 1899, Vol. II, No. 8, p. 630) ; 
»* also the pesulte reported by Henry Rofkar and W. V. Latham & Son, of Catawlm 
Ii^land, Ohio, as reported by A. D. Selby, Bull. No. 104, pp. 208, 209, Ohio Agr. Exp. 
Sta., March, 1899. 

*Rept. Cal. State Bd. Hort, 1885-86, p. 221. 

Mbid., 1887-88, p. 93. 

*Rept. Cal. State Bd. Hort., 1889, p. 172. 

♦Reply to circular letter of Nov. 25, 1893. 



52 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

As early as 1890 the effectiveness of lime, sulphur, and salt against 
curl appears to have been observed in Oregon. Mr. J. D. Whitman, 
of Medford, Oreg., who was horticultural commissioner for the third 
district of that State, wrote under date of January 27, 1894, that four 
years' observation as commissioner had demonstrated beyond a doubt 
that a spray of lime, sulphur, and salt is an effectual remedy for leaf 
curl. He states that the application in every instance was made for 
the purpose of destroying the San Jos^ or pernicious scale, and gener- 
ally on only a portion of the orchard, the other portion showing the 
curl as usual. 

The first practical experiments with copper sprays on dormant trees 
for the control of curl, after the sprays applied by Mr. Sol. Runyon 
in 1886 and 1887, were conducted, so far as learned, in the year 18iK). 
The summer use of these sprays had been tested in Australia, and 
probably elsewhere, for several years, but with slight success in the 
control of curl. 

About the 1st of December, 1889, Mr. L. E. Benton, then of Berke- 
ley, Cal., wrote to the United States Department of Agriculture for 
information relative to the nature and treatment of curl. These inqui- 
ries were answered at length, the literature on I^jxoohchjs d'eforuutntt 
being quite fully cited. No method of controlling this disease was 
then known at Washington, and as winter spraying had not yet" reached 
its present importance, the recommendations for treatment were nec- 
essarily inadequate, and were based upon the then accepted views 
respecting the strict perennial nature of the mycelium of the fungus, 
and the consequent difficulty of controlling the parasite by sprays. 

After gathering such information as he desired, Mr. Benton insti- 
tuted a series of spraying experiments in the university orchard at 
Berkeley in the spring of 1890. The work done by Mr. Benton, 
although limited in extent, was of the utmost practical importance, as 
well as of great theoretical interest. A summary of his results was 
published in August, 1890.^ Three copper sprays were tested, the 
ammoniacal copper carbonate, basic copper acetate solution, and Bor- 
deaux mixture. The ammoniacal copper carbonate was applied on 
February 28, 1890, before the opening of the buds. All three of the 
sprays mentioned were also tested soon after the leaves started. The 
results demonstrated that winter treatment of the trees with the salb< 
of copper will effectively control the disease, but that summer treat- 
ment will not control it, and also that infection of the spring growth 
by perennial mycelium was the exception and not the rule with \h\> 
disease — facts of the utmost practical importance for the orchardist. 
Mr. Benton's studies likewise led him to the view that the mycelium, 
passing from infected leaves to the stem, is able to infect new foliage 

* Pacific Rural PresH, Aug. 2, 1890. 



mSTOBY OF TREATMBNT. 53 

by following close behind the growing point of the stem. His observa- 
tions seemed to point to this young mycelium, resulting from the first 
spring infections, as the source of the later infections through the 
branches rather than the perennial mycelium of the previous year. 
He says that not only does the fungus live in the leaf of the peach, but 
it at once pushes its way into the young growing stem, following the 
growing point as fast as it lengthens and passing into the leaves as fast 
as they appear. On this account he concludes that no external appli- 
cations can stop such a fungous growth, and spraying after the buds 
burst and the fungus has become established will have little effect. It 
may be added that several years' observation in large blocks of trees 
sprayed after the foliage had started has shown the writer that the dis- 
ease can not thus be controlled, and that Mr. Benton's conclusions are 
correcl. Whether this failure is due to the causes pointed out by Mr. 
Benton, however, or simply to the lack of the prevention of the infec- 
tion by spores, or to both sources of infection, should be given further 
study. Mr. Benton states that in the spring of 1890, the time his 
experiments were undertaken, " no remedy was known; since, some 
practical growers have found successful means of combating it, and 
these experiments now deserve no further credit than that they were 
intentional and not a matter of chance." It is now known that curl 
had been controlled by numerous growers in widely separated regions 
ill California through the use of various sprays many years prior to 
1890. Mr. Benton says he was unaware of these facts when he began 
his work, and his experiments are worthy of full credit, not alone for 
the enterprise shown in undertaking them, but for the results' of 
unquestioned value to which they led. 

In 1891 the copper treatment for peach leaf curl was independently 
discovered and clearly demonstrated in Australia. The successful 
results of this work were observed in Nov^ember and December, 1891, 
and were published in the South Australian Register of March 30, 1892. 
At a meeting of the Nuriootpa branch of the South Australian Agri- 
cultural Bureau, held in Angaston during November, 1890, the sub- 
ject of fungous diseases affecting fruit trees was discussed and the 
appointment of a committee to conduct preventive experiments was 
considered. At a subsequent meeting Messrs. F. C. Smith, W. Sage, 
and A. B. Robin were selected for this work. During the interval 
before spraying, Mr. Smith corresponded with those in charge of the 
pathological departments in Australia, England, California, and Wash- 
ington. The report in the South Australian Register says that among 
the replies received was a series of valuable reports from Professor 
Galloway, showing that up to 1889 modified eau celeste, ammoniacal 
copper carbonate, and Bordeaux mixture had proved most successful 
in the United States. "These were therefore selected by the commit- 
tee for their experiments." Mr. Smith, of this committee, informed 



54 PEACH LEAF OUBLI ITS NATURE AND TREATMENT. 

the writer that their work was based largely upon that of Prof. E. S. 
Goff on Fusidadium.' 

The spray work was began in July, before the trees leafed out, the 
main object being to control apple scab and the shot-hole fungus on 
the apricot. The sprayed apricot trees belonged to Mr. Trescowthick, 
and were treated with Bordeaux mixture. In the block was one 
peach tree, which was spray^ed when the apricots were treated. This 
tree had suflFered severel}^ from curl, so much so, in fact, that it had 
not borne for four or five years, but after spraying it yielded eight 
cases of fruit of 60 pounds each, or 400 pounds, the curl being almost 
entirely prevented. Mr. Smith writes, respecting this work, that 
when applying Bordeaux mixture from July to October, 1891, for the 
various diseases with which they were coping he had. not the slightest 
idea that this or any of the fungicides would have any effect whatever 
on curl leaf, and the members of the committee were the more sur- 
prised to see its marvelous effects in January and February. '* It was 
the most conclusive of all our tests," it was stated.' 

The work was continued the following season, and some contrasts 
obtained on the place of Messrs. Sidney Smith & Son, of Yalumba^ are 
of interest in this connection. In an article published at that time it 
is stated that the effects of spraying with Bordeaux mixture upon both 
peaches and apricots were very noticeable. On one side of the fence 
was seen a healthy set of trees, well clothed with fruit and dark green 
foliage, and with no curled leaves, while on the other side, where spray- 
ing had not been done, was a block of apricots, among which were a 
few peach trees very badly attacked by leaf curl. At this time the 
orchard of Mr. A. B. Robin, of Nuriootpa, secretary of the committee 
for experiments, was inspected by Mr. Molineaux, general secretary' 
of the South Australia Agricultural Bureau, and by several prominent 
horticulturists, and was found to have a splendid crop of fruit, nearly all 
the apricot and peach trees having been sprayed. One peach tree had 
been spmyed on only one side with the Bordeaux mixture, and on this 
side the foliage was clean and healthy, while on the unsprayed side it 
was curled. ^'Here again," says the reporter of this examinatipn* 
''was absolutely conclusive evidence of the preventive effect of spray- 
ing for curl leaf." 

In the United States, in 1892, the use of both the sulphur and copper 
sprays on dormant trees was much more common. The control of 
curl was a new discovery to several growers who had not heard of 
the published experiments. Mr. George Woolsey, of lone, CaL, had 
been considerably troubled by a shot-hole fungus affecting peach twigs — 
a common trouble in the northern portion of the State. A bundle of 
the affected twigs was sent to Professor Woodworth, of Berkeley, who 

* Letter dated Angaston, South Australia, Feb. 11, 1895. 

* Letter dated Angaston, South Australia, Apr. 6, 1895. 



HI8T0BY OF TBEATMENT. 55 

advised the use of Bordeaux mixture; but as this fungus is active in 
the spring before the trees leaf out, Mr. Woolsey sprayed the trees while 
dormant. He says, in relation to his results, that he found Bordeaux 
mixture corrected the trouble with the twigs, and at the same time acted 
as a specific for the leaf curl. * His work for the control of curl in the 
following year was strikingly conclusive as to the effectiveness of this 
spray. Mr. D. W. Sylvester, of Geyserville, Cal., conducted some 
spraying experiments in 1892 with the direct object of controlling curl. 
His spray was composed of 12 pounds of copper sulphate and 20 pounds 
of lime to 100 gallons of water, and was applied to the dormant trees. 
Mr. Sylvester states that having formed the opinion that the disease 
was of fungous nature, and knowing of the value of copper sulphate as 
a fungicide, he determined to test it against curl. He believed better 
results would be obtained by killing the ''germ" than by waiting until 
the disease appeared, and this, he says, induced him to make the appli- 
cation to the dormant trees. For the experinient he selected a row of 
10 trees, spraying 5 and leaving 6 unsprayed' for comparison. He 
states that the 6 sprayed trees held their leaves and fruit and bore a 
crop, but the others shed every leaf and every peach, and for more 
than a month looked as if a fire had gone over them. In spite of this 
experience, Mr. Sylvester neglected to spray in 1893, when, he states, 
the trees shed all their leaves and nearly all their fruit through curl, ' 
and adds that the best time to spray is just as the buds begin to swell. 
A portion of the peach trees on the Rio Bonito ranch at Biggs, Cal., 
were sprayed with the lime, sulphur, and salt spray in 1892, the spray 
being applied to the dormant trees as elsewhere. The contrast that 
season between the sprayed and unsprayed trees was well marked, the 
unsprayed trees being much affected by^ curl, while those treated were 
practically free from it. These observations were made at the time 
by Mr. McDonald, the foreman, and by others on the ranch. 

The preceding examples could be greatly extended if necessary, as 
winter spraying was a common practice in California after 1886. By 
1892 the San Jos^ scale had also become more widely distributed in 
Oregon, and was being quite generally treated by winter sprays in that 
State. Mr. A. H. Carson, of Grants Pass, Oreg. , began spraying his 
orchard about this time. In reply to a communication sent to him 
November 25, 1893, Mr. Carson says that his knowledge as to the lime, 
sulphur, and salt remedy for leaf curl was gained by observing that 
trees on which this remedy was used to destroy the San Jos^ scale were 
not affected by curl, although they were varieties much subject to the 
disease. On the other hand, he states that unsprayed trees, with the 
same conditions as to exposure, altitude, etc., were badly affected. 
Mr. J. H. Stewart, of Medford, Oreg., writes that he sprayed his peach 

» Letter dated lone, Cal., Aug. 26, 1899. 

'Letters dated Geyserville, Cal., Nov., 1893, and Sept. 18, 1899. 



56 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

trees in 1892,* He says he used a spray in 1892, 1893, and 1894, 
which was effectual against scale and most fungi. This spray was 
composed of lime, sulphur, and sulphate of copper, and was applied 
in the winter. 

In the Ekist, about this time, mildew, brown rot, black spot, rust, and 
curl were attracting the attention of peach growers and causing 
serious losses in some sections, and a good many growers were trying 
summer sprays for the control of one or more of them. Mr. F. P. 
Herr, of Ridgely, Md., writes* that for three successive years prior 
to 1895 he sprayed with limewater, Bordeaux mixture, and arsenical 
mixtures, and that everything he used produced absolutely negative 
results, except the arsenites, which injured both foliage and fruit It 
would appear probable from these results that the sprays were applied 
too late to be effective against curl. Mr. L. B. Geiger, of Hoffman. 
Pa., writes' that he was formerly troubled with leaf curl in his 
orchard, but has had very little of late years. The reason of this, he 
thinks, is the fact that he has sprayed his peach trees with Bor- 
deaux mixture several times each year since 1892. He states that at 
least 75 per cent of the crop of one variety was thus saved. Whether 
the spray work was done in the winter, or whether, owing to the 
number of applications made, the summer spray persisted in its action 
through the following winter, is not known. 

It was in 1892 that Prof. L. R. Taft, of the Michigan Agricultural 
Experiment Station, first obtained the idea that peach leaf curl could 
be controlled by the application of winter sprays. This gentleman 
has supplied the leading facts respecting his work.* He says: ''In 
1892 I was making a series of experiments with Bordeaux mixture 
and solutions of copper sulphate to learn the strength that could be 
used upon various plants and trees without injury. These materials 
were applied at different times, the sprayings being at intervals of 
about four weeks, from April to July, and while some trees received 
but one application, others were sprayed two, three, and four times. 
It was noticed, the trees sprayed in April with either copper sulphate 
or Bordeaux mixture had no curled leaves, while unspmyed trees and 
those that were not sprayed until June or July were seriously injured 
by leaf curl. 

''From the marked difference in the injury from the leaf curl to 
the sprayed and unsprayed trees, I felt very confident that the disea.se 
could be held in check to a large extent by the use of fungicides, and 
in writing Bulletin 92, in December, 1892 (published in March, 1893), 
I make the statement that ' it is quite certain that the disease can be. 
to some extent, held in check b}' their use,' in referring to the effect 

* Letters dated Medford, Oreg., Dec. 14, 1894. 
Matter dated Ridgely, Md., Feb. 15, 1895. 
•letter dated Hoffman, Pa., Mar. 18, 1895. 

* Letter dated Agricultural Collej?e, Mich., Aujf. 31, 1899. 



HI8T0BY OF TREATMENT. 57 

of fungicides in preventing the development of leaf curl on peach 
tre€5s." 

It would seem that the work in Austi*alia, as well as that of the pre- 
eeding ten yeai-s in California^ had not come under the notice of Pro- 
fessor Taft at the time of his observations in 1892, and that the same 
was true at the close of the succeeding year's experiments. In his 
ai*ticle on curl, published in the American Agriculturist for February, 
1894, he* says,* in speaking of the treatment of curl prior to his 
work in 1893: ''Although there were some vague suggestions as to 
the possible value of some of the fungicides as remedies for this dis- 
ease, nothing was really known until the past season." 

May 20, 1893, while working on plant diseases at Yuba City^ Cal., 
in company with Mr. R. C. Kells, then horticultural commissioner of 
Sutter County, that gentleman told the writer of a peach orchard in 
the vicinity where peach leaf curl had been controlled by the previous 
winter's sprays. The orchard was that of Mr. W. H. Campbell, of 
Yuba City, and was at once examined by the writer in company with 
Mr. Kells. The trees were of the Orange Cling variety, and had been 
sprayed with lime, sulphur, and salt up to the base of the smaller 
branches of the main limbs, for the purpose of killing the San Jos6 
scale upon the older wood, the spraying of the tops of the trees not 
being necessary. The result of this treatment was to protect the 
lower half of the trees from the attack of curl, while the tops were 
left unprotected. Curl developed seriously in the Sacramento Valley 
that spring, and as a consequence these trees were badly diseased and 
stripped of foliage down to the line where the limbs had been sprayed 
for San Jos^ scale. The resulting appearance was most striking, and 
showed the advantages of spraying in a marked degree. The lower 
half of the trees was well supplied with normal green foliage, while 
the upper half was either bare or the leaves present were yellow and 
badly curled. Photographs of these trees were taken on May 21, 1893. 

May 22, 1893, the writer visited the Riviera orchard, at Live Oak, 
Cal. This orchard is situated on the Feather River bottom and is 
under the management of Mr. A. D. Cutts, of Live Oak, one of the 
proprietors. In this orchard was found a most striking case of the pre- 
vention of curl by the use of winter sprays. In the winter of 1892-93 
one block of trees was thoroughly sprayed for San Josd scale with lime, 
sulphur, and salt. After this work was completed the weather became 
unfavorable for further spraying. The soil was so wet from rains that 
a 40-acre block of Crawf ords Late trees could not be sprayed, and it was 
so late in the winter before the work could be done that Mr. Cutts 
feared it might injure the fruit buds if he sprayed the trees entire. 
He therefore had the trees in this block examined, and rags were 
tied upon the limbs of those which appeared to most need a thorough 

*The Curl of the Peach, American Agriculturist, Feb., 1894, pp. 71, 72. 



58 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

spraying for scale. These marked trees were scattered, here and there 
one, throughout the entire 40-acre block. In February the marked 
trees were very thoroughly sprayed over all parts, as much as two 
gallons of spray being applied to each tree. After this work was 
completed the entire block, with the exception of the trees already 
treated, was sprayed as high bs the forks of the main limbs, thus 
avoiding any injury to swelling buds. As before stated, curl devel- 
oped seriously in the Sacramento Valley in the spring of 1893, and 
the result was that the unsprayed trees, as well as those sprayed 
only on the main limbs, were nearly denuded by the disease, while 
the scattered trees which had been sprayed throughout were in 
full and vigorous foliage and growth. In the writer's notes upon the 
examination of this orchard on May 22, 1893, it is stated that the 
trees fully treated in this block were loaded with fruit and in full leaf, 
while the trees sprayed only to the forks of the limbs were nearly bare 
and almost wholly destitute of fruit on the unsprayed parts. Such 
fruit as was found on the unsprayed branches was inferior in size and 
quality. It is further stated that the absence of fruit on the untreated 
branches as compared with the abundant yield of the treated branches 
gives such a striking contrast as to be almost beyond belief.* 

Mr. William N. Runyon, of Courtland, Cal., treated a large acreage of 
peac^h tree.s with lime, sulphur, and salt in the winter of 1892-93. He 
stiites that the trees sprayed once while dormant were practically free 
from curl, while trees of the same variety not sprayed were badly 
aflFected.* He also gives an observation of interest in connection 
with the habits of the fungus, and one since indorsed by the writer, 
that is, that the disease "' will not spread from an unsprayed to a spraj-ed 
tree." In letters from Mr. Bunyon^ relative to this work, he 
remarks that although he had heard that a mixture of lime, sulphur, 
and salt was beneficial in controlling curl, he had no idea that the i^esult 
would be so nearly a complete prevention. He says that it was only 
when curl leaf had become quite prevalent on unsprayed trees that 
he noticed its almost total absence on those that had been sprayed. 
The most striking instance, he states, was where about 60 three year 
old nectarine trees stood in rows adjoining about a dozen full-grown 
trees of the same variety that had shown curl for years. The young 
trees, not having shown any scale, were left unsprayed, and were a 
mass of curl, while the old trees, which were given the regular treat- 
ment, were almost entirely free. In this orchard about 60 acres of 
peach trees were also sprayed, the work being done about the 1st of 

* For further notes and tabulated records of some of this work of the spring of 
1893 the reader is referred to Chapter VII under Notes on the Auxiliary Experi- 
ments in California. 

^ Answer to circular letter of Nov. 25, 1893. 

■ Letters dated Courtland, Cal., Jan. 31, and Mar. 8, 1894. 



HISTORY OF TREATMENT. 59 

February, and 40 acres of young trees left unsprayed. In the Santa 
Clara Valley the sulphur sprays were in general use by the leading 
growers in 1893. Mr. A. B. Elder, of Santa Clara, writes, in reply 
to a circular letter of November 26 of that year, that this spray is 
giving good satisfaction for the control of curl and ''is used bj^ large 
growers of peaches." Mr. John Rock, of Niles, Alanaeda County, 
Cal., writes, under date of December 28, 1893, that a mixture of lime, 
sulphur, and salt is a preventive of curl if applied before the flower 
buds expand. 

Bordeaux mixture was used in the winter of 1892-93, in the Caiinel 
Valley, near Old Monterey, with the express purpose of controlling 
curl. Mr. Daniel Snively, of Gubserville, Cal., writes^ that his 
brother used Bordeaux mixture for the control of this disease, and 
that its action is "so certain that any twig not touched is sure to 
curl." Mr. George Woolsey, of lone, Aniador County, Cal., sprayed 
his orchard with Bordeaux mixture in the winter of 1892-93, for the 
express purpose of controlling curl, and as a result of his experiments 
in the winter of 1891-92, to which reference has already been made. 
Relative to his work in the spring of 1893, Mr. Woolsey says* that he 
sprayed all of his apricot trees, but as time pressed he found that he 
would not be able to spray all of his peach trees, so he sprayed the 
most valuable portion, i. e. , the young lower growth, and left the top 
unsprayed. He states that the season of 1893 was damp, and leaf curl 
very prevalent in his neighbors' orchards, but on his place all the 
trees and parts of trees sprayed were exempt, all the others being 
badly affected by curl and the crop on them almost a failure. A 
healthy growth on the lower sprayed part of the trees, and the branches 
denuded of foliage on the upper unsprayed part, formed ''a most 
striking object lesson," and, Mr. Woolsey adds, has made him ''an 
enthusiast on Bordeaux mixture." A few demonstrations such as 
he obtained in the season of 1893, he remarks, would convince the 
growers of the profitableness of the work. 

Many peach orchards were sprayed in Oregon in the winter of 
1892-93. A favorite spray was a combination of the sulphur spray 
with copper sulphate, although the former was used separately by 
some growers. The object of the combined spray was to unite, as far 
as possible, the insecticidal qualities of the sulphur spray with the 
fungicidal qualities of the copper salts. ^ The winter application of 
ammoniacal copper carbonate was tested in Oregon also, by Mr. M. O. 
Lownsdale, of Lafayette. In reply to the circular letter dated Nov- 
ember 25, 1893, Mr. Lownsdale says he had fair success in prevent- 
ing curl with lime, sulphur, and salt applied in the winter, followed 

^ Reply to circular letter of Nov. 25, 1893. 

•Letter dated lone, Cal., Mar. 26, 1894. 

•See results of the tests of combined Bprays made by the writer, pp. 84, 86, 117, 118. 



60 PEACH LEAF OUBL: ITS NATURE AND TREATMENT. 

by three applications of animoniai'al copper carbonate after the appear- 
ance of the foliage. He had better .suc<;e«s, however, from anmioniacal 
copper carlx)nate applied in late winter, before the swelling of the 
buds, followed by three applications of a weaker solution upon the 
foliage. "This/' he says, ''was a complete success." 

Tn Michigan the work in 1893 was very satisfactory. Mr. Charles 
Youngreen, of AVhitehall, sprayed one row of peach trees before they 
leafed out in the spring. He states^ that not one of the sprayed tree- 
showed curl, while the unsprayed trees were all affected. The follow- 
ing year he sprayed the entire orchard and not a tree sufl'ei'ed from 
the disease. At Shelby, Oceana County, several growers sprayed 
with Bordeaux mixture with good success. Mr. R. Morrill, of Bentou 
Harbor, stated at a meeting of the Michigan Horticultural Society 
held at Shelby, June 14 and 15, 1893, that he found there, in four or five 
cases, that men had sprayed peach trees with Bordeaux mixture, and 
the effect in decrease of leaf curl was plain to be seen.* Mr. Morrill 
fails to state, however, whether the first spraying was done while the 
trees were dormant. The effects of curl at Shelby at that time were 
marked, the same gentleman remarking that in one morning he had seen 
enough damage done by it to pay for spraying all the orchards within 
five miles. 

Professor Taft reports his work in 1893 as follows:' ''In order to 
secure definite knowledge upon the subject [treatment of curl], I 
arranged for a series of experiments, and in the fall of 1892 had a 
number of peach trees sprayed with a solution of copper sulphate 
(1 pound in 25 gallons), and in a similar expeiiment at South Haven 
Bordeaux mixture was used as soon as the leaves dropped in Novem- 
ber, 1892. During the first half of April, 1893, the same trees were 
again sprayed with similar mixtures, and other trees were treated that 
had not been sprayed in the fall of 1892. The result was that where 
fully 50 per cent of the leaves and all of the fruit dropped from the 
unsprayed trees, there was little injury to the same varieties that were 
treated in both fall and spring or that were sprayed only once, in 
April; but where they were not sprayed until after the leaves had 
come out only a slight benefit was secured. The results were given 
in Bulletins 103 and 104 of the Station. On June 14, 1893, 1 gave the 
results, up to that time, at the meeting of the State Horticultural 
Society." 

The orchards of the Michigan Agricultural Experiment Station at 
South Haven, in charge of Mr. T. T. Lyon, had suffered severely from 
curl in 18H0. 1891, and 1892.* Mr. Lyon says, respecting the spray 

^Letter dated Whitehall, Mich., Sept. 6, 1899. 

* Kept. Mich. State Hort Soc., 1893, p. 68. 

* Letter dated Agricultural College, Mich., Aug. 30, 1899. 

*See Repta. Mich. Hort. Soc., 1890, p. 144; 1891, p. 228; 1892, pp. 160, 161. 



HISTOKy OF TREATMENT. 61 

work done in the winter of 1892-98,* that as the apparent result of 
the fall and spring sprayings, there was almost a total absence of leaf 
curl, although it had usually been quite prevalent there in early spring, 
and was present in 1893 in neighboring orchards, causing many of the 
leaves and fruits to drop. He says* further, that to him "the effect 
of the spray upon leaf curl in pai*ticu]ar was a revelation." The work 
of Professor Taf t in this orchard in 1893 was reported on several occa- 
sions during 1893 and 1894.' 

The work of the writer began in Michigan by the publication, in 
the fruit belt of that State, in the latter part of July, 1893, of notices 
of the work done in California,* and of requests for the names of 
peach growers who had sustained losses from this disease. In 
August, plans for experiments at Shelby and Ludington were in 
progi-ess, and in November a circular letter, stating that leaf curl had 
been successfully prevented in California, was addressed to the peach 
growers of all the leading peach centers of the country. In this 
circular it was stated that ''It is proposed to carry on during the 
coming season some work in diflferent parts of the United States." 
The circular reached many of the leading peach growers of Michi- 
gan. During the winter, that of 1893-94, plans for the testing of 
winter sprays for the control of curl were undertaken by growers, at 
. ;ie request of this Department, at Whitehall, Albion, Gangers, Beulah, 
tliverside, Benton Harbor, St. Joseph, Kalamazoo, Covert, Hawk- 
head, South Haven, Ludington, Shelby, Douglas, Millgrove, Custer, 
Amber, Mears, Hart, Gobleville, Ortonville, Monterey, Fenville, 
Saugatuck, Allegan, Wayland, Bradley, Peach Belt, etc. During the 
winter of 1894-95 the above list was greatly extended. Within these 
two years over 400 Michigan peach growers were sent full instruc- 
tions for controlling curl. Ekch grower was requested to make his 
tests according to an experiment sheet sent him, leaving unsprayed 
trees for comparison. In this way many striking object lessons were 
obtained, aiding materially in the early and widespread introduction 
of the methods of treatment recommended. Reports of a few of these 
experiments are given in a subsequent chapter. 

The Department's tests in Ohio were instituted through a circular 
letter in November, 1893, announcing to a large nurnber of peach 
growers in that State the successful treatment of curl in California, 
and stating that experiments would be undertaken in the East. As a 
result of replies to this circular, full instructions for controlling curl 

«Mich. Exp. Sta. Bull. No. 104, pub. Feb., 1894, pp. 64, 65. 

* Letter dated South Haven, Mich., Dec. 16, 1897. 

'Paper read at Shelby, June 14, 1893, Kept. Mich. Hort. Soc., 1893, pp. m, 67, and 
79; article in Allegan Gazette, July 1, 1893; Mich. Exp. Sta. Bull. No. 104, p. 64; pub. 
Feb., 1894; American Agriculturist, Feb., 1894, pp. 71, 72. 

*LAiiiington (Mich.) Appeal, insue of July 20, 1893, quoted by Shelby Sentinel, etc. 



62 PEACH LEAF OUEL: ITS NATUEB AND TBBATMENT. 

were sent to a number of orchardists in the peach-growing centers 
of Ohio in the winter of 1893-94. During this and the succeeding 
winter over fifty orchardists, located in twenty-five different peach- 
growing centers of the State, received carefully prepared instructions 
for winter spraying for curl. The instructions for both winters were 
planned in the usual manner of experimental work, a number pf 
unsprayed or control trees being left for comparison with the trees to 
be treated with each spray to be tested. The object in thus planning 
the work was the same as for that in Michigan and elsewhere — that is, 
to obtain such striking contrasts between sprayed and unsprayed trees 
that they would form long-remembered object lessons for aU who 
should chance to see them. 

The spray work of the Ohio Agricultural Experiment Station after 
1890 was quite extensive; but the treatment of peach leaf curl is not 
mentioned in the bulletins on orchard spraying published by that 
station in December, 1891, and February, 1893,* although in the 
latter (Bui. No. 48, p. 12) the spraying of peach trees for other 
diseases is considered. In the spring of 1893, however, Prof. W. J. 
Green sprayed a considerable number of young peach trees, just 
planted, the object being '*to determine the truthfulness of the 
statements that had been made concerning the effect of spraying upon 
peach trees." In relation to curl, Professor Green says that he *^did 
not see any effect until the season of 1894," during which and in 1895 
''there was some effect noticeable." He says further, in this connec- 
tion: ^'I am aware that other work in this direction had been done 
before I commenced, because I received my suggestions from some 
other source, but 1 can not now recall the particular case." (Letter 
dated September 30, 1899.) 

Upon these results obtained by Professor Green, and supported by 
the work of Benton in California and Taft in Michigan, were based 
the subsequent experiments of Prof. A. D. Selby in the orchard of 
William Miller, of Gypsum, Ohio.* These experiments were begun, 
according to Professor Selby, in April, 1896,' but no results with 
leaf curl were obtained until 1896,* as in 1895 there was no difference 
between sprayed and unsprayed trees in the amount of curl developing, 
it being so insignificant as to be without evident effect. The curl 
which developed in 1896 enabled Mr. Selby to obtain some contrasts 
between sprayed and unspra3'ed trees, but these contrasts were not as 

*Green, W. J., The Spraying of Orchards, Ohio Agr. Exp. Sta. BuL No. 9, Dec,, 
1891, Vol. IV, second series; Bui. No. 48, Feb., 1893, p. 12; and a letter from Pro- 
fessor Green, dated Wooster, Ohio, Sept. 30, 1899. 

•-'Letter from Prof. A. D. Selby, dated Wooster, Ohio, Sept 13, 1899. 

»L. c; also Ohio Agr. Exp. Sta. Bui. No. 92, March, 1898, pp. 237-245. 

M)hio Agr. Exp. Sta. Bui. No. 92, March, 1898 p. 245; also Thirtieth Ann. Rept 
Ohio State Hort Soc., pp. 87. 



HI8T0RY OF TREATMENT. 68 

marked as they would have been had the disease developed seriously.* 
As it was light in 1895 and 1896, no gain in fruit was shown by 
sprayed over unsprayed trees these years. In 1897 the work was con- 
tinued, and owing to the serious development of curl the desired 
contrasts in foliage were obtained. Unfortunately, however, the fruit 
buds had been killed by cold and no fruit records were obtainable. 
The first contrasts in fruit on sprayed and unsprayed trees in Mr. 
Miller's orchard were reported to Mr. Selby in 1898, and they are 
both valuable and conclusive.' 

The announcement of the Department's work on leaf curl was sent 
to the growers of peaches in Illinois, Indiana, and Pennsylvania at the 
same time that it was sent into Ohio and other States of the East, viz, 
in November, 1893 ; and during the winters of 1893-94 and 1894-95, 
135 peach growers in Pennsylvania, 81 in Indiana, and 36 in Illinois 
were requested to spray for the control of curl and report to the 
Department. A complete plan for these tests, control trees being 
provided for in every case, was sent to each of the growers. So far 
as reported, where instructions were followed, the results of this work 
were satisfactory in all cases where curl developed and where frost 
did not prevent the obtaining of results. 

Winter spraying for the control of curl began in New York, so far 
as known to the writer, in the winter of 1893-94, during which and 
the following winter over seventy peach growers of the State received 
from the writer full instructions for the treatment. These instruc- 
tions were sent out through personal correspondence with orchardiste 
in over twenty of the peach-growing centers, and by means of care- 
fully prepared circulars. Among others, Mr. W. T. Mann, of Barkers, 
undertook spray work for the Department in the winter of 1893-94. 
Carefully planned experiments were carried out by him in his young 
orchard, the spraying being done on April 9, and before growth 
started, and alternate rows being left untreated for comparison. Mr. 
Mann reported the results of this work as satisfactory, and they are 
elsewhere given in this bulletin. Mr. James A. Staples, of Marl- 
boro, also conducted spray work for the Department in 1894, 1895, 
and 1896, and where the instructions were carried out respecting 
the time of first spraying his results were fully satisfactory. Prof. 
L. H. Bailey' reported the work of Mr. Henry Lutts, of Youngstown, 
for the spring of 1894; and Mr. A. D. Tripp, of North Ridgeway, 
reports exceUent results from his work. 



"Ohio Agr. Exp. Sta. Bull. No. 92, pp. 246, 247. 

HMo Agr. Exp. Sta. Bull. No. 104, March, 1899, p. 210; also Rept. Ohio State 
Hort 8oc., 1898, p. 13. 

* Bailey, L. H., Impreflsions of the Peach Industry in Western New York, Cor- 
neU Agr. Exp. Sta. Bull. No. 74, Oct., 1894, pp. 382,383. 



64 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

A bulletin of the Cornell Agricultural Experiment Station, by 
George F. Atkinson/ which appeared in September, 1894, treats of leaf 
curl and plum pockets. Respet^ting the treatment of leaf curU Mr. 
Atkinson says that some experiments had been made in various places 
by spraying the trees with Bordeaux mixture for the prevention of the 
disease. Some of the experimenters regard it as certain, he states 
chat the disease can to some extent be checked by this method, and 
adds: '^ It is quite likely that, in some cases at least, another disease 
is confused with leaf curl, and this fact might account in those instances 
for the results claimed." The doubts here expressed as to the results 
of the work in New York do not appear to have been supported by any 
field work of the station , and may have arisen from Mr. Atkinson's under- 
standing of the perennial habits of the fungus causing the disease. 
There seems to have been no winter spraying for curl by the Cornell 
Station before the spring of 1898, and the results then obtained ai-e in 
perfect accord with those obtained in 1894 by growers cooperating 
with the Department. In the spring of 1898 several experiments were 
instituted and carried out by B. M. Duggar and H. P. Gould. The 
results of this work are given in a bulletin by Mr. Duggar, published 
in February, 1899." 

The efforts to control peach leaf curl by winter sprays in Canadii. 
so far as concerns the work of the Canadian Government, appear u 
have begun nearly simultaneously in Ontario and British Columbia. 

At the experiment farm at Agassiz, British Columbia, the peach 
orchard had suffered severely from curl prior to the introduction of 
winter spraying. The superintendent, Mr. Thomas A. Sharpe, 
reported for 1892 that of the large number of peach varieties at that 
time on the farm — about 116 — only 6 escaped leaf curl, and the attack 
was severe.' In the report for 1893 it is said that leaf curl was worse 
that year than ever before. Of about 129 varieties on the farm the 
Malta was the only variety on the level land that was entirely free.* 
In the spring of 1894 the trees were sprayed with strong Bordeaux mix- 
ture when the leaves were partly expanded, but no leaf curl developed 
that year, even the unsprayed orchards not being troubled by it* 
It should be stated here, however, that the work done was too late to 
have given good results had curl developed, and that it did not properly 
constitute a preventive spraying. Whether this late spraying w^a< 
owing to the nature of the season, or whether it was supposed thiM 
such treatment would control the disease, is not known to the writer. 



^ Atkinson, Geo. F., Leaf Curl and Plum Pockets, Coraell Agr. Exp. Sta. Bull. 
No. 73, Sept., 1894, pp. 324-326. 

"Dujjjjar, B. M., Pea<!h I>eaf Curl, ete., Cornell Agr. Exp. M-. Bull. No. 164, Feb., 
iwm, pj). 377-384. 

» Kept. Exp. Farnifi, 1892, p. 278. 

* Re[)t. Kxp. P'anuH, 1893, pp. 342, 343. 

* Kept. Exp. Farms, 1894, p. 404. 



HISTOBY OF TREATMENT. 65 

In 1895 Mr. Sharpe reports that the peach trees at Agassiz were 
sprayed with Bordeaux mixture before leafing out, and again when 
the leaves were nearly full grown. He states that the sprayed trees 
bad very little curl, and made a very strong j^d healthy growth, while 
on a few unsprayed trees of several varieties the leaves were nearly 
all destroyed by curl, and the trees themselves made a very feeble 
growth.* 

This treatment, so far as known, is the first successful experiment 
for the control of curl by the Canadian Government. Leaving con- 
trol trees for comparison added greatly to the value of the work, 
which was also strengthened by the results at .Agassiz the following 
year, 1896.' The writer regrets to add, however, that unfavorable 
results attended the spray work at Agassiz in 1898.' The reasons 
for this failure are not apparent. 

In Ontario the early results were not so satisfactory as at Agassiz, 
owing to the nondevelopment of the disease in Ontario. Mr. John 
Craig, horticulturist of the Central Experimental Farm, at Ottawa, 
planned the Ontario work. He states that the work on peaches in 
1894 was planned to prevent the rotting of fiiiit and injury from 
insects, and that the first spraying was not given until May 1.* Mr. 
Craig's work on leaf curl began in 1895, by the application of winter 
sprays,* but owing to the absence of the disease that year no con- 
clusive results were obtained. Later work, I am informed by Mr. 
Craig, has given more conclusive and satisfac^toiy results.* The vari- 
able results reported in Bulletin No. 1, second series, leads the writer 
to wonder, however, if the early spray work was done with suflScient 
thoroughness. Mr. W. M. Orr, of Fruitland, Ontario, met with very 
convincing and satisfactory results from winter spraying in 1898.' 
The same is true for the experiments of Mr. A. H. Pettit, of Grimsby, 
Ontario, who carried on work in 1898 and 1899, the results of the latter 
year, when one row of trees was left untreated for comparison, being 
very striking. 

The work of this Department in extending the use of sprays for 
the control of curl on the Pacific coast began in the spring of 1893. 
In the fall of that year a circular letter on the subject was addressed to 
man}^ Pacific coast growers, and this was closely followed by requests 
that growers undertake preventive spray work in the winter of 

* Kept. Exp. Farms, 1895, p. 396. 
^Rept. Exp. Farms, 1896, p. 449. 
*Rept. Exp. Farms, 1898, p. 403. 
*Rept. Exp. Farms, 1894, pp. 110, 111. 

* Peach Culture in Canada, Bull. No. 1, second series, pp. 35-57; Central Exp. 
Farm, Dept. of Agr., Ottawa, Canada, Sept., 1898. 

•letter dated Ottawa, Oct. 7, 1897. 
'Canadian Horticulturist, Jan., 1899, pp. 18-20. 
19093— No. 20 6 



66 PEACH LEAF CUBL: ITS NATURE AND TEEATMENT. 

1893-94. During the winters of 1893-94 and 1894-95 the writer sent 
full instructions for preventing curl by winter sprays to over two 
hundred and seventy California peach growers, and requests to carry 
on spraying experiments,, with similar instructions, to more than one 
hundred growers in Oregon, and to many in Washington. In all of 
this work for the extension of spraying an effort was made to intro- 
duce it in as large a number of leading peach-growing centers as pos- 
sible, especially in those sections of the coast where leaf curl had been 
most prevalent. The results of some of these experiments are g'iven 
in Chapter Vll, and the facts gathered and experiments conducted under 
the direct charge of the writer in 1893, 1894, and 1896 are detailed in 
full in other portions of this bulletin, and require no discussion here. 



CHAPTER IV. 

PLAN OF PREVENTIVE SPRAY WORK CONDUCTED BY THE 

DEPARTMENT. 

PRELIMINABY PLAJIS FOR THE WORK. 

The partial control of peach leaf curl in the spring of 1893, in a few 
orchards of the Sacramento Valley in which the trees had received a 
winter spraying for the control of the San Jos^ scale {Aspidiotua per- 
niciosys)^ showed to the writer the importance of conducting careful 
experiments for the prevention of curl. As a foundation for experi- 
mental work a circular of inquiry was sent to some 1,500 peach growers 
of the United States in the fall of 1898. The facts thus obtained were 
of much value, but the general lack of accurate knowledge respecting 
both the nature and control of the disease, as well as the heavy losses 
reported from this cause in diflferent sections of the country, strikingly 
emphasized the need for widespread and thorough preventive experi- 
ments. 

After careful consideration it was concluded to inaugurate two series 
of ex]>eriments. The first, which had been planned before the sending 
out of the circular, was to be conducted in California under the direct 
supervision of the writer, and the second, planned somewhat similarly, 
though on a more limited scale, was to be carried out by the growers 
themselves in various peach-growing sections of the country. The 
personally conducted work is described here, while the results of the 
cooperative work are given farther on. 

Observation and correspondence had already shown which sections 
of California were most subject to frequent and serious recurrences of 
the disease.' Facts thus gathered led to the opening of correspondence 
with Mr. George F. Ditzler, the manager of the Rio Bonito orchard, 
situated in the Sacramento Valley, in the bottom lands of the Feather 
River, near Biggs, Cal. This orchard is the property of the Hatch & 
Rock Orchard Company, and comprises some 1,600 acres, several 
hundred of which have as fine peach trees as any in the State. Among 
the varieties of peaches in this orchard is a large acreage of Lovell 
trees. The Lovell, it was learned, while presenting as thrifty growth 
as any variety in the orchard during years when curl did not prevail, 
had been especially subject to it in seasons favorable to its develop- 
ment, the crop of this variety, which would amount to several 

67 



68 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

thousand dollars, having been largely lost in 1893. After a brief 
correspondence Mr. Ditzler kindly oflfered to allow the Department to 
select from the orchards of Lovell peaches a block of several hundred 
trees of exceptionally uniform and vigorous growth and especially 
suited to the purposes of the experiments planned, and no finer or 
more uniform block of trees has ever been seen by the writer than 
that eventually selected and assigned to this experimental work. It 
consisted of nearly 600 trees at the southwest corner of a 40-acre block 
of Lovells, and was nearly level. The soil was sandy loam — deep, 
rich, and almost uniform in quality. The trees had been set in 
orchard less than five years, were 25 feet apart each way, and had 
grown so vigorously that before pruning the branches met between 
the rows in many cases, thus presenting tops of exceptional size for 
trees so young. 

The experiments planned included a rectangular block of the orchard, 
20 trees wide from east to west by 29 trees long from north to south. 
The tract selected was 500 feet east and west by 725 feet north and 
south, or nearly Si acres in extent. At the south of these Lovells is 
an almond orchard of the same age; at the west a young apple orchard. 

Through the center of the experiment tract, extending from south 
to north, was planned a driveway, thus dividing the trees into two long 
rectangular blocks, each block being 10 trees wide from east to west, 
and 29 trees long from north to south. Each cross row of 10 trees W8u< 
numbered. The south 10 trees, forming the south east-and-west row 
on the east side of the driveway, was designated 1; the second row 
from the south, 2; the third row, 3; etc., the north row on the east 
of the drivewa}^ being row 29. On the west of the driveway the 
south row was 30, the second row 31, etc., the north row being 58. 
This arrangement gave 580 trees, divided into 58 rows of 10 trees 
each, one-half of these, rows 1 to 29, being east of the driveway and 
the other half, rows 30 to 58, west of the same. This arrangement 
may be fixed more clearly in the mind by the diagram on page 69. 

This diagram, in addition to showing the arrangement of the rows, 
as already described, is planned to represent and distinguish the 
rows which were to be treated with sprays from those which were to 
be left untreated as check or control trees in each experiment. The 
trees of the rows to be treated are represented by a star (*) and the 
trees to be left unsprayed are shown by a circle (^), with the exceptions 
to be noted. It may thus be seen that each row of 10 trees intended 
for treatment has at its side 10 untreated trees as a check or control 
row. With the exception of rows 29 and 58 each control row serves 
for comparison with two sprayed rows, one on either side. This 
method of contrasting each control row with a sprayed row on either 
side admitted of the planning of 38 experiments in the block of 58 
rows, each experiment comprising 20 trees — 10 sprayed and 10 
unsprayed, in two immediately adjoining and parallel rows. 



PLANS FOB, SPRAY WORK. 



69 



After locating and numbering each of the 38 experiments to be 
tested the block was carefully examined to determine if any of the 
trees were mlssmg or so injured as not to represent entire trees. The 
results of this examination are also embodied in the plat. Where 
trees were missing the f ct is shown by a cipher (0) in the place of the 



We I. 



58 
57 
66 
55 

m 

52 
51 
50 
49 

48 
47 

$ 46 

i 44 

a 

I « 

OS 42 
41 
40 



87 
36 
35 
34 
33 
32 
31 
30 



North. 

2,1 

> o , o 

I! 



10 9 8 



6 5 4 
ee numbers.- 



3 2 1 10 9 8 7 6 5 



-Tree numbers. - 



29 

28 

27 

26 

25 

24$ 

'23 

22 

21 

20 

19 

18 

17 

16 

15 

14 

13 

12 

11 

10 



5 
^ 
8 
2 

1 



3 2 1 



s East. 

5 



* sprayed In 1894 and 1896, except where noted. 

'' Unsprayed in 1894 and 1895. 

S sprayed in 1891 and left unsprayed in 1895. 

tree, but it was found that only two trees, both from row 39, were 
wanting in the block. The cross (+) in row 35 represents a nectarine 
tree, omitted in results of work. In cases where main limbs had been 
broken off or the tree otherwise injured, the proportion of the tree 
remaining is expressed in numerals, i. e., 8 in the place of a tree indi- 
cates that the tree was eight-teriths perfect, 5 that it was five-tenths 



70 



PEACH LEAF OUSLI ITS NATURE AND TREATMENT. 



perfect, etc. As will be seen, however, there were very few imperfect 
trees. 

In all the following calculations of fruit, etc., these few discrepan- 
cies in the number of trees are carefully taken into account in arriv- 
ing at results intended for comparison with other rows. The amounts 
produced by the trees of each row are first divided by the number of 
trees actually in the row to obtain the average per tree, and this 
amount is multiplied by 10 to obtain the amount a full row would 
yield at the given average. By reference to the plat it may be seen 
that the trees and parts of trees missing amount to but 5.8 equivalent 
trees for the entire block, that 61 of the 58 rows have the whole com- 
plement of 10 perfect trees, and that the missing trees or parts of 
trees are divided among the remaining 7 rows. 

SPRAY WORK CONDUCTED IN 1894. 

The spray tests conducted in the Rio Bonito orchard in 1894 
included the application of sprays prepared according to 3S different 
formulae, making 38 distinct experiments. Each experiment included 
two adjoining rows of 10 trees each, one sprayed and the. other 
unsprayed for comparison. Of these 88 experiments 11 involved two 
sprayings of the trees treated and 27 a single treatment. All treat- 
ments were made during the dormant period of the trees and varied 
in date from February 1 to March 6. The consideration of the 
preparation of sprays for this work will be discussed in a subsequent 
chapter devoted to that subject, as will also the methods of applica- 
tion, which will be given for use in both small and large orchards. 

The table which follows is prepared to show as concisely as possible 
the arrangements adopted for the experiments of 1894. The rows of 
trees once treated and those twice treated are shown, the date or dates 
of treatment and the formula or formulae used in each case. 

Tablb I.— Showing theformuUs of (he sprays applied in 1894j dutes of application, and 

rows treated. 



Row No. 



Date of 
spraying. 



Formulae for 45 gallons of spray. 



1 


Feb. 20 


2 




3 


Feb. 24 


4 


/Feb. 16 
iFeb. 28 


6 


6 


Feb. 23 


7::..:.:: 


Feb. 24 


8 




9 


Feb. 23 


10 


/Feb. 20 
\Mar. 3 


11 


12 


Feb. 24 


13 


Feb. 13 


14 




16 


Feb. 18 


16 


/Feb. 26 
\Mar. 6 





16 lbs. sulphur, 30 lbs. lime, 10 lbs. salt. 

Control row. 
10 lbs. sulphur, 20 lbs. lime, 7 lbs. salt. 
10 lbs. sulphur, 20 lbs. lime, 7 lbs. salt. 

5 lbs. sulpnur. 10 lbs. lime, 3 lbs. salt 

Control row. 

6 lbs. sulphur, 10 lbs. lime, 3 lbs. salt 
15 lbs. sulphur. 30 lbs. lime. 

Control row. 
10 lbs. sulphur, 20 lbs. lime. 
10 lbs. sulphur, 20 lbs. lime. 
5 lbs. sulpnur, 10 lbs. lime. 

Control row. 
5 lbs. sulphur, 10 lbs. lime. 
20 lbs. lime, 20 lbs. salt 

Control row. 
20 lbs. lime. 
45 lbs. salt (hot). 
45 lbs. salt (hot). 



SPRAT WOKK OF 1894. 



71 



Tablb 1. — Showing the formula of the gprays applied in 1894y dales of applicationj and 

rows treated— Contmued. 



Row No. 


Date of 
spraying. 


17 




18 


Feb. 26 


W 


Feb. 27 


20 




21 


/Feb. 16 

\Feb. 20 

Feb. 21 


22 


23 




24 


/Feb. 6 
\Mar. 1 
Feb. 23 


25 


26 




27 


/Feb. 6 

\Mar. 1 

Feb. 26 


28 


29 




30 


Feb. 2 


31 




32 

33 


Feb. 2 
/...do... 
tMar. 2 


34 


35 


Mar. 3 


36 


Feb. 27 


37 




38 


Feb. 26 


39 


/Feb. 1 
\Feb. 28 


40 


41 


Feb. 23 


42 


/Feb. 14 
\Mar. 8 


43 


44 


Feb. 24 


« 


Feb. 27 


46 




47 


/Feb. 14 


48 


Mar. 3 
/Feb. 14 


49 


\Mar. 6 


50 


Feb. 14 


51 


Mar. 8 


92 




58 


/Feb. 14 
tMar. 6 
Feb. 27 


54 


55 




56 .*:;;.;*;: 


Mar. 6 


57 


do 


58 '.'.'....'.'.. 





Formulae for 46 gallons of spray. 



Control row. 

3 lbs. copper sulphate, 5 lbs. sulphur, 10 lbs. lime. 

2 lbs. copper sulphate, 5 lbs. sulphur, 10 lbs. lime. 

Control row. 
5 lbs. copper sulphate, 5 lbs. lime. 

5 lbs. copper sulphate, 5 Ibe. lime. 

4 lbs. copper sulphate, 5 lbs. lime. 

Control row. 
4 lbs. copper sulphate, 5 lbs. lime. 

3 lbs. copper sulphate, 5 lbs. lime. 
3 lbs. copper sulphate, 6 lbs. lime. 

Control row. 

3 lbs. copper sulphate, 2 lbs. lime. 
2 Ibe. copper sulphate, 5 lbs. lime. 
2 lbs. copper sulphate, 5 lbs. lime. 

Control row. 
2 lbs. copper sulphate, 3 lbs. ammonia. 
Control row. 

4 lbs. copper sulphate. 
2 lbs. copper sulphate. 

2 Iba. copper sulphate. 

Control row. 

4 Iba. copper sulphate, 6 lbs. soda, 3 lbs. ammonia. 

3 lbs. copper sulphate, 10 Ibe. sulphur, 10 lbs. lime. 

Control row. 

6 oc. copper carbonate, 3 lbs. ammonia. 

5 OB. copper carbonate, 3 lbs. ammonia. 
5 oc. copper carbonate, 3 lbs. ammonia. 

Control row. 

5 lbs. copper sulphate, 10 Iba. lime. 

6 pints spray solution. 
6 pints n>ray solution. 

Conurol row. 
6 lbs. copper sulphate, 16 lbs. lime. 
3 lbs. copper sulphate, 16 Iba. lime. 

Control row. 
8 pints spray solution. 
8 pints spray solution. 
6 pints spray solution, 3 lbs. lime. 
6 pints spray solution, 10 lbs. lime. 

Control row. 
8 pints spray solution. 3 lbs. lime. 
6 lbs. sulphur, 6 lbs. lime. 

Control row. 
10 lbs. spray solution, 1 lb. soap (hot). 
8 pints spray solution, 1 lb. soap (hot). 
8 lbs. copper sulphate, 10 lbs. lime. 

Control row. 
8 pints spray solution, 2 lbs. copper sulphate, 10 lbs. lime. 
6 lbs. sulphur, 16 lbs. lime. 

Control row. 



The spray work outlined in the above table was fully completed before 
the opening of many of the peach blossoms in the spring. Following 
this work, plans were laid for the preservation of records of fruit 
thinned from the trees, etc., should peach leaf curl develop. As the 
J^pring advanced, however, it became evident that the disease would 
not appear to any serious extent in that portion of the State that sea- 
^n, it not being sufficiently severe to produce a contrast either in 
foliage or fruit between the sprayed and unsprayed trees, hence the 
action of the sprays applied could not be determined. While this fail- 
ure to arrive at the results hoped for in 1894 was much regretted, the 
failure, nevertheless, led to the acquisition of certain facts at a later 
date which are of prime importance to the orchardist wishing to com- 
bat the disease with sprays. The treatment of the trees in 1894 made 
it possible when the work was resumed in 1896 to ascertain if the 



72 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

effects of one year's treatment extended to the crop or foliage of the 
second year. 

While peach leaf curl did not develop seriously in the Sacramento 
Valley in 1894, it prevailed quite extensively in other portions of the 
United States. This resulted in acquiring facts bearing on the experi- 
ments for 1896 in the Rio Bonito orchard. The experiments planned 
by the Department and carried out by growers in the East and in the 
north Pacific States, where leaf curl developed, showed that one 
thorough spraying during the dormant period of the tree was sufficient. 
The experiments of 1895 were consequently modified from those of 
1894 in respect to the number of applications made, as well as in other 
respects found to be advisable. 

SPRAY WORK CONDUCTED IN 1895. 

In the spray work in the Rio Bonito orchard during the winter and 
spring of 1895, the same block of Lovell peach trees was selected as 
that treated the previous year, and in each case the same unsprayed or 
control rows were left as in 1894. In 1895 the number of experiments 
made in this block was 38, as in the previous year, but three of the 38 
rows were not sprayed, being left without treatment for the purpose 
of obser\ang the action of sprays applied in 1894 upon the crop and 
foliage of 1895. These three rows were numbers 4, 24, and 53, each 
of which had received two treatments in 1894. The facts thus learned 
are considered farther on. The spray work of 1895 included but a 
single spraying of each row designed for treatment. As already indi- 
cated, each experiment included one treated and one untreated i-ow, 
each row having 10 immediately adjoining trees. By treating one row 
on either side of each control row the latter served as a contrast row 
for both sprayed rows. By referring to the plat of the block, p. 69, 
this arrangement may be seen. Row 1 is sprayed; row 2, unsprayed; 
row 3, sprayed. These three rows make two experiments — rows 1 
and 2 compared make the first experiment, while rows 3 and 2 com- 
pared make the second experiment. In like manner rows 4 and 5 and 
5 and 6 make two experiments. These illustrations will be sufficient, 
as the entire block, with the exception of the three rows already 
noted, was treated according to the same general plan. 

In considering the application of sprays in the experiments of 1895,* 
the nature of the sprays used, the fomiulte according to which they 
were prepared, the location of the rows treated, and the dates of appli- 
cation, as well as the location of the control rows for comparison, are 
set forth in the table which follows. That the reader may better grasp 
the nature of all treatments which each row had received the previous 
year, the foi-mulae for the sprays applied in 1894 are placed at the left 
of the treatment given the same rows in 1895. 



Spray work of 1895. 



73 



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74 



PEACH LEAF OUBL: ITS NATUKE AND TBEATMENT. 










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GENEBAL GONSIBEBATIOK OF SPRAYS APPLIED. 75 

The methods of preparing and applying the'sprays used in 1895 are 
considered in subsequent chapters. In each case an effort was made to 
do thorough work in applying the sprays, but, as is true with all such 
work in the field, more or less variable results could not be avoided 
owing to the weather conditions and other influences. The treatment 
was given the 35 rows during the ten days immediately preceding the 
general opening of the flowers, that is, at the close of the dormant 
period of the trees, or from February 26 to March 5. In a few of 
the more forward trees a small percentage of the flowers had opened 
before the completion of the work. 

GENERAL CONSIDERATION OF SPRAYS APPLIED. 

Several distinct types of sprays were tested in the preventive work 
on curl in 1895, and these were prepared in many forms and propor- 
tions. The two fungicidal bases, copper and sulphur, which are now 
recognized in all countries as most valuable for this class of work, 
enter into the composition of a large proportion of the sprays used, 
in one form or another. 

In testing sprays considerable weight was given to the fact that 
the peach tree is subject to the attacks of certain serious insect pests, 
prominent among which is the San Jos^ scale, and that a spray com- 
bining both fungicidal and insecticidal properties would often prove 
of greater value than one the action of which was solely fungicidal. 
Having these facts in mind, and knowing the demonstrated value of 
the sulphur, lime, and salt spray as an effective remedy for the San 
Jos6 scale, tJiis spray, together with various modifications, was tested 
and compared (rows 1, 3, and 6). Besides quantitative modifications 
of the spray, tests of its constituents were made to acquire such facts 
respecting their value as were obtainable. The sulphur and lime 
united were tested in several proportions without salt (rows 7, 9, 10, 
12, 16, 51, and 57). The lime and salt were tested together (row 13), 
and the lime was tested separately (row 44). The trial of a strong 
Halt solution was made the previous year (row 16), but as it injured 
the foliage somewhat it was omitted in 1895. Other modifications 
of the sulphur spray were prepared by adding different fungicides, 
with the hope of increasing its fungicidal action without detracting 
from its effectiveness as an insecticide. Sulphate of copper was 
added in different proportions (rows 18, 19, and 36), and the addition 
of iron sulphate was also tried (row 56). 

The copper sprays tested for leaf curl were numerous and were 
variously prepared and combined. As already said, copper sulphate 
was added to the sulphur sprays, but it was most extensively used in 
the preparation of the Bordeaux mixture, in which form it was applied 
in many experiments and of various strengths (rows 15, 21, 22, 25, 28, 
33, 41, 45, and 54). Copper sulphate with ammonia (eau celeste) was 



76 PEACH LEAF CURL: ITS NATURE AND TREATMENT, 

tested (rows 27 and 80), as was the modified eau celeste, composed of 
copper sulphate, sal soda, and ammonia (rows 35 and 89). Two experi- 
ments were also conducted with ammoniacal copper carbonate (rows 32 
and 38). 

The action of sulphide of potassium was tested (row 47), as well as 
sulphide of potassium combined with milk of lime (rows 42 and 4S). 

Iron sulphate in connection with lime was applied in one experiment 
(row 50), and, as already stated, was also used in connection with 
sulphur and lime (row 56). 

Of the three rows left unsprayed in 1895 (rows 4, 24, and 53), one 
(row 4) had received two applications of the sulphur, lime, and 
salt spray in 1894; another (row 24) had been twice sprayed in 1894 
with Bordeaux mixture; and the third (row 53) had received two spray- 
ings in 1894 with a hot saponified solution of sulphide of potassium. 






} 



Bull. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture, 




DESCRIPTION OF PLATE VII. 

Sprayed and unpprayed Crawfords Late trees in the orchard of Mr. A. D. Cutt8, 
Live Oak, Cal. The tree seen at the right was sprayed with lime, sulphur, and salt 
in February, 1893; that at the left was unsprayed and was denuded of foliage and 
fruit by curl. (See records of fruit of 8])rayed and unsprayed trees in this orchard, 
p. 141.) The trees were photographed in May, after most of the curled leaves 
had fallen from the unsprayed tree. (Compare with PI. XX.) 



CHAPTER V. 

INFLUENCE OF SPRAYS ON THE VEGETATION OF THE TREES. 

SAVING OF FOLIAGE FROM INJURY BY CURL. 

(PI. VII.) 

The effectiveness of the winter sprays discussed in the previous chap- 
ter in saving the foliage of peach trees from injury by peach leaf curl 
has been carefully considered. The relative importance of this matter 
appears from the fact that it is the injur^^ from the loss of foliage which 
is responsible for the ultimate loss of thfe fruit. The spray work 
already mentioiied was completed, in 1895, about the close of the first 
week in March. From this time on the flowers opened rapidly, and 
they were soon followed by the pushing of the leaf buds and the com- 
plete resumption of the vegetative growth of. the year. By the mid- 
dle of April the trees were well in foliage, while peach leaf curl was 
nearing the height of its development. By the 22d of the month 
the contrast between healthy and diseased foliage on the sprayed and 
unsprayed trees had become so great that a careful estimate was made 
of the percentage of the diseased leaves upon every tree in the block. 

The first estimate of the condition of the foliage was made to deter- 
mine the amount and percentage of disease present on sprayed and 
unsprayed trees. The estimate of each tree was calculated upon the 
basis that the foliage present represented 100 per cent, and the amount 
of badly diseased leaves was taken as a certain per cent of the leaves 
present at that date. Badly diseased leaves were considered as those 
.seeming to have sufficient curl present to cause their premature fall 
from the tree. The ultimate comparisons of sprayed with unsprayed 
rows are not based upon this first estimate of foliage as the disease was 
still progressing. The parasite was still in the vegetative state, few of 
the swollen leaves as yet showing the fruit of the fungus, and still fewer 
having fallen from the trees. The trees sprayed with the stronger 
.sulphur preparations were injured somewhat by the sprays, many of 
the more tender twigs being killed. This delayed the leafing of these 
trees, and resulted in their showing rather a smaller percentage of 
diseased foliage at the time this estimate was made than would have 
been the case had the leaves pushed earlier. These discrepancies 
influence only a few of the sprayed rows. In other respects, it is 
believed the numerous influencing conditions would apply, ho far as 

cotdd be told, with equal force to all rows. 

77 



78 



PEACH LEAF CURL: ITS NATUBE AND TBEATMENT. 



In taking the percentage estimates of disease shown in the following 
table, the trees were examined in north and south rows. This was 
done so as to work across the lines of the experiment rows rather than 
with them, and for the purpose of avoiding any influence which a 
knowledge of the sprays used on the trees estimated might be thought 
to exert. 

Table 4. — EiAimaled percentage of diseased leaves on trees April 2S and tS, 1895. 



Row No. 



Feicentaffe of diseased leaves estimated 
Apr. 22 and 23, 1896, on tree Na— 



1. 2. 3. 4. 6. 6. 7. 8. 9. 10. 



Average 
percent 
of dis- 
eased 
leaves 

per 

tree in 

sprayed 

rows. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
18 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
88 
89 
40 
41 
42 
43 
44 
45 
46 
47 
48, 
49 
GO 
51 
52 
53 
54 
55 
56 
57, 
58, 



85 I 80 

13 I 27 

14 I 12 
85 85 
70 70 
30 1 40 
90 I 87 
35 i 40 
30 1 26 
85 ' 80 
85 I 80 
17 10 
85 , 75 
30 I 22 
26 31 
90 89 



20 



13.5 



31.0 
080.5 



41.5 
28.5 



85.0 
32.0 



89.3 
45.5 



11-4 
28.9 



86.5 
21.4 



12.7 
10.7 



<i82.5 
18.7 



20.1 
23.7 



18.3 



81.5 
9.0 



18.7 
14.2 



29.0 
20.3 



15.7 
55.0 



26.5 
12.6 



68.0 
36.8 



40.8 
29.1 



083.0 
14.6 



20.8 
22.1 



a Bows sprayed in 1894, but left uusprayed in 1895. 



SAVING OF FOLIAOB. 79 

General consideration of the above table develops some striking 
contrasts. By adding the figures corresponding to the average per- 
centage of diseased leaves on the trees of the control rows, and dividing 
this amount by the number of rows, we find that in the entire block, 
containing 200 control trees, 83.6 per cent of the leaves were badly 
diseased at the date of this estimate. In contrast to this„ the total of 
the average percentages of disease shown by the trees of the sprayed 
rows, divided by the number of sprayed rows in the block, shows the 
average amount of disease in the i^prayed rows to have been 26.2 per 
cent. Evidently this average is much above the percentage of disease 
shown at that date by many separate rows, as it included the rows 
treated with noneffective sprays as well as those giving the best 
results. Adding the averages of rows 4, 24, and 53 and dividing the 
amount by 3 gives 82 per cent of disease as the average of the 
three rows. As noted in the table, these rows were not sprayed in 
1895, but were left in order to ascertain the effects of the sprays 
applied to them in 1894, and the average of disease is seen to be prac- 
tically as great as upon rows never sprayed. 

From the date of this first estimate the progress of the disease in 
the orchard was very marked. Within the next two weeks the fungus 
fruited quite generally upon the swollen leaves, and a large percentage 
of the* worst diseased leaves had fallen from the trees. By May 9 
the contrast between sprayed and unsprayed trees had quite generally 
reached its highest point, and any irregularities of special trees, etc., 
could no longer be considered. On May 9 a second careful estimate of 
the foliage was made. In this work, however, it was impossible to 
estimate the amount of disease on the trees as compared with the total 
amount of foliage present, as had first been done, for much of the 
diseased foliage had already fallen. To avoid this difficulty a new 
method of estimating was adopted. From the entire block of trees 
were selected two rows, Nos. 21 and 22, which showed only from 4 to 
6 per cent of disease, and were in other respects in perfect foliage. A 
careful study of these rows was made to get a clear idea of the con- 
dition of a tree in full foliage at that date, and with these types in 
mind each tree of the entire block was carefully examined. An esti- 
mate was made for each tree, based on the twenty typical trees studied, 
to determine the per cent of perfect foliage upon it, taking the amount 
which should be upon the tree at that date, if no disease existed, as 
UK) per cent. The following table gives the results of this work. The 
percentages in the last column represent the gain in leaves of sprayed 
trees over the average of all control trees in the block. The manner 
of obtaining these percentages is discussed on page 85. 



80 



PEACH LEAF CURL*. ITS NATURE AND TREATMENT. 



Table 5. — Estimated percentage of healthy foliaae on the sprayed and unsprayed tree* May 
9f 1895, as compared wiih the amount a healthy tree should have at that date. 



Row No. 


Percentage of healthy foliage compared 
with the amount the tree should nave, 
estimated May 9, 1895. 

Tree No. — 


Average 
percent 

of 
healthy 
leaves 
per tree 

in 

sprayed 

rows. 


Average 
per cent 

of 

healthy 

leaves 

per tree 

in control 

rows. 


Gain in 
leaves of 
sprayed 

averair..' 
of all CI >n- 
trol tret^, 
expresPtti 

in 
pendent. 




1. 2. 


3. 

93 
.12 
80 
15 
12 
87 
90 
13 
87 
88 
10 
88 
75 
15 
95 
80 
12 

11 
92 
9 
97 
96 
12 
92 
20 
55 
94 
16 
88 
85 
10 
68 
93 
10 
95 
45 
15 
80 
80 
13 
40 
55 
20 
50 
75 
10 
18 
90 
10 
70 
65 


4. 

92 
9 

82 
10 
10 
80 

85 


5. 

94 
15 

85 
15 
18 
86 
ft'? 


6. 

95 
10 

86 
•20 
15 
60 
84 
10 
80 
82 
20 
80 
86 
13 
88 
87 
13 
86 
85 
10 
99 
98 
10 
9 
87 


7. 

92 

8 
85 
18 
15 
83 
87 
12 
88 
87 
10 
78 
86 
20 
92 
85 
10 
88 
77 
10 
96 
95 

8 

10 
96 
11 
89 

9 
90 
21 
45 
85 
15 
98 
.50 
12 
80 
85 
15 
90 
45 
10 
40 
75 

8 
.50 
45 
10 
45 
5.5 
18 
10 
85 
10 
60 
80 
11 


8. 

92 
13 
80 
20 
25 
78 
85 
25 
80 
85 
10 
72 
80 
20 
88 
85 
22 
80 
84 
10 
98 
96 
20 

7 
92 

8 
85 
86 

8 
95 
23 
45 
95 
15 
95 
90 
12 
75 
86 
11 
78 
45 
18 
65 
87 
18 
45 
50 
12 
65 
70 
10 
10 
80 
^9 
75 
70 

8 


9. 

93 
10 
90 
12 
10 
80 
90 
20 
85 
89 
12 
80 
70 

85 
10 
85 
75 
20 
98 
90 

9 

8 
85 

9 
98 
95 

8 
82 
23 
45 
92 
10 
93 
75 
12 
70 
78 
10 
^7 
48 
22 
40 
75 
15 
30 
50 
15 
65 

a5 

18 
15 
88 
10 
68 
70 
10 


10. 

87 
5 
86 
15 
18 
66 
70 
20 
78 
80 
18 
75 
76 
15 


1 


92 
9 
90 
15 
10 
85 
95 
10 
88 
90 
9 
92 
87 
8 

95 
92 
20 
92 


93 
10 
86 
8 
12 
65 

as 

10 
75 
80 
8 
80 
87 

65 
11 


92.3 




6i'»7 


2 


10.1 




3 


84.7 
a 14. 8 


.549 


4 




lo 


5 


14.6 




6.. . . 


76.8 
85.4 


48^ 


7 :.. 




5M 


8 


9 12 
80 90 
83 90 
20 1 11 

85 i 80 

86 65 
10 20 

90 90 
80 ! 86 
10 I 8 
86 1 88 

91 85 

8 1 9 

89 92 

90 1 90 
10 ' 8 

9 i 9 
85 1 88 


14.1 




9 


83. i 
85.4 


.=vw; 


10 




.V>4 


11 


12.8 




12 


8i.6 
79.6 


5J) 


18 




50? 


14 


14.3 




16 


80 


on n 


5*^ 


16 


75 *w n 




••^2^ 


17 


12 
(i8 




i2.8 




18 


84.7 


>if 


19 


90 ' 85 
10 9 
97 ' 95 
96 1 96 
8 ' 10 
8 9 
«9 t «0 


70 
12 
98 
98 
25 
14 
94 
35 
90 
92 


83.2 




.\r7 


20 


16.7 




21. . . . 


95.9 
94.5 


6^U 


22 




tvM 


23 


i'2.2 


b'S^f 


24 


a9.4 
89.8 




26 




f*.*'-'^ 


26 


10 
91 
87 

9 
96 
11 
65 
92 

9 
86 
65 
10 
05 
73 
15 
93 
45 
10 
78 
89 
11 
40 
70 

9 
70 
80 

9 


10 
92 
88 
10 
95 
18 
50 
92 
9 

90 
80 
13 
45 
82 
10 
92 
25 
12 
75 
89 
16 
40 
75 
10 
65 
70 

in 


8 10 1 12 

87 1 92 1 91 

88 , 85 ' 92 
10 1 8 1 13 
91 ! 90 1 <N^ 


i2.2. 




27 


91.2 
8Q a 


.'n«^ 


28 




.'>M 


29 


10 1 

95 1 92 'i 


9.7 




30 


a€ 


31 


20 
60 
94 
20 
92 
90 
12 
70 
(c) 
12 
85 
28 
10 
55 
90 
15 


15 22 
65 46 
90 ' 90 

16 1 14 
92 1 90 
75 i 80 
15 1 16 
70 1 75 
(r) 1 92 
10 , 12 
8.5 80 
45 50 
15 1 18 
(id ' 5.5 
90 1 95 

9ii 9ft 


20 
60 
96 
18 
94 
92 
17 
85 
78 
18 
.85 
40 
16 
35 
87 
18 
26 
50 
12 
60 
66 
15 
22 
70 
12 
90 

m 

10 




i9.3 




32 


62.5 
91.9 


riji 


33 


604 


34 


i4.2 




85 


91.8 
78.2 


64"« 


36 




1 A9^ 


37 


i2.8 




38 


70.3 
83.4 


1 4;> 


39 




.V{y 


40 




i2.h 




41 


87.0 
41.6 


.V/> 


42 

43 


14* 5* 


219 


44 


.58.8 
86.7 


1 3.S0 


45 


h'lb 


46 


15.9 




47.... 


45 1 28 i 45 
70 1 65 50 
18 i 20 , 15 
60 1 40 50 
70 , 70 65 
10 1 IS 1 12 

8 15 15 
70 1 82 85 

9 15 15 


88.8 
68.0 


197 


48 




aw 


49 


14.1 




60 


67.0 
68.5 


3S6 


61 


iio* 


1 4-2A 


52 




iSS 


20 15 


a 14. 8 
82.2 


1 is 


54 


■So 
9 
ho 
70 

H 


87 
14 

m 

83 
10 




.VJ^ 


55 


11.3 




5<; 


75 , 65 
rtn 7ri 


90 

87 


75.8 
74.8 


4SI) 


57 




4TS 


58 


11 1 10 1 12 


10.2 






III 




1 



a Trees Rprayed in 1894. but unsprayed in 1895. 
5 Gain of control row over row sprayed in 1894. 
c Tree missing. 

The comparison of some of the general facts brought out in the esti- 
mates of foliage April 22 and 23 and May 9, 1895, shows the progress 
of the disease during that time. 



SAVING OF FOLIAGE. 



81 



Table 6. — Comparative percentage of diseased foliage on sprayed and unsprayed trees 
April 22 and 23 and May 9, 1895. 



Trees examined. 



April 22 

and 
23, 1895. 



May 9, 



Average per cent of diseaae on the trees of all control rowh 

Average per cent of diseaae on the trees of all sprayed rows 

Avtrajfe per cent of disease on the trees of the three rows sprayed In 1894, but 
left unsprayed in 1895 



83.6 
26.2 



82.0 



86.9 
21.2 



87.0 



The»se comparisons show 3.3 per cent more diseased foliage on the 
control trees May 9 than April 22. The percentage of foliage of the 
spi-ayed trees showing disease had decreased, however, 5 per cent. Of 
the total foliage of the trees sprayed in 1894, but left unsprayed in 
181^5, 5 per cent more was diseased at the second date than at the first. 
These figures indicate that the divergence in the percentage of disease 
on sprayed and unsprayed trees was still increasing just prior to the 
second estimate. The second estimate may thus be considered as taken 
before any of the trees had begun to recover from the effects of the 
dis<?ase. The time of maximum contrast was the true time to make 
the estimates, and it is believed the date of this second estimate was 
certainly not too late to fully comply with this requirement. This 
l)elief was substantiated by a third partial estimate made a week later, 
which gave in general very similar results to those obtained May 9. 
It should also be said that the decrease in the percentage of disease on 
the sprayed trees between the dates of the first and second estimates 
did not indicate that the second estimate was made too late, or after 
the trees had begun to recover, but merely that the leaf buds had not 
fully pushed at the time of the first estimate. This is further shown 
by the fact that the percentage of disease was still increasing on 
unsprayed trees up to that time. 

Ifefore considering the action of individual sprays in saving the 
foliage from curl, the following comparisons are given of the action 
of the classes of sprays used: 

Table 7. — Percentage of healthy foliage on trees differently sprayed. 



I'vn-entages of healthy foliage shown by trees sprayed with 
differpnt classes of sprays. Estimated April 23 and May 
9.1896. 



Average of 90 trees sprayed with sulphur, lime, and salt 

Average of 70 trees sprayed with sulphur and lime 

Averiiice of 100 trees sprayed with the two preceding sulphur 
oi^niys 

Average of 90 trees sprayed with Bordeaux mixture 

Arvrage of 20 trees sprayed with cau celeste 

Average of 20 trees sprayed with modified eau celeste 

Average of 180 trees sprayed with the three preceding copper 
sprays 

Average of 20 trees sprayed with ammoniacal copper car- 
bonate 

19093— No. 20 6 





«i-i • 


^^c\ . 


c«o» 


•2 -S 


^>. 


V t^x 


V eS 


ercentag 
healthy 
age Ap 
and 2:?, 1 


B^'^ 




PU 


fl. 


71.4 


84.6 


69.3 


80.0 


70.3 


82.3 


86.2 


89.6 


83.3 


91.7 


83.0 


87.6 


84.2 


89.6 


69.8 


61.4 



•^ as 

O 






13.2 . 
10.7 . 

12.0 |. 

4.0 |. 
5.4 ". 



82 PEACH LEAF CURL: ITS NATURE AND TREATMENT- 

Table 7. — Percentage of healthy foliage on tree* differerUly »}traycd — Continued. 



Percentages of healthy foliage shown by trees sprayed with 
different clasBes of sprays. Estimated April 23 and May 
9, 1896. 



Average of 

and lime 

Average of 

Average of 

lime 

Average of 
Average of 

lime 

Average of 
Average of 



30 trees sprayed with copper sulphate, sulphur, | 

(a) ; 

10 trees sprayed with iron sulphate and lime 

10 trees sprayed with iron sulphate, sulphur, and 

lb trees sprayed with sulphide of potassium I 

20 trees sprayed with sulphide of potassium and 



10 trees sprayed with milk of lime 

10 trees sprayed with milk of lime and salt. 



Percentage of 
healthy foli- 
age Apr. 22 
and 23, 1896. 


'Sao: 

pa 


Qaln in percent 
of foliage 
from Apr. 23 
to May 9, 1896. 


pi 


76.3 


82.0 
67.0 

75.8 
88.8 

49.8 
6ft.8 


6.7 




69.2 


2.2 


79.2 




3.i 


32.0 


6.8 




64.8 


4..=^ 


73.6 




It: 


64.6 1 79.6 


25.0 











a Compare text. 

The table shows the average of healthy foliage on the trees sprayed 
with the sulphur sprays (sulphur, lime, and salt, 30 trees; sulphur and 
lime, 70 trees) to have been 82.3 per cent May 0. The average on the 
trees sprayed with the leading copper sprays (Bordeaux mixture, IHi 
trees; eau celeste, 20 trees; modified eau celeste, 20 trees) was 8i^»5 
per cent. The average amount of healthy foliage saved on treses 
sprayed with a combination of these two leading classes of spray > 
(Bordeaux mixture added to the sulphur and lime sprays, 30 tn»es) 
was no greater than the average saved by all sulphur and lime sprays 
alone, being 82 per cent as against 82.3 per cent for the sulphur 
sprays. This result was a sui*prise, but by carefully looking into the 
reason it would seem that the low average in the case of the combined 
sprays was due to the low average of the single row 36, while the high 
average of the sulphur sprays arose from including in the average the 
results of those sprays which contained much more sulphur than wa> 
used in the combined sprays. Notes on the spray applied to row 36 
show that considerable sulphur was precipitated in cooking, probably 
through overheating, and for this reason it would be as well to omit 
this row in deteimining the average saving of the combined sprays. 
The two remaining rows, 18 and 19, sprayed with combined sprav>, 
showed 84.7 and 83.2 per cent of healthy foliage, respectively — ^an 
average of 83.1) per cent. The formula for each of these experiments 
contained 5 pounds of sulphur. In the experiments with uncombiniHl 
sulphur sprays there were four formulas containing 5 pounds of sul- 
phur each. The average per cent of saving of these four experiments 
was 75.3. These facts show that when the amount of sulphur wa> 
equal there was an average gain of 8.6 per cent in healthy foliagt^ 
resulting from the addition of Bordeaux mixture to the sulphur 
sprays. 

The average percentage of foliage saved by the use of the ammo- 
niacal copper carbonate (20 trees) was. May 9, 61.4. As the ammoniacal 



SAVING OF FOLIAGE. 83 

copper carbonate spmys used contained much less basic copper car- 
bonate than the other copper sprays applied, their comparatively low 
effectiveness against curl is fully accounted for, and for this reason 
they were not included when calculating the average action of the 
copper sprays in general. They were outclassed by the amount of 
copper used in the other sprays. 

The foliage saved by the use of iron sulphate and lime (10 trees) 
was but 57 per cent May 9. This shows a much less satisfactory action 
than either the copper or the sulphur sprays. The iron sulphate com- 
bined with the sulphur and lime sprays showed a saving of foliage 
May 9 of 76.8 per cent. While this is a good showing, the beneficial 
action was evidently due to the sulphur of the spray and not to the 
iron, and the result was even below the average obtained b}'^ the sulphur 
sprays alone, or equal to those having the same amount of sulphur. 

One experiment (10 trees) was made with sulphide of potassium, but 
the average percentage of foliage saved by this spray was. May 9, only 
38.8. Sulphide of potassium combined with milk of lime (20 trees) 
showed a greater saving of leaves, being 49.8 per cent, but as the 
sulphide alone gave a saving 11 per cent lower, and as milk of lime 
saved as high as 58.8 per cent, it is questionable if the lime was not 
the more active agent in the combination. As already stated, the 
milk of lime applied as a spray (10 trees) showed a saving of 58.8 
per cent of the leaves, which was quite satisfactory for a spray con- 
taining none of the standard fungicides. The spray prepared from 
lime and salt (10 trees) gave a high record, the healthy foliage May 9 
being 79.5 per cent. While it is possible that the fungicidal action of 
this spray may be somewhat higher than that of milk of lime alone, 
it is perhaps more probable that the re^^ults noted arose from another 
influence. It was learned in the previous year's work that a solution 
of salt injured the new growth and tender leaves, and it is thought 
likely that in the present case the earliest growth and that which first 
showed . disease was destroyed by the spray, and that the foliage 
estimated was a new and somewhat later growth, showing much less 
disease than the first foliage would have shown. It would be well, 
however, to repeat this test. 

Some interesting facts are brought out by the preceding table in 
relation to the continued action of the fungicides used. By comparing 
the first column, the percentages of healthy foliage taken April 22 
and 23, with the second column, the percentages taken May 9, it will 
be seen that the percentage of healthy foliage on all trees spraj'cd 
with the sulphur or copper sprays increased decidedly between the 
two dates of estimate, as shown in the third column. On the other 
hand, the action of the weaker sprays was overcome by the disease, 
and the percentage of healthy foliage May 9 was much less than April 
23, as shown in the fourth column. These weaker sprays checked the 



84 



PEACH LEAF CURL*. ITS NATURE AND TREATMENT. 



action of the fungus at first, but were not sufficiently active or per- 
sistent to prevent its gradual increase upon the trees. An apparent 
exception to this in the case of the sulphide of potassium appears to 
arise from the fact that the disease was never greatly checked b}" this 
fungicide, the amount of healthy foliage being only 32 per cent April 
23. Another and more marked exception is seen in the trees sprayed 
with lime and salt in solution. It is thought, however, that the true 
explanation of this exception is that given in the preceding paragraph. 

What has been stated will be sufficient to indicate the comparative 
value of the main classes of sprays used in these experiments. It i.s 
shown that the highest degree of effectiveness in sa\'ing foliage is 
possessed by the copper sprays, that the sulphur sprays also possess a 
high degree of fungicidal activity, and that where Bordeaux mixture 
is added to the sulphur sprays the effectiveness of the latter is some- 
what increased. It is also made clear tliat sulphide of potassium, 
sulphate of iron, and several other sprays, as tested, are of secondary 
value in this work. It should be noted that the average saving 
obtained from the use of the sulphur spniys is sufficiently high to well 
warrant the use of these sprays, either in combination with Bordeaux 
mixture or alone, in cases where it is desired to use a spray having 
both fungicidal and insecticidal qualities. 

It will now be advantageous to briefly consider the leading indi- 
vidual sprays composing the classes of spmys already discussed, in 
respect to their action on peach foliage and peach leaf curl. The fol- 
lowing table gives a compact presentjition of the number and nature 
of these sprays, as well as their action in controlling curl: 

Table 8. — Nature and rompoMon of sj>rayit applied. 



Row 
No. 



10 
16 
57 
12 
61 

36 
18 
19 



ClaH8C8 and formula* of sprays applied. 



Sulphur, lime, and wilt : 

If) lbs. sulphur. W lbs. lime, 10 lbs. salt 

10 lbs. sulphur, 20 lbs. lime, 6 lbs. salt 

5 lbs. sulphur, 10 lbs. lime, 3 lbs. salt 

Sulphur and lime: 

15 lbs. sulphur, 30 lbs. lime 

10 lbs. 8ulphur,20 lbs. lime 

10 lbs. sulphur, 8 lbs. lime 

6 lbs. sulphur, 4 ^b.K. lime 

6 lbs. sulphur, 15 lbs. lime 

5 lbs. sulphur, 10 lbs. lime 

5 lbs. sulphur, 6 lbs. lime 

I^)rdeaux mixture and sulphur sprays combined : 

3 lbs. copper sulphate, 10 lbs. sulphur, 20 lbs. lime. 
3 lbs copper sulphate, 5 Iba. sulphur, 10 lbs. lime. 
2 lbs. copper sulphate, 5 lbs. sulphur, 10 lbs. lime. 
Bordeaux mixture : 

6 lbs, copper sulphate, 15 lbs. lime 



-53 









92.3 

84.7 
76.8 



S o &> «: ' 
OiJ^ si 03 



607 , 
549 

488 



m 



6t» 



86.4 


554 1 


6fi 


83.1 


636 1 


6ii 


86.4 


5M 


6i» 


82.0 


528 1 


SO 


74.8 


473 i 


«♦ 


81.0 


520 


6ii 


68.5 


424, 


W 


78.2 


499 


70 


84.7 


549 i 


Ni 


83.2 


537 1 


J*' 



90.0 I 



SAVING OF FOLIAGE. 



85 



Table 8. — Nature and composition of sprays appUM — Continued. 



Row 1 
No. ! 



41 1 
4o 

22 I 
•25 . 

28' 

27 ! 
30 

35 I 



32 

50 

4$ 
42 

13 

44 



Claasen aird foraiuloe uf sprayR applied. 



3 lbs. copper galphate, 15 lbs. lime 

6 lbs. copper sulphate, 10 lbs. lime 

3 lbs. copper sulphate, 10 Iba. lime 

3 lbs. copper sulphate, 10 lbs. lime 

5 lbs. copper sulphate, 6 lbs. lime 

4 lbs. copper sulphate, 5 lbs. lime 

3 Ibe. copper sulphate, 6 lbs. lime 

2 lbs. copper sulphate, 5 lbs. lime. 

Eau celeste : 

4 lbs. copper sulphate, 3 pints ammonia 

2 lbs. copper sulphate, 3 pints ammonia 

Modified eau celeste : 

4 lbs. copper sulphate, 5 lbs. sal soda, 3 pints ammonia 

2 lbs. copper sulphate, 3 lbs. sal soda, 2 pints ammonia 

Ammoniacal copper carbonate : 

5 ounces copper carbonate, 3 pints ammonia 

3 ounces copper carbonate, 2 pints ammonia 

Iron sulphate and lime : 

6 lbs. iron sulphate, 10 lbs. lime 

Iron sulphate, sulphur, and lime : 

5 lbs. iron sulphate, 5 lbs. sulphur, 10 lbs. lime 

Potassium sulphide solution : 

8 pints potassium sulphide solution 

Potassium sulphide solution and lime : 

12 pints potassium sulphide solution, 10 lbs. lime 

8 pints potassium sulphide solution, 5 lbs. lime 

Lime and salt : 

20 lbs. .ime,20 lbs. salt 

Lime : 

20 lbs. lime 







oS" 


o« o 


*>s 


s«s. 


^ 


r ce 
iage 
r ce 
trees 


i^ 




>* , 




et gai 
health 
averag 
all con 


< 


^ 



O « as 

"I I 



♦91.9 
87.0 
85.7 
82.2 
95.9 
94.5 
89.8 
89.3 


•604 
566 
556 
529 
634 
624 
588 
584 


80 
100 
90 
80 
100 
100 
80 
80 


91.2 
t92.2 


598 
t606 


80 

tioo 


91.8 
83.4 


603 
539 


80 
80 


70.3 
52.5 


438 
802 


80 
60 


57.0 


33(i 


40 


75.8 


480 


40 


38.8 


197 


40 


58.0 
41.6 


344 

219 


50 
40 


79.5 


509 


60 


58.8 


350 


50 



* Exceptional, see p. 87. 



t Outside row, next to driveway. 



The above table is planned to give for each experiment the following 
facti>: (1) The number of the row to which <^he spray was applied; (2) 
the nature and amount of the ingredients used in each erase; (3) the 
average per cent of healthy foliage shown by the trees of the row 
May 9, 1895; (4) net gain in healthy foliage above the average per cent 
of healthy foliage produced by all of the control trees of the block 
('20i) unsprayed trees), and which is expressed in per cent; (5) thrift 
of uninfected leaves in color, texture, and size. The figures under 
the fourth head were obtained in the following manner: The average 
porcent^e of healthy foliage of all the trees of each control row w as 
first ascertained. These amounts were added together and divided by 
the number of rows (20) to obtain the average percentage of healthy 
foliage of all control trees of the block. This average was 13. OG. 
From the average percentage of each sprayed row was then subtracted 
the average of all control trees to obtain the gain in healthy foliage 
of each spi-ayed row. This net gain was then divided by the 13.00 
per cent of the control trees to obtain the net gain per cent of each 
sprayed row. For example, take row 1: 92.3 7^ 13.06 7r =-79.24 % 
gain; 79.24 %-^ 13.06 % shows the net gain to f)e yoJ = 607 7; of the 



86 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

average amount of healthy foliage of the control trees. The fifth sub- 
ject, thrif tine88 of leaves, is discussed in the next general head of this 
chapter. 

In considering the saving of foliage induced through the use of the 
sulphur, lime, and salt sprays (rows 1, 3, and 6) in comparison with 
the average saving of sprays containing an equal amount of sulphur 
but no salt (rows 7, 9, 10, 16, 57, 12, and 51), there appears to be a 
slight gain in favor of the former sprays. The average saving from 
both classes, taken together or separately,, is in proportion to the 
amount of sulphur contained in the spray. With 15 pounds of sul- 
phur the average net gain in healthy foliage was 580 per cent; with 
10 pounds, 547 per cent; with 6 pounds, 528 per cent; and with 5 
pounds, 480 per cent. 

In considering the combined sulphur and copper sprays (rows 18, 
19, and 36), it is well to omit comparisons of row 36, on account of 
the injury caused to the effectiveness of the spray applied to it through 
the precipitation of a portion of the sulphur in boiling, as has already 
been noted. Rows 18 and 19, containing 3 pounds and 2 pounds of 
copper sulphate, respectively, and each containing 5 pounds of sulphur 
and 10 pounds of lime, show a gain in healthy foliage of 549 per cent 
and 537 per cent, or an average gain of 543 per cent. The average 
gain from the sulphur sprays, which contained the same amount of 
sulphur but no copper, was, as already stated, 480 per cent. This 
shows the advantage of adding the copper to the sulphur sprays. 

In the table the experiments with the Bordeaux mixture are 
arranged according to the amount of copper and lime used in each. 
The results obtained in the 9 experiments bring out some valuable 
facts respecting the most desimble proportions of copper and lime to 
be used. Of the 9 experiments with Bordeaux mixture, 2 formula? 
contained 15 pounds of lime each, 3 formulsB 10 pounds each, and 4 
formulae 5 pounds each. 

By comparing rows 15 (6 pounds copper sulphate, 15 pounds lime), 
41 (5 pounds copper sulphate, 10 pounds lime), and 21 (5 pounds cop- 
per sulphate, 5 pounds lime), it will be seen that there was a gain in 
healthy foliage of 589 per cent, 566 per cent, and 634 per cent, respec- 
tivel3\ Dividing these gains b}'^ the number of pounds of copper in 
the respective formula?, which may be fairly done, owing to the nearly 
equal amounts of copper contained in each, the following results will 
be obtained: 

Per eent 
Row 15 (6 pounds copper sulphate, 15 pounds lime = l pound copper to 2.5 

pounds lime) shows a gain of foliage per pound of copper sulphate of 98 

Row 41 (5 pounds copper sulphate, 10 pounds lime = 1 pound copper to 2 

pounds lime) shows a gain of foliage per pound of copper sulphate of 113 

Bow 21 (5 pounds copper sulphate, 5 pounds lime = 1 pound copper to 1 pound 

lime) shows a gain of foliage per pound of copper sulphate of 127 



SAVING OF FOLIAGE. 87 

These comparisons indicate a decided increase in activity of the 
sprays as the percentage of lime is lessened — the total amount of cop- 
per remaining the same, at least to that point where the nmnber of 
pounds of copper sulphate and lime are equal. The formulee contain- 
ing 8 pounds of copper sulphate can not all be compared as justly as 
the above formulse have been, owing to a difference in the make of 
copper sulphate used on row 33. However, rows 45 and 54, each hav- 
ing been sprayed with a formula containing 3 pounds copper sulphate 
and 10 pounds lime, may be compared with row 25, which was treated 
with 3 pounds of copper sulphate and 5 pounds of lime. The average 
saving of foliage per pound of copper sulphate in the former two 
experiments (10 pounds lime) was 180 per cent. The saving per pound 
of copper sulphate in the latter experiment (5 pounds lime) was 196 
per cent. These comparisons also show most gain in foliage per pound 
of copper sulphate where least lime was used. 

That no misconception may be formed from the preceding com- 
parisons, it is weU to consider that the sprays were applied in these 
cases immediately before the opening of the buds, so that prompt action 
of the copper was of greater importance than the enduring qualities 
of the sprays. As will be elsewhere shown, however, the endurance of 
sprays upon the trees is largely increased with the increase of the 
amount of lime they contain. A large increase of lime above the 
absolute requirements for the Bordeaux mixture is not necessary when 
the spray is applied so near the date of the opening of the buds that 
its action can not be delayed without loss in effectiveness. On the 
other hand, if the spray is applied at an earlier date, so that it is 
required to withstand weathering for a longer period, a considerable 
increase in the amount of lime may be an advantage in increasing its 
enduring quality. 

The amount of copper sulphate used in the preparation of the Bor- 
deaux mixture varied from 2 to 6 pounds for 45 gallons of spray. Of 
the nine formulae tested, that containing 5 pounds of copper sulphate 
and 5 pounds of lime (row 21) gave the highest gain in foliage over 
the average healthy foliage of the control trees, or 634 per cent. 
There was an actual average saving of 95.9 per cent of the spring 
foliage of the 10 trees sprayed, consequently the average loss of foliage 
in this experiment was only 4.1 per cent. The next best results were 
obtained with the spray containing 4 pounds copper sulphate and 5 
pounds lime (row 22). This spray gave a gain in foliage above the 
average produced by the control rows of 624 per cent. The average 
amount of foliage saved on the 10 trees was 94.5 per cent, showing 
that all but 5.5 per cent of disease had been prevented. While row 33 
shows the next highest saving in foliage, these results, as already 
indicated, are exceptional, as shown by comparison. The yield of 
fruit which this row produced also shows the foliage records to be 
exceptional, and they may properl}' be omitted in these comparisons. 



88 PEACH LEAF CURL: ITS NATUEE AND TREATMENT. 

The results obtained by the use of eau celeste and modified eau 
celeste were very satisfactory, but in no case was as high a percentage 
of foliage saved by them as in the better tests with Bordeaux mixture. 
The exceptionally high percentage of foliage saved on row 30 with but 
2 pounds of copper sulphate may be in part due to the fact that tlie 
row was an exterior one of the block and next to a driveway, where 
the trees may have been better nourished than those of interior rows. 
By comparing the formula used on row 27 with that used on row 85 
(each" containing 4 pounds of copper sulphate) it will be seen that the 
saving of foliage was about equal with eau celeste and modified eau 
celeste. Comparison of these results with those shown by row tl. 
which was sprayed with Bordeaux mixture containing the same amount 
of copper, will show that the latter saved the highest percentage of 
foliage. 

Ammoniacal coppei carbonate gave less satisfactory results than the 
preceding sprays, probably owing to insufficient copper. The various 
results given by the other sprays tabulated require no special comm^^Mt. 

Another fact is made evident by the preceding table. Of two 
formulae of the same class, as the Bordeaux mixtures, one containing 
more of the fungicide than the othei', the percentage of foliage saved 
for each pound of fungicide will be the greater in the weaker spiiiy. 
Each of the Bordeaux mixtures used in spi-aying rows 21, 22, 25, rnd 
28 contained 5 pounds of lime, but the amounts of copper sulphate 
used were 5, 4, 3, and 2 pounds, respectively. The total net amount 
of foliage saved by these sprays and the net saving per pound of copper 
sulphate each contained may be thus shown. 

Row 21: 5-poun(i formula, 634 per (ient saved; per pound of copper sulphate, 127 
per cent. 

Row 22: 4-pound formula, 624 per cent saved; jier pound of copper sulphate, lo6 
per cent. 

Row 25: 3-pound formula, 588 per cent saved; per pound of copper sulphate, 196 
per cent. 

Row 28: 2-pound formula, 584 per cent saved; per pound of copper sulphate, 292 
per cent. 

These figures show a gradual decrease of the total per cent of foliage 
saved as the amount of the fungicide is decreased, but a decided increase 
in the percentage of foliage saved per pound of fungicide. 

COMPARISONS OF WEIGHT AND COLOR OF FOLIAGE FROM SPRAYED AND 

UNSPRAYED TREES. 

Besides the direct loss of leaves through infection by Exodsca^defifr- 
mans^ there is an indirect loss through the retarding of growth of such 
foliage as has not been directly infected by the fungus. A limited 
examination of this matter was made May 17 and 18, 1895. Two 
typical trees were selected in adjoining rows, one of which had been 






V-, 



'i;? 



- i. » J ^, 



^> 



Bull. 20. Div. Veg. Phys & Path., U. S. Dept of Agriculture. 



Plate VIM. 




DESCRIPTION OF PLATE VIII. 

Experiments at Biggs, Cal. (Unsprayed.) Looking north through the Lovell 
treea from row 28 of the experiment block, showing the unsprayed trees on l)oth 
sides as they appeared May 15, 1895, in the unsprayed orciiard. These should be 
contrasted with the two sprayed rows, 21 and 22, shown in PI. IX. 




, F'. A n' y ^•*. 



•*^\ F: A ;f y -. 




COMPABATIVE WEIGHT AND COLOR OF FOLIAGE. 89 

sprayed and the other not. These were trees No. 10 of rows 20 and 
21. Tree No. 10 of row 21 was sprayed the first week in March, 1895, 
with Bordeaux mixture (5 pounds copper sulphate, 6 pounds lime). 
Tree No. 10 of row 20 had not been sprayed. From each of these trees 
was gathered 2 pounds of healthy foliage. Careful measurements 
were made of the length of the branches of 1894 growth necessary to 
yield this weight of healthy leaves, and it was found that on the 
unsprayed tree it required 186 feet 2 inches, while on the sprayed tree 
it required only 49 feet 4 inches. The work was done as similarly as 
possible on both trees. The 2 pounds of foliage from the sprayed 
ti"ee contained 2,428 leaves, and the 2 pounds from the unsprayed tree 
2,546. In other words, 118 more healthy leaves were required from 
the unsprayed tree than from the sprayed tree to equal 2 pounds in 
weight, or 59 more leaves per pound. This result is due to the indi- 
rect rather than the direct action of the disease. The leaves from the 
unsprayed trees, being healthy, should average as great in weight as 
those from the sprayed trees, were it not for the retarding and 
impoverishing action of the disease upon the general growth of the 
tree. In comparing diseased with healthy leaves, however, this ratio 
would be reversed. The number of diseased leaves required for a 
given weight would be much less than the number of healthy leaves 
required. The diseased leaves are greatly curled and distorted through 
the irritation or stimulative action of the fungus present in the tissues, 
and in many instances they also become enoiinously increased in width, 
thickness, and weight. 

The contrast observed in the color and general appearance of the 
leaves of the sprayed and unsprayed trees was very marked. The 
foliage of the trees treated with the stronger copper sprays, especially 
the Bordeaux mixtures, presented the finest appearance. On May 8, 
1895, two months after the spray work was completed, and at the 
height of the disease, the foliage on trees thus sprayed presented the 
greatest perfection. It was so abundant and so dense as to throw 
very dark shadows beneath the trees, making it difficult to obtain 
good photographs among them. This dense foliage existed upon both 
the lower and the upper branches. The leaves were of a very dark 
and rich green color, long, soft, and beautiful. Upon the unsprayed 
trees comparatively few leaves presented the appearance of full 
health, and much of the diseased foliage had already fallen, leaving 
many trees nearly bare. The color of much of the remaining foli- 
age was yellow and sickly. Many of the uncurled leaves were small 
and light colored on both the lower and the upper limbs. What 
growth these trees had made up to that date was largely terminal, very 
little healthy or comparatively healthy growth being apparent from 
lateral buds. (Compare Pis. VIII and IX.) 



90 PEACH LEAF CURL; ITS NATURE AND TREATMENT. 

The influence of the various sprays on the thriftiness of the leaves 
was especially examined. This examination was confined to such foliage 
as was free from infection by the fungus, but was extended to sprayed 
and unsprayed trees alike, and to all rows of the block. In recording 
the comparative thrift of uninfected foliage, attention was given to the 
depth of the green color, to the softness of texture, and to the size of 
the leaves. These features of the foliage were considered collectively 
and recorded on the scale of 100; for instance, the most thrifty foliage 
was recorded at 100 per cent of thrift, and the less thrifty at a lower 
percentage. This method enables one to distinguish at a glance those 
sprays giving the best results in color, texture, and size of leaves — in 
other words, in functional ability. The records for each row and 
formula are given in the general table under the preceding head of this 
chapter, to which the reader is referred. It will there be seen that the 
trees of 5 rows produced foliage of the highest quality in spite of the 
presence of disease. These rows were all sprayed with the copper 
sprays, and all but one with Bordeaux mixture. Owing to the fact 
that row 30, showing first-quality foliage, was an outside row, it 
may be well to omit it in comparisons. The remaining 4 rows, Nos. 
15, 41, 21, and 22, were all sprayed with Bordeaux mixture, containing 
6 pounds, 5 pounds, 5 pounds, and 4 pounds of copper sulphate, 
respectively. Smaller amounts of copper sulphate did not give equally 
high results. 

The average results shown by the different classes of sprays are as 
follows: 

Percent. 

Sulphur, lime, and salt (3 rows) 67 

Sulphur and lime (7 rows) 63 

Bordeaux, sulphur, and lime combined (3 rows) 77 

Bordeaux (9 rows) 90 

Bordeaux, 4, 5, and 6 pound formulae (4 rows) 100 

Eau celeste (2 rows) 90 

Modified eau celeste (2 rows) 80 

Ammoniacal copper carbonate (2 rows) 70 

Iron sulphate and lime (1 row) 40 

Iron sulphate, sulphur, and lime (1 row) 40 

Potajssium sulphide (1 row) 40 

Potassium sulphide and lime (2 rows) 45 

Lime and salt (1 row) 60* 

Lime (1 row) 50 

Trees sprayed in 1894, but not in 1895 (3 rows) 20 

Control trees (19 rows) - 20' 

The Bordeaux mixture is here shown to give the best average results 
as to thrift of foliage. The excellence of texture, color, and size of 
the leaves on rows sprayed with the stronger Bordeaux mixtures 
would be hard to surpass. 

* First leaves probably injured by spray. 

"One exceptional row, showing 40 per cent, omitted; perhaps benefited by wind- 
borne spray. 



INFLUENCE OF 8PBAY9 ON THE VEGETATION OF TfliJ TREES. 91 

(JROWTH OF BRANCHES AN1> LEAF BUD8 ON SPRAYED AND UNSPRAYED 

TREES. 

Besides knowing the action of the disease and of the sprays upon 
foliage, it is desirable to ascertain their action on leaf buds and the 
growth of branches. Two months after growth started — from May 
10-14, 1895 — a study was made of the growth of 20 trees in the experi- 
ment block, 10 sprayed and 10 unspmyed. The rows selected for this 
work were Nos. 20 (unsprayed) and 21 (sprayed). These rows were 
types of the injurious action of the disease and of the beneficial action 
of the spray applied, which was 5 pounds of copper sulphate and 5 
pounds of lime. Much time was given to making measurements of the 
new growth and recording the results, the time being equally divided 
between the 10 sprayed and the 10 unsprayed trees. Typical limbs 
were measured upon both the lower and upper portions of the trees, 
and the length and comparative health of the new growth was recorded. 
The length of 1891 growth and that which was older was first ascer- 
tained, and was followed by careful measurements of all spring growth 
of 1895 arising from wood of 1894 or from that which was older. The 
i-esults of this work are shown in the following table: 

Table 9. — Records of iiieamrements of healthi/ and diseased wood on unsprayed and 
sprayed trees, taken May 10-14^ 1895. 



Tree No. 



1 , 

2 

3 

4 

5 

6 

7 

« 

9 

10 

Total 



Row 20, unsprayed trees. 






In. 
1,422 
1,614 
1,»>4 
1,:«M 
1,576 
1,886 
1,366 
1,7.^ 
1,986 
1,912 



length of spring growth 
of 1896— 



On wood of 
1894. 



1 



In. 

492 I 
570 I 

:«i 

557 

499 I 

298 

527 

686 

977 

670 



In. 
249 
229 
251 
'iM 
326 
257 

2:w 

516 
550 
582 



On wood more 

than 1 year 

old. 



Row 21, sprayed trees. 

Length of spring growth 
of 1895— 



X 



.2 
Q 



16,188 5,577 3,4W 1,126 



In. 

76 
219 

83 
234 

85 
182 

18 

5;^ 

120 

5() 



/«. 




From the footings in the preceding table it appears that the total 
length of 1894 wood measured upon the unsprayed trees was nearly 
twice as great as that measured on the sprayed trees. This arose from 
the scarcity of new growth on this unspmyed wood, hence an equal 
time given to taking measurements upon each tree included more old 
wood upon unsprayed than upon sprayed trees. 



92 PEACH "LEAF CUBL: ITS NATURE AND TREATMENT. 

On the unsprayed trees, prior to the middle of May, the total amount 
of new growth on 16,188 inches of 1894 wood, including the older wood 
from which this arose, was 10,590 inches. On the sprayed trees the 
new growth amounted to 17,045 inches during the same time (two 
months) on 8,260 inches of 1894 growth, including the older growth 
from which the latter arose. This was a net gain of 215 per cent, 
length of old wood considered, over the growth produced by the 
unsprayed trees. Otherwise stated, the unsprayed trees had averaged 
a new spring growth of 7.85 inches per running foot of 1894 wood and 
older, while the sprayed trees had produced a growth of 24.75 inches 
per foot of 1894 wood and older during the same time. This shows 
a gain in growth on the sprayed trees during these two months of 
16.90 inches per foot of old wood. The importance of this matter 
will appear to all growers who have peach orchards situated where the 
spring growth represents the major part of that of the season, as is 
true in man}^ peach-growing regions. In such orchards this would 
frequently represent a reduction of 25 per cent in the annual growth. 
In the peach, the growing wood of one year is the bearing wood of 
the next, hence the amount of wood produced would have added sig- 
nificance. 

Considering the total growth of the spring of 1895 from wood grown 
prior to 1894 — the pushing of dormant or quiescent buds — an analysis 
of the table shows a net gain by the old wood of sprayed trees of 173 
per cent above the growth produced from like wood of unspra3'ed 
trees. This action of spray enables the grower to renew bearing wood 
on the lower portions of his trees, which is an advantage where trees 
are old or close set and tending to grow upward, or where curl or other 
causes have tended to denude the lower limbs of young and productive 
wood. This tendency of Bordeaux mixture to aid in the forcing and 
active growth of dormant !)iids was especially well marked in the case 
of a tree spra} ed very thoroughly on one side (6 pounds copper sul 
phate, 4 pounds quicklime, 45 gallons of water) and left unsprayed on 
the other. From the base of the main limbs on the sprayed side there 
arose 13 shouts from dormant buds during the first two months of 
spring growth, while the unsprayed limbs produced practically none. 
The 13 shoots on the sprayed side had made the following growth to 
May 17, growth beginning about the close of the first week in March: 



Shoots. 1. 2. 



Length in Inches ' 3(3 44 I 29 

I I I 



A. 6. 6. 7. 8. 9. 10. 11. 12. 13. Total. 



6. 


6. 


7. 


8. 


9. 


10. 


11. 


12. 


13. 


46 


21 


36 


86 


36 


46 


22 


21 


23 



37 46 21 36 86 36 46 22 21 23 36 feet 1 inch. 



As shown by the table, the growth coming from 13 dormant buds 
at the base of the main limbs of the sprayed side of the tree during 
the first two months of spring growth amounts to 36 feet and 1 inch, 



OOMPABAUVE GBOWTH OF BBANCHES AND LEAF BUDS. 93 

or an average of over 33 inches for the 13 shoots. That this astonish- 
ing pushing of new basal buds was not due to injury of the top by the 
spray was shown by the immense amount of dark green foliage the 
sprayed half of the tree produced and from the amount and perfec- 
tion of the fruit it bore. It was evidently an aided or stimulated basal 
growth. In table 9 is shown the comparative health or disease of 
the spring wood measured. Where shoots had suffered from disease 
to such an extent that they were enlarged, crooked, or otherwise dis- 
torted or injured by the disease, they were classed as diseased ; when 
not so injured, they were classed as healthy. In respect to this classi- 
fication the table gives the following facts: On the unsprayed trees the 
new shoots measured on growth of 1894 or older amounted to 10,599 
inches, of which 6,703 inches was of healthy wood and 3,896 inches 
of diseased wood, or, in other words, 63 per cent of the wood was 
healthy and 37 per cent diseased. On the sprayed trees the total 
length of new shoots measured on 1894 growth or older was 17,045 
inches; of this, 16,988 inches was of healthy wood and only 47 inches 
of diseased wood, or 99f per cent was healthy and ^ per cent diseased.^ 
Many peach orchards are cultivated under conditions of moisture and 
nourishment that enable the trees to grow throughout the entire sum- 
mer. In such situations trees badly diseased in the spring are apt to 
so far recover before frost that there is little apparent diflference between 
them and the trees saved from curl by the use of sprays. That this 
recovery is not entire, however, is shown by actual comparisons. In the 
Riviera orchard. Live Oak, Cal. , were obtained the following records, in 
February, 1894, f ron 10 sprayed and 10 unsprayed Crawf ords Late peach 
trees. The trees are fully described under the f ollowi ng heading of this 

* These comparative records of the length of healthy and diseased branches upon 
sprayed and unsprayed trees fully serve the purpose of comparison for which they 
are here intended. There is another phase of the matter, however, which should 
not be overlooked or misunderstood at this time. A branch classed as diseased does 
not mean that it was diseased or swollen throughout its entire length, but that 
external signs of a diseased or injured condition were noted at some point in its 
course. If it be supposed that one-third of the injuries noted were dead ends or 
other imperfections not due to the infecting of the branch by the fungus, but indi- 
rect injuries arising from the loss of foliage, there remain twothirds of the injuries 
which may be properly assmned to be due to the infection of branches by means of 
mycelium coming from diseased leaves. There would then api)ear to be 25 per cent 
of the cases which might be classed as diseased from mycelium infection. As already 
indicated, however, this does not mean that these l)ranches are infected throughout 
their entire length, but show one or more points of infection at the buds. It is 
thought by the writer that not more than 1 bud in 10 is actually infected in these 
diseased branches. If this estimate is approximately correct, the number of infected 
buds on the unsprayed trees would be represented by one-tenth of 25 per cent, or 2.5 
per cent of the buds on the tree. In brief, it is believed that it is rare for more than 
3 per cent of the buds of a badly diseased tree to become infected by the mycelium 
from diseased leaves — in other words, that rarely more than this percentage of buds 
of one year carry a perennial mycelium to the next spring. 



94 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

chapter, and it will here be sufficient to state that the growth on the 
sprayed and unsprayed trees could be fairly compared. The spra^^ed 
trees were treated with the sulphur, lime, and salt spray in the winter of 
1892-93. Leaf curl developed seriously in the orchard in the spring of 
1893. The sprayed trees saved their foliage and bore a full crop of fruit 
in 1893, while the unsprayed trees, everywhere surrounding those that 
were sprayed, lost the spring foliage and most of the fruit. All trees 
stood upon moist, deep, rich river bottom land, where growth could 
continue throughout the season. In the fall of 1893 the unsprayed 
trees had apparently largely overtaken the sprayed trees in growth, as 
the former had carried little crop, while those that were sprayed had 
matured a full crop. That the unsprayed trees were not, however, 
fully abreast of the sprayed trees when growth ceased in 1893, Ls 
shown by the measurements rexrorded in February, 1894 (table 11). 
These measurements were made on various sides of each tree, and on 
lower and upper limbs, and as a week was devoted to the work, the 
measurements are believed to be sCifficiently extensive to give reliable 
results. 

Table 10. — Gain in number of lateral f<ho*ttK and xpurs from old vsx>d on sprayed tree$. 



Records. 


Trees. 


Sprayed. 

8,255 

2,922 

0.a589 

13 


Unsprayed. 


Lengrth of old wood, measured in inches, on sprayed and unsprayed trees. . . . 

Number of lateral shoots and spurs that pu.shed from old wood in 1893 

Number of lateral shoots and spurs per inch of old wood 


7,363 

2.300 

0.3124 


Gain in favor of sprayed trees per cent. . 









The above table shows that 13 per cent more buds had pushed into 
shoots and spurs on the spiwed trees, in the summer of 1893, than on 
the unsprayed trees. All represented new growth from old wood. 

The following table shows that the length of the new growth for the 
entire season of 1893 on the sprayed trees was 6.4 per cent more than 
that produced on the unsprayed trees. This wiis in spite of the facts 
that the unsprayed trees were so situated that growth could continue 
until frost and that they had not carried a crop of fruit as had the 
sprayed trees: 

Table 11. — (lain in length of neiv growth in favor of sprayed trees. 



I Trees. 

Records. , , - 

I Sprayed. Unsprayed. 



I^ength of old wood, measured in inches, on sprayed and unsprayed trees 8,255 I 7,3»^ 



Length of new branches 18, 174 | 16. 390 

I>ength of spurs, estimated at 2 inches per spur i 2,692 1, 100 

Total length of new growth in inches ' 20,866 ■ 17.490 

Inches of new growth per inch of old wood ■ 2. 527 2, 375 

Gain in new growth \n favor of sprayed trees per cent..! 6.4 



1 



COMPABATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 



95 



The number of leaf buds produced on the sprayed and unsprayed 
trees per lineal inch or foot of old wood did not greatly differ. There 
was, however, a gain of 1 per cent in favor of the sprayed trees, as 
shown below: 

Table 12. — Gain in number of leaf buds in favor of sprayed trees. 



Records. 



Length of old wood, measured in inches, on sprayed and unsprayed trees. . , 

Number of leaf buds 

Average number of leaf buds to inch of wood 

Gain in favor of sprayed trees per cent 



Trees. 
Sprayed. Unsprayed. 



8,255 
5,408 
0.654 

1 



7.363 
4,763 
0.647 



The tendency of the new growth to send out lateral branches and 
spurs was much more marked upon the sprayed than upon the 
unsprayed trees, the gain in this case being 109 per cent. This is a 
decided advantage, for the tree is thus enabled to bear a heavier and 
more equally distributed crop than where such laterals are few. 

Tablb 13. — (iain in number of lateral nhootj* arid sjmrMfrom. new vood on sprayed trees. 



Trees. 



Reconls. 



LenjTth of new wood, measured in inches, on sprayed and unsprayed trees. . 

Number of lateral shoots and spurs from new wood 

Number of lateral shoots and spurs per inch of new wood 

Gain in favor of sprayed trees per cent. 




A complete tabular presentation of the data from which the four 
preceding tables have been drawn will be found under the following 
heading. 



THE DEVELOPMENT OF NEW FRUIT BUDS AND FRUIT SPURS FOR THE 
YEAR FOLLOWING AN ATTACK OF CURL. 

In February, 1894, while the action of the sulphur sprays was being 
considered in the Riviera orchard, the question arose as to the rela- 
tive ability of sprayed and unsprayed trees to produce fruit buds and 
fruit spurs for the year following a severe attack of curl. Many trees 
in this orchard had been sprayed with the sulphur sprays in the 
winter of 1892-93 for the destruction of the San Jose scale {Aspidw- 
tuspemiciosus). The manner in which this work was done furnished 
an excellent opportunity to asceiiain the facts desired respecting the 
development of fruit buds. It was noted during the early part of the 
winter that individual trees, scattered through a 40-acre block of 4-year- 
old Crawfords Late, had become infested with San Jos6 scale. A 
careful examination of this part of the orchard was then made, and 
each tree found to be infested with the scale was marked for spraying. 



96 PEACH LEAF OURL: ITS KATURE AND TREATMENT. 

Later in the winter Mr. A. D. Cutts, one of the proprietors and the 
superintendent of the orchard, had these marked trees thoroughly 
sprayed with sulphur, lime, and salt, the formula used being as fol- 
lows: Sulphur 15 pounds, lime 30 pounds, salt 10 pounds, water 60 
gallons. 

While this spray was known to be effective against San Jos6 scale, 
it also proved very effective against curl, which developed seriously 
in the orchard in the spring of 1893. The result of the spraying was 
to produce a most striking effect. When the disease developed, the 
unsprayed trees, which represented the major portion of this 40-acre 
orchard, were almost wholly denuded of foliage and largely of fruit, 
while the sprayed trees, scattered through the block, were in full foliage 
and fruit. This orchard was selected as a very suitable place in which 
to study the relative thrift and number of fruit buds and spurs pro- 
duced on sprayed and unsprayed trees for the year following, and for 
this puipose 20 trees were selected from this block in February, 1894. 
Ten of these trees had been sprayed in the winter of 1892-93, and had 
thus escaped serious injury from curl in the spring of 1893, while 10 
of them had not been sprayed and had suffered considerably from the 
disease. These 20 trees were all Crawfords Late, 5 years old in the 
winter of 1893-94, and similar in other respects, the soil, situation, 
etc., being the same. 

The work of counting and grading buds upon these sprayed and 
unsprayed trees was begun about the middle of February, 1894, and 
continued for a week, an equal amount of time being given to each tree. 
To make all records as representative as possible of all portions of the 
trees studied, the limbs were measured and the buds counted and classi- 
fied upon different sides of each tree and upon both lower and upper 
limbs. In the selection and measurement of limbs, as well as in the 
counting and classification of the buds, an effort was made to correctly 
represent the conditions existing in all parts of each tree, and of all 
trees alike. After the selection of a limb for study, all wood grown 
prior to 1893 was measured and the length recorded. Following this 
all the shoots and spurs of 1893 growth, and arising from the old 
wood measured, were counted and the number set down. All these 
new shoots, with the exception of fruit spurs 4 inches or less in length, 
were then measured. Records were kept of the length of the new 
shoots, the number of well-developed fruit buds, the number of poorly 
developed fruit buds, and the number of leaf buds they bore. A 
lecord of the number of lateral shoots and fruit spurs from the growth 
of 1893 was also preserv^ed. The results of this work are brought 
together in the two tables which follow: 



COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 97 



>4« 



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1909a— No. 20- 



98 






PEACH LEAF CURL: ITS NATUBE AND TBEATMENT. 



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-(C^«i*<»C«3t^000»O 



CX)MPABATIVE DEVELOPMENT OF FBUIT BUDS AND SPURS. 99 

In the preceding tables, the number of shoots and spurs of 1893, 
which arose from wood of 1892 or earlier (old wood), as well as the 
length of the old wood itself, are classed under the general head of 
new growth from old wood. The measurements of the growth of 
1893, and the number of lateral shoots and fruit spurs, as well as the 
number of fruit and leaf buds the new growth produced, are classed 
under the head of new wood. The buds were counted in a uniform 
manner upon all growth measured, except the buds borne by fruit 
spurs, which are estimated at 3 buds per spur in the tabulated calcula- 
tions which follow. The fruit buds have been divided into two classes — 
well developed and poorly developed. 

In considering the information given in the preceding tables, only 
those facts having a direct bearing on the fruit buds of the sprayed 
and unsprayed trees will be taken up under this heading. Those 
relating to length of new growth, number of new shoots, and number 
of leaf buds have already been considered under the preceding head- 
ing of this chapter. 

The following digest from the general tables shows that 23,879 fruit 
buds of all kipds were produced by the new growth arising from 8,256 
linear inches of old wood on 10 sprayed trees in 1893 — an average of 
2.892 buds per inch of old wood. The average number of buds per 
inch of old wood on the 10 unsprayed trees, obtained in a similar man- 
ner, was 2.686. These figures show that the sprayed trees produced 
7 J per cent more fruit buds of all kinds in the summer of 1893 than 
were produced by the unsprayed trees. These were fruit buds for 
the crop of 1894, and upon trees bearing a full crop in 1893, while the 
contrasted unsprayed trees bore very little. 



Tablb 16. — GcUn in total number of fruit bads on sprayed trees. 




Records. 


Trees. 


Sprayed. 


Unsprayed. 


Length of old wood, measured in inches, on sprayed and unsprayed trees .... 
Total miinbpr nf fmit budi of all kind* 


8,255 

23,879 

2.892 

71 


7,363 
19,777 
2.686 


Average number of same to inch 


Gain in favor of sprayed trees per cent.. 









The percentage of gain in the gross number of fruit buds shown by 
the sprayed trees is considerable, but it represents only partially the 
advantages derived from the spray. Examinations of the unsprayed 
trees showed that a large percentage of the fruit buds they had pro- 
duced in 1893 were imperfect, many of them being so poorly developed 
that fruit could not be expected from them. The following table shows 
the avei'age number of imperfectly developed fruit buds on the sprayed 
trees to be 0.944 per linear inch of old wood, while on the unsprayed 
trees the average per inch of old wood was 1.249. This shows 32 per 
cent more imperfect fruit buds on the unsprayed than upon the sprayed 
trees at the close of the growing season of 1893. 



100 PEACH LEAF CUBL'. ITS NATURE AKD TREATMENT. 
Table 17. — Excess of imperfectly developed fruit buds on unsprayed trees. 



Records. 


Trees. 


Sprayed. 


Unsprayed. 


Length of old wood, meiurared In Inched, on sprayed and unsprayed trees.... 
Number of Imperfectlv developed fruit buds 


8,255 
7,792 
0.944 


7,3© 
9. 200 


Average number of imperfectly developed fruit buds to inch of wood 

In favor of unsprayed trees percent.. 


1.249 
32 









In comparing the number of well-developed fruit buds which were 
produced in 1893 by the sprayed and unsprayed trees, independent of 
the number of spur buds, it was learned that the number upon the 
sprayed trees was 20 per cent greater, as shown in the following table, 
than the number produced by the unsprayed trees. 

T.\BLB 18. — Gain in mdl'developed fruit hudSy exclusive of sjmrs, on sprayed over 

unsprayed trees. 



Records. 


Trees. 


Sprayed. ^ Unsprayed. 


Length of old wood, measured in inches, on sprayed and unsprayed trees 

Number of well-developed fiult buds, exclusive of spur buds 


8,255 
12,049 
L469 


7.963 
8,927 

1 919 


Average number of well-developed fruit buds to incn of wood 


Gain in favor of sprayed trees percent.. 


20 






Taking the aggregate of all well-developed fruit buds, including the 
spurs, at an average of 3 buds each, the sprayed trees make a still better 
showing when contrasted with the unsprayed. The average number of 
all well-developed buds on the sprayed trees was 1.949 per linear inch 
of old wood, and on the unsprayed" trees 1.437 per inch of old wood. 
This shows a gain of 35 per cent in well-developed fruit buds in favor 
of the sprayed trees. These facts are shown in tabular form as follows: 

Table 19. — Gain in spur buds and other well-developed fruit buds on sprayed over 

unsprayed trees. 



Reeords. 


TreesL 


Sprayed. 


tlnspraycd. 


Length of old wood, measured in Inches, on sprayed and unsprayed trees.... 
Aggregate of spur buds and of other well-developed fruit buds 


8,255 

16,087 

1.949 

35 


7.3© 
laftT? 


Average number of same to inch 


1.437 


Qain in favor of sprayed trees ' .per cent. . 









One of the most striking contrasts shown by the data obtained in 
these field studies is that existing between the number of fruit spurs 
and spur buds produced by the sprayed and unsprayed trees in 1893. 
There was a net gain in the number of fruit spurs and spur buds on 
the sprayed trees of 118 per cent above the number produced by the 
unsprayed trees, a fact that should certainly appeal directly to the 
business faculties of every grower of peaches. It should also be 
remembered that these sprayed trees had carried a crop while pro- 



OOMPABATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 101 

diieing these fruit spurs for the following j^ear, while the unsprayed 
trees had borne but few peaches. The facts here discussed are shown 
in the table that follows. 

Table 20. — Gain in number of spur buds on sprayed over unsprayed trees. 



Records. 




Lenffth of old wood, measnred in inches, on sprayed and unsprayed trees 

Total number of spun 

Number of spur buds, estimated at 3 buds per spur 

Average number of spurs per inch 

Average number of spur buds per Inch 

Gain in favor of sprayed trees per cent. . 



Besides comparing the number of fruit buds produced in 1893 by 
the sprayed and unsprayed trees, it is desirable to contrast the bud- 
producing abilities of the upper and lower portions of these trees. 
It is generally conceded as desirable that the crop of a peach tree should 
be borne as largely as possible upon the lower limbs, and anything 
tending to this result may prove of value. Peach leaf curl, being due 
to a fungous parasite, has a tendency to do more injury to the lower 
than to the upper portions of the trees affected. The atmospheric con- 
ditions are more favorable for the germination of spores and to fungous 
growth in the lower and more shaded portions of the tree, and the 
lower branches accumulate greater numbers of fungous spores than the 
upper branches. In the following table it is shown that the total number 
of fruit buds produced by the lower limbs of the sprayed trees was 7 
per cent greater than the number produced by the upper limbs, com- 
paring equal lengths of new wood in each case. On the unsprayed 
trees, however, the upper limbs produced 5 per cent more fruit buds 
per linear unit of new wood than the lower limbs. This shows a 
difference of 12 per cent in favor of the sprayed trees. The tabulated 
figures are as follows: 

Tablb 21. — Gain in total number offruU buds on lower limbs of sprayed trees over those 
of unsprayed trees, as compared wUh upper limbs of each, respectively. 



Records. 



Length of new wood, measured in inches, on upper limbs. 
Length of spurs, estimated at 2 inches per spur 



Trees. 



Sprayed. Unsprayed. 



Total length of new wood on upper limbs 

Length of new wood, measured in inches, on lower limbs. 
Length of spurs, estimated at 2 inches per spur , 



Total length of new wood on lower limbs. 



Total number of fruit buds on upper limbs 

Total number of fruit buds on lower limbs 

Average number of fruit buds per Inch on upper limbs 

Average number of fruit buds per inch on lower limbs 

Gain in favor of lower limbs on sprayed trees per cent. . 

Gain in favor of upper limbs on unsprayed trees do 

Difference in favor of sprayed trees do 



10,964 
1,358 



12,322 



7,210 
1,334 



8,544 



13,724 

10, 155 

1.114 

1.189 

7 



12 



9,770 
554 



10,324 



6,e20 
546 



7.166 



11,901 
7,876 

1.16;^ 

1.099 



102 



PEAOH LEAF CURL: ITS NATUBE ANn TREATMENT. 



By contrasting only the well-developed and spur fruit buds it 18 
learned that there was 14 per cent in the niunber of buds in favor of 
the lower, limbs on the sprayed trees and 4 per cent in favor of the 
upper limbs on the unsprayed trees. This showed a difference of 18 
per cent in favor of the lower limbs of the sprayed trees. The entire 
comparison is given in the table which follows: 

Table 22. — Gam in number of weUrdevdoped and gpur fruU buds on the lower Imbi of 
sprayed otter umprayed trees, as compared wUh upper limbs of each, respectivdy. 



Records. 


Trees. 


Sprayed. 


Unsprayed- 


liPTigth of new woo<^, nieftflim"e<l ^ti inc'he^ on upper lln^lw 


10, 9M 
1,358 


9.770 


Length ol spurs, estimated at 2 inches per spur 


'564 






Total length of new wood on upper limbs 


12,322 


10,324 






Length of new wood, m^usured in inches, on lower limbs 


7,210 
1,334 


6,63) 


Length of spurs, estimated at 2 Inches per spur.'. 


SS 






Total length of new wood on lower limbs 


8,544 


7,166 






Number of well -develop*^ uTid «pnT fmit bnds on iipper itTnbs 


8.975 
7,112 
0.728 
0.832 
14 


6,310 
4,237 


Number of same on lower limbs 


Average number of same per ^nch on upper limbs 


0.614 


Average number of twmo. per ineb on lower I1m>>8 


0.501 


Gain in favor of lower lim'bs on sprayed trees per cent. . 




Gain in favor of upper limbs on unspraved trees do 


4 


Difference ir favor of sprayed trees....'. do 


18 







CHAPTER VI. 

INFLUENCE OF SPRAYS ON THE FRUITING OF THE TREES. 
THINNING THE FRUIT OF SPRAYED TREES. 

The^eneral discussion of the spray work conducted in the Rio Bonito 
orchard will be found in Chapter IV, and it is therefore not necessary 
to review these matters here. As soon as growth was well started 
in this orchard in the spring of 1895, it became evident that the fruit 
would have to be thinned on a portion of the Lovell trees comprising 
the experiment block. The peaches were setting thickly on both 
spra^-ed and unsprayed trees, but as leaf curl developed, the young 
fruit upon the control trees began to fall, while that upon the sprayed 
trees remained firmly attached and grew rapidly. 

When the young peaches had reached the size of hickory nuts, and 
the pits were forming, the danger of dropping from curl had jmssed, 
and the thinning of fruit on overloaded trees was then undertaken. 
To enable the writer to make just comparisons of the merits of the 
various sprays in saving fruit, it became necessary to carefully record 
the amount and number of peaches thinned from all trees in the experi- 
ment block. Thinning fruit is an equalizing process, and to equalize 
the crop upon sprayed and unsprayed trees or upon trees treated with 
different sprays, would be to destroy the contrast in the amount of 
fruit arising from the use of different formulro. This would result in 
the loss of the very facts which it was hoped to obtain from the experi- 
ments, unless records of the fruit thinned off were preserved. For 
the preservation of such records the following plan was adopted; 
Canvas sheets of large size, commonly used in the harvest of the almond 
crop in the same orchard, were spread beneath the trees to be thinned. 
The young peaches were allowed to fall upon the canvas as picked, and 
the canvas was moved as necessary. • The fruit thus thinned was 
poured from the canvas into picking boxes beneath the tree from which 
it was thinned. By this plan the fruit thinned from each tree was 
kept by itself. After an experiment row of 10 trees had been thinned, 
the fruit picked from each tree was sepamtely weighed and the weight 
recorded. • From 3 trees of the row sufficient fruit was now taken to 
amount to 25 pounds. The peaches in this 25 pounds were then 
counted, the number entered with the other records of the row, and 
on ihis basis the average number of small peaches per pound for the 
row was determined. By multiplying the number of pounds of young 
peaches thinned from each tree by the average number of peaches 
per pound, as above obtained, the writer was able to determine quite 
accurately the number of peaches thinned from each tree of the row. 

103 



104 P£AOH LEAF OUBL: IT6 KATUBE AND TKEATMENT. 



When the work on one experiment row was completed, the fruit from 
a second row of 10 trees was gathered, weighed, and counted in like 
manner, and this process was followed for each row of the block which 
required thinning. 

From the field records thus gathered two tables have been carefully 
compiled, the first showing the actual weight of young peaches picked 
from each tree thinned in the block, and the second the computed 
number of peaches which these weights represent, as determined by 
the above-described method. 

Table 23. — Weight of peaches thinned from the sprayed Lovdl peach trees in the experi- 
menl block of the Rio Bonito orchard in the spring of 1895. (o) 



Row No. 


Actual weight In pounds of thlnni^ 
peaches from trees Nos. — 


Tnml 
Wilwht of 

m row. 


Number 

of 
peaches 

in 25 
pounds. 


Average 
number 

of 
peaches 

per 
pound. 


Total 

number 

of 




1. 


2. 


3. 


4. 


5. 


6. 


7. 


8. 
45 


9. 
50 


10. 
36 


peaches 
per row. 


1 


15 


161 


18 


88 


20i 


22* 


27 


PoundB. 


482 


19.28 


6.442 


2 




3 


27 


22 


16 


20 


22i 


21 


30* 


16* 


29 


16 


2i9* 


550 


22.00 


4,K5 


4 




5 






























6 


18 
17 


2 
25 


15 
11 


6 

7* 


15 

12 


3 
9* 


21* 
15 


6 
6 


19 
5* 


16* 

8* 


121 
117 


486 
484 


19.44 
19.36 


2,352 
2,265 


7 


8 




9 


36 

SO 


21 


15 
24 


13* 
10 


18* 
17 


25 
25 


36 
40 


6* 
19* 


6 
17 


^ 


185 
283* 


622 
466 


20.88 
18.64 


Am 


10 


11 




12 


31 

234 


13 
14* 


8 
2 


10 
2* 


6 

18 


16* 
13* 


1* 

7* 


19* 
2* 


't 


U 


^i* 


611 
496 


20.44 
19.80 


2,729 


13 


1,S41 


14 




16 


82 
20i 


44 
6 


27 
15 


31 
3i 


24 

9i 


40 
5 


45 
17 


23 
17* 


S* 


22 
13 


367* 
121 


628 
496 


21.12 
19.84 


7,762 


16 


2,401 


17 




18 


32 
24 


17 
36 


26 
29 


16 
16 


17 
26 


8 
14 


10 
13 


6 
11 


14 
7 


4 
12 


150 
186 


604 
486 


20.16 
19.44 


3,024 


19 


3,616 


20 




21 


68 
33 


48 
61 


26 
85 


28 
21 


48* 
85 


49 

68 


58 
41 


21 
22 


29* 
29 


61* 
60 


437* 
885 


484 
472 


19.36 K470 


22 


18.88 


7,269 


23 




24 






























25 


42 


20 


22 


18 


28 


21 


37 


38 


43 


61 


320 


449 


17.96 


5,747 


26 




27 


34 

18 


84 
21 


36 
32 


11 
29 


14 
31 


35 
33 


30 
34 


22 
30 


.21 
63 


23 
60 


259 
341 


495 
421 


19.80 
16.84 


5,128 


28 


5,742 


29 




S:..::..::.: 


65 


49 


42 


43 


60 


43 


41 


35 


70 


86 


524 


487 


19.48 


10,208 


31 




82 


31 
47 


15 
61 


18 
34 


20 
40 


22 
22 


18 
89 


27 
33 


8 
29 






i59 
881 


514 
483 


20.56 
19.82 


8,269 


83 


39 


47 


7,361 


84 




35 


62 
23 


63 
35 


23 
14 


"io" 


67 
11 


42 
SI 


46 
26 


57 
31 


54 

28 


62 
46 


466 
255 


522 

480 


20.88 
19.20 


9.790 


86 


4.896 


87 


.... ::. 




88 


16 
40 


6 
26 


6 
39 


8 


10 


22 
37 


26 
34 




17 
29 


15 
34 


25 
27 


150 
266 


553 
547 


22.12 
21.88 


8.318 


89 


5.820 


40 








41 


54 


52 


27 


24 


26 


12 


27 


8 


36 


28 


293 


506 


20.32 


5,963 


42 




43 






























44 


6 
25 


8 
28 


11 
21 


6 
11 


6 
22 












36 
196 


537 
504 


21.48 
20.16 


773 


45 


17 


20 


16 


27 


14 


3,951 


46.. V 




47 






























48 


7 


6 


3 


5 










8 


4 


33 


511 


20.44 


675 


49 . 












50 






























51 


15 


22 


8 


12 


11 


12 


12 


13 


18 


17 


140 


633 


21.32 


2,985 


52.. 




53 






























54 


30 


34 


44 


18 i 17 


27 


30 


21 


36 


17 


274 


608 


20.82 


5^568 


55 




66 


22 
21 


40 
85 


44 
16 


18 
20 


17 
11 


27 
19 


30 
20 


21 
29 


36 
32 


17 
37 


272 
240 


520 
647 


20.80 
21.88 


5,658 


57 


5,251 


58 



































o For plat of orchard see p. 69; for .sprays applied see p. 78. 



THINNINa THE FRUIT OF 8PBATED TREES. 



105 



By referring to the above table it will be seen that only those rows 
which were sprayed in the spring of 1896 were thinned, and that a 
portion of these required but little thinning. The reasons for this lie 
in the severe action of the disease upon the unsprayed rows and those 
sprayed with weak or unsatisfactory sprays, in which cases the fruit 
fell from disease. The table shows the weight of thinned peaches per 
tree, the total weight of peaches thinned from the row, the number 
of peaches contained in 25 pounds, the average number of peaches per 
pound, and the total number of peaches thinned from the row. 

In the table which follows the pounds have been reduced to show 
the number of peaches, the reduction being made according to the 
method already described. Ciomparison of the total number of peaches 
thinned from the separate rows, as given in the two tables, will show 
slight variations in the units column in several cases. These varia- 
tions arise from the gain or loss in fractions resulting from the use 
of the diflPerent methods which it was necessary to employ in obtain- 
ing the figures shown in the two tables. 

Tablk 24. — Number of peaches ikirmed from the gprayed LoveU peach trees in the experi- 
ment block of the Rio Benito orchard in the spring of 1896. \a) 



Row 




Number of peaches thinned from sprayed trees No& 


- • 




Total 


No. 


1. 


2. 


8. 


4, 


6. 


6. 


7. 


8. 


9 


10. 




1 


289 


318 


847 


636 


390 


434 


521 


868 


964 


675 


5,442 


2 . 




3 


594 


484 


830 


440 


496 


462 


671 


368 


638 


352 


4,829 


4.. 


5 












:::::::::::::::: 


::::::::::::::: 







6 


SSO 
S29 


89 

484 


292 
213 


ii7 

146 


292 

232 


58 
184 


418 
290 


97 
116 


369 
106 


321 
165 


2,353 


7 


2,264 


8 


9 


7S2 
569 


438 
669 


313 
447 


282 
186 


386 
317 


522 
466 


762 
746 


136 
363 


125 
317 


157 
382 


3,863 
4,852 


10 


11 




12 


684 
466 


266 

287 


61 
40 


204 
60 


i23 
356 


837 
267 


81 
148 


899 
60 


215 
69 


460 
109 


2,780 
1,842 


13 


14 


15 


1,732 
407 


929 
119 


670 
298 


655 
69 


507 
188 


846 
99 


960 
837 


486 
847 


623 
278 


465 
258 


7,702 
2,400 


16 


17 


18 


646 

467 


843 
680 


524 
664 


823 
311 


343 
486 


161 
272 


202 
258 


121 
214 


282 
136 


81 
233 


3,025 
3,616 


19 


20 


21 


1,816 
623 


929 
968 


608 

661 


542 
396 


989 
661 


949 
1,096 


1,123 
774 


407 
415 


671 
648 


1,191 
1,183 


8,470 
7.269 


22 


23 


24 
























25 


754 


859 


395 


823 


608 


877 


665 


682 


772 


916 


5,746 


26 


27 


673 
308 


673 
354 


698 
539 


218 
488 


277 
522 


698 
666 


694 
573 


436 
606 


416 
1,061 


455 
842 


5,128 
5,748 


28 


29 


ao 


1,071 


966 


818 


838 


1,169 


838 


799 


682 


1,864 


1,675 


10,209 


31 


32 


637 
908 


806 
966 


370 
657 


411 
778 


452 
425 


370 
763 


555 
638 


164 
560 






8,267 
7,360 


83 


753 


906 


34 


85 


1,295 
442 


1,315 
672 


480 
269 


**'"i92* 


1,190 
211 


877 
695 


960 
499 


1,190 
596 


1,128 
538 


1,295 
883 


9,730 

4,896 


36 


37 


88 


882 

875 


183 
569 


133 
863 


177 


221 


487 
810 


575 
744 


376 
685 


832 
744 


553 
591 


8.819 
5,821 


39 


40 






41 


1,097 


1,067 


549 


488 


628 


244 


549 


163 


711 


569 


6,955 


c ;;:. 



a For plat ol orchard see p. 69; for sprays applied see p. 73. 



106 



PEACH LEAF CURL: ITS NATUBE AND TBEATMENT. 



Table 24. — Number of peaches ikirmed from the sprayed Lovell peach trees in the erperi- 
ment block of the Rio BonUo orchard in the spring of 1896 — (Continued. 



Row 




Number of peaches thinned from sprayed trees Noa 


- 




Total 


No. 


1. 


2. 


3 ' 4. ' 5. 6. 


7. 


8. 


9. 


10. 




43 






1 










44 


129 
501 


172 
464 


236 id? . 129 
423 222 1 444 






, 


773 


45 


• aLV 


JUS 


323 


544 


282 


8,952 


46 






47 




















48 


14S 


123 


61 1 102 










164 


82 


675 


49 











60 






















51 


820 


469 1 i7i 256 


2S5 


256 


75^ 


277 


384 


362 


2.986 


52 




58 


1 


1 














54 


610 


691 


894 866 


845 


549 


610 


497 


732 


345 


5.569 


55 




66 


458 
459 


832 
766 


9i5 i 374 
350 1 438 


354 

241 


562 
416 


624 1 437 

4SR eS& 


749 
700 


354 
810 


5,659 
5 253 


57 


58 










1 , 1 ' 





GATHERING FRUIT OF SPRAYED AND UNSPBAYED TREES. 

The fruit of the Lovell variety ripened rapidly in the Saci-amento 
Valley after the middle of August, 1895. On the experiment trees a 
large portion of the crop was suflSciently matured for shipment to the 
canneries by the 20th of that month. By that date the plans had 
been made for the gathering of the crop, which work was completed 
before the 1st of September. The fruit was gathered at two pick- 
ings, the second picking beginning shortly after the close of the first. 
The crop was marketed in three ways: 

(1) All perfect peaches above a standard size adopted by the (tan- 
neries, and sufficiently firm to bear shipment ])y rail from Biggs to 
Oakland, Cal., a distance of about 140 miles, were sold to a tirai at 
the latter point at $30.80 per ton, f. o. b. ears at Biggs. This fruit 
comprised about 54 per cent of the yield of the experiment block. 

(2) All perfect peaches of canning size which were too mature to 
bear the delay and long shipment by rail to Oakland were shipped to 
a cannery at Chico, Cal., a distance of about 30 miles. This fruit 
brought $30 per ton, f. o. b. cars at Biggs. It comprised about 30 
per cent of the yield of the experiment block. 

(3) Such fruit as was below cannery size, overmature, or imperfect 
in any respect was sent to the drying ground to be dried. In the cal- 
culations of the present work this fruit is valued at three-fourths of a 
cent per pound in the green state. This is less than the equivalent of 
dried fruit was worth at the time of curing after allowing for the cost 
of drying. The fruit sent to the drying ground represented about 16 
per cent of the yield of the experiment block. 

The work of gathering, weighing, and grading the crop of the 
experiment rows was carefully systematized. As before shown, the 
experiment block was 20 trees wide from east to west, and through 
the center from north to south a driveway wa« made, so that the rows 



xjn:-. -■-•■■■ 



Bull. 20. Div. Veg Phys. & Path.. U. S. Dept of Agriculture. 



Plate X. 




DESCRIPTION OF PLATE X. 

Experiments at Biggs, Cal. (Bordeaux mixture.) Fruit gathered from row 15 of 
the experiment hlock of the Rio Bonito orchard in the summer of 1 895. The formula 
for the spray used on this row was 6 pounds copper sulphate, 15 pounds quicklime, 
45 gallons of w^ater. The 10 trees of the row matured 4,351 pounds of fine peaches, 
which are shown in the picking boxes. The trees of the adjoining unsprayed row. 
No. 14, bore only 928 pounds. The value of the fruit matiired on row 15 was 160.02; 
on row 14 it was $13.24, a net gain from spraying 10 trees of $46 after allowing for 
the cost of spraying. This gain resulted after more than one-third of the peaches 
had been thinned from the sprayed row, while none had been thinned from row 14. 
The total number of peaches set by the trees of row 15 was 21,272, by those of row 

14 it was 2,855. The comparative average net gain shown by the spray used on row 

15 was 619 per cent 



GATHERING FRUIT OF SPRAYED AND tJNSPRAYED TREES. 107 

on either side were 10 trees long from east to west. One picker was 
aligned to each tree of the row across the block, thus making ten 
pickers on each side of the drive, or twenty in all, and an extra man was 
assigned as superintendent of the twenty pickers, to see that all instruc- 
tions were carefully carried out. Every man was instructed to leave 
all fruit he picked beneath the tree from which it was gathered, pick- 
ing boxes having been previously distributed for this purpose. 

The work of picking began at the south end of the experiment 
block. When the fruit which was suflScientfy matured had been 
gathered and placed in the boxes beneath a tree, the picker proceeded 
to the next tree north, thus following the same north-and-south row 
until he had passed entirely through the block, and when each man 
had thus completed his north-and-south row the entire block had been 
picked over, the fruit being beneath the trees from which it came. 
The first and second pickings were conducted in this manner, but the 
second was not begun until after the first was completed and the 
gathered fruit had been removed from beneath the trees. 

The process of collecting the fruit of the first picking began as soon 
as the pickers had completed an east-and-west row and had proceeded 
to the next row toward the north. Four men were employed to collect 
and weigh the peaches— two to collect the fruit in the orchard and 
two to weigh, count, and keep the records. The fruit was brought 
from the east and from the west to the central driveway on a low plat- 
form wagon drawn by one horse. The boxes of fruit gathered from 
the 10 trees of each experiment row were piled at the side of the 
driveway, close to the last tree of the row. The boxes of fruit from 
each tree were also distinguished by means of cards bearing the 
number of the tree from under which the boxes were taken (PI. X). 

The weighing began as soon as the fruit from the 10 trees of an 
experiment row had been piled at the side of the central drive. Plat- 
form scales were placed on a level base close to the fruit boxes, and 
the fruit from each tree of the row was weighed separately. The gross 
weight was recorded for each tree, as well as the number of picking 
>x)xes. The average weight of the picking boxes used was afterwards 
carefully determined, and from these data the net weight of fruit was 
ascertained and tabulated for each tree of each row of the block. 
After the weight of fruit for each tree of an experiment row was thus 
learned, 100 pounds of peaches were weighed out from typical boxes 
of several trees of the row. The number of peaches in this 100 poimds 
of fruit was then ascertained by counting, the number being re<'orded 
with the other data for the row. The fruit of all the experiment rows 
was weighed and the average size of the peaches determined })y count- 
ing, as here indicated. 

Following close after the weighers came five or six sorters. These 
men graded the fruit, according to the requirements already outlined, 
into three classes — one for an Oakland <»anner3% one for a Chico can- 
nery, and a third class for diying. These three chisses constituted 



108 



PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



really but two qualities of fruit — a first quality for canning, and h 
second quality for drying. After the fruit of a row was graded a 
careful count of the number of picking boxes of each class of fruit 
was made, and the numbers recorded. From these figures were deter- 
mined the proportions of the total yield of the row which belonged to 
the different classes of fruit. The same process of picking, collecting, 
weighing, counting, grading, and recording was followed for the 
second picking as for the first. 

In the following table are shown the net weights of fruit gathered 
at the first picking from each tree of the entire block of 58 experi- 
ment rows, with the total weight for each row. 

Table 25. — Weight of peaches of first picking from the LoveU trees of the experiment 
block of the Rio Bonito orduxrd, gathered in the fall of 1895. 



Row No. 



Weight of fruit, in pounds, gathered at first 
picking from trees Nos.— 



10. 



Total net 
weight 
of fruit 
in row. 



Number Average 
of trees weight 
in row. I per tree. 



1 
2 
8 
4. 

5. 

6. 

7, 

8. 

9. 
10. 
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26, 
27. 
28. 
29. 
SO. 
31. 
32. 
83. 
34. 
35. 
36. 
87. 
88. 
89. 
40. 
41. 
42. 
48. 
44. 
45. 
46. 
47. 
48. 
49. 
50. 
51. 
62. 
53. 
54. 
55. 
56. 
57 
58. 



259 
216 

65 
229 
232 
121 
492 
157 
133 
383 
261 

61 
426 

:»4 

22 

65 
380 

70 
345 
313 

29 
188 

71 
177 
283 

87 
393 
298 

80 
246 
283 
135 
412 
287 

92 
171 
328 

52 
130 

97 

77 
250 
264 
162 
140 
337 

93 



109 

89 

121 

I 71 

74 
I 75 
I 267 

29 

I 271 

I 276 

I 71 

166 

192 

55 
357 
112 

56 
241 
324 

99 
438 
624 

80 

50 
236 
121 
400 
386 

36 
198 
152 
139 
271 
128 
291 
213 

96 

91 
154 
123 
268 
176 

85 
150 
220 

87 
149 
155 

91 
TJM 
330 



I 207 

137 

' 147 

I 31 
56 

, 175 

I 169 
U 

I 202 



65 
274 
128 
108 
246 
296 
64 
189 
137 
61 
214 
277 
126 
68 I 62 
457 449 
166 97 
361 I 314 
400 I 277 
64 99 



118 
111 
179 
120 
140 
97 
183 
151 
248 
240 
107 
154 
203 
114 
474 
216 
119 
233 
364 
27 
481 
556 
95 
52 
424 
62 
425 
489 
90 
219 
179 
218 
373 
148 
491 
354 
84 
234 
384 
49 

430 200 

179 145 

32 45 

70 164 

510 ' 324 

I 90 56 

I 228 i 116 

, 117 1 79 

78 60 

107 120 

I 247 207 

I 147 , 84 

I 54 I 63 

311 421 

' 45 , 153 

I 294 181 

' 2.*>4 282 

, 86 ' 195 



147 

54 
167 

67 

78 
228 
181 

39 
218 
219 

83 
304 
161 

47 
474 
298 

88 
341 
331 

32 
498 
544 

62 

43 
426 

19 
166 
400 

60 
323 
149 
315 
250 
107 
563 
188 
198 
273 



90 
289 

87 
159 
212 
180 
115 
I 233 
I 249 
114 
247 
209 

91 
573 
451 

58 
296 
245 

32 
617 
469 

75 

48 
566 
109 
513 



296 
111 
209 
428 

79 
597 
365 
127 
284 
439 I 

53 I 
410 
223 1 

97 

139 ! 
413 

42 I 
105 
182 I 

86 ' 
118 , 
251 I 

25 , 

44| 
392 
I 137 I 

244 
' 313 

I «» 



190 
140 
241 
74 
100 
212 



234 
297 
41 
168 
187 
114 
340 



56 
459 

96 
290 
879 

95 
318 
199 
298 
429 
133 
590 
365 
163 
341 
461 

47 

8a5 

119 

28 
231 
363 

73 
169 
142 

41 
229 
193 

63 

73 
408 

67 

381 ^ 
399 1 

40 



180 
166 
200 

69 

64 
237 
169 

63 
153 
467 
166 
240 
145 

47 
453 
291 

44 
288 
189 

23 
343 
332 
105 

24 
285 

49 
206 
421 

25 
236 
215 
299 
387 
127 
424 
315 
138 
274 
339 
114 
314 
299 

52 
182 
326 
103 
190 
151 

74 
295 
299 

94 

90 
2»4 

92 

268 ; 504 
327 471 

51 52 



Pounds, 
1,570 
1,007 
1,687 

741 

810 
1,813 
1,708 

568 
2,101 
2,553 

883 
1,957 
1,676 

844 
4,227 
2,348 

715 
2,609 
2,594 

674 
4,307 
4,276 

672 

'547 
3,771 

658 
3,116 
4,126 

576 
2,615 
1,552 
2,282 
8,189 
1,102 
4,084 
2,681 
1,125 
2,452 
2,804 

986 
8,464 
1,924 

655 
1,742 
8,288 

727 
1,572 
1,347 

696 
2,114 
2,641 
1,067 

753 
8,797 
1.024 
8,298 
8,412 



10 

9.5 
10 

9.8 
10 
10 
10 
10 
10 
10 
10 

9.4 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.8 
10 

8.6 
10 
10 
10 

8 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.6 
10 
10 

9.5 
10 
10 



PwndM, 
157 
106 
168.7 

75.6 

81 

ISl.S 
170.8 

56. H 
210.1 
255.3 

83.3 
206.2 
167.6 

84.4 
422.7 
234.8 

71.5 
260.9 
259.4 

57.4 
43a 7 
427.5 

67.2 

54.7 
377.1 

65.8 
811.6 
412.6 

67.6 
261.5 
155.2 
228.2 
825.4 
110.2 
469 
268.1 
112.5 
245.2 
350.^ 

93.6 
S46.4 
192.4 

65.5 
174.2 
328.?* 

72.7 
157.2 
134.7 

69.5 
211.4 
264.1 
lOd.7 

78.4 
ST9.7 
102.4 
347.1 
341.2 

85.9 



GATHEEINQ FBUIT OF SPRAYED AND UNSPBAYED TREES. 109 

At the side of the total column in the preceding table is given a col- 
umn showing the number of trees in each row. The total amount of 
f niit gathered at the first picking from each row has been divided by 
the number of trees in the row, giving the average amount of fruit 
picked per tree for each row of the block. This average is shown in 
the right-hand column. 

In the table which follows is given the net weight of fruit gathered 
at the second picking from each tree of the block not picked clean at 
the first picking. 

Tablb 26. — Weight of peaches of second picking from the LoveU trees of the experiment 
block of ihe^Rio Bonito orchard, gathered in the fall of 1896. 



Row No. 


Weight of fruit, in pounds, gathered at second 
picking from trees Noe.— 


Total net 
weight 
of fruit 
in row. 


Number 
of trees 
in row. 


Average 
weight 




1, 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


per tree. 


1 


64 
25 
79 
12 


121 

6 

124 


41 
12 
38 
44 
18 
60 
99 

8 
26 
25 

5 


133 
99 

151 
39 
90 
32 
28 


112 


127 


132 
25 
26 
4 


112 
41 

162 
26 


242 
67 
108 
34 
23 
38 
80 
18 
26 
63 
18 
15 
14 
12 
22 
6 
7 

14 
13 
5 
53 
8 
2 
4 

"T 

16 
89 


168 
68 

187 
51 
37 
43 

140 
20 
66 
90 
31 
54 
55 
18 
38 
58 
9 
80 
17 
18 
83 
80 
12 
13 
70 

"51' 

62 

5 

385 

148 

210 

218 

57 

80 

53 

44 

•37 

29 

23 

100 

25 

22 

32 

33 

14 

"'h' 

5 
10 


Pownd*. 

1,242 

343 

1,109 

265 

236 

452 

517 

107 

857 

415 

136 

146 

184 

84 

124 

152 

43 

91 

118 

74 

136 

146 

40 

52 

217 

14 

100 

137 

26 

2,526 

786 

1,136 

1,082 

222 

840 

893 

245 

424 

439 

173 

566 

198 

84 

265 

208 

47 

102 

92 

61 

55 

91 

64 

47 

266 

75 

92 

91 

43 


10 

9.5 
10 

9.8 
10 
10 
10 
10 
10 
10 
10 

9.4 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.8 
10 

8.6 
10 
10 
10 

8 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 
10 

9.6 
10 
10 

9.5 
10 
10 


PtmwU. 
124. 2 


2 


36.1 


3 


151 

"ei' 

83 
120 


88 
45 
12 
20 


110.9 


4 


26 


5. 


28 6 


6 


49 
60 
11 
31 
29 

7 
11 
2? 
19 
33 
20 
11 
28 
10 

7 
12 
11 

6 

6 
23 

5 


8 
9 
10 
16 
10 
5 
12 
18 
6 
6 
11 

"io' 

6 
3 

8 
28 


109 

31 

27 

82 

76 

31 

41 

85 

8 

7 

11 

6 


10 
"13' 

"28* 

"is' 

"28' 


45.2 


7 


61.7 


8 


10.7 


9 


14 
16 
11 


96 
19 


"87* 


85.7 


10 


41 5 


11 


86.6 


12 




18 


15 5 


13 


21 

"is' 

18 
11 

'is' 

15 
18 
19 


'"% 


23 


18.4 


14 


8 4 


15. 






12 4 


16 








15 2 


17 








4.3 


18 


14 
'5' 






9 1 


19 


81 

22 




14 

4 
12 


11 


11.8 


20 


7.4 


21 


13 6 


2J 






14 6 


23 


18 






7 

5 

• 24 

6 


"is' 

29 

'.'ie' 


4 


24 


6 
11 








5 2 


25 


28 




82 




21 7 


26 


1 4 


27 


9 

19 

3 

191 

107 

145 

192 

62 

251 

75 

81 

62 

142 

82 

103 

78 

"is' 

16 
12 
11 


8 








10 


28 






17 
5 
201 
27 
10 
3 






13 7 


29 




1 
295 
33 
160 
212 
62 
63 
119 

"so' 

108 

so 

149 
23 
9 
60 
18 


'267* 
85 
81 

126 


12 
199 
103 
113 
104 






2.6 


30 


270 
40 
20O 
113 

8 
89 

6 
12 
23 
26 
15 
47 
21 

7 
16 
19 

8 
10 
11 

5 

4 
12 


138 
27 

107 
14 
18 
35 

""s' 

24 
23 


141 
23 
30 
19 
6 
94 
72 
24 

"i4* 


439 
193 
90 
81 
' 14 
146 

"si" 

30 


252 6 


31 


78 6 


32 


113.6 


38 


110 4 


34 


22 2 


36 


"42* 
55 
77 


30 
11 
44 
63 


52 
15 
27 
27 
67 
25 
62 
38 
13 
41 
17 
7 
32 
15 
13 
10 
13 
12 
12 
65 
18 
17 
30 


97 6 


36 


89.3 


87 


24 5 


38 


42 4 


39 


54 8 


40 


48 
48 




17 3 


41 


15 
13 
7 
15 
17 
2 
6 

" '9' 

"is' 
"io' 


21 
5 

12 
9 

26 
9 
9 

12 
2 

10 

10 
3 
9 

18 

26 


21 

"si* 

33 

"25' 
6 
5 
11 
15 
6 


56.6 
19 8 


42 


43 


14 
43 


"24" 


8.4 
26 5 


44 


45 


20 3 


46 \, 


4 7 


47 


9 

18 
17 






10 2 


48 ::*. 


30 
10 
14 
25 
6 
9 
17 
16 
27 


-•%•• 


9 2 


49 , 


6.1 
5 5 


SO :/: ■ 


51 




11 
9 
10 
92 
11 
32 


9.1 
6 4 


52 ::**•• 


58 ;:: 


7 
19 


"21 
4 

"is' 


4 9 


54 


34 




26 6 


66 


7 5 


56 


3 

1 


13 

"ii" 


"ie" 


9 7 


57 :: 


"26" 


26 
6 


1 


58 








4.8 

















110 



PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



The total yield of the trees and rows of the experiment block is 
shown in the following table, which was compiled from the preceding 
records of fruit gathered at the first and second pickings. 

Table 27. — Total weiglit of pe<u:hes of firgt and second pickings gathered from the Lovdl. 
trees of the experiment block of the Rio Bomto orchard in the fall of 1895. (a) 



Row No. 



1.. 

2., 

3.. 

4.. 

5.. 

6.. 

7.. 

8.. 

9.. 
10.. 
11.. 
12.. 
13.. 
14.. 
15.. 
16-. 
17. 
1«.. 
19., 
20.. 
21. 
22. 
23.. 
24., 
25.. 
26.. 
27.. 
28.. 
29., 
30., 
31. 



34.. 
35.. 
36.. 
37.. 
38.. 
39.. 
40., 
41.. 
42.. 
43.. 
44.. 
45.. 
46.. 
47.. 
48.. 
49.. 
50.. 
51. 
52., 
53., 
54. 
55., 
56., 
57., 
58.. 



Total weight in pounds of fruit gathered at first and second pickings from trees Nos.- 



1. 



2. 



129 
76 
243 
81 
42 
239 
148 
104 
290 
245 
72 
240 
255 
140 
525 
177 
144 
406 
261 



28 , 

71 
403 I 

75 

345 I 
313 ; 

29 

458 ' 
111 , 
377 
396 

95 

482 I 
304 

92 I 
269 
309 
150 
459 
308 



280 

95 

245 

71 

74 

83 

276 

39 

287 

285 

76 

178 

205 

61 

363 

123 

56 

251 

330 

102 

446 

552 

80 

56 

247 

121 

409 

404 

39 

389 

259 

284 

463 

190 

542 

288 

127 

153 

296 

155 

371 

249 

85 



187 


168 


347 


236 


55 


99 


140 


160 


108 


155 


82 


91 


2M 


284 


276 


830 


162 


99 


147 


68 


356 


478 


93 


170 


339 


361 


331 


418 


91 


64 



568 




'I 



s. 


7. 


245 


894 


111 


116 


267 


315 


165 


91 


152 


159 


U7 


321 


183 


211 


151 


142 


248 


815 


827 


825 


107 


145 


167 


288 


203 


244 


114 


99 


474 


580 


216 


462 


U9 


63 


233 


296 


364 


259 


27 


86 


431 


629 


556 


469 


95 


82 


52 


53 


424 


589 


62 


115 


425 


518 


489 


489 


102 


33 


418 


434 


282 


138 


331 


316 


477 


442 


148 


92 


543 


632 


369 


865 


111 


135 


261 


308 


451 


462 


74 


53 


262 


425 


188 


236 


58 


104 


205 


154 


341 


430 


63 


44 


148 


111 


94 


182 


73 


95 


180 


118 


220 


251 


96 


43 


75 


44 


476 


402 


171 


137 


198 


244 


812 


313 


195 


109 



8. 



302 
181 
408 
100 
100 
222 
222 
52 
234 
297 



187 
127 
840 



144 
212 

22 
252 
324 

88 

74 
488 

96 
306 
379 

95 
459 
222 
S28 
448 
189 
684 
437 
187 
341 
475 

47 
826 
124 

40 
240 
889 

82 
178 
154 

48 
239 
203 

66 

82 
426 

98 
881 
425 

52 



202 

28 , 
396 I 
840 
107 

28 
285 

52 
222 
460 

25 
675 
406 



141 
570 
815 
188 
805 
369 
114 
335 
299 

52 
213 
859 
108 
215 
157 

79 
806 
814 
100 

90 



281 

827 

62 



9. 


10. 


422 


808 


232 


116 


808 


236 


108 


85 


87 


108 


275 


247 


199 


250 


71 


36 


179 


187 


530 


259 


184 


101 


255 


201 


* 159 


132 


59 


50 


475 


311 


297 


256 


51 
.<tfK2 


30 
149 



Total. 



197 

77 
460 
426 

65 
109 
500 

45 
268 
441 

51 
727 
363 
458 
426 
208 I 
528 , 
863 
187 
440 
44S I 
245 I 
500 
236 
106 
258 
319 

67 
228 
181 

32 
356 
815 
142 

54 
285 

94 
504 
487 



2,812 
1,350 
2,796 

99ii 
1,046 
2,265 
2.225 

67J> 
2,4.'* 
2,968 

9r.9 
2,103 
1,860 

928 
4. .351 
2,501) 

7.i8 
2,700 
2,712 

W» 
4,443 
4,421 

712 

599 
3,»« 

672 
8,216 
4,263 

602 
5,141 
2,338 
8,418 
4,271 
1,324 
4.K74 
8,074 
1.370 
2,876 
8,243 
1,109 
4.030 
2,1-22 

739 
2,007 
3*491 

774 
1,674 
1,439 

756 
2,169 
2,732 
1,131 

800 
4,063 
1,099 
3.390 
3.50S 
902 



a For plat of orchard see p. 69; for spra}!) applied see p. 78. 

As already said, after the weight of fruit for each tree of a row had 
been ascertained and recorded, the number of peaches in 100 pounds 
of this fruit was determined by counting. From several picking 
boxes of fruit, coming from different trees of the row, was weighed 
out 100 pounds of peaches fairly representing the fruit of the row. 
The peaches of this 100 pounds were then carefully counted and the 
number recorded. This was done both foi the first and second pick- 



GATHERING FRUIT OF SPRAYED AND UN8PRAYED TREES. Ill 



ings and for the sprayed and unsprayed rows. Where less than 100 
pounds of fruit was gathered the number of peaches per 100 pounds 
was determined by counting a less weight of fruit, usually 50 pounds. 
The following table gives the results of this work for both first and 
second pickings: 

Table 28. — Number of peaches per 100 pouiuh; rveight of fruit gathered; and number of 
peaches thinned^ gath^redf and set by the trees of ea^ih row in the experiment block of the Rio 
Bonito orchard in 1895. (a) 



I Number of ' 
peaches in 100 
' iwunds. 



s 


E 


^ 


S 


1 


259 


2 


296 


3 


286 


4 


300 


h 


303 


6 


278 


7 


280 


s 


282 


9 


288 


10 


282 


11 


292 


12 


283 


13 


293 


14 


306 


15 


309 


16 


294 


17 


296 


18 


300 


19 


289 


20 


290 


21 


308 


22....:. 


320 


23 


296 


24 


292 


25 


284 


26 


280 


27 


276 


28 


291 


29 


277 


30 


292 


31 


304 


32 


294 


33 


291 


34 


290 


35 


825 


36 


285 


37 


282 


38 


282 


39 


289 


40 


300 


41 


284 


42 


303 


43 


293 


44 


309 


i5 


309 


46 


303 


47 


289 


48 


308 


49 


292 


50 


287 


61 


299 


52 


308 


58 


300 


54 


306 


55 


295 


56 


296 


57 


298 


58 


282 



I 



i 



317 
810 



324 

328 

322 

323 

313 

316 

321 

812 

6324 

362 

317 

6327 

6339 

6340 

6332 

6314 

6362 

6344 

6356 

6368 

6354 

6360 

6370 

6360 

813 

326 

311 

885 

330 

845 

332 

330 

330 

828 

312 

339 

835 

6804 

337 

346 

6880 

356 

6824 

6312 

6866 

6356 

6336 

6325 

6352 

6334 

6384 

6370 

6360 



lV>undfl of 
fruit — 



t 



1,570 
1.007 
1,687 

741 

810 
1,813 
1,708 

568 
2,101 
2,553 

833 
1,957 
1,676 

844 
4,227 
2,348 

715 
2,609 
2,594 

574 
4,307 
4,275 

672 

547 
3,771 

658 
8,116 
4,126 

576 
2,615 
1,552 
2,282 
8,189 
1,102 
4,084 
2,681 
1,125 
2,452 
2,804 

936 
8,464 
1,924 

655 
1,742 
3,288 

727 
1,572 
1,347 

695 
2,114 
2,641 
1,067 

753 
3,797 
1,024 
3,298 
3,412 

859 



I 



1,242 

348 

1,109 

255 

236 

452 

517 

107 

357 

415 

136 

146 

184 

84 

124 

162 

43 

91 

118 

74 

136 

146 

40 

52 

217 

14 

100 

137 

26 

2,626 

786 

1,136 

1,082 

222 

840 

393 

245 

424 

439 

173 

566 

198 

84 

265 

208 

47 

102 

92 

61 

56 

91 

64 

47 

266 

75 

92 

91 

43 



Number of 

peaJ^hcsfiTfith- 

t:ru4ut— 



4,366 
2,971 
4,808 
2,223 
2,464 
5, (MO 
4,782 
1,602 
6,051 
7,199 
2,432 
5,538 
4,911 
2,683 

13,061 
6,903 
2, 116 
7,827 
7,496 
1,666 

13,266 

13,680 
1,989 
1,597 

10,710 
1,842 
8,600 

12,006 
1,596 
7,686 
4,718 
6,709 
9,280 
3,196 

18,111 
7,641 
3,173 
6,915 
8,104 
2,808 
9,838 
5.830 
1,919 
6,383 

10,160 
2,203 
4,543 
4, 149 
2,029 
6,067 
7,897 
3,233 
2,259 

11,619 
3,021 
9,66:? 

10, ir.8 
2.422 



I 



3,577 

1,0K7 

8,438 

854 

762 

1,464 

l,68f. 

8^15 

1,153 

1,299 

430 

469 

574 

272 

449 

482 

140 

308 

401 

246 

427 

629 

138 

185 

799 

50 

860 

507 

94 

7,906 

2,562 

8,533 

3,625 

733 

2,898 

1,305 

809 

1,399 

1,440 

540 

1,919 

663 

255 

893 

702 

155 

363 

298 

190 

201 

324 

215 

15:3 

936 

260 

35:3 

3:37 

155 



Niimbtr of 
juaAoht:*— 



pr 

7,643 
4,a'>8 
8,246 
3,077 
3,216 
6.504 
6,467 
1,947 
7,204 
8,498 
2,862 
6,007 
5,485 
2,856 

13,610 
7,386 
2,256 
8,136 
7,897 
1,911 

13.693 

14,209 
2,127 
1,782 

11,509 
1,892 
8.960 

12,618 
1,690 

15.642 
7,280 

10,242 

12,905 
8,929 

16,009 
8,946 
3,982 
8,314 
9,544 
3,348 

11,757 
6,493 
2, 174 
6,276 

10,862 
2,858 
4,906 
4,447 
2,219 
6,268 
8,221 
3,448 
2,412 

12,555 
3,271 

10.016 

10, mvs 

2,577 









5,442 
4,829" 



2,352 
2,265 



3,863 
4,352 



2,730 
1,841 



7,762 
2,401 



3,024 
3,616 



8,470 
7,269 



6,747 



6,128 
6,742 



10,208 



8,269 
7,360 



9,730 
4,896 



8,318 
5,821 



5,953 



773 
3,961 



675 



2,985 



5,568 



5,659 
5,251 



18,086 
4,068 

13,076 
3,077 
3,216 
8,856 
8,732 
1,947 

11,067 

12,850 
2,862 
8,737 
7,326 
2,855 

21,272 
9,786 
2,256 

11,159 

11,613 
1,911 

22,168 

21,478 
2,127 
1,782 

17,256 
1,892 

14,088 

18,255 
1,690 

25,750 
7,280 

13,511 

20,26f. 
3,929 

26,739 

13,842 
8,982 

11,632 

15,365 
3,348 

17,710 
6,493 
2,174 
7.049 

14,813 
2,358 
4,906 
6,122 
2,219 
6,268 

11,206 
3.448 
2,412 

18,123 
3.271 

15.675 

15, 756 
2.677 





Average 


> 


number of 


8 


peaches set 


d 


per 


tree. 












"S 




•% 


u 


•o 


>. 


% 


o 


t 


s 


t 


% 


3 


p 


^ 


c» 


P 


10 


1,308 




9.6 




427 


10 


1,307 




9.8 




814 


10 




322 


10 


886 




10 


873 




10 




195 


10 


1,107 




10 


1,285 




10 




286 


9.4 


929 




10 


733 





10 




285 


10 


2,127 




10 


979 




10 




226 


10 


i,ii6 




10 


1,151 




10 




191 


10 


2,216 




10 


2,148 




10 




•iis 


10 




178 


10 


1,726 




10 




i89 


10 


1,409 




10 


1,825 




10 




i69 


10 


2,575 




10 




728 


10 


1,351 




9.8 


2,068 




10 




393 


8.6 


2,993 




10 


1,384 




10 




398 


10 


1,16:3 




8" 


1,921 




10 




334 


10 


1,771 




10 


649 





10 




217 


10 


7a5 




10 


1,481 




10 




236 


10 


491 




10 


612 




10 




222 


10 


627 




10 


1,120 




10 




345 


9.6 




251 


10 


1,812 




10 




327 


9.5 


l.e.'iO 




10 


1,576 




10 





258 



a For plat of orchard see p. 69; for sprays applied see p. 73. 

6 Number calculated from a less weight than 100 j)ound8, usually from 60 iwunds 



112 PEACH LEAF CURL I ITS NATUBE AND TREATMENT. 

Following the figures in the above table which show the number of 
peaches in 100 pounds of fruit are those giving the number of pounds 
of fruit gathered at the first and second pickings. From these four 
columns of figures has been calculated the number of peaches gathered 
from the trees of each row of the block for both the first and second 
pickings. By adding these numbers the total number of peaches 
matured by the trees of each row was quite accurately determined. 
To this amount is now added the number of peaches thinned from the 
trees, where thinning was required, the grand total representing the 
number of peaches fimily set by the trees of each row. By dividing 
this grand total by the number of trees in a row it has been possible 
to show the average number of peaches set per tree on both sprayed 
and unsprayed trees, and for every row in the experiment block. 

COMl'ARATTVE QUANTrTY, QUALITr, AND CASH VALUE OF FRUIT FROM 
SPRAYED AND UNSPRAYED TREES. 

(Pis. XI and XII.) 

The ai*tual yield in pounds of peaches, the quality, and the cash 
value of the fruit produced by the sprayed and unsprayed trees of the 
experiment rows of the Rio Bonito orchard in the season of 1895 are 
fully and accurately shown in the table which follows. This table 
gives a full record of the yield as it was taken in the orchard, and the 
results are of the greatest value from a practical standpoint, convey- 
ing an accurate idea of the cash gain resulting from this spray work. 
If the reader will compare the average value of the fruit produced by 
the sprayed trees of row 21, for example, with that of the fruit pro- 
duced by the unsprayed trees of row 20, some conception of the 
possible gains resulting from thorough spraying may be obtained. In 
studying this table, it should be remembered that the results shown 
were obtained from the use of 35 different formulae and sprays. Some 
of the sprays were of little value, others of medium value, etc., hence 
the gains shown for the entire block are far below what they would 
have been had the trees of each of the rows been sprayed with such 
sprays as those used upon rows 21, 22, or others of the better-yielding 
rows of the block. 



DESCRIPTION OF PLATE XI. 

Experiments at Biggs, Cal. (Sulphur, lime, and salt.) Looking west between rows 
2 and 3, May 14, 1895. Row 2 was unsprayed; row 3 was sprayed before blooming 
with 15 pounds sulphur, 20 pounds lime, 5 pounds salt, and 45 gallons of water. 
The average value of fruit matured per tree in row 2 was $1.96 and in row 3 $3.90. 
The spray used showed a net gain from the treatment, as determined by the compar- 
ative value of the peaches set by the trees of both rows, of 216 per cent (p. 117) . 



Bull. 20. Div. Veg. Pnya. & Path., U. S. Oept. of Agriculture. 



Plate XI. 




DESCRIPTION OF PLATE XH. 

Experimente at Biggs, Cal. (Sulphur and lime.) Looking west between row8 9 
and 10, May 14, 1895. Both rows were sprayed before blooming. Row 9 was treated 
with 10 pounds sulphur, 20 pounds lime, and 45 gallons of water, and row 10 with 
10 pounds sulphur, 8 pounds lime, and 45 gallons of water. Row 8, adjoining row 9 
at the south, and row 11, adjoining row 10 at the north, were untreated. The aver- 
age value of fruit matured per tree on row 9 was $3.35, and on row 8 only 91 cents. 
The average value of fruit matured per tree on row 10 was $3.90, and on row 11, $1.35. 
As determined by the comparative value of the peaches set by the trees, the spray 
used on row 9 showed a net gain over row 8 of 457 per cent, and that used on row 
' 10 showed a net gain over row 11 of 337 per cent (p. 117) . It may be seen that the 
lower limbs are not as thickly covered with foliage where the sulphur sprays are 
used as where the copper sprays are used. This is especially true where the former 
is applied too late or too strong. (See PL XI.) 



BuK 20, Dt^. Vog. Pfty*. Bt Path , U. S. D«pt, of Agriculiur*. 



Plate XIL 



-^ '' * '-? 



X'y 



COMPARATIVE QUANTIXy, QUALITY, AND VAtUE OP FEUIT. 113 






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-""■"^•'-"•Sflaasssssasaaasassas 



114 



PEACH LEAF CITRL! ITS NATURE AND TREATMENT. 



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Plate XIII. 




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DESCRIPTION OF PLATE XIII. 

Experiments at Biggs, Cal. (Bordeaux mixture.) Looking west })etween rows 
20 and 21, May 11, 1895. Row 20 was unsprayed; row 21 was sprayed before bloom- 
ing with 5 pounds copper sulphate, 5 pounds lime, and 45 gallons of water. The 
average value of fruit matured per tree in row 20 was 90 cents; in row 21, $6.19. The 
spray used on row 21 showed a net gain over row 20, as determined by the com- 
parative value of the peaches set by the trees of both rows, of 1,028 per cent (p. 117) . 






V ': r 



EuH. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture 




DESCRIPTION OF PLATE XIV. 

Experiments at Biggs, Cal. (Eau celeste.) Looking west between rows 26 and 27, 
May 11, 1896. Row 26 unsprayed ; row 27 sprayed before blooming with 4 pounds cop- 
per sulphate, 3 pints ammonia, and 45 gallons of water. Average value of fruit 
matured per tree in row 26 was 90 cents; in row 27, $4.32. The spray used on row 
27 showed a net gain over row 26, as determined by the comparative value of the 
peaches set by the trees of both rows, of 662 per cent (p. 117) . 



. r^\ 3 R A ^ y ^ 

r UNIVERaTTY ' 



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(; UNIV-ERSITY ^ 



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/ 



INFLUENCE OF 8PBAY8 ON THE FRUITING OF THE TREES. 115 

COMPARATIVE VALUE OF SPRAYS IN RELATION TO FRUIT. 

(Pis. Xin, XIV, and XV.) 

A review of the preceding table will show that no account has been 
taken there of the peaches thinned from the trees, and for this reason 
the results given in dollars and cents for the different rows can not be 
taken as representing the full comparative value of the sprays used. 
The value of a spray in controlling curl, so far as quantity of fruit is 
concerned, should be based upon its power to prevent the fall or loss 
of fruit from the disease. A spray may enable a tree to set more 
fruit than it can carry to maturity in a favorable season, but the value 
of the spray should not be decided from the amount of the crop after 
thinning. This will be evident from a consideration of the fact that 
in many years the trees may not set more peaches than can be properly 
matured without thinning. In such cases it would be the spray that 
enabled the trees to set and hold the greatest number of peaches in 
the presence of curl which would prove of the highest value to the 
grower. A less effective spray would not enable the trees to set and 
hold a full crop. It is thus seen that the comparative value of several 
sprays rests in their power to prevent the fall of the greatest num- 
ber of peaches from disease, this being, of course, where other influ- 
ences of the sprays are equal. Thinning is necessary only when the 
trees can not carry all the fruit set, or when it is desired to improve the 
size and quality of the fruit, and it bears no direct relation to the 
value of a spray in preventing curl. 

In view of the preceding facts, a table has been prepared embodying 
those features of the fruit records by which the comparative value of all 
the sprays used may be determined. 

To show the full comparative value of all influences of each spray 
upon the fruit, it has also been necessary to consider the quality as 
well as the number of peaches and weight of same. To obtain the 
ultimate comparative value of the sprays the writer has been obliged 
to treat the thinned peaches as if matured, assigning them the same 
value, in proportion to number, as the matured fruit. There is also 
one other calculation in the table which requires explanation. A con- 
siderable percentage of the better quality of fruit was picked while 
still immature. This fruit is tabulated as that for the Oakland can- 
nery. It was' necessary to gather this fruit while still hard so that it 
would arrive at the Oakland cannery in good condition. By weighing 
a large number of matured peaches and an equal number of peaches 
as picked for the Oakland cannery it was learned that the Oakland 
fniit should be increased by 11 per cent to make it equal in weight to 
mature fruit. This has been done, so that the quantity, quality, and 
full comparative value of all fruit considered could be accurately 
determined. 



116 FEAOH LEAF OUBL*. ITS NATURE AND TREATMENT. 

It ha8 been possible in the manner just outlined to calculate the 
total comparative value of all fruit set by the trees of each row, as 
determined by the actual cash value of fruit of equal quality when 
matured. By dividing this sum by the number of trees in the row 
the averse comparative value per tree of all fruit set is shown, both 
for sprayed and unsprayed rows. While these average values do not 
represent the money actually obtained, as in the case of the preceding 
table, they accurately show the average values for comparison of all 
fruit set by the trees, as determined by the market price of that fruit 
which the trees were able to bring to maturity. For these reaeions 
the figures for the different rows may be rightly compared, and they 
fairly determine the comparative values of the 35 sprays tested in the 
block, so far as those values relate to the quantity and quality of the 
fruit. 

To further facilitate the comparison of the values of the sprays in 
increasing the quantity and quality of fruit, as determined by the cush 
value of such fruit when matured, the results have been reduced to 
average net gain per cent of the sprayed trees of each treated row over 
those of the adjoining unsprayed row. For illustration, it may be seen 
that in row 30, sprayed, the average calculated value of all fruit set 
per tree would have been when matured $12.62; in row 31, unsprayed, 
$3.43. Deducting the calculated average value of the fruit set on the 
trees of row 31 from that set on the trees of row 30, there is shown an 
excess of $9.19 in favor of the trees of the sprayed row, and by divid- 
ing this excess by $3.43, the calculated average value of fruit set by 
the trees of the unsprayed row, there is shown to be a net gain of 268 
per cent resulting from the use of the spray applied to the trees of 
row 30. The gain per cent has in this manner been calculated for 
every spray tested in the block, and it may be seen that on row 21 the 
spray gave a net gain of 1,028 per cent. 



OOICPABATIVE VALUE OF 8PBAY8 IN BELATION TO FBUIT. 117 



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118 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



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INFLUENCE OF SPRAYS ON THE FEUITING OF THE TREES. 



119 



COMPARATIVE SIZE OF FRUIT ON SPRAYED AND UNSPRAYED TREES. 

Owing to the fullness of the records obtained relative to the weight 
and number of peaches gathered from the sprayed and unsprayed 
trees in the present experiments, it is possible to learn the compara- 
tive average weight of the fruit produced on treated and untreated 
trees. It might seem that the unsprayed trees, having to mature on 
an average 291.3 peac^hes per tree, would yield larger fruit than the 
sprayed trees, which had to mature 949.2 peaches per tree; in other 
words, that the increased number of peaches upon sprayed over 
unsprayed trees would,' to a considerable extent, be counterbalanced 
by an increase in the size of the fruit on the lightlv loaded unsprayed 
trees. It has been found, however, that where the conditions for vig- 
orous growth of a tree are present, and where the fruit upon a tree is 
so thinned that the tree is not overloaded, the peaches of the full- 
bearing tree are practically as large when mature as are those of the 
tree which has lost much of the crop from curl. The following table 
has been compiled from the facts in hand upon this matter. It is 
shown in this table that the fruit from the sprayed trees avemged 
for the whole block (345.3 trees) 299.0344 peaches per 100 pounds, and 
the fruit from the unsprayed trees averaged for the whole block 
(228.9 trees) 299.0312 peaches per 100 pounds. This shows that the 
gain in size of peaches on unsprayed trees over those on sprayed trees, 
as determined by the average number of peaches to 100 pounds, is 
fuVWiF per c^^t^ ^^ o'^ly about xc^i^ff of 1 per cent. This amounts to 
nothing from a pi-actical standpoint. 

Table 31. — Sise of fruit on sprayed and unsprayed trees as determined by the average 
numi>er of peaches per 100 pounds. 



I 



SpraytHl ... 
Unsprayed. 



Num- 
ber , 
of 

treeal 
in 

block 



Fruit 

produced 

by all trees 

of block. 



First 
pick- 
ing. 



I Sec- 
; ond 
pick- 
1 ing. 



345.3 



Lbs. IJ>8. 



95, (m 



228.9 



19,085 



14,5(M 
3,257 



Average 

production 

per tree. 



Average number of 
peaches— 



Per 
100 pounds. 



First I ?^^- i First 
mg. I *"«• 



ing. 



Sec- 
ond 
pick- 
ing. 



Per tree. 



Proportion- 

I ate 

percentage 

vield 

oi trees. 



I 
Aver- 
age 
num- 
ber of 

peaches 



First 
pick- 
ing. 



Lbs. 
275.4 



42 I 293.2 



14.2' 293.(5 



Sec- 
ond 



First 



P."2-:1L^- 



Ing- I 



ing. 



Sec- 
ond 
pick- 
ing. 



Average 

per- 
centage 
of gain 
in size 
of fruit 
on un- 



pounas, jj^gg ^ygj. 



per 
tree. 



3:^7.4 HOT. 5 141.7 8(5.8 13.2 299.0344 



244.3 



85.4 



106_ 

100000 

per cent, 

or about 

1 

14.G;299.0312| fooo 

ofljier 



I 



that of 
sprayed 

trees. 



It should not be understood by the above that a ci'op of 950 pea-ches 
draws no more heavily upon a tree than a crop of 800 peaches when 
other conditions are equal. All observation tends to show that such 
is not the case. A tree too heavily loaded will often produce 



120 PEAOH LEAF OrBL: ITS NATUBE AND TBEATMENT. 

much smaller fruit than a properly thinned tree, even upon exceed- 
ingly rich soil. The facts given in both the preceding text and table 
show clearly, however, that the severe attack of curl in the spring of 
1895 drew upon the vitality of the unsprayed trees as heavily as did 
the excess of 650 peaches each on the sprayed trees. Otherwise stated, 
the trees averaging 300 peaches were drawn upon as heavily by the 
attack of curl, combined with the maturing of 300 peaches, as were 
the sprayed trees in maturing 950 peaches. If this had not been the 
case, the unsprayed trees would have better nourished their crop, and 
would have produced larger and heavier fruit than those which were 
sprayed. These facts should receive the attention of all thoughtful 
growers, as no one can afford to have his trees drawn upon to the 
extent of two-thirds of a crop of peaches without return, even when 
frost or other causes would not have allowed him a crop on sprayed 
trees. To permit trees thus to suffer from curl even in such a year 
would be equivalent to draining them of much vitality, even though 
they failed to show this drain in the reduction of wood or fruit buds 
for the ensuing year. But it has already been shown that a marked 
reduction in the number and quality of fruit buds is a result of a 
spring attack of curl. The soil is also certain to sustain an unnec- 
essary drain upon its resources. 

Another phase of this subject is made clearer by the above table. 
There are very many varieties of peaches so resistant to leaf curl that 
the fruit does not drop, even when a large percentage of the leaves 
are lost. Many growers leave such varieties unsprayed, thinking that 
the saving of the fruit is the all-important point, and that the loss of 
the spring foliage alone does not warrant the spraying of such varie- 
ties. The above facts will show the error of such deductions. When 
the loss of the foliage upon the Lovell is equal to the drain upon the 
tree brought about in maturing two-thirds of a crop, the loss of the 
foliage upon a semiresistant variety must be approximately the same. 
This drain will be apt to show also in the size and weight of the fruit, 
if not in the number of peaches. Certainly no grower is warranted 
in leaving any variety unsprayed simply because that variety holds its 
fruit in spite of the loss of foliage. The trees have suffered in such 
a case, and the orchardist can scarcely avoid feeling the loss in the 
reduced vigor of his trees, the reduced weight and size of his fruit, 
and the added drain upon his soil. 

coijok of sprayed and unsprayed fruit. 

The Lovell peach is normally a fruit of fine color, but under the 
action of certain of the sprays used its color was greatly heightened. 
In observing this action of the sprays no color scale was used, but the 
marked brightening on (certain sprayed rows was too distinct to be 
mistaken by the most careless observer. This heightening of color 



METHOD OF THINiaNG AND COST OF PICKING PEACHES. 121 

was not due to excess or lack of crop, for it was distinct on both 
heavily and lightly loaded trees, where the fruit was of medium size 
and where it was exceptionally large, but was due to the use of the 
copper sprays, especially of the stronger Bordeaux mixtures applied. 
Here is another advantage in the use of the copper salts. This increase 
in color would certainly mean dollars to the grower where the fruit 
was placed on the market in competition with unsprayed fruit, even 
of the same variety. The writer regrets that a color scale could not 
have been used in this connection, so that the true heightening of 
color could be stated, but the contrast between sprayed and unsprayed 
fruit, where the spraying was done with the Bordeaux mixture, was 
observed and discussed by many who had this fruit to handle. 

METHOD OF THINNING AND COST OF PICKING PEACHES. 
THINNING BY HAND AND BY CURL. 

An argument advance^d by certain peach growers and requiring con- 
sideration is that a moderate spraying under ordinary conditions is 
sufficient. By avoiding too thorough work enough curl is allowed to 
develop to cause the dropping of one-fourth to one-half of the peaches 
being set by the tree. If soil conditions are favorable it is thought 
the trees will still retain a sufficient crop, and the expense of thinning 
will be avoided. 

At first thought the plan here suggested might seem the easiest and 
cheapest way of thinning fruit. A consideration of all points involved 
will show, however, the faults of this method. To do effective pre 
ventive spraying against curl the spray must be applied to the dormant 
tree, and to judge of the severity of a coming attack of curl before 
growth begins is too uncertain a method to warrant the indorsement of 
practical growers. AH influencing conditions may appear to favor a 
light attack of curl till after the spraying is completed, when a sudden 
change of temperature or a cold rain may develop a severe attack 
within the course of a few days. Under such conditions, incomplete 
or light spray work may cost the grower the major portion of his 
crop* 

In case the severity of curl is about as presupposed, the number 
of peaches remaining on the tree being about what the tree should 
carry, it is still very probable that the grower has sustained a loss in 
the stoppage of growth of wood and fruit and in the fall of foliage 
equal to or above the expense of thinning. There is also a difference 
between hand-thinned trees and those thinned by curl. This disease 
is local in its action, not general. If one branch in the midst of dis- 
eased branches is thoroughly sprayed it will hold its fruit, while the 
peaches will fall from those not sprayed. This will show that the 
peaches of a diseased tree are not thinned evenly, as the disease is fre- 
quently not uniformly distributed over all branches of the tree. Then 



122 PEACH LEAF CDEL: ITS NATURE AND TREATMENT. 

the fruit is for the most part nourished by the foliage of the branch 
which bears it, and hence if the disease is not equally distributed the 
foliage will be unequally distributed and the fruit unequally nourished. 
One portion of a tree may have an excess oiF fruit, even to the break- 
ing of limbs, while another portion shows a deficiency. Besides the 
unequal thinning of fruit on different portions of a tree, arising from 
the unequal action of curl over the tree as a whole, there will also 
appear an unequal thinning of the fruit of individual branches. In 
this respect, one of the prime objects of hand thinning, the equalizing of 
the fruit distribution upon the branches, is lost when the thinning is 
caused by curl. Such fruit as remains upon the curl-thinned branches 
is apt to be largely toward the ends of the limbs. 

The statements here made respecting the local action of the disease 
and the local tiourishing of the fruit upon a limb or portion of a tree, 
are known to be correct, and have been established by a series of care- 
fully conducted experiments on sprayed halves of trees. The details and 
results of this work are given in the concluding se<;tion of this chapter. 

CX)8T OP PICKING PEACHES. 

When considering the picking and sorting of peac^hes from sprayed 
and unsprayed trees a marked difference is noted in cost in favor of 
those sprayed. In the Rio Bonito orchard, where our experimental 
work was prosecuted, it has cost . the proprietors $1 per ton to pick 
fruit from fully loaded sprayed trees. In cont^ust to this the cost 
of picking and sorting the fruit of the unsprayed trees just north of 
the experiment block, in the summer of 1895, was $3 per ton. This 
was on account of the scattered condition of the fruit on these trees, 
which were affected by curl in the spring like the control trees of the 
experiment block. This cost per ton was calcidated with wages at ^1 
per day, the men boarding themselves, and where one sorter to tive 
pickers was employed. We have here a difference of $2 per ton in the 
cost of picking and sorting fruit from sprayed and unsprayed trees. 
This added expense on unsprayed trees arises, of course, through the 
necessity of picking over a greater expanse of tree and orchard surface 
to obtain a given amount of fruit. It is believed that in this single 
item of picking the fruit enough is saved to more than cover the expense 
of spraying the trees and thinning the fruit. 

THE IX)CAT. ACTION OF CURL ON FOLIAGE AND FRUIT. 

RECORDS OF TREKS SPRAYED ON ONE SIDE. 

The study of the habits of Kr/mmm (l>ef<mmxm and its influence upon 
its host led to the following investigation into the localization of the 
parasite upon the tree and its local rather than genei-al effects. 



,\ l; r< A , 






Bull. 20, Oiv. Veg. Phyt. St Path., U. S. Oept. of Agriculture. 



Plate XVI. 




DESCRIPTION OF PLATE XVI. 

Fig^. 1 shows the condition of the trees sprayed on one side (considered in the text, 
p. 123). The right side of the tree shown was sprayed with Bordeaux mixture, the 
left side was unsprayed. (Compare with Pis. XVII, XVIII, and XIX.) 

Fig. 2 shows the condition of the tree sprayed on one side after curl had largely 
denude<i the unsprayed half at the left. 



LOCAL ACTION OF OUBL ON FOLIAGE AND FRFIT. 123 

Just north of the experiment blocl^, in the continuation of the .same 
orchard, was selected a row of 6 trees for treatment on one side. The 
spray used on half of each of the first three trees from the east was the 
standard Bordeaux mixture recommended by the Department, viz, 6 
pounds copper sulphate, 4 pounds quicklime, and 45 gallons of water. 
The spray used on the following three trees was lime and sulphur, con- 
sisting of 10 pounds sulphur, 20 pounds lime, and 45 gallons of water. 
In doing this spraying an eflFort was made to treat only one-half of 
each tree. Each tree was first examined, and, in some instances at least, 
a large canvas stretched through it in such a manner as to divide it as 
nearly as possible into two equal parts. All the branches on one side 
were thoroughly sprayed, the canvas preventing any of the spray 
reaching the limbs of the other half. In this way the half of each of 
three trees was sprayed with each of the above-mentioned sprays. 

A photograph showing the appearance of one of these trees shortly 
after treatment is shown in PI. XVI. 

May 10 and 18, 1895, when curl had reached its highest development, 
careful estimates of the loss of foliage were made for the sprayed and 
unsprayed sides of the 6 trees used in the experiment. The following 
table shows the results of these estimates: 

Table 32. — Foliage IfMUfrom »prayed and unsprayed halves of trees. 



Percentage of leaven which fell from— 



Sprayed half . . , 
Lnsprayed hal> 



Trees treated 

with Bordeaux 

mixture, (a) 

Tree No.— 



1. , 2. ; 3. 



Trees treated 

with sulphur 

apray.(6) 

Tree No.— 

4. I o. ; 6. 



4 , 6 

92 90 



15 



15 
85 



a Pclia^ estimated May 18, 1895. b Foliage estimated May 10, 1895. 



On May 8 the trees were examined, and the notes made at that time 
state that the sprayed and unsprayed sides presented a striking con- 
trast. It is said that "the foliage on the sprayed half of the trees is 
perfection itself in almost all cases. It is very dense and abundant, 
both below on the limbs and above. The leaves are of a very dark, 
rich green, and are long, soft, and beautiful. The growth is very 
thrifty, in fact, unusually so. There are probably not more than 2 to 
•^ per cent of the leaves curled at all on the sprayed half, and these are 
confined to points at the top of the branches not properly sprayed. 
On the unsprayed half of these trees there is very little healthy growth. 
Probably 96 per cent of the leaves are curled, and most of them ])adly 
curled and distorted. Probably not less than 90 per cent of those 
produced thus far this spring will drop. The color of the foliage is 
yellow and sickly. Such leaves as are not curled arc small and light 
in color. The foliage upon both lower and upper limbs is badly affected. 



124 



PEAOH LEAF OURL! ITS NATURE AND TREATMENT. 



What little growth there is which is thus far free from curl is termi- 
nal — very little healthy or comparatively healthy growth is seen from 
lateral buds. As to fruit, I may say that much is dropping from the 
curled side and little from the other." (Pis. XVI and XVII.) 

The work of thinning the fruit from the sprayed halves of these 
trees was not conducted at the time the sprayed trees of the general 
experiment block were thinned. The writer believes that the records 
of the fruit thinned from these trees were not kept except for one tree 
sprayed on one side with Bordeaux mixture. The fruit on the spraj^ed 
half of this tree was thinned May 8, 1896, and amounted to 1,145 
peaches, which weighed 23 pounds, or very nearly 50 peaches to the 
pound. These peaches were very uniform in size and stuck tightly to 
the limbs. If they ex)uld have grown to the usual size when picked 
in the fall they would have given 381 pounds of fruit. No peaches 
were thinned from the unsprayed half of this tree. 

The yield of the 6 trees was carefully determined by weighing and 
counting the fruit from the sprayed and unsprayed sides of each tree 
separately. The results of this work are shown in the following table: 



Table 33. — Yield of sprayed and unsprayed halves of trees. 



Bordeaux mixture, I Sulphur spray, tree 



tree No.— 



No.— 



Pounds of fruit gathered from— 

Sprayed half 

iiMprayed half 

Number of peaches gathered from- 

Sprayed half 

unsprayed half 



284.8 
14.8 



718 
40 



861.6 
50.6 

1,064 
147 



286.7 
25.8 



74 



112.2 
48.6 



SOS 
132 



189.3 
80.4 



4S0 
220 



64.6 
35.3 



172 



By the preceding table it is shown that the sprayed half of tree 1 
bore 718 peaches, weighing 284.8 pounds, while the unsprayed half 
bore only 40 peaches, weighing 14.3 pounds. In this case, as in the 
case of the other trees of this series, the localized position and action 
of the fungus of curl upon a tree is shown. The unsprayed half of 
the tree suffered so severely from the disease that it lost 92 per cent 
of its foliage and all but 14.3 pounds of fruit. This severe attack 
on one side of the tree appeared to have no influence whatever over 
the sprayed limbs of the other side, as the fruit on the sprayed half 
was thinned of 1,145 peaches, lost but 2 per cent of its foliage, and 
bore 284.8 pounds of as fine peaches as any in the orchard. On the 
other hand, the full and healthy covering of foliage on the sprayed side 
of the treeappeai-s to have had no beneficial influence over the diseased 
side. Had it had any well-marked beneficial influence the fruit of the 
unsprayed half would have been retained, which was not the case. 
The same local action of the disease, and the same local nourishing 
influence due to the assimilative action of the healthy foliage may be 



DK^MIIIT'IOX OF PLATE XVII. 

This plat** hIiows tlio condition of one of the treefl sprayed on one side at the time 
of picking the fniit. The leaves have ])een cut away with pruning shears to enable 
the photograph to show the fruit upon the sprayed half (right side) of the tree, and 
the al)t<t»nce of fruit uiK)n the unsprayed half (left side) . The sprayed half matured 
284.8 pounds of the finest j)eaches; the unspraye<l half matured only 14.3 pounds. 
Over 1,100 iKUwht^s werti thinned from the sprayed half of this tree to enable the 
limbs to l)ear the crop, while the unsprayed half was unthinned except by curl. 
(For records of this and other trees sprayed on one side see Chapter VI, aleo compare 
with Pis. XVI, XVIII, and XIX.) 



O, D*w. Vrng. Pti^ ie Path,, U. S- Di^pi, rf Agricwituris. 



Plate XVIi. 





DESCRIPTION OF PLATE XVIII. 

Peaches gathered from the tree sprayed on one side shown in the preceding plate. 
The fruit shown on the two drying traya at the left, together with that in the lower 
compartment of the tray at the right, was gathered from the sprayed half of this tree. 
The peaches shown in the upper right-hand compartment were all that matured on 
the unsprayed half of the same tree. The sprayed half l)ore 718 peaches, weighing 
284.8 pounds; the unsprayed half l)ore only 40 i)eache«, weighing 14.3 ]K>und£. 
(Compare with Pis. XVI, XVII, and XIX.) ' 



Bull. 20. Div. Veg. Phys. 8c Path.. U. S. Dept. of Agriculture. 



Plate XVIII. 




DESCRIPTION OF PLATE XIX. 

This is a photograph of a limb of the sprayed half of the tree shown in Pla. XVI 
and XVII, after the removal of the leaves with pruning shears. A good idea of the 
size and perfection of this fruit may be obtained from the plate. The color wa^ 
strikingly high and rich. The size of the fruit is further shown by the fact that the 
peaches averaged 252 per 100 pounds. (See note on this work at the close of Chai>- 
ter VI, p. 122; also refer to Pis. XVI, XVII, and XVIII.) 



Bull. 20. Div. Veg. Phys & Path., U. S. Dept. of Agriculture. 



Plate XIX. 




\ '^ R A n 



I T''>"«'T' 



,-.Jc V 



'^^ ^ 



LOCAL AC5TI0N OF CUBL ON FOLLA.GE AND FRUIT. 125 

seen in the condition of the foliage and crop on the sprayed and 
iinsprayed sides of the other trees included in these experiments. 

It even appears likely, both from observation of the trees and from 
the general laws of use and disuse and supply and growth, that the 
influence of the sprayed upon the unsprayed portions of the tree, in 
the presence of an attack of curl, is detrimental mther than beneficial. 
It is probable that the half of the tree in full foliage, instead of lend- 
ing material aid to the defoliated side, tends to further rob that side, 
at least of the crude sap coming from the roots. 

For the purpose of showing the reader the striking results obtained 
from these trees, several photographs were made at the time the crop 
was matured. In order that the fruit might be seen upon the tree 
the foliage was carefully cut away and a screen placed behind the 
tree (PL XVII). A single limb was also photographed, as shown in 
PL XIX. The fruit gathered from the sprayed and unsprayed halves 
of tree 1 is likewise shown in PL XVIII. The unusual size and 
brightness of color of the fruit from the sprayed half of this tree was 
very marked. The peaches averaged 252 per 100 pounds. The aver- 
age of peaches for the large experiment block was, as before stated, 
299 per 100 pounds. There was thus a gain of 18.66 per cent in size 
of fruit on the sprayed half of this tree over the average for the block. 



CHAPTER VII. 

PREVENTIVE SPRAY WORK CONDUCTED BY ORCHARDISTS. 
GENERAL CONSIDERATION OF THE AUXILIARY WORK. 

While planning the experiments already detailed it seemed desirable 
to set on foot a similar line of work among peach orchardists in gen- 
eral. It was thought that several advantages could be attained from 
such auxiliary and coincident work: (1) It would indicate the effective 
ness or noneffectiveness of the sprays recommended, in cx)ntrolling curl 
under the various conditions of variety, situation, soil, temperature, 
atmospheric humidity, seasonal variations, etc., existing in the many 
peach-growing sections of the country. (2) It would eliminate the 
personal element of the other experiments being conducted, and 
would introduce various new conditions of orchard work, thus point- 
ing out the efficiency or needs of the general grower and indicating 
what features of the work should receive special attention in offering 
final recommendations. (3) It would introduce the methods of treat- 
ment in many peach-growing centers, and by means of the object 
lessons thus set up, it would effect a much more rapid and general 
adoption of such spraying methods than could be hoped for otherwise. 

In advance of the inauguration of this work, which was begun in 
the fall of 1893, correspondenc>e was opened with over 1,600 peach 
growers in all peach-growing centers of the United States. To each 
of these growers was sent a circular describing the nature and cause 
of peach leaf curl, outlining a series of spraying tests which it was 
desirable to have conducted for its prevention, and supplying the 
spray formulae known to have given good results in California. Each 
grower was given the facts necessary to enable him to carry out the 
work, and was requested to furnish the Department with the results of 
his experiments. 

A very large number of growers expressed their willingness and 
desire to assist in conducting these experiments, and a very consider- 
able number have done so in many of the peach-growing centers. It 
may also be said that the number of growers who have adopted annual 
spraying methods as a result of this introductory experimental work 
is large and is constantly increasing. In fact, the spraying of peach 
trees for curl has become very general in many of the peach-growing 
centers of the United States where the disease prevails. 
126 



AUXILIARY WORK. 127 

Of the reports which have been received of work conducted by the 
trrowers, it is thought best to include a few from those regions where 
curl is most common. The reports given are of much value, and in 
numerous cases they show that the experiments were carefully carried 
out. Representative repoiis will be given from the lake shore fruit 
belt of Michigan, from the Willamette Valley, Oregon, where peach 
culture has been greatly checked by curl, and from several growers in 
California and elsewhere. An effort has been made to present these 
reports, which have been carefuUy tabulated, in as compact form as 
possible. 

NOTES ox THE AUXILIARY EXPERIMENTS IN MICHIGAN. 

A verj' considerable number of peach growers in the more northern 
portion of the Michigan fruit belt received from the Department a 
request to undertake spraying experiments in the winter of 1893-94 
for the prevention of peach leaf curl. Among these orchardists was 
Mr. Smith Hawley, of Ludington. This gentleman, as well as several 
other growers of Mason and Oceana counties, entered heartily into 
the work, the result being that at present a very large number of 
orchardists are annually spraying for curl in that region. The work 
conducted Iw Mr. Hawley involved the testing of a number of sprays 
in early and late winter with one and two applications. It was very 
carefully carried out, and as the disease developed quite seriously in 
that region in the spring of 1894 his results are most interesting and 
valuable. The data supplied by his report are presented in the fol- 
lowing table and notes: 



128 



PEACH LEAF CURL: ITS KATUBE AND TREATMENT. 



I 



i 

I 
1 



u 
1! 


-899J1 peXtudfmn 


S 


a 




§ 


^ 


i 




i 


s 




*89dJi peiCtudg 


^ 


§ 




% 


§ 


1 


g 




•55 . 


»' 








si 










1 


Date when loss ( 

leaves was esti 

mated. 


1 

a 


•§ 


1 


a 

c 


1 

e 


• — ^ 




o 


c 


1 


si 

n 
II 


•99911 paXtudsuQ 


S 


s 


s 


s 


S 


S S 


s 


8 


•soaii paXuids 


o 


X 


.fi 


»« 


eo 


lO 00 


s 


CO 










!>- 


cs 


c* 












r 


'JSuiXuds puoods 






i fe ti 












o 

1 








-< 


•< 


-< 














!>■ 


O) 


9! 


O) 


00 


o> 


o» 


00 


'Su(X«jdfi )8JU 




s 

-< 


^ 1 


• 1 


1 


c 

c 




xi 

I 


1^ 


'peiudsua 


s 


cs 


cJ 


55 


o 


?5 


o 


I^ 




'poXiMds 


o 


Cs 


^ 


51 


s 


a 


o 


X 






^A-^ 




—^ 




,-^-^ 




^-*-^ 


^A_ 




AUXILIABY WORK. 129 

The preceding table gives the details of eight of Mr. Hawley's 
experiments. The experiments are distinguished by numbers (1-8), 
and the formulae used by letters (A, B, and C). Mr. Hawley's notes 
on these experiments were written chiefly on two dates, the first 
immediately after the estimates of foliage were made and the second 
fshortly after the fruit was gathered. His statements in general are 
given in the following notes: 

Experiment I: 

June 23, 1894.-— This experiment was made under rather unfavorable circum- 
stances, as the wind came up quite strong after I had commenced, and consequently 
I cou]d not do the work as thoroughly as I wished, but the results now promise to 
be entirely satisfactory. The foliage is perfectly fresh and green, and apparently the 
peaches are going to hang on. Another thing that now appears to be well estab- 
lished is that the earlier spraying is the better. [See notes under experiment 2.] 
There is now quite a perceptible difference to be noticed between early and late 
graying as regards the foliage. 

October 1, 1894. — ^This experiment has demonstrated the effectiveness of the spray 
used. While the crop was not large, owing to the unhealthy state of the trees 
from leaf curl last year, yet it was about three times as lai^ on the sprayed as on 
the unsprayed trees. The fruit was much nicer. I could easily pick out the baskets 
of fruit from the sprayed trees. 

Erperiment S: 

June 23, 1894.— This experiment has given entire satisfaction so far, as the foliage 
of the trees is perfect and the fruit is hanging on well. This experiment, taken in 
nmnection with the others, indicates that the blue vitriol solution, C, acts quicker 
than the sulphur solution. The winter sprayings seem fully as effective with the sul- 
phur solution as with the blue vitriol, but the spring spraying is not quite as good. 

October 1, 1894. — While the difference in the amount of fruit gathered from the 
sprayed and unsprayed trees is not as great as in some of the other experiments, yet 
the effect is fully as apparent, for these trees were not nearly as badly affected last 
year as some others, and consequently they all had a fair load of fruit. There was a 
far greater difference noted in the foliage than in the fruit. 

Erperiment S: 

The first spraying of this experiment was on January 19, and was followed by a 
heavy rain storm, which lasted twenty-four hours, and will undoubtedly prevent the 
full benefit of the work from being realized, but the work was very thoroughly done 
and may be effective. 

June 23, 1894. — ^The second spraying was well done, and at this date the effect 
Hwms to show (1) that formula B is not strong enough to have the desired effect; 
and (2) that two sprayings are not much better than one, provided the work is 
thoroughly done with one spraying, and provided, also, the spraying is followed by 
good weather. 

October 1, 1894.— This experiment has given greater satisfaction than anticipated. 
The proportion of sprayed to unsprayed fruit is better than expected at the time of 
the estimate on the loss of foliage. 

Erperiment 4-' 
.. June 23, 1894. — ^The contrast between the sprayed and unsprayed trees at this date 
is very decided in this experiment. The first spraying was on the same date as 
experiment 3, and followed by rain. The last was done April 12 with formula O, 
and was well done, and the trees now look fine. 
19093— No. 20 9 



130 P£^CH LEAF OUBL: ITS NATUBB AND TBEATMENT. 

October 1, 1894. — ^The results of this experiment are rather disappointing, as I was 
led to believe when I niade the estimate of the loss of foliage in June that the reeulte 
would be more satisfactory than with experiment 3, Whether the solutions used 
had the effect of neutralizing each other, or whether formula B, having been first 
applied, prevented any benefit from formula C, I can not tell. 

Experiment 6: 

June 23, 1894. — The first spraying of this lot was followed by ten hours' rain, the last 
spraying by good weather. The treated trees (ft^esent a fine appearance, but the con- 
trast is not so great as in some other experiments, for the control trees are an outside 
row and apparently not as badly affected as those farther in the orchard. I do not 
anticipate a very large difference in the fruit yield. 

October 1, 1894. — ^This experiment has turned out just as I thought it would. The 
difference in the amount of fruit from the sprayed and unsprayed trees is not great, 
yet it is quite satisfactory considering the conditions. 

Experiment 6: 

June 23, 1894. — ^This experiment was thoroughly made, but was unfortunately 
followed by twenty-four hours of warm rain, commencing ten hours after the spray- 
ing, so that the result is not as satisfactory as desired, but the effect is so noticeable 
that the difference can be seen half a mile away. 

October 1, 1894. — The results of this experiment are entirely satisfactory. In spite 
of the fact that the spraying was followed by rain and then by very cold weather, 
the yield of fruit was one-third more on the treated trees than on the untreated treee, 
but what pleases me most is the very great difference in appearance of the trees now. 
Those that were treated have made double the growth this season that the untreated 
trees have. They are holding their leaves late and have twice the buds set for another 
year, and are fresher and healthier in every way. 

Experiment 7: 

June 23, 1894. — The result of this experiment thus far seems to show that the 
formula used is not strong enough to accomplish the work desired. There is at thifi 
date less difference to be noted between the treated and untreated trees than in any 
other experiment. 

October 1, 1894. — ^This experiment has resulted about as I thought it would, from 
the appearance of the trees in Jime. I do not think formula B is strong enough. 

Experiment 8: 

June 23, 1894. — I regard this as one of the most valuable experiments in the series. 
It has so far shown the best results. The untreated trees look as though a blight had 
struck them, appearing at this date as if they were going to die, while the sprayed 
trees look as fresh and healthy as young trees that never had any disease. One 
curious thing I have noticed is in relation to a branch from one of the untreated trees 
which reaches across to one of the treated ones. This branch, of course, got sprayed 
when the tree was sprayed with which it mingles, and it is as full of leaves and fruit 
as the treated tree, while the balance of the tree to which it belongs is bare of leaves 
and fruit. 

October 1, 1894.— The final results of this experiment have proved what I expected. 
There is a greater difference in yield than in any other experiment, while the differ- 
ence in appearance between the treated and untreated trees is yet very marked. The 
treated trees look as fresh and healthy as young trees, while the others still look 
very bad. These trees have always been very heavy bearers, and consequently hav 
not attained a very large size. They were never very badly affected by leaf curl till 
this year. 



AUXILIARY WORK. 



131 



In the eight experiments described by Mr. Hawley the percentages 
of net gain in fruit of the sprayed trees over the unsprayed wore as 
follows: 

Tablb 36. — Percenlageg of net gain in fruit shown in eight spraying experiments concluded 
by Mr. Smith Hawley , of Ludingtariy Mich. 



Experiment No. 




Net gain. 

F^cerU. 
191 

46 
174 

41 




Experiment No. 


Formula. 


Net gain. 


1 


A 


6.. 
6.. 
7.. 
8.. 




C 


Percent. 
35 


2 - -. 


c 




A 


49 


s 




B 




B 


24 


4 


B and C. . 




C 


1,424 











aSee table 84. 

Owing to the fact that Mr. HawW's experiments were conducted 
with different varieties of peach, an accurate comparison can not be 
instituted between them. From the very excellent results obtained in 
experiment 8, where the unsprayed trees lost 90 per cent of their 
leaves and the sprayed trees only 3 per cent, and where the net gain 
in fruit by the sprayed trees was 1,424 per cent of the yield of the 
unsprayed trees, the writer believes Mr. Hawley's conclusions are 
correct, viz, that the spray used in this experiment gave the best 
results. That the same spray did not give equally striking contrasts 
in experiments 2, 4, and 5 is probably due mainly to the fact that 
the trees of these experiments were not of the same variety as those 
of experiment 8, but were much more resistant to disease, hence no 
spray could have produced in the former experiments the same con- 
trast between sprayed and unsprayed trees. That the trees of experi- 
ments 2, 4, and 5 were not as badly diseased as those of experiment 8 
is shown to be a fact, for the unsprayed trees of the latter experiment 
lost 90 per cent of their leaves from curl, while those of the former 
experiments lost only 50 per cent. The same evidence is given by the 
fruit. The unsprayed trees of experiment 8 bore only 3.7 pounds of 
fruit per tree, while the unsprayed trees of experiments 2, 4, and 6 
averaged 45.7, 11.6, and 32.4 pounds of fruit per tree, respectively. 

From the preceding facts it appears that the most active and satis- 
factory spray used by Mr. Hawley was that containing 5 pounds of 
copper sulphate, 5 pounds of quicklime, and 45 gallons of water. This 
ia especially interesting from the fact that this spray also gave the 
best results among the 35 formulae tested by the writer in the Sacra- 
mento Valley. 

The relative value of the stronger sulphur spray (formula A) and the 
Bordeaux mixture used by Mr. Hawley (formula C) is well brought out 
in an experiment conducted by him on a somewhat similar scale, but 
with a single variety of peach — ^"Hills Chile. This experiment admits 
* of very satisfactory comparisons being drawn, and is summarized in 
tiie following table: 



132 PEACH LEAF CUBL: ITS NATUBE AND TREATMENT. 

Table 36. — Experiment No. 9^ conducted by Mr. Smiih Hawley. 



Row 
No. 


Formula 
used. 

A 


Variety of ttees. 


Age of 
trees. 


Num- 
ber of 
trees. 


Date of spraying. 


Net gain of 
Total fruit over 
yield of yield of un- 
fruit 1 sprayed 


1 


Hllla Chile , 


Years. 
5 
5 
5 
5 


6 
6 
6 
6 


April 12 


Pounds. 
270 
63 
806 
189 


Per end. 
S2S 


2 


do 


Unsprayed 

Februarys 

January 19 




8 


c 


do 


854 


4 


A 


do 


200 











The preceding experiment shows that Mr. Hawley obtained from 
his Hills Chile trees a net gain in fruit of 354 per cent by spraying 
with the Bordeaux mixture (formula C), and a net gain of 328 per 
cent with the stronger sulphur spray when applied on April 12 and 
200 per cent when applied on January 19. These results indicate that 
the early winter treatment will probably not prove as effective in 
Michigan- as a treatment of the trees shortly before the buds swell in 
' the spring. It is probable, however, that the copper sprays will act 
more quickly than the sulphur sprays, on which account the latter 
should be allowed somewhat more time for action than the copper 
sprays, by applying them a little earlier in the spring. The copper 
sprays may be applied until the first buds begin to open, if neces- 
sary, but such a late application of the sulphur sprays would endanger 
the buds and new growth. 

The following are Mr. Hawley's notes on this expej-iment : 

Kcj)erimeni 9: 

June 23, 1894. — This experiment, although on a small scale, has been very inter- 
sting and instructive, and has been noted and admired by all who saw it. The 
rees stand on a slope, and a person standing on the opposite slope, only a few ro<L» 
away, can see every tree, and the best possible chance is had to observe the effect of 
the different sprays, and to compare the treated with the untreated trees. The con- 
trast at this time is very remarkable. The trees were quite badly affected by leaf 
curl last year. 

October 1, 1894. — ^The contrast between the treated and untreated trees is very 
great as regards yield of fruit, and the contrast in the trees themselves at this date is 
quite as remarkable. The treated trees look fresh and healthy and have made a fine 
growth, while the untreated trees look sickly and have made verj' little growth, 
looking, in fact, a year or two younger, as regards size, than the others. 

Late in the season of 1894 Mr. Hawley tested the sulphur and copper 
sprays to ascertain the comparative action of the same upon buds 
which were considerably swollen. He learned that the sulphur spray 
injured the buds to such an extent as to reduce the yield, while it 
prevented curl. The copper spray, however, prevented curl and gave 
a decided increase in yield. He thus reaches the conclusion that 
foiinula A is more injurious to buds than formula C. While this is 
true if the spray is applied at too late a date, it may be safely applied 
at an earlier date. It should also be mentioned that the sulphur sprays 



AUXILIAEY WORK. 



133 



have insecticidal properties much superior to those of the copper 
sprays. 

The Department work conducted by Mr. Hawley seems to have clearly 
demonstrated the possibility of controlling the most severe attacks of 
curl in the lake shore region of Michigan with a single spraying, when 
this is done thoroughly and at the proper time. In experiment 8 the 
untreated trees were so badly affected that, as alread}'^ stated, 90 per 
cent of the foliage and all but 3.7 pounds of the fruit fell from the trees, 
but by spraying similar trees Mr. Hawley saved all but 3 per cent of the 
leaves — a gain of 2,900 per cent of foliage — ^besides increasing the yield 
of fruit 1,424 per cent. In other words, the sprayed trees held 30 
times as much spring foliage and over 15 times as much fruit as the 
unsprayed trees at their side, all being of the same variety. 

In the southern portion of the Michigan fruit belt a number of 
growers assisted the Department in conducting experiments. Among 
the reports received from that section is one by Mr. George Lannin, 
of South Haven. Mr. Lannin's work is summarized in the following 
table: 



Table 37. — ExperimerUal work ccmduded by Mr. George Lannin, of SoiUh Haven^ Micfi., 
in tht spring and summer of 1895. 









Nature of soil, sandy. 
















Formulae for 

45 gallons of 

water. 


Variety of trees. 


trees. 


Number 

of 
trees— 


Date of— 


Percentage 
of leaves 
lost by— 


Date 
when 
loss of 
leaves 
was 
esti- 
mated. 


Fruit 

produced 

by- 


It 

o 

u 

5 


1 


i 

1 


First 
spray- 
ing. 


Second 
spray- 
ing. 


I 
I 
1 


! 

c 


1 


i 


3 
4 


flO Ibe. snl- 
phur, 20 lbs. 
lime, 5 lbs. 
salt. 

5 IbR. copper 
sulphate, 10 

I Ibe. lime. 

2 lbs. copper 
sulphate, 8 
pts. ammo- 

l nia. 

6 oz. copper 
carbonate, 3 
pts. ammo- 
nia. 


Barnard 

mils Chile 

VHales Early 

Icrawfords Late. 


years. 
6 

6 

6 

6 


10 
10 
10 
10 


10 
10 
10 
10 


Apr. 10 
...do.. 
...do.. 
...do^. 


May 17 
June 25 
...do.. 

Junes 


20 
15 
20 
10 


40 
35 
40 
30 


July 10 
...do.. 
...do.. 
...do.. 


Lb8. 

1,200 
1.300 
1,760 
1,800 


Lba. 
830 

600 

680 

700 



The spray formulro tested by Mr. Lannin were not included in the 
work of Mr. Hawley, and are therefore chaiTicterized as Formulae D, 
E, F, and G. As Mr. Lannin sprayed diflFerent varieties of peach trees 
with 4 formulae, the experiments can not be compared with one another 



134 



PEACH LEAF OUBL; ITS KATUBE AND TEEATMENT. 



to advantage. The value of all the sprays used is shown, however, 
by the gain in fruit obtained. The percentage of net gain in fruit 
was 44, 116, 158, and 167 per cent, respectively. These figures show 
that the eau celeste (Formula F) and the ammoniacal copper carbonate 
(Formula G) gave satisfactory results. The action of the disease on 
the foliage of the trees of experiment 3 was more severe than it was on 
the foliage of the trees of experiment 4. The unsprayed trees of the 
former experiment lost 10 per cent more of their leaves than the trees 
of the latter. The percentage of gain in fruit from the sprayed trees 
of experiment 3 was, however, fully as great as that from the sprayed 
trees of experiment 4. This shows that the eau celeste (Formula F) 
was more effective in combating the disease than the ammoniacal copper 
carbonate, which was applied in experiment 4. 

Mr. F. N. Chesebro, of South Haven, sprayed 19 Crawfords Late 
and 19 Oldmixon trees in the spring of 1894, leaving 19 trees of each 
variety for comparison. The formula used was 15 pounds of sulphur, 
30 pounds of lime, and 10 pounds of salt to 60 gallons of water. Mr. 
Chesebro did not report, the exact yield of his trees, but stated that 
the sprayed trees lost 20 per cent of their foliage and the unsprayed 
trees 80 per cent — a saving of 60 per cent of the foliage by a single 
spraying. His report is as follows: 

Table 38. — Experimental work conducted by Mr. F. N. Chesebro , of South Haven, Midi., 

in the spring of 1894- 





[Variety of trees, Crawfords Late and Oldmixon Cling; nature of soil, sandy loam. 










Nimiberof 




Per cent of 




a 






trees— 


1 


leaves lost by— 




S 






. 


i 


Date 
when 


H 


Formula. 


1 




i 


1 

"S ■ 


1 


loss of 
leaves 







O 


I 


>* 


1 


g 


was es<!ti- 
mated. 


i 




1 




t3 


1 




1 








Years. 
















(15 lbs. sulphur 


] 
















J 30 lbs. lime 


\ " 


38 


88 


Mar. 7 


20 


80 




1 


ilO lbs. salt 


June. 




1.60 gal. water 













Mr. J. F. Taylor, of Douglas, Mich., reported favorably upon the 
spray work conducted by him in 1894. He used three different sprays, 
treating 50 trees with each; and leaving a like nunoiber unsprayed 
for comparison. The formulae used were those designated as A, B, and 
i\ in the spray work of Mr. Smith Hawley. Mr. Taylor says, in regard 
to his work: 

The blossom buds had swollen somewhat when I began spraying, but the leaf buds 
were quite dormant. Formula A was used on March 29, Formula B on April 6, and 
Formula C on April 20. Blossoms began to open on the last days of April, and by 
the 6th of May trees were well covered with bloom. The trees sprayed were 6 years 



AUXILIABY WOBK. 135 

old, and of the following varieties: St. John, Bamards Early, Hinman, Switzerland, 
Gold Drop, and Early Freestone. Some of these varieties curled very badly last 
year, especially Early Freestone. The soil is quite uniformly a gravelly loam, with 
clay subsoil under all varieties. I made only one application with each formula. I 
think two applications would have been better. I sprayed 50 trees and then omitted 
50 in each plat, or with each formula. I think Formula C gave as good results sm 
any of them.^ 

After the trees were in full leaf I invited neighboring fruit men to go through the 
orchard and note the conditions of the trees sprayed and unsprayed. They found 
the foliage of tnses that had been sprayed almost fn^e from curl, while the unsprayed 
trees were badly curled. * * * The unsprayed trees had a larger percentage 
of small dead limbs through the top than those that were sprayed, and the prospect 
for future crops is therefore better where the trees were sprayed. * * * I hope to 
follow the work up more extensively next spring, and will begin the work earlier in 
the season, if necessary. If Formula C will continue to give as good results as it did 
last spring, I prefer to use it. 

Mr. S. I. Bates, of Shelby, Mich., sprayed a few Stump the World 
trees in the spring of 1894, leaving an equal niunber unsprayed for 
comparison. The crop from the sprayed trees was double that from 
the unsprayed trees at their side, and a large percentage of the foliage 
was also saved. Mr. Bates states that the spray seems to put new life 
and vigor into the trees, especially young trees. With respect to the 
action of curl on old trees, he writes that there is un old orchard just 
across the road from his own which has had curl until the trees have 
no bearing wood left except at the extreme tops, and the owner "does 
nothing to prevent the disease and gets but little fruit."* 

NOTBS ON THE AUXILIARY EXPERIMENTS IN OREGON. 

The climatic conditions under which peach culture is pursued in Ore- 
gon and Washington vary greatly. At the east of the Cascade 
Mountains the conditions approximate in many districts those pre- 
vailing in much of California. At the west of this range local 
influences determine the greater or less adaptation of each valley or 
region to the cultivation of the peach. Generally speaking, however, 
the humidity of the atmosphere for a major portion of the year is 
much in excess of that prevailing generally at the east of the Cas- 
cades or in California. In this respect also this northwest region 
is quite distinct from the conditions met with in most of the peach- 
growing regions of the East. In fact the climate of western Oregon 
and Washington is such as to call for separate consideration in connec- 
tion with our present work. For this reason special effort has been 

*This is tlie same formula that was found very satisfactory by Mr. Smith Hawley, 
at Ludington, Mich., and by the writer in the Sacramento Valley. 

' There are thousands of such peach orchards in the peach districts of the United 
States. To those who are interested in the renewal of young and bearing wood upon 
lower limbs and upon old trees, the writer would refer to the data presented in Chap- 
ter V of this bulletin, where the influence of sprays on the vegetation of trees has 
bean quite fully considered. 



136 . PEACH LEAF CUBLt ITS NATURE AND TREATMENT. 

made to carry out spraying experiments in western Oregon, so that 
the ne^ds of the growers west of the Cascades could be supplied. 

The great rainfall which annually occurs on the west side of the 
Cascade Mountains makes the vegetation of that region especially 
liable to fungous diseases, and the peach is no exception to this rule. 
In the Willamette Valley, Oregon, along the lower Columbia, and in 
the basin of Puget Sound in Washington, peach leaf curl has become 
a great hindrance to extensive peach culture. In view of these facte, 
many peach growers of Oregon and Washington were requested by 
the Department to conduct experiments for the control of the disease, 
and it was taken up by a number in 1894 and again in 1895. Several 
of the gentlemen who conducted such work prepared reports of the 
same, which should prove of much interest and value to the peach 
growers of both States. 

Among those who entered heartily into the work was Mr. M. 0. 
Lownsdale, of Lafayette, Oreg. This gentleman conducted very 
extensive spraying tests ao<5ording to plans supplied by the Depart- 
ment, both in 1894 and 1896, using in his work as many as 30 acres of 
young peach trees in 1894. At the close of his experimental spray 
work Mr. Lownsdale gave the following general facts respecting the 
situation in the Willamette Valley, in which Lafayette is situated, 
being the center of an extensive fruit-growing region of Yamhill 
County: 

I hand you herewith my report of experiments for the prevention of peach leaf 
curl for the season of 1895, to which I desire to add a few words upon the status of 
the jxjac^h industry in the Northwest. 

Peach growing has been abandoned to a great extent in the Willamette Valley 
because of the attacks of the shot-hole fungus and leaf curl. Growers have not 
understood the causes of their troubles, and have attributed them to peculiar climatic 
conditions, or have grouped them under the indefinite term blight; but now that the 
nature of these fungous troubles is better understood, and the remedies suggested 
have proved so efficacious, it seems that the abandonment of the industry may have 
been premature. The success of the preliminary experiments has restored the con- 
fidence of orchardists in a great measure, and as it becomes widely known that our 
fungous troubles can be controlled, increased attention wall be given to peach 
growing. 

Exi)erimentfl through a stories of four years on a block of 6 acres of Early C?har- 
lotte i)euches indicate that it may be possible to prevent these destructive fungi 
from getting a foothold in an orchard. This block of trees, which was plante<l in 
dormant l)ud, has rec^eived an annual treatment in October and two treatments each 
spring with the ammoniacal copper carbonate, with the exception of the spring of 
1895, when your m(Kiifie<l Bordeaux was applied. Neither leaf curl nor shot-hole 
fungus has developed in this block. A fair crop of fruit was harvested this summer— 
the fourth from the bud — and the trees are healthy and have grown luxuriantly. If 
intending planters would select perfectly healthy trees— either yearling or dormant 
buds — and would give them one treatment in autumn, as the Department has sug- 
gested, in addition to the spring treatment for leiif curl, it is probable that peach 
growing would again Ix^come pr()fital)le in the Willamette Valley. I am convinced 
that if the efficacy of tlie modified Bordeaux mixture for the control of U?af curl 
hid been known five years ago the industry would have been flourishing to-day, for 



AUXILIABY WORK. 137 

with the treatment for leaf curl, which adds so much vigor aad sturdinese to the tree, 
as indicated by the pushing out of dormant buds on lower branches, the liability to 
attacks of other fungi would have been lessened, and it would then have been diffi- 
cult for the great shot-hole wave to sweep over our orchards as it did in 1893 and 
1894. 

The quality of peaches grown in the Willamette Valley is unsurpassed. No 
locality in the United States can produce more delicious fruit. It seems judicious, 
then, to attempt to save this industry and render it profitable again. To this end it 
is to be hoped that the Department's methods for the prevention of these fungous 
attacks will be widely adopted. 

The spray work conducted by Mr. Lownsdale in the spring of 1894 
involved the spraying of some 1,700 young trees and the testing of 
10 spray formulse. With each of the 10 experiments was included 
a considerable number of unsprayed trees left for comparison, these 
control trees being of the same variety as the trees sprayed in the 
same experiment, and in each case they were so located at the sides or 
among the sprayed trees as to admit of just comparison. Mr. Lowns- 
dale's report upon this extensive work is given below. AU the spray 
foi-mulfe prepared by him were for 45 gallons of water: 

Thirty acres of peach trees were devoted to experimental work under your direc- 
tion. These trees were Crawfords Early and Early Charlotte (a seedling from the 
Grawfords Early) . In addition to these tests 10 acres were left wholly untreated 
a^ a block check against the main experiments. All these trees were 3 years old, 
an<l had curled so badly in 1893 that they had twisted into shapeless masses, though 
they had partially recovered later in the season. The general plan of w^ork was to 
treat a block of at least 100 trees with each formula, leaving intervening check rows 
untreated. In some instances check rows were interspersed through the treated 
block, it being desirable to have all conditions as nearly alike as possible. 

Formula A (10 pounds sulphur, 20 pounds lime, 10 pounds salt) was applied March 
21, 1894, to 264 trees in 8 rows, with 2 control rows on each side of the block. Curl 
appeared in about 3 per cent of the foliage jf the sprayed trees, w^hile 60 per cent of 
the foliage of the untreated controls was affected. 

Formula B (5 pounds sulphur, 10 pounds lime, 5 pounds salt) was applied March 
23 to 204 trees in 4 rows, with 2 check rows on each side of block. About 3 per 
cent of foliage was affected, w^hile untreated check rows curled very badly. 

Formula C (5 pounds sulphur, 10 pounds lime) was applied to 166 trees on March 
22 in a block 4 rows wide, with the customary 2 check rows. Curl developed on 
about 10 per cent of the foliage of the treated trees, and upon about 60 per cent of 
that of the controls. 

Formula G (6 pounds copper sulphate, 10 pounds lime) was Applied to 42 trees 
on March 17. About 5 per cent of foliage was affected on the sprayed trees, but the 
controls were so badly affected that they scarcely sun-ived the summer. 

Formula H (3 pounds copper sulphate, 5 pounds lime) was applied March 20 to 
186 trees in a block 6 rows wide. About 8 per cent of the foliage of the sprayed 
trees was affected, while the controls were as under Formula G. 

Formula I (2 pounds copper sulphate, 3 pints 26° ammonia) was applied March 20 
to 26 trees with 26 check trees. About 5 per cent of curl developed on treated trees, 
while the check row was very badly injured. 

Formula J (4 pounds copper sulphate, 5 pounds sal soda, 3 pints 26° ammonia) was 
applie<l March 20 to 26 trees, with 2 check rows of 26 trees. Curl developed on 3 
per cent of the foliage of the treated trees, but the controls were almost destroyed. 



188 PEACH LEAF OUBL: ITS NATUBK AND TBEATMKNT. 

Formula K (5 poiinde sulphur, 15 pouuds lime) wae applied March 19 to 278 trees 
in a block 10 rows wide, with control rows of 69 trees each on each side. Curl 
appeared on about 2 per cent of the foliaf^e of the treated trees, while the check rows 
were, as in the previous year, a mass of curled leaves and twisted branches. Formula 
K was also applied to 25 Salway trees and to 15 Alexanders, which had curled very 
badly for many years, the Salways always being defoliated completely. These trees 
were 8 years old. No curl appeared on either variety. 

Formula L (5 pounds copper sulphate, 15 pounds lime) was applied March 13 and 
again March 21 to 262 trees, with 7 check rows interspersed through the block. LesB 
than one-fourth of 1 per cent of curl appeared on the treated trees of this test, whilp 
the check rows were almost destroyed by the disease. The greater portion of these 
untreated trees have been dug up and replaced (February 13, 1895) . Treated trees 
in this block made an excellent growth, though cultivated only moderately, and a 
great majority were absolutely free from curl. 

The ammoniacal copper carbonate. Formula M (5 ounces copper carbonate, 3 pints 
26° ammonia) , was applied March 22 to 210 trees, 2 check rows of 69 trees being left 
alongside. Less than 3 per cent of curl appeared on the block, while 65 per cent of 
the foliage of the control trees was curled. This formula was also applied twice, at 
intervals of two weeks, upon 5 acres of trees upon which no curl could be found. 
This experiment, though remarkably successful, was not as conclusive as desired, as 
no control trees were left. This was upon a block of thrifty trees, of which I did 
not care to sacrifice any portion to an experiment. The same treatment had pre- 
served them the previous year, and I feared a change. 

All my treated trees have grown satisfactorily this year, but the 10-acre check 
block of untreated trees was so nearly destroyed by curl that all the trees will lie 
dug up. Several hundred are dead, and of the remainder I tliink no tree has hat! a 
growth of 12 inches. 

It will be seen from Mr. Lownsdale's report of the work in 18t*4 
that several of the sprays used gave most excellent results. On May 
18 of that year he wrot/e: 

Curl has developed moderately, and everywhere the better condition of treated 
over untreated trees is apparent. The trees treated with 5 pounds of copper sul- 
phate and 15 pounds of lime may be said to be absolutely free from the curl and the 
experiment a success. This block was sprayed twice in March. The check rows in 
this block and alongside are curled as badly as any trees except seedlings. 

The modified eau celeste (Formula J) is also giving good results, as is the 5 pounds 
of sulphur and 15 pounds of lime; but I l)elieve the copper sulphate, 5-pound for- 
mula, is in the lead. This may be attributed to more thorough work, as most of the 
other sprays were only applied once. 

Owing to the fact that no fruit records could be obtained from Mr. 
Lownsdale's experiments in 1894, as the trees were yet too small, 
arrangements were made for the testing of some of the more valuable 
sprays in the spring of 1895. The experiments of 1896 show the gain 
in both foliage and fruit, though the yield was low, resulting from the 
use of 5 sprays — 1 sulphur and 4 copper. The experiments were con- 
fined to the Crawf ords Early variety, and in each experiment the trees 
received two sprayings in March. All trees were 4 years old, but 
rather small. Mr. Lownsdale's data on this work are presented in 
the following table: 



AUXILIABY WOBK. 



139 



Tablr 39. — JSxperimental work conducted by Mr. M. 0. LownsdcUej of Lafayette, Oreg.y 
in the spring and summer of 1896. 

[Variety of trees, Crawfordfi Early; nature of soil, red hill.] 



FormnlfD for 45 
gallons of water. 






1 
2 
3 
4 
5 \ 



101lM.8alphtir... 

20 lbs. lime 

51b8.8alt 

5 Iba. copper sul- 
phate 

10lbB.lime 

^2 lbs. copper sul- 
phate 

3 pts. ammonia... 

5 oz. copper car- 
bonate 

3 pts. ammonia.., 

5 lbs. copper sul- 
phate 

15 lbs. lime 



Age 

of 

trees. 



Yn. 
4 

4 

4 

4 

4 



Number 

of 

trees. 



110 
116 

268 



Date of— 



First 
spray- 
ing. 



Mar. 7 
...do... 
Mar. 9 
Mar. 8 
Mar. 9 



Second 
spray- 
ing. 



Mar. 27 
....do... 
....do... 

Mar. 28 
....do... 



Leaves lost 
by- 



I 



Percl. 
10 



Tri- 
fling. 

None, 



Date 
when loss 
of 
leaves 
was esti- 
mated. 



Perd. 
85 



June 18 846 



Fruit 
duced 



^/i- 



...do... 
...do... 
...do... 
...do... 



480 

867 

1,264 

1,048 



Lbs. 
187 



16 



But few comments upon the preceding table are required. It makes 
the fact perfectly evident that two spring sprayings are sufficient to 
almost absolutely control leaf curl in the Willamette Valley. In a 
letter written June 25, 1895, Mr. Lownsdale says: 

Peach leaf carl has not developed as badly in this section as it did last year. I 
have estimated that about 40 per cent appeared on most of my control trees. Two 
8pra3rs with lime, 10 and 15 pounds, and copper sulphate, 5 pounds, were an abso- 
lute succees. Lime in the amount of 15 pounds gives the best results, there being 100 
per cent of healthy foliage on trees sprayed with this amount and 5 pounds of cop- 
per sulphate. Practically the same results were obtained with two applications of 
the ammoniacal copper carbonate. It is impossible to fuid a curled leaf on acres and 
acres of treated trees. 

In the Rogue River Valley, in the southern tier of counties of Oregon, 
the conditions are somewhat more favorable for peach culture than in 
much of the Willamette Valley. The climate is somewhat intennedi- 
ate in character between that of northwestern Oregon and northern 
California. Peach culture is quite extensive about Ashland, Medford, 
etc. The reports of Mr. E. F. Meissner, of Kerby, Josephine County, 
and of Mr. N. S. Bennett, of Medford, Jackson County, are fairly rep- 
resentative of those received from experiments conducted in southern 
Oregon. Mr. Meissner's report again shows the great effectiveness of 5 
pounds of copper sulphate, 10 pounds of lime, and 45 gallons of water. 
With this formula he sprayed 4 Salway trees 4 years old, leavingan equal 
number unsprayed for comparison. Two treatments were given, the 
first February 22, the second March 10, 1895. From the sprayed 
trees 10 per cent of the foliage was lost from curl, while from the 



140 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

unsprayed trees 90 per cent was lost, leaving the trees nearly bare. 
Unfortunately, frost killed the buds, and no comparison of fruit wa.*? 
possible, but it is safe to say that the fall of 90 per cent of the leavei^ 
would have caused the loss of the crop, while 10 per cent loss would 
have occasioned little, if any, falling of fruit. Mr. Meissner writes 
respecting his work that the copper sulphate spray "has given far 
better results than the sulphur, lime, and salt," and that " the tree< 
sprayed with the bluestone mixture look the best of any in the 
orchard." 

Mr. Bennett used the 6-pound formula for the Bordeaux mixture 
as given for Mr. Meissner. He sprayed but once, on March 11, 1895. 
The 29 trees sprayed averaged 44 pounds of fruit per tree, while the 
single control tree yielded but 9 pounds, or a net gain in fruit of 388 
per cent. The fact of most interest in connection vrith this work is. 
however, that the variety treated was the Elberta, which is probably 
more universally susceptible to leaf curl than any other variety now 
grown in the United States. The control of curl on this variety was 
almost absolute, as will be seen from the following letter from Mr. 
Bennett: 

I send you to-day a report of the spraying for leaf curl. The experiment was an 
honest trial, and I feel very jubilant over the Buccess. I have reported only the 
Elberta variety, as it was one of that kind which I left unsprayed. I am more than 
pleased with the results, and can say that a good trial is all that any man needs who 
has the welfare of his orchard at heart (his pocketbook as well) . The peaches from 
the sprayed trees were first-class, clean, and sold at the highest market price. I 
notice a very marked difference in the general health of the trees in favor of tho«» 
sprayed. The leaves lost by the sprayed trees were, perhaps, one-half of 1 per cent. 
The unsprayed tree was a little above an average tree in the spring. There were 29 
sprayed trees, which yielded an average of 44 pounds of choice fruit to the tree^ 
nearly half of which packed 56 peaches to the box. I sprayed 75 Wheatland tretfs 
with the same success as far as leaf curl is concerned. They are fine, healthy trees 
now, and bore a good crop this season. They have been bad about curling, but I 
left an Elberta because that variety is the worst to curl, and if spraying did them no 
good I intended to grub them out. 

Mr. P. W. Olwell, of Centralpoint, Oreg., applied the sulphur 
spray to 400 Muir trees in his orchard, leaving 25 trees unsprayed for 
comparison. The formula used by Mr. Olwell was 15 pounds of sulphur, 
30 pounds of lime, and 10 pounds of salt to 60 gallons of water. Wis 
trees were 5 years old, growing in black, loamy soil. They were 
sprayed March 10. The sprayed trees did not lose any foliage from 
disease, while the control trees lost 25 per cent. The fruit i-ecorck 
were not reported. 

NOTES ON THE AUXILIARY EXPERIMENTS IN CALIFORNIA. 

Besides the experimental work conducted by the writer in the Sac- 
ramento Valley in the years 1894 and 1805, a considerable number of 
growers assisted in carrying on experiments in different portions of 



AUXILIABY WORK. 



141 



California. Reports have been received from several of these growers, 
and while in some instances they are not as complete as desired, the 
results shown are amply sufficient to determine the practical value of 
the work undertaken. 

Among the more complete and carefully prepared repoi*ts is one 
from Mr. A. D. Cutts, of Live Oak, Sutter County. The work was 
carried out in the winter of 189^93, and was one of the experiments 
which led to the writer's detailed series of experiments outlined in the 
present bulletin. In this orchard the spray was not used in 1893 for the 
control of leaf curl, but was applied for the purpose of destroying the 
San Jose scale, which was gaining a foothold in the orchard. The 
trees infested by scale were scattered through a 40-acre block of the 
Crawf ords Late variety. These trees had been marked, and in Febru- 
ary, 1893, were thoroughly sprayed with the sulphur spray, consist- 
ing of 16 pounds sulphur, 30 pounds lime, 10 pounds salt, and 60 gal- 
lons water. Only a few of the trees were entirely sprayed. As curl 
developed seriously in that region in the spring of 1893, the contrast 
between the scattered sprayed trees and the remainder of the block 
was very striking, and Mr. Cutts kindly consented to preserve the 
records of yield of a few of the sprayed and unsprayed trees for use 
in this connection. In the table which follows is shown the amount 
of fruit produced by each of the 9 sprayed trees included in Mr. 
Cutts's records, as well as the weight and number of first, second, and 
third quality peaches. The same facts are given for an equal num- 
ber of neighboring unsprayed trees for comparison. 



Table 40. — Expervmental work conducted by Mr, A, D, CiUts, of Live Oak^ Oal., in the 

spring and mmmer of 189S, 

[Crawfordfl Late, 4 years old.] , 



No. of 
tree. 



Total. 



Sprayed trees. 



Total pounds of- 



166 
226 
ISO 
119 
180 
176 
279 
55 
126 



a 



115 
189 
145 
100 
146 
154 
225 
38 
106 



1,497 i 1,218 



196 



'o£ 



83 



Number of— 






276 
735 
615 
386 
605 
568 
815 
148 
367 



4,514 



u 



96 
126 
110 

70 
138 

86 
151 

60 

65 



902 






29 
ISO 
46 
54 
60 
32 
139 
30 
27 



Unsprayed trees. 



Total pounds of— 



58 



u 

u 



23 



81 



u 



21 



1^ 



Number of— 



2S, 



102 






56 



56 



The average yield of fruit of the sprayed trees given in the table 
was 166.22 pounds per tree, while the average yield of the unsprayed 
trees was but 6.44 pounds. This represents a gain in fruit by the 



142 PEACH LEAF OUBL: ITS NATURE AND TREATMENT. 

sprayed trees above the yield of the unsprayed trees of 24.8 times the 
yield of the latter. In other words, there was a gain in yield of 2,481 
per cent from spraying. Much valuable information was also supplied 
by Mr. Cutts in relation to the preparation and application of sprays, 
and the writer has considered these subjects in other portions of the 
bulletin. Some of the more striking photographs of sprayed and 
unsprayed trees have also been obtained from Mr. Cutts's orchard, 
as well as the records of fruit buds elsewhere discussed (Pis. VII 
and XX). 

The report of a test of the Bordeaux mixture (5 pounds copper 
sulphate, 10 pounds lime, and 45 gallons water) was furnished by Mr. 
H. B. Gay lord, of Auburn, Placer County. This experiment was 
made in the spring of 1896. Mr. Gaylord sprayed 10 Heaths Cling 
peach trees and 4 nectarine trees, the variety of which was not stated. 
The spraying was done February 15. Mr. Gaylord states that the 
unsprayed nectarines curled so badly that they bore no fruit at all, 
while the 4 sprayed trees yielded 320 pounds. He says that every 
alternate tree was sprayed in a row of nectarines, and that the sprayed 
peach trees were in the worst places in. the orchard. Respecting the 
result of the work Mr. Gaylord writes, in part: 

I herewith send you a partial report on the experiment for leaf curl. I used only 
one formula. The result is iteriecily satisfactory. I sprayed some peach and K»nie 
nectarine trees, both with good results. One nectarine tree sprayed has not a curled 
leaf, while one of the same kind, ahout 15 feet from it, which was not sprayed, ha*? 
lost nearly all its leaves. The contrast is so great that it would he worth while to 
have them photographed. A neighbor, Mr. G. P. Dixon, used formula .3 (2 |)onnds 
copper sulphate, 3 pints ammonia, and 45 gallons water) with the same results, so 
that I am satisfied that the copper sulphate is what does the work. 

Mr. Guylord also states that no leaves were lost from the peach trees 
sprayed, while all of the leaves curled on the unsprayed trees of the 
remainder of the orchard. 

In Amador County an extensive experiment was made in the spring 
of 1895, by Mr. George Woolsey, of lone. Mr. Woolsey sprayed some 
2,500 trees of various varieties of peach and nectarine with 5 pounds of 
copper sulphate, 10 pounds of lime, and 45 gallons of water, and left 
720 trees unsprayed for comparison. The spraying was done from 
February 20 to March 10. Most of the sprayed trees lost no foliage, 
but a few in a wet situation lost not to exceed 25 per cent, while the 
, unsprayed trees lost not less than 50 per cent of the leaves and a large 
amount of fruit. 

Mr. Woolsey gives some notes respecting the work in the spring of 
1895, as follows: 

A block of about 200 trees, Salways 12 to 15 years old, on well-drained soil, and 
500 Salways 4 years old, adjoining, I did not spray, thinking they were curl proof. 
I regret I did not spray them. * * * The leaves are dropping, as well as a large 
percentage of the fruit. I shall certainly spray them in the future. * * » The 



DESCRIPTION OF PLATE XX. 

Sprayed and unsprayed Crawfords Late trees in the orchard of Mr. A. D. Cutt*', 
Live Oak. The tree at the right wa£i sprayed in February, 1893, with lime, sulphur, 
and salt; the trees at the left were untreated. See "Notes on auxiliary experi- 
ments in California," for a full account of the work at Liveoak. (Photographed 
in May, 1893, after most of the diseased leaves had fallen from the unsprayed trees. 
Compare with PI. VII.) 



Bull. 20, Oiv. Veg. Phys. & Path.. U. S. Oept. of Agriculture. 



Plate XX. 



O 

> 



o 

> 




AUXILIABY WOBK. 143 

apparent result of spraying, one application, is as follows: Four control trees of Early 
Rivers, adjoining trees sprayed March 2, are badly curled, leaves dropping, and also 
the greater portion of the fruit. The adjoining sprayed trees of this tender variety 
are all right (no curl) and make quite a marked contrast. Besides these, 4 white 
nectarines and 4 Bilyeau peaches, left at the same time, show curl and loss of fruit, 
although not as badly as the Early Rivers. The surrounding sprayed trees look 
vigorous and healthy, with no curl. 

Mr. Woolsey was among the first peach growers to adopt the copper 
sprays for the control of curl. His first experiments were made in 
1892, and they proved so satisfactory that he sprayed quite extensively 
in 1893 and again in 1894. The work in 1893 was of special interest, 
as the following extract from a communication received from him will 
show: 

I sprayed nearly all my peach and apricot trees. I say nearly all; for, time press- 
ing, I found I would not get over all the peaches, so to save what I considered the 
most valuable portion, viz, the young lower growth, I had that sprayed and left the 
tops unsprayed. The season was a damp one and leaf curl was very prevalent with 
my neighbors. On my place all trees sprayed were exempt, all others badly affected 
and crops on them almost a failure. On the ones partly sprayed there was a healthy 
growth on the lower part of the trees, while they were denuded of foliage above. 

Mr. Woolsey's work in 1894 was negative, owing to the nondevelop- 
nient of the disease that season. 

Two peach growers of Eldorado County, Mr. John M. Day, of 
Placerville, and Mr. A. L. Kramp, of Diamond Spring, furnished the 
writer with reports of their experiments conducted in the spring and 
summer of 1895. Mr. Day tried 4 formulse, each showing a decided 
saving of foliage, but the fruit was lost from frost. The spray used 
by Mr. Kramp was composed of 10 pounds sulphur, 20 pounds lime, 5 
pounds salt, and 45 gallons of water. He sprayed 600 trees, 3 years old, 
of the Hales Early, Briggs Early, and Wilcox Cling varieties, and 3,000 
unsprayed trees were left for comparison. The sprayed trees lost no 
foliage and yielded 48,000 pounds of peaches, while the unsprayed 
trees lost not less than 50 per cent of their leaves and yielded 60,000 
pounds. The average yield of the sprayed trees was thus 80 pounds 
per tree, while the average yield of the unsprayed trees was but 20 
pounds, a net gain of 300 per cent. 

Gen. N. P. Chipman, of Red Bluff, has been using for at least two 
years a f ormida for Bordeaux mixture which gave the writer exceed- 
ingly S^^^ results at Biggs (see row 21 of the writer's experiments, 
p. 117). Mr. Chipman writes that his experiments were upon several 
varieties of peach trees and that excellent results were obtained. He 
further says: *'l used equal parts, or 5 pounds bluestone, 5 pounds 
quicklime, and 45 gallons water. I believe you have found an infalli- 
ble remedy. I have used this spray two years with good effect." Mr. 
Chipman first observed the effects of this spitiy in the experiment 
block at the Rio Bonito orchard, in the summer of 1895. 



144 PEACH LEAF CURL! ITS NATUEE AND TREATMENT. 

NOTES ON THE AUXILIARY EXPERIMENTS IN NEW YORK, INDIANA, AND 
OTHER PEACH-GROWING STATES. 

Much experimental work for the control of leaf curl has been under- 
taken at the suggestion of the Department by the peach growers of 
New York, Indiana, Illinois, Ohio, Kentucky, Maryland, Pennsylva- 
nia, Georgia, Tennessee, North Carolina, Arkansas, Missouri, Kansas, 
and other peach-growing States not already considered in this bulletin. 
For instance, 80 prominent peach growers of various peach-growing 
centers of New York were given full instructions for the control of 
curl in the winters of 1893-94 and 1894-95, and requested to report their 
work, which in a number of instances was carefully done. The same 
is true of 54 growei-s in Ohio, 135 in Pennsylvania, etc., and in each 
case where the work was properly conducted the results were in har- 
mony with those already discussed in this chapter. For this reason, 
as well as from the fact that the work already considered has been 
selected from those sections of the country which are fully represen- 
tative of the different climatic conditions, it is not thought necessary 
or desirable to enter much further into the details of the work. One 
or two experiments may be mentioned, however, before closing the 
consideration of this phase of the subject. 

Mr. Joseph M. Cmvens, of Madison, Ind., reported almost absolute 
success in the control of curl in his orchard. The sprayed trees of 
the 4 experiments made in no case showed more than 3 per cent of 
curled leaves, while the amount of curl on the foliage of the unsprayed 
trees ranged from 25 to 45 per cent. Mr. Cravens states in a letter 
accompanying his report that he sprayed separate rows through his 
orchard which were sufficiently far apart not to have the spray affect 
the intervening rows even if the wind blew at the time of application, 
and further that he is satisfied that two of the sprays used would have 
given absolute results had they been applied to every portion of every 
twig. 

Mr. W. T. Mann, of Barkers, N. Y., sprayed 25 trees with the lime, 
sulphur, and salt spray April 9, 1894, and left 25 trees at their side 
without spraying for comparsion. On May 28 only 42 diseased leaves 
were found on the 25 sprayed trees, while as high as 40 per cent of 
curled foliage was present on some of the unsprayed trees. On the 
same date as the other spraying was done 25 trees were sprayed with 
Bordeaux mixture, while 21 were left for comparison. By May :?S 
only 59 curled leaves had developed on the entire 25 sprayed trees, 
while of the 21 unsprayed trees several had as high as 30 to 35 per cent 
of curled leaves. Mr. Mann says that from the fact that among the 
50 trees treated not one showed an appreciable amount of disease, 
while all through the orchard trees were badly affected, was to him 
very satisfactory evidence of the value of the treatment, especially as 



AUXILIARY WORK. 145 

he did not undertake the work with any great degree of confidence as 
to successful results. 

Mr. James A. Staples, of Marlboro, N. Y., states that in the sea- 
sons of 1894, 1895, and 1896 he made the spray tests on peach trees 
for leaf curl which had been suggested by the writer, and says he 
I."- well satisfied that the disease can be controlled by proper spraying. 
He states that the winter treatment gave him the best results. 

Mr. A. D. Tripp, of North Ridgeway, N. Y., states in his report of 
spray work for curl that he treated 208 trees and left 320 trees 
unsprayed. From the sprayed trees he gathered "360 baskets of as fine 
fruit as ever went to market." The baskets were one-third of a bushel, 
and the peaches averaged 56 to the basket. Trom the untreated trees 
only 15 baskets were gathered, and a portion of this fruit was imper- 
fect. The variety was the Elberta. 
19093— No. 20 10 



CHAPTER VIII. 

PREPARATION, COMPOSITION, AND GENERAL CHARACTERS OP 

THE SPRAYS USED. 

PREPARATION OF THE COPPER SPRAYS. 

It is not the intention to consider in this place the many forms of 
copper sprays which have been used at one time or another in the 
treatment of fungous diseases, but to confine the discussion to those 
forms tested in the present work. 

Most of the formulae for those copper sprays which have been tested 
in the treatment of peach leaf curl have been personally prepared at 
one time or another and the results they gave have been carefully 
studied. Several other formulae have been recommended by the writer, 
but these were prepared and applied by the growers themselves, so 
that for the results of this work their reports have been consulted. 
There are still a few other formulae for copper sprays which have 
been reported upon, but these are the suggestions of others or were 
chosen by the growers themselves. 

The different copper sprays which have been tested in separate form 
(not in union with other fungicides) are shown in the following list 
This list includes 22 distinct formulae. Each formula is that used with 
45 gallons of water, except the first for Bordeaux mixture, which was 
with 4:8 gallons. 

Table 41. — Copper sprays applied for the control ofj)each leaf curl. 

Copper siUphate solution: 

* 4 pounds copper sulphate, 45 gallons water. ^ 

* 2 pounds copper sulphate, 45 gallons water. 
Bordeaux mixture: 

1 24 pounds copper sulphate, 45 pounds lime. 
*6 pounds copper sulphate, 15 pounds lime. 
X 5 pounds copper sulphate, 15 pounds lime. 
*3 pounds copper sulphate, 15 pounds lime. 
X 6 pounds copper sulphate, 10 iK>unds lime. 

* 5 pounds copper sulphate, 10 pounds lime. 

* 3 pounds copper sulphate, 10 pounds lime. 

* 5 pounds copper sulphate, 5 pounds lime. 

* 4 pounds copper sulphate, 5 pounds lime. 

* 3 pounds copper sulphate, 5 pounds lime. 



* Prepared and tested by the writer, and in many cases also tested by growers. 
t Chosen and tested by grower. 

X Recommended by the writer, but tested by the growers. 
146 ' > 



PREPARATI' N OF THE COPPER SPRAYS. 147 

Bordeaux mixture — Continued 

* 2 pounds copper sulphate, 5 pounds lime. 
*6 pounds copper sulphate, 4 pounds lime. 

* 6 pounds copper sulphate, 3 pounds lime. 
*3 pounds copper sulphate, 2 pounds lime. 

Eau celede: 

*4 pounds copper sulphate, 3 pints ammonia (26°). 

* 2 pounds copper sulphate, 3 pints ammonia (26°) . 
Modified eau celeste: 

*4 pounds copper sulphate, 5 pounds sal soda, 3 pints ammonia (26°). 
*2 pounds copper sulphate, 3 pounds sal soda, 2 pints ammonia (26°) . 
Ammoniacal capper carbonate: 

* 5 ounces copper carbonate, 3 pints ammonia (26°) . 
*3 ounces copper carbonate, 2 pints ammonia (26°) . 

* Prepared and tested by the writer, and in many cases also tested by growers. 

The preparation of the copper sprays containing different chemical 
coQstituents will be considered in the order in which they appear in 
the preceding list. 

COPPER SULPHATE SOLUTION. 

Copper sulphate (CuSO^.SH^O), commonly called blue vitriol or 
bluestone, forms, when dissolved in water, one of the most active 
fungicides known. This chemical, the composition, manufacture, and 
sources of supply of which will be more fully considered in a follow- 
ing chapter, dissolves in cold water, but somewhat more readily in 
hot water. As usually sold, the crystals are large, but a fine form 
may also be had in the market. If the large crystals are purchased 
and it is desired to dissolve them rapidly, they may be ground in a 
bone or shell mill before placing in the water. This has frequently 
been done by the writer when quick work was necessary. 

Copper sulphate may be manufactured by dissolving the black oxide 
of copper in sulphuric acid, or by the various modifications of this 
process hereinafter discussed. A watery solution of this chemical is 
strongly acid, and for this reason a simple solution of copper sulphate 
is very corrosive and injurious to tender plant tissues, as foliage and 
opening buds. To avoid this injurious action, efforts have been made 
to obtain from the copper sulphate solution a spray retaining the 
fungicidal action of the copper, but by the addition of other chemicals 
to neutralize or largely remove its acid reaction and consequent cor- 
rosive effects upon plants. As a result there are a very considerable 
number of copper sprays, representing various modifications of the 
simple solution of copper sulphate. 

Owing to the acidity of a solution of copper sulphate, the sulphate 
should not be dissolved or handled in metal dishes of any kind, espe- 
cially those of iron. The copper will often go to the metal, thus 
injuring the effectiveness of the spray, and the acid may also injure 
or destroy the dishes. The most suitable vessels for dissolving copper 



148 PEACH LEAF OURLI ITS NATURE AND TREATMENT. 

sulphate for work such as here discussed are those composed wholly 
of wood, preferably of oak, and may be in the form of barrels, casks, 
vats, or tanks, of a capacity corresponding to the respective needs of 
the growers. For small orchards a few good oak barrels of 45 or 00 
gallons capacity are very suitable. As concentrated solutions of cop- 
per sulphate can be made, enough of the sulphate can be easily dis- 
solved in a 60-gallon barrel to serve for 300 or even 1,200 gallons of 
spray when properly reduced. It is well, when possible, to use 2 
gallons of water to each pound of sulphate when dissolving the latter, 
but stock solutions may be of two to four times this strength. A 
solution of copper sulphate is heavier than water, so that it is an 
advantage in hastening the dissolving process to retain the chemical 
near the top of the water. If this can be done, the heavier copper 
solution will settle to the bottom of the barrel, leaving the purer 
water to continue the dissolving action upon the sulphate. The 
placing of the copper in a gunny sack and suspending the latter in 
the water has been recommended, but it is thought that other means 
more suitable may be found. The use of sacks or other cloths about 
the spray tanks is hardly advisable, as the freer the tanks are kept 
from lint, strings, fibers, etc., arising from straining cloths, sack?, 
frayed staves, and stirring sticks, the less trouble the sprayer will 
have with his nozzles in the orchard, and the better, quicker, and 
cheaper can the spray work be done. 

Instead of a sack, a clean willow or hard- wood splint basket may be 
used for suspending the chemicals. A box may also -be easily made 
for the purpose. It should have a diameter, when about 1 foot 
deep, sufficient to hold the copper sulphate to be dissolved, and it 
should be open at the top, with strong 1-inch slats across the bottom, 
the latter to be set one-fourth inch apart. If the box be fitted with 
a strong hoop bail it may be suspended in the barrel by placing a stick 
through the bail and across the top of the barrel. As a rule, how- 
ever, the writer has found it sufficient to place the copper sulphate 
directly in the bottom of a good oak barrel, filling the latter one-third 
to one-half full of water, and stirring and crushing the crystals with a 
clean hard-wood pounder. A half hour's work is sufficient to dissolve 
many pounds of copper sulphate in this manner. With three or four 
good barrels one man can thus keep a large spraying gang supplied 
with material, if the water be convenient. It is always an advantage 
to place the copper in water in the barrels over night, when possible, 
as sufficient material is thus easily made ready in the morning for a 
half day's spraying. It is an advantage to strain all water before the 
copper sulphate is added, as afterwards ordinary strainers are liable 
to be injured by the acid, and, as before stated, the use of cloth 
strainers is not advisable. 

The eyes and hands should be protected as much as possible from 



PBEPABATION OF THE COPPER SPRAYS. 149 

injury b}' this spray (p. 171). The unaltered solution of the copper 
sulphate is not only unpleasant to handle and apply, and injurious to 
tender vegetable tissues, but it is quite injurious to all metallic parts 
of pumps, hose, extension rods, and nozzles, nozzles being eaten out 
very rapidly by it. For these various reasons the solution of 
copper sulphate is rarely used as a spray in an unmodified form. In 
most cases its corrosive action is more or less altered or neutralized 
through the addition of some modifying agent. In other words, the 
copper sulphate solution is used as a base or stock solution for the 
preparation of several more or less noninjurious and equally effective 
sprays, as the Bordeaux mixture, the eau celeste, the modified eau 
celeste, the ammoniacal copper carbonate, etc. For this purpose it 
may be prepared in a concentrated solution, to be used as a stock 
solution for the preparation of any of the modified sprays mentioned, 
as already pointed out. 

A convenient strength for stock solutions is 1 pound of copper sul- 
phate to 1 or 2 gallons of water. In using stock solutions, two matters 
should always be considered: (1) The pails, barrels, or tanks used 
should be carefully gauged and marked, so that the number of gallons 
of water or of the solution they contain may be known and not guessed 
at.* (2) Before dipping from a stock solution any required number 
of gallons, the solution should be thoroughly stirred, othei'wise the 
last dipped out will be very much stronger than that coming from the 
top, and consequently the work will be inaccurate and often very 
unsatisfactory; moreover, neglect of this precaution might, in many 
cases, lead to the injury or even to the destruction of the plants 
treated. It may also be said that the copper sulphate solution should 
be cold when used in the preparation of Bordeaux mixture, eau celeste, 
modified eau celeste, or ammoniacal copper carbonate. 

BORDEAUX ItflXTUKE. 

Bordeaux mixture is prepared by uniting the milk of lime with a 
solution of copper sulphate. The reaction which takes place when 
the two solutions are united as well as the other chemical phases 

' The following rales for measuring square and round tanks and casks may prove 
of value in this connection: 

Circular cUtems. — Multiply the square of the diameter in feet by the depth in feet 
an<l the product by 5J for the contents in gallons. 

Circular casks or barrels. — Multiply the square of the average diameter in inches by 
34, and that by the height in inches, and point off four figures. The result will be 
the contents in gallons and decimals of a gallon. The average diameter of a barrel 
may usually be obtained by adding the greatest diameter to the least diameter and 
dividing by 2. 

Square tanks. — ^Multiply the width in feet by the length in feet, and that by the 
depth in feet, and that again by 7jVo> which will give the contents in gallons. 
Another and simple method is to multiply the length, width, and depth in inches, 
and divide by 231, which will also give the contents in gallons. 



150 PEACH LEAF CURL! ITS NATURE AND TREATMENT. 

of the subject, have formed the base for much discussion and investi- 
gation, which it is not necessary to consider here, especially as these 
chemical changes are variously interpreted by different writers. 
Those interested in the history and chemistry of Bordeaux mixture 
may learn of the extensive literature upon these subjects by referring 
to the writings of Lodeman/ Fairchild,* and others. 

In the union of the milk of lime with a solution of copper sulphate 
there is produced a mixture having great value as a general fungicide, 
and, as already shown, of especial value for the treatment of peach 
leaf curl. The mixture possesses several advantages for orchard work 
over a simple solution of copper sulphate: (1) The addition of suffi- 
cient milk of lime to a simple solution of copper sulphate neutralizes 
the acids of the latter to such an extent that the resulting niixtm*e is 
practically noninjurious to foliage and buds, while still retaining the 
fungicidal qualities of the simple sulphate solution. (2) The corrosive 
action of Bordeaux mixture upon pumps, pipes, nozzles, etc., is com- 
paratively slight. This is of great advantage in doing uniform and 
thorough work. (3) The lime of Bordeaux mixture causes the spray 
to become visible upon the trees sprayed, and while this is not 
desirable in the spraying of maturing fruits, and is avoided by adopt- 
ing other sprays, it is of very great value in the treatment of bare 
dormant trees, as it enables the workman to distinguish the sprayed 
from the unsprayed portions of the tree, and thus to complete his 
work more thoroughly than could otherwise be done. In case of the 
employment of hired help for applying sprays, as is usually done, the 
superintendent or owner of the orchard may know beyond question 
by the appearance of the trees whether or not his men are doing satis- 
factory work. As thoroughness is a matter of prime importance in 
the treatment of peach leaf curl, too much stress can hardly be placed 
upon this advantage of Bordeaux mixture over several other sprays. 
(4) The adhesive qualities of Bordeaux mixture are very great, 
and therefore it is even more desirable for a winter than for a 
summer spray. This is especially so in portions of the country where 
the sunmiers are dry, as on the Pacific coast. (5) The whitening of 
the trees by the use of Bordeaux mixture, provided the spraying 
is done somewhat early in the winter, is claimed to retard the develop- 
ment of the buds. The unsprayed trees absorb more heat, which 
causes the buds to swell during warm days in winter, thus making 
them liable to injury from subsequent cold.' 

The methods of preparing Bordeaux mixture for large and small 
orchards may vary according to the requirements and facilities of the 

^Lodeman, E. G., The Spraying of Plants, Macmillan A Co., 1896. 

'Fairchild, D. G., Bordeaux Mixture as a Fungicide, Bull. No. 6, Division of Vege- 
table Pathology, U. S. Dept of Agr. 

» Whitten, J. C, Winter Protection of the Peach, Mo. Agr. Exp. Sta. BulL No. 38. 
Some of the concUisions from the work of Mr. Whitten are: Whitening the twigs and 
buds by spraying them with whitewash is the most promising method of winter pro- 
tection tried at the Missouri Station; whitened buds remained practically donnant 



PREPARATION OF THE COPPER SPRAYS. 151 

growers, but the general principles involved remain the same. As a 
common example, the manner of preparing the 5-pomid formula will 
be described: In a 46 or 60 gallon barrel place 5 pounds of copper sul- 
phate and add 10 or 12 gallons of water. Pound and stir the copper 
sulphate until wholly dissolved. In a half barrel slake 5 pounds of 
quicklime and reduce with 10 or 12 gallons of water. Strain the milk 
of lime into the copper solution, stir thoroughly, and add sufficient 
water to make 46 gallons in all. The copper and lime solutions should 
both be cold when united. When the water is added and the whole is 
well stirred the spray is ready to be applied. 

For the manner of preparing the stock solution of copper sulphate to 
be used for Bordeaux mixture the reader is referred to pages 148 and 
149, where full instructions will be found. In respect to the addition of 
lime to the copper solution, it may be said that the milk of lime result- 
ing from the slaking of 2 pounds of good quicklime in 6 or 8 gallons 
of water is sufficient to neutralize a solution of 3 pounds of copper 
sulphate. Larger amounts of copper should receive larger amounts 
of lime in proportion. In case foliage is to be treated, however, it is 
well before using the mixture to test it according to one of the methods 
given,* or to bring the weight of quicklime used to three-fourths, 

until April, when unprotected buds swelled perceptibly during warm days late in 
February and early in March; whitened buds blossomed three to six days later than 
unprotected buds; 80 per cent of whitened buds passed the winter safely, and only 
20 per cent of unwhitened buds passed the winter unharmed. These facts point to 
those sprays having large amounts of lime as most valuable in protecting buds, and 
they should be considered in those sections of the country where the buds are liable 
to winter injury. A Jbll spraying may also l>e a decided advantage in such situations 
in addition to the early spring spraying for curl. 

See also on this subject the January number of the Canadian Horticulturist, 1899, 
pp. 18-20. 

' There are at present several convenient methods practiced in making Bordeaux 
mixture to determine if enough lime has been added to the copper sulphate solution 
to prevent injury when the mixture is applied to foliage. We adapt the following 
two tests from Farmers* Bulletin No. 38 of this Department, p. 7: (a) After the 
milk of lime and copper sulphate solutions have been united and thoroughly stirred, 
hold the blade of a penknife in the mixture for at least a minute. If metallic copper 
forms on the blade or the polished steel surface assumes the color of copper plate, 
the mixture is still corrosive and should receive more milk of lime. If the blade 
remains unchanged, the mixture may be safely applied to most foliage under favor- 
able weather conditions, (b) Pour some of the mixture into a saucer, hold between 
the eyes and the light, and breathe gently upon it for at least half a minute. If the 
mixture is properly made, a thin pellicle, looking like oil on w^ater, will begin to 
form on the surface. If no pellicle forms, more milk of lime should be added. A third 
test (c) may be made with a 20 per cent solution of ferrocyanide of potassium: After 
the milk of lime is added to the copper sulphate solution, and the whole is thoroughly 
stirred, dip up a coffee cup full and add to this a few drops of the ferrocyanide of potas- 
sium solution. Allow the cup to stand a few minutes and then pour off the mixture 
carefully. If a red precipitate is found at the l)ottom of the cup, the mixture requires 
more milk of lime, which should he added until no such red precipitate is formed 
when the test is repeated. 



152 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

four-fifths, or five-sixths of the weight of the copper sulphate used 
With the present experiments it has been unnecessary to take this 
matter into consideration, for the spray was applied to dormant trees, 
not likely to be injured by any moderate spray. In nearly all thefor- 
muIaB tested for curl the pounds of lime employed were equal or 
greater than the number of pounds of copper sulphate used. 

The lime used in preparing Bordeaux mixture should be unslaked 
lime or quicklime of the best quality. There is no economy in using 
poor lime, and air-slaked lime should never be used. The use of poor 
or air-slaked lime is apt to result in an imperfectly neutralized, and 
very granular, unsatisfactory spray. While the slaking of lime and 
the preparation of a milk of lime is a very simple matter, it is one 
which few people not accustomed to the process will do well the first 
time. If not properly slaked, there are apt to be hard particles in the 
spray, causing trouble with the nozzles. In slaking lime, water should 
be added to the lime only fast enough to keep it from overheating, 
adding a little more each time as the heat increases. With some lime 
the use of a little hot water to start the slaking will hasten the pro- 
cess. With a little practice this work can be done so as to result in a 
perfect putty or cream of lime. When the thick, creamy consist-ency 
is obtained, it is well to allow the mixture to stand for half an hour, 
if possible, while hot, being sure that enough water is present to pre- 
vent drying out. If the Bordeaux mixture is then to be made, cold 
water should be added to the lime putty, or cream, and the whole 
stirred until it becomes a milk of lime and is cool. About 3 gallons 
of water should be added for each pound of lime. This cool or cold 
milk of lime should now be strained through a wire sieve or strainer 
into the copper sulphate solution, previously prepared, and the whole 
thoroughly stirred. 

The solution of copper sulphate should also be cold when the milk 
of lime is added. After the two solutions are thoroughly united the 
mixture may be reduced to the required amount with cold water, when 
the spray is ready for use. The lime and copper solutions should 
never be united more than a few hours before the spray is to be applied. 
When making Bordeaux mixture wooden vessels should be used, a^? 
barrels, half barrels, tanks, etc. 

For peach leaf curl the amount of copper sulphate and lime to bo 
used to 45 gallons of water will vary according to the views of the 
grower, after making a study of the results obtained from the diflferent 
formulae tested in the present series of experiments. 

EAU CELESTE. 

The preparation of eau celeste is very simple. To each 2 pounds 
of copper sulphate dissolved in 6 or 8 gallons of water add 3 pints of 
strong ammonia, stir thoroughly, and dilute to 45 gallons. The stock 



PREPABATIOK OP THE COPPER 8PBAYS. 153 

solution of copper sulphate may be used in preparing this spray. 
Four pounds of copper to 3 pints of ammonia for 45 gallons of water 
has also proved an effective winter spray. 

For dormant trees this spray is safe, but for the treatment of foliage 
it is too corrosive and burning. It is also quite corroding to nozzles and 
other metallic portions of the spi'aying outfit. 

MODIFIED EAU CELESTE, 

The modified eau celeste is less injurious to foliage than the eau 
celeste, but is more liable to injure tender leaves and buds than is well- 
made Bordeaux mixture. Its preparation is nearly as simple as that 
of the eau celeste. To 4 pounds of copper sulphate dissolved in 10 or 
12 gallons of water add 3 pints of strong ammonia, dilute with water 
to 45 gallons, and stir in this mixture 5 pounds of sal soda (common 
washing soda) until dissolved. In preparing this spray of different 
strengths the same proportions of the chemicals may be maintained. 

AMMONIACAL COPPER CARBONATE. 

The ammoniacal copper carbonate spray is one of great usefulness 
in the treatment of fruits for fungous diseases, especially where the 
spotting of fruits by the ;ise of lime is to be avoided. The fungicidal 
value of this spray is, however, far inferior to the ordinary Bordeaux 
mixture. In the treatment of peach leaf curl it has proved less satis- 
factory than several of the other copper sprays. 

The manner of preparing this spray is simple. Place 5 ounces of 
copper carbonate in the bottom of a 3-gallon crock. From a i^-gallon 
vessel full of water pour about one-half pint of water upon the copper 
carbonate and stir the latter until it becomes like paste. Now add the 
remainder of the 2 gallons of water, stir again, and then pour into 
the mixture 3 pints of 26^ ammonia. After this has been thoroughly 
stirred, it should be covered and allowed to stand for half an hour, 
when the whole should be added to a barrel containing 43 gallons of 
water. When well mixed this spray is ready to be applied. 

A concentrated solution of copper carbonate in strong ammonia may 
be made as above described, using but one-half of the amount of water. 
If such a solution is very tightly stoppered in a large demijohn or jug 
it may be kept as a stock solution, ready for use at any time. By 
knowing the amount of copper carbonate in each quart of such a stock 
solution enough may be measured out at any time to prepare a given 
number of gallons of spray of any desired strength. 

The copper carbonate used in the preparation of the present spray 
is frequently not obtainable in quantity at the drug stores in smaller 
towns. It is also frequently the case that druggists in such places 
charge two or three and sometimes four or five times as much as it is 
worth, making the ultimate cost of the spray beyond the reach of the 



154 PEACH LEAF CXTRL: ITS NATURE AKD TREATMENT. 

grower. For this reason the writer gives, on page 183 of this bulletin, 
a simple way of preparing the copper carbonate on the farm at a 
minimmn figure.* 

PREPARATION OF THE SULPHUR SPRATS. 

While the use of copper sulphate as a base for sprays intended for 
the control of fungous diseases is very general, there are special dis- 
eases or combinations of diseases which may be more cheaply, and 
often more successfully, treated with sulphur in the form of powder 
or spray. The world-wide use of sulphur for the control of powdery 
mildew of the grape is a well-known example. It is also known that 
sulphur possesses valuable insecticidal qualities, and many of the scale 
insects and mite diseases of our fruit trees may be readUy controlled 
by the use of sulphur so combined and prepared as to be applicable 
as a spray. For many years the most successful and almost the only 
treatment of the San Jos6 scale on the Pacific coast has been by sulphur 
sprays. This scale ii very injurious to peach trees, and the time for 
the application of sulphur for its treatment is during the winter, at the 
time of treatment for peach leaf curl, when the tree is dormant. It 
has already been shown in this bulletin that such a winter treatment 
of the peach tree with sulphur sprays will also control peach leaf curl. 
For this reason, and the fact that the San Jos6 scale is constantly 
spreading throughout the East, much attention is here given to the 
presentation of this form of spray, one application of which may con- 
trol two serious diseases. Experiments conducted by the writer have 
shown that the pear leaf mite may be controlled by the winter use of 
sulphur sprays, and it is thought probable that their use will also con- 
trol the oyster-shell bark louse of the apple, which has become almost 
a scourge over much of the East and in the Pacific Northwest. 

As in the case of copper sulphate sprays, it has also been found 
that the sulphur sprays may be most satisfactorily prepared by coni- 

* In view of the work of Mr. C. L. Penny, published in Bulletin 22 of the Delaware 
Agr. Exp. Sta,, 1893, the amount of water recommended to be added before the strong 
ammonia water is poured upon the carbonate of copper is much greater than formerly 
used by the Department. Mr, Penny conducted a somewhat extended series of 
experiments to ascertain the solubility of copper carbonate in ammonia gas as it is 
contained in ammonia water of different strengths. He found that a given aiiiourt 
of ammonia gas in a weak solution of ammonia water dissolves more copper than the 
same amount of gas in a strong? solution. A given weight of ammonia gas in a 2 to 4 
per cent solution of ammonia water dissolves more copper carbonate than an equal 
weight of gas in either a weaker or stronger solution. The gas in a 2 to 4 per cent 
ammonia water will dissolve its own weight or more of copper carbonate. On the 
other hand, the ammonia gas in a 10 per cent solution of ammonia water will (iii»- 
Bolve but 60 per cent of its weight of copper carbonate, and ammonia gaa in a 20 per 
cent solution dissolves only about 35 per cent of its weight of copper. Furthermore, 
the ammonia gas contained in ammonia water of less than 2 per cent strength rapidly 
loses its power to dissolve copper carbonate as the solution ia weakened. 



PREPARATION OF THE SULPHUR SPRAYS. 155 

biniiig sulphur with lime. Salt has also been used in connection with 
these sprays in several f onnulse. 

In the following table are shown the various f ormute for sulphur 
sprays which have been tested for the control of peach leaf curl. All 
formulse are for 45 gallons of water, except where otherwise stated. 

Table 42. — Sulphur sprays applied for tfie control of peach leaf curL 

* 15 poondB sulphur, 30 i>oun<ls lime, 10 pounds salt, 60 gallons water. 

* 10 pounds sulphur, 20 pounds lime, 10 pounds salt, 60 gallons water. 
1 15 pounds sulphur, 30 pounds lime, 10 pounds salt. 

* 10 i>ounds sulphur, 20 pounds lime, 10 pounds salt 
1 10 i>ounds sulphur, 20 pounds lime, 5 pounds salt. 

* 5 pounds sulphur, 10 i>ounds lime, 5 pounds salt. 

1 5 pounds sulphur, 10 pounds lime, 3 pounds salt. 
1 15 pounds sulphur, 30 pounds lime. 

1 10 pounds sulphur, 20 pounds lime. 
1 10 i>ounds sulphur, 8 pounds lime. 

1 6 pounds sulphur, 4 pounds lime. 
1 5 pounds sulphur, 15 pounds lime. 
1 5 pounds sulphur, 10 pounds lime. 
t5 pounds sulphur, 5 pounds lime. 



* Recommended by the writer, but tested by the growers. 

t Prepared and tested by the writer, and in numerous cases also tested by growers. 

It takes longer and is more difficult to prepare the sulphur than the 
copper sprays; but where the sulphur may be obtained at liberal whole- 
sale rates the expense of the two classes does not vary greatly. For 
facts respecting the sources of sulphur, etc., the reader is referred to 
page 190. 

The sulphur sprays are prepared by boiling the ingredients (sul- 
phur, lime, and salt, or sulphur and lime) in water for not less than 
two hours. So far as the writer's experiments are concerned, there 
has resulted no apparent advantage in the treatment of curl by the 
addition of salt to these sprays. The usual method which growers 
having small orchards follow in preparing sulphur spi-ays is to slake 
one-third to one-half of the lime required, in the vessel in which the 
boiling is to be done. When slaked to a thin cream the sulphur is 
stirred in, all lumps of sulphur having been first pulverized. Boiling 
water is now added to make one-half to two-thirds the amount required 
by the formula. This mixture is boiled for not less than one and one- 
half hours, only boiling water being added if it becomes necessary to 
reduce the mixture. If the boiling is done in a kettle or iron pan, great 
care is necessary to prevent the caking and burning of the materials. 
When the mixture has boiled for the time stated or longer, the remainder 
of the lime is slaked and the salt is added to it and well stirred in. This 
lime and salt mixture is now added to that which has been boiled and the 
boiling is continued for at least one-half hour longer. The boiled 



156 PEACH LEAF OUBL: ITS NATURE AKD TREATMENT. 

spray should now be strained through a fine wire strainer into the 
spray tank or barrel, and enough boiling water added to make up the 
full amount of spray required by the formula. The spray naay be 
boiled to advantage longer than two hours, but should never be boiled 
for a less time if the best results would be obtained. The sprays should 
be applied to the trees as hot as possible. The spray is more eflfective 
and easier to apply when hot, and contact with the air cools it suffi- 
ciently so that twigs of dormant trees are not injured by the heat 

The method of preparing the sulphur sprays here outlined is prac- 
tically that which has been followed in California for noiany years. 
In the series of experiments here described, however, an effort has 
been made to ascert&in if salt is necessary in this spray, and also 
whether there is any disadvantage in uniting all of the lime and sul- 
phur at first. After a comparison of the results obtained from sprays 
with and without salt and of those in which the lime was added in two 
portions and at diflFerent times with those prepai'ed by adding all of 
the lime and sulphur at first, it has not been possible to detect any 
advantage from the salt nor from the more complex method of pre- 
paring. This relates, of course, to the use of these sprays for the con- 
trol of curl, but it is believed that the same will hold true in their use 
for the control of insect pests. The writer has personally prepared 
and tested a very large number of these sprays, and recommends tlie 
omission of salt, and further, that all of the lime and sulphur be united 
and reduced with boiling water before the cooking begins in all case^ 
where the spray is to be applied either as a fungicide or insecticide, 
and where the method of boiling below described is followed. This 
will both cheapen and simplify the process. 

While many growers may feel obliged to prepare the sulphur sprays 
in kettles or iron pans, experience has shown that they may be boiled 
much more uniformly, more easily, and oftentimes better in barrels or 
wooden tanks by iLsing live steam as the source of heat. These facts 
are widely recognized on the Pacific coast, and the knowledge is put 
into practice by some of the leading fruit growers, many of whom 
have established special steam cooking plants for preparing and hand- 
ling the sulphur sprays. Some of these spray-cooking appliances are 
on quite an extensive scale and others more limited, being adapted to 
the needs or facilities of the growers. As the sulphur sprays have 
been widely used in California and Oregon, and are likely to become 
much more generally used throughout the East, especially as they are 
particularly intended for winter application to all deciduous trees and 
are known to be of marked value both as insecticides and fungicides, the 
more improved methods of preparing them will be of general interest 
to orchardists, and several are here given. Three types of cooking 
plants are described: (1) One adapted to the needs of an orchard of 10 
acres, (2) one suited to the needs of an orchard of 100 acres« and (3) 



PREPABATION OF THE SULPHUR SPRAYS. 157 

one of sufficient capacity to prepare sprays for the treatment of 500 to 
1,000 acres of trees. 

For small orchards sulphur sprays may be prepared in barrels by 
the use of steam. Upon a solid plank platform 3 feet wide, 12 feet 
long, and raised 18 inches above the ground, place three oak barrels 
holding 60 gallons each. Each barrel should have a bunghole through 
one side about 1 inch above the bottom, which is stopped with a long 
wooden plug while the spray is boiling in the barrel. The upper 
heads of the barrels should be removed, and each may be nailed in two 
parts to serve as a cover for the barrel while the spray is being boiled. 
Near one end of the row of barrels is set the boiler in which steam is 
to be generated. From the dome of this boiler a steam pipe should 
extend horizontally over the row of barrels, and not less than 2 feet 
above them. The farther end extends downward at a right angle, by 
means of an elbow, to within 6 inches of the bottom of the last barrel. 
WTiere the pipe passes over the first and second barrels, downward- 
extending pipes are connected by means of proper couplings, and 
extend to within 6 inches of the bottoms of the respective barrels 
into which they reach. In each of the downward-extending pipes is 
fitted a valve about 18 inches above the barrels, by means of which the 
inflow of steam may be controlled for each barrel separately. The 
lower end of each of the pipes leading into the barrels is left open 
for the escape of steam. With a sufficient head of steam a barrel of 
water may be brought to the boiling point with such an appliance in 
about five minutes. By having three barrels, as here suggested, two 
may be kept almost constantly filled with boiling sprays, while the third 
is filled with boiling water for use in slaking lime, filling the barrels 
after the sulphur is added, and reducing the spray to the required 
amount in the spray tank. With such an appliance for boiling, pro- 
vided the two barrels for spray are charged alternately one hour apart, 
60 gallons of well-made spray may be sent to the orchard about once an 
hour, after allowing each lot two hours of constant boiling. In pre- 
paring the spray for boiling, the lime is first slaked to a cream of lime 
in the bottom of the barrel, the pulverized sulphur is stirred in, the 
barrel is filled two-thirds full of boiling water, a top is placed over 
the barrel, and the steam is turned on by opening the valve above the 
barrel. Within a very few minutes the steam will bring the contents 
to a seething boil, and this can be maintained for the two hours 
required without danger of overheating and with little care, except of 
course that required to maintain and regulate the steam supply. The 
steam stirs the spray sufficiently when boiling. When thoroughly 
boiled the bunghole near the bottom of the barrel is opened by remov- 
ing the long plug, and the spray is drawn oflF into pails and strained 
into the spray tank through a fine wire strainer. When the barrel is 
nearly empty enough boiling water is added to make up the amount of 



158 PEACH LEAF OUELI ITS NATURE AND TREATMENT. 

spray required by the formula, and this is then drawn off. Before a 
new charge of spray materials is placed in the barrel, the latter should 
be removed from beneath the steam pipe and cleaned. Convenient 
boilers suited to boiling one or more barrels of spray are shown in the 
illustrations given. (PL XXI.) 

For orchards of 100 acres the boiling of sprays in barrels is too 
slow. The plan adopted by Mr, A. D. Cutts, at the Riviera Orchard, 
will here be given as admirably answering the purpose for such 
orchards. In this spray -boiling plant the live steam is obtained from 
the dome of the boiler of a 20-horsepower thrashing engine, and 
while cooking sprays from 60 to 80 pounds steam pressure is main- 
tained. The spray is boiled in two rectangular vats or tanks, built of 
2-inch dressed sugar pine. The inside measure of these tanks is, 
length 5 feet, breadth 3 feet, depth 30 inches. These tanks have the 
ends mortised into the side and bottom planks from one-fourth to 
three-eighths of an inch. Two long bolts run diagonally across at ea^^h 
end to hold the head in place, and in addition the planks are nailed 
together with 40** cut nails. E^h of these tanks will hold approxi 
mately 280 gallons of spray. They are raised 4 feet above the ground 
upon a strong and well-braced framework. They stand side bv side 
with a platform between about 4 feet wide, on which a man may stand 
to attend to the spray while boiling. One end of each tank is toward 
the boiler, and the other, which is supplied with a faucet or sirup 
gate for drawing oflF the spray, extends to the side of a driveway. 
The steam is supplied to each of the tanks directly from the dome of 
the boiler. From the steam dome a li-inch pipe leads to near the 
ends of the tanks. This is connected with a transverse 1-inch horLzontal 
pipe extending laterally to a point opposite the center of each tank and 
level with the tops of the tanks. The ends of this 1-inch pipe now turn 
at a right angle and extend to the center of the top of the ends of the 
tanks, turn down on the inside of the tanks to the bottom of the same, 
and then extend along the center of the bottom to near the farther end, 
where they are closed by having an iron cap screwed over the end. 
Through each side of that portion of the 1-inch pipe which extends 
along the inside of the bottom of each tank are drilled 6 smsJl holes 
for the escape of the steam into the tanks. In the pipe leading to 
each tank is placed a globe valve for separately controlling or prevent- 
ing the flow of steam to each of the tanks. When a tank of spray is 
ready to go to the orchard, the spray is run into another tank situated 
on a low truck wagon, the truck being first driven under the end of 
the boiling tank which is to be emptied. The low truck with the 
spray is then driven to the spray tanks in the orchard, and the spray 
is pumped from the truck tank to the spray tank, without delaying 
the work of the sprayers. The spi'ay is strained twice, first when drawn 
off from the boiling vats through the faucet, and second when it k 



DESCRIPTION OF PLATE XXI. 

Steam spray-cooking appliances for small orchards. FigK 1 and 3 show boilers suital 
to cooking sprays in 1 to 3 barrel lots; fig. 2 shows a boiler connected with a tank in 
which larger quantities of spray may be boiled at one time. These cooking appli- 
ancoH are well adapted to use in ten-acre orchards (p. 157) . (Ck)mpare with PL 
XXII.) 



Bull. 20, 0\^ Veg Hnys. 8c Pain. J. S. Dept. of Ag'icuhure. 



Plate XXI. 









O 

o 

I 
> 

O 




'J\ B « A R y^ 
or ri A 



.->\-^\ 



■J 



PREPARATION OF THE SULPHUR SPRAYS. 159 

pumped from the truck tank into the spray tank in the orchard. The 
brass strainer cloth employed by tinners in making strainer pails is used 
for this purpose. It is very necessary to strain well, as in the unstrained 
spray there are always dregs that fill the nozzle and delay work. Mr. 
Cutts says that in tanks of this kind it is necessary to stir the spray 
frequently while boiling to thoroughly mix the different ingredients. 
Three hours' boiling is better than two. He also says that one man, at 
|2 per day, will tend the boiler and prepare from 1,500 to 2,000 gallons 
of spray per day, and that it will require about one-half cord of 
4-foot wood to generate the steam in such a boiler as he uses. 

In preparing the sulphur sprays for orchards containing 500 to 
1,000 acres of trees it is desirable to have tanks of larger size than 
those used by Mr. Cutts and to avoid as much pumping and trans- 
ferring of the sprays as' possible. One of the most convenient and 
complete spray-cooking plants for orchards of large size which has 
thus far been seen by the writer will here be described. This plant is 
at the Rio Bonito orchaM. The water for preparing sprays at this 
orchard is obtained from a well and is forced by means of a rotary 
force pump run by steam power into a large storage tank elevated 
upon a heavy framework some 30 feet above the ground. About 
10 feet above the ground and at one corner of the open framework of 
the tank house is placed a circular tank holding about 300 gallons. 
This is a storage tank to receive the spray when prepared for the 
orchard. The bottom of this circular tank is supplied with steam 
pipes, so that the contents may be kept hot and ready for use. From 
the outer side of this storage tank, near the bottom, is a discharge 
pipe with valve and hose attached, through which the spray may be 
run by gravity into the tops of the 300-gallon spray tanks on wagons 
which are used in the orchard. These wagons are driven to the side of 
the storage tank and filled with boiling spray in a few minutes, much 
as street-sprinkling tanks are driven under the elevated hydrants and 
filled. The boiling tank proper is built of 2-inch surfaced pine plank 
within a firm framework, properly bolted, and rests firmly upon the 
ground. It is situated within the heavy framework of the water tank 
house. This boilingtank is approximately 18 feet long, 3 feet wide, and 
3 feet deep, and its full capacity is 1,200 gallons. In the center of the 
tank house is a water pipe connected with the large water tank above. 
Near the bottom of this standpipe are hydrants for the attachment of 
hose, thus allowing of water being drawn directly from the water supply 
above into the boiling tank by opening a hydrant. An unlimited supply 
of cold water is thus always at hand without the necessity of lifting 
a pailful by hand. The steam pipe for heating the sprays in the boil- 
mg tank extends from end to end along the bottom within the wooden 
tank, and every 2 or 3 feet along this pipe are cross pipes leading toward 
each side of the tank. The ends of the central pipe and its branches 



160 PEACH LEAF CUELI ITS NATURE AND TREATMENT. 

are closed. Along both sides of this main pipe and its lateral 
branches are drilled small holes for the escape of steam into the tank. 
The flow of steam to the tank is controlled by means of a globe valve 
in the steam supply pipe, the valve being conveniently placed for the 
workman at the tank. Broad board cx)vers are made for covering the 
whole tank when the boiling is in progress. As in the case of the 
spray -boiling plant of Mr. Cutts, the main steam pipe leads from the 
tank directly to the steam dome of the boiler. The spray is prepared 
in the boiling tank of double strength, and when sufficiently boiled is 
elevated to the storage tank above by means of an appliance planned 
like an injector of a boiler. An iron pipe about 2 inches in diameter 
leads from the boiling tank upward and over the top of the storage 
tank described. In this pipe is placed the injector, which is supplied 
with two lateral connections. One of these connections is with the 
cold-water supply pipe, and the other is with the main steam supply 
pipe. In each of the pipes connected with the injector are placed 
globe valves for the control of the inflow of water, steam, and hot 
spray. When it is desired to fill the storage tank above with hot 
spray from the boiling tank below, the valve opening into the 
steam pipe leading from the injector to the steam dome is opened. 
The live steam at once escapes through the injector into the piix* 
leading to the storage tank and then out of the end of the pipe. 
The valves leading to the boiling tank and the cold-water supply arc 
now opened in such a manner that about equal parts of cold water and 
hot spray are admitted to the injector, and the escaping steam, by 
means of its tendency to form a vacuum, soon causes a combined 
stream of hot spray and cold w^ater to follow up the pipe and escape 
into the storage tank above. There is thus established a kind of steam 
siphon, which soon carries up 150 gallons of boiled spray and an 
equal amount of cold water, filling the 300-gallon storage tank with 
spray of the required strength, the strength of the spray in the boil- 
ing tank being double that required. This work is accomplished by a 
careful adjustment of the inflow of steam, spray, and water to the 
injector, the storage tank being filled without the necessity of lifting 
a pound of spray by hand. The combining of the cold water with the 
hot spray in the injector is found to be necessary to the proper working 
of the latter as the temperature of the injector would otherwise become 
too high for efficient work. When the storage tank is full, steam is 
turned into the pipes situated at its bottom, and the spray is again 
heated to the boiling point and kept very hot until drawn off into 3 
spray tank and taken to the orchard. The facility with which a plant 
of this description may be operated will depend to quite an extent upon 
the nature and capacity of the boiler used for generating steam. The 
more easily steam can be generated and the greater capacity for steam 
which the boiler possesses the better for the work. 



. '^'\ BRA «y^ 
y* or rim 

f UNI-^' ERSITY 



CAuI^ 




Bull 20, Div. Veg. Phy«. 8c Path., U. S. Dept. of Agriculture. 



PLATE XXII. 










m ■ 



Steam Spray-cooking Appliances for Large Orchards. 



DESCRIPTION OF PLATE XXII. 

Fig. 1 shows sulphur, lime, and salt spray-cooking appliances used on the Rio Bonito 
Rancho. The heavy framework at the left supports a large water tank not shown 
in the photograph. This tank is filled from a well by means of a steam rotary force 
pump, and supplies all water required in cooking and reducing sprays. On the 
ground, at the farther side of the framework of the tank, is shown a long wooden 
vat from which steam is issuing. This rectangular vat, described on page 159, is capa- 
ble of cooking about 900 gallons of sulphur spray of double strength, and is seen in 
full operation in the illustration, the heat being applied by means of steam pipes at 
the bottom. The steam pipe is shown leading from the dome of the boiler in the 
shed at the right and in the background of the photograph. The round tank shown 
above the right end of the cooking vat holds 300 gallons of spray, ready for appli- 
cation to the trees. This tank is tilled from the cooking vat by means of a steam 
injector, described on page 160, and the spray is maintained at a high temperature 
by means of steam pipes in the bottom, as in case of the cooking vat proper. 

Fig. 2 should be considered in connection with fig. 1. The large, round tank, 
standing above the barrels, is the storage tank for sulphur spray after it has been 
prepared in the long vat below. This tank holds 300 gallons — sufficient spray to fill 
the tank seen on the wagon. The wagon tank is filled by gravity, the spray flowing 
into it through hose running directly from a spout at the bottom of the storage 
tank. A valve in this spout regulates or stops this flow of spray as desired. One of 
the spray wagons used in this large orchard is shown. The pump stands crosswise 
behind the comer stakes at the back of the wagon. These stakes serve to prevent 
the hose from falling beneath the wheels, as ail lines of hose extend from the rear of 
the wagon when in use in the orchard. 



PBEPABATION OF COMBINED COPPEB AND 8ULPHUE 8PEAYS. 161 

By referring to PI. XXII and the descriptions; of figures the 
reader may obtain a good idea of the arrangement of this extensive 
spray cooking plant, as well as of the boiler supplying steam. 

PREPARATION OF COMBINED COPPER AND SULPHUR SPRAYS AND NOTES ON 
OTHER SPRAYS TESTED. 

For many years the use of combined copper and sulphur sprays has 
been practiced by peach growers in Oregon, and as they have reported 
good results the writer prepared the following four fonnulas of this 
character for the control of curl. 

BORDEAUX MIXTURE AND SULPHUR SPRAYS COMBINED. 

The formulro of the combined Bordeaux mixture and sulphur 
sprays tested are given in the following list: ' 

Ligt of sulphur uprays combined v/dh Bordeaux mixture. 

3 pounds copper sulphate, 10 pounds sulphur, 20 pounds lime. 
3 pounds copper sulphate, 10 iwunds sulphur, 10 pounds lime. 
3 pounds copper sulphate, 5 pounds sulphur, 10 pounds lime. 
2 pounds copper sulphate, 5 pounds sulphur, 10 pounds Ume. 

In preparing these combined sprays, which were found somewhat 
more eflfective in the control of peach leaf curl than the sulphur sprays 
alone, the Bordeaux mixture was added to the fully prepared sulphur 
spray. A portion of the lime given in the formula was reserv-ed for 
making the Bordeaux mixture, while the remainder of the lime was 
combined and boiled with the sulphur in the manner already described. 
When the sulphur spray had been placed in the spray tank, the Bor- 
deaux mixture, which had been freshly prepared from the copper 
sulphate and the remainder of the lime, was added, and after thorough 
mixing was at once applied to the trees. The union of the yellow 
sulphur spray with the blue Bordeaux mixture forms a spray of a 
distinct green color. The application of this spray is similar to that 
of the sulphur spray, requiring the same class of nozzles. 

MISCELLAN>X)rS SI'RAYS. 

A large number of sprays not included in the preceding descrip- 
tions have been prepared and tested for peach leaf curl, and some of 
them have been discussed in other portions of this bulletin. Several 
of them were tested for the purpose of learning the value of the 
separate ingredients of the leading sprays, as salt, lime, etc. Among 
these were lime, applied as a simple milk of lime; salt, applied in 
solutions of different strengths; and lime and salt combined, applied as 
a whitewash. Sulphur was tested in the form of sulphide of potassium, 
applied in various strengths in liquid form, and tfie union of this sul- 
phide of potassium with milk of lime was also tested. Iron sulphate, 
19093— No. 20 11 



162 PEACH LEAF CURL'. ITS NATUEE AND TREATMENT. 

sulphur, and lime were tested in combination by adding to the sulphur 
spray a mixture prepared by uniting the milk of lime with a solution 
of iron sulphate. The union of the milk of lime with the iron sulphate 
solution produced a lead-colored mixture resembling Bordeaux mix- 
ture in consistency, and when united with the sulphur solution* the 
color was dark green or approaching black. Iron sulphate and lime 
were also tested separately. 

While some of these sprays gave evidence of considerable fungi- 
cidal action, none of them gave results which would warrant their 
substitution for the sprays already considered in previous chapters, 
and hence it is unnecessary to enter further into details respecting 
their preparation. The results of their use may be learned in the 
chapters of this bulletin which relate to the action of the sprays on 
the foliage and the fruit. 

GENERAL CHARACTERS OF THE SPRAYS TESTED. 

There are certain general characters of sprays adapting them or 
making them unsuitable for various classes of work, and to these it 
may be well to allude. 

THE ENDURING QUALITIEB OF THE SPRAYS. 

In the worK here described careful notes were made on the enduring 
or weathering qualities of the sprays tested. 

During the last week in April and first week in March, 1895, 35 
sprays, of different formulae, were applied in the experimental block 
in the Rio Bonito orchard, most of them to 10 large trees, as has 
heretofore been show^n. On August 10, or five months after the 
spraying was completed, the trees of each experiment row were 
examined to ascertain as far as possible the enduring or weathering 
qualities of the sprays, and according to the notes made at that time 
the appeai-ance of the sprays upon the trees, after five months' weather- 
ing, may be grouped under the following four heads or classes: 

(1) Sprays showing quite distinctly upon the trees on August 10. 

(2) Sprays moderately evident on August 10. 

(3) Sprays little evident on August 10. 

(4) Sprays not observable on August 10. 

The sprays classed under the first head, were those applied to rows 1, 
3, 7, 9, 13, 15, 18, 19, 21, 22, 25, 33, 36, 41, 44, 45, 50, 54, 56, and 57; 
under the second head, those applied to rows 6, 10, 12, 16, 28, 42, 48, 
and 51; under the third head, those applied to rows 27 and 35; and 
under the fourth head, those applied to rows 30, 32, 38, 39, and 47. 
By referring to page 73 the reader w ill find a table giving the formula 
for sprays applied to each of the rows named, and an examination of 
these fonnulse will bring out the following facts: All the sprays 



OENEBAL CHABAGTEBS OF THE SPBAYS TESTED. 16S 

included under the first two headings contain lime, while those under 
headings 3 and 4 contain none; all formulae containing 15, 20, or 30 
pounds of lime to 45 gallons of water fall under the first head. Of the 
18 sprays containing 4, 5, 8, and 10 pounds of lime, 10 fall under the 
first heading and 8 under the second; copper sulphate enters into the 
composition of 8 of the 10 sprays falling under the first head, while 
the remaining 2 contain iron sulphate; of the 8 sprays which fall under 
the second heading, only 1 contains copper sulphate, and that but 2 
pounds, while 5 are sulphur sprays. 

These facts seem to show that the union of copper sulphate and lime 
produces a spray possessing decidedly greater weathering qualities 
than the union of sulphur and lime. 

In the following list are shown the pounds of lime contained in the 
various sprays tested; the numbers of the rows of trees to which each 
amount of lime was applied; the position of each spray as grouped 
according to its apparent weathering qualities into classes 1, 2, 3, or 
4; and references showing the nature of all the sprays containing lime: 

Weather-resigting qualities of sprays. 

30 pounds lime in formula, class 1, rows 1 1 and 7t. 

20 pounds lime in formula, class 1, rows 3t, 9t, 13t, 36t* and 44°. 

15 |K>unds lime in formula, class 1, rows 15*, 33*, and 57t. 

10 pounds lime in formula, class 1, rows ISf*, lOf*, 41* 45*, 50tt, 54*, and 56ttt; 

class 2, rows 6t, 12t, and 48t°. 
8 pounds lime in formula, class 2, row lOf. 
5 pounds lime in formula, class 1, rows 21*, 22*, 25*; class 2, n)W8 28*, 42t°, and 

olt. 
4 i)oun<ls lime in formula, class 2, row 16t. 
Xo lime in formula, cla*« 3, rows 27 and 35; class 4, rows 30, 32, 38, 39 and 47. 



t Sulphur and lime, or sulphur, lime, and salt. 

t* Copper sulphate, sulphur, and lime. 

•'Lime. 

* Copper sulphate and lime. 

tt Iron sulphate and lime. 

ttt Iron sulphate, sulphur, and lime. 

t^ Potassium sulphide and lime. 

It may be well to state in connection with the above list that while 
all the sprays not containing lime are classed under the third and 
fourth heads, this arrangement may not correctly represent their 
respective enduring qualities. As the}- are without lime, the eye can 
not detect their presence in many cases where it is possible the chemi- 
cals may really be present in eflfective quantity, and it is therefore 
apparent that the value of such a list is largely of a comparative 
nature among those spmys containing more or less lime in various 
combinations. 

The general facts appear to be, as already indicated, that the copper 
sprays are more enduring than the sulphur spi-ays, considering pound 



164 PEACH LEAF CUBL: ITS NAT0BE AND TBEATMENT. 

for pound of lime in their composition, and also that the amount of 
lime may l>e much less in the copper than in the sulphur sprays and 
still maintain the enduring qualities. It is likewise the opinion of the 
writer that where a winter spray of copper and lime has proved of 
poorer weathering quality than is desirable in a given climate, the cop- 
per should he increased as well as the lime when greater i-e^istance to 
weathering is sought. In other words, while the increase of lime 
enhances the weathering qualities of the spray, it also has a tendency 
to retard or obscure the action of the copper it contains, unless the 
latter is increased somewhat in proportion to the increase of lime. 

THE CORROSIVK ACTION OF THE SPRAYS. 

As the present use of sprays has been limited to their winter appli- 
cation, the notes on their corrosive action relate largely to the action 
upon dormant trees or upon the vegetation immediately following 
the commencement of spring growth. In each case these remarks 
relate to the use of sprays upon peach trees, which are known to be 
among the most tender deciduous fruit trees conamonly grown in the 
temperate zone. * 

The sulphur sprays of the greater strengths used in these experi- 
ments caused in many cases the loss of some of the finer and weaker inner 
growth of the trees. This is more apt to be the case, it is believed, 
when the spray is applied shortly before growth begins in the spring. 
Where very strong sprays of this class are to be used, it is well to 
apply them compai-atively early in the donnant period, say four weeks 
earl ier than the copper sprays. Sprays having not more than 10 pound** 
of sulphur to 45 gallons of spray may be used with little danger up 
to within four weeks of the swelling of the buds. 

There is no danger of injuring twigs or buds with the copper sprays if 
properly prepared and applied before the buds have opened. Well- 
made Bordeaux mixture may })e used even as late as the opening of the 
first blossom buds. The ammoniacal copper carbonate may also be safely 
used to a latt^ date, and both may be again applied, if desired, after the 
tree« have passed out of bloom. The simple solution of copper sul- 
phate and the eau celeste may be safely used to within a week of the 
opening of peach buds, but they should never be used upon the foliage 
of the tree. Modified eau celeste is less coiTosive than the eau celeste, 
and may be used until the first buds begin to open, but from observa- 
tion in other classes of spray work it is believed to be unsafe to apply 
this spray to the leaves of the peach. 

The injurious action of the sulphur sprays when combined with Bor- 
deaux mixture is fairly to be compared with the action of the sulphur 
sprays alone when containing equal amounts of sulphur. 

The spray composed of iron sulphate and lime is more apt to injure 
tender shoots and buds than the Bordeaux mixture, and such a spray 
can not be recommended for use upon foliage. 



GENERAL CHARACTEBS OF THE SPRAYS TESTED. 165 

Milk of lime appears to be practically harmless when applied to 
dormant trees or to trees in leaf; hence any injurious action resulting 
from the use of sprays containing lime should be charged to the other 
ingredients or to the lime as altered or modified through combination 
with such other constituents. 

ADVANTAGBS OF DISCERNIBLE AND INDISCERNIBLE SPRAYS. 

Reference has been made in a brief way to the advantages possessed 
by certain sprays in forming a visible deposit upon the surfaces 
sprayed. While sprays forming such a visible deposit are decidedly 
advantageous for all winter work, those leaving no such distinct deposit 
are most desirable for the treatment of fruit, especially when approach- 
ing maturity. The advantages of white sprays in the winter treat- 
ment of deciduous trees are obvious, it being possible with such sprays 
to clearly see what portions of the plant have been thoroughly and 
properly covered. This advantage may even make the diflference 
between success and failure in the work. 

Some recent exj)eriments in applying whitewash or spmys contain- 
ing large amounts of lime have tended to show that the opening of the 
buds may be somewhat retarded by such winter treatment. The theory 
is that whitening the trees prevents, to some extent, their absorption 
of heat from the sun's rays, and that this aids in keeping the trees in 
a doiTnant condition somewhat later than would otherwise be the case. 
Whether this will prove of enough importance to warrant the outlay 
for spraying remains to be shown. An illustrated article on this sub- 
ject appeared in the Canadian Horticulturist for January, 1899.^ 

All sprays, both copper and sulphur, which contain lime are adapted 
to the purposes here considered. The Bordeaux mixtures and sulphur 
sprays used in the work described are distinctly observable upon the 
trees when applied, and after drying for a very short time the treated 
trees become decidedly white. The greater the amount of lime the 
whiter the trees. (PI. XXUI.) 

In the summer treatment of trees and plants having fruit approach- 
ing- maturity, the use of clear sprays is often most to be reconoLmended. 
The spray now best adapted for this purpose is the ammoniacal 
copper carbonate. A stronger spray, though making less showing 
than Bordeaux mixture, is the modified eau celeste. As this is apt 
to cause injury in some cases, it is desirable to use Bordeaux mixture 
for summer work up to a date when the fruit is approai^hing maturity, 
and then to adopt the ammoniacal copper carbonate. The time at 
which the summer use of Bordeaux mixture should be discarded for the 
ammoniacal copper carbonate will depend largely upon the amount 
of summer rains in the locality where used. In New York State, for 
instance, where summer showers are frequent, the lime-containing 

* Orr, W. M., 1. c, pp. 1&-20. See further remarks on this subject on p. 160. 



166 PEACH LEAF CURL I ITS NATURE AND TREATMENT. 

Bordeaux mixture could be used upon fruit until a later date in the 
summer than it could in California, where almost no summer showers 
occur, and where the lime would remain upon the fruit until the latter 
was mature. This matter leads us naturally to the consideration of 
sprays adapted for wet and for dry localities. 

SPRAYS ADAPTED TO USE IN WET AND IN DRT LOCALITIES. 

Little can be said on this subject that has not been previously 
touchexi upon in this bulletin. A few general remarks, however, 
may be of advantage to the grower. The enduring qualities of sprays 
containing lime increase where the ratio of the other ingredients is 
maintained, very largely in proportion to the increase of the lime 
which the f ormulee contain. For instance, the relative proportions of 
copper sulphate and lime being maintained, a Bordeaux mixture 
which contains 10 pounds of lime to 45 gallons of spray will obviously 
endure much longer upon the trees in a wet climate than a Bordeaux 
mixture containing but 5 pounds of lime to the same amount of spray. 
To avoid the loss in activity and effectiveness of a spray containing a 
large amount of lime, the fungicide, be it copper or sulphur, should 
be increased so as to maintain the same or nearly the same ratio 
between the copper and lime which exists in the spray containing less 
lime. It is advised, therefore, that sprays to be used in a wet climate, 
especially those intended for winter application, should be made 
stronger, both in lime and in the essential fungicide they contain, 
than is found necessary in a dry climate. If two sprayings are neces- 
sary, both should be given the dormant trees. 

In wet climates the conditions favorable to the development of curl 
and other fungous diseases are increased. This supplies a further 
reason for using sprays containing increased amounts of fungicide and 
having greater enduring qualities than sprays used in dry localities. 
The soil conditions in wet situations are apt to delay spray work till the 
last moment compatible with effective work. In such cases the amount 
of copper should be sufficient, if this class of sprays be used, to act 
promptly. If the Bordeaux mixture be applied under such circum- 
stances, it will not be found desirable to reduce the copper below the 
equivalent of 1 pound of copper for each pound of lime, and a higher 
proportion may often be used to advantange on dormant trees. 



CHAPTER IX. 

THE APPLICATION OF SPRAYS. 
GENERAL ACCESSORIES FOR WINTER SPRAYING. 

To those who have sprayed for years and have learned by experience 
the most suitable appliances for such work the present remarks may 
not prove of direct value. They are especially intended, however, for 
those undertaking such work for the first time. 

NOZZLES SUITED TO WINTER WORK. 

The past few years have seen in the United States a very great 
increase in the styles and places of manufacture of nozzles and other 
spraying appliances. At the present time the number of styles and 
makes of nozzles often leads to confusion in the mind of the prospective 
sprayer. In fact, however, there are but few essential features to a good 
nozzle. The form of greatest importance for most classes of work is 
that which gives to the discharged spray a rotary or cyclone motion. 
This movement is given in a very simple manner by admitting the 
stream at an angle into a circular chamber in the nozzle, so that it first 
strikes the curving side of the chamber, and is thus forced to assume 
a circular or rotary motion. The revolving stream then passes through 
the small central opening of the discharge plate and widens into a cone- 
shaped spray, which gives to this nozzle certain advantages not enjoyed 
by several other types now on the market. Spray from such a nozzle 
covers a greater area without moving the nozzle than is covered with 
most other types. There are nozzles, however, capable of throwing 
spray to greater heights. The rotary motion assumed by the spray in 
the cyclone or Vermorel nozzles is a dissipation of force, at least in 
most forms of these nozzles, so far as concerns the throwing of sprays 
to a great distance. A type of nozzle first used near San Jos^, Cal., 
and now bearing the name of that town, is perhaps better adapted to 
long-distance spraying, and has been extensively used on the Pacific 
coast. The spray is formed by the fluid passing, under high pressure, 
through a narrow slit in a rubber or metallic plate. Where the rubber 
plate is used the escape of small particles may take place through the 
temporary expansion of the opening in the plate. 

The cyclone nozzles are now made by many manufacturers in diflferent 
portions of the country, and may be obtained through any first-class 

167 



168 



PEACH LEAF CURL: ITS NATURE AND TREATMENT. 




Flo. 1.— Cyt'louu nozzle, 
with direct discharge 
and degorger, for thin 
sprays. 



hardware doalcM- in the United States. The San Jose nozzle is also 
obtainable through hardware dealers generally. 

There are many types and styles of cyclone nozzles. Some are planned 
to throw the spray away from the workman, with direct or forward 
discharge (fig. 1). Others are so constructed that the 
spray is discharged laterally or at a more or less 
acute angle (figs. 2 and 3). In using these nozzles 
for winter work on deciduous trees it has been found 
that most thorough and most satisfactory work can 
be done with less waste of spray when nozzles having 
a lateml discharge are employed. The reasons for 
this are evident. Dormant deciduous trees are but 
a skeleton or framework, presenting to the sprayer 
but a limited surface for stopping a direct spray. 
For this reason, where a nozzle hav- 
ing a direct discharge is employed, a 
large portion of the spray will of 
necessity jmss through the limbs of the tree and fall upon 
the ground, while at best it will pass through the tree but 
once. By using the cyclone nozzle with lateral discharge, 
however, the cone of spray may be directed upward 
through the whole top, and in falling back it passes through 
the tree a second time. Here is a decided gain in the 
limb surface which will bo reached by the use of a given 
amount of spray. The nozzle having lateral discharge 
can also be handled to much greater advantage than the 
nozzle with direct discharge. By turning the extension 
pipe which ])ears the nozzle, the cone of spray may be 

directed upward, downward, or laterally upon 
the limbs jis desired. This has proven of gi-eat 
advantage in doing thorough work. 

The ordinary lateral discharge cyclone nozzles 
are suitable for use with most of the copper 
sprays. For use with the sulphur sprays or 
Bordeaux mixture containing a large amount of 
lime, the common Vermorel or cyclone nozzle is 
rather too light and the opening too small. In 
California a special form of nozzle is in use for 
the application of such sprays (fig. 3). This nozzle 
is mamifactured in San Francisco, and may be 
obtained from the leading hardware firms of that 
city. The nozzle is of the cyclone pattern, but is much larger, heavier, 
and stronger than the ordinary type of cyclone or Vennorel. The dis- 
charge opening is of sufficient size to allow of the use of thick sprays, 
and the discharge plate is heavy enough to withstand much wear from 
corrosive fluids. A fact of prime importance, however, for the work 




Fig. 2.— Cyclone 
nozzle, with 
lateral dis- 
charge, for 
thin sprays 




Fig. 3. —Heavy cyclone noz 
zle, with obli(iuo discharj^e, 
for thick sprays. 




GENEBAL ACCESSORIES FOR WINTER SPRAYING. 169 

being considered, is that the nozzle discharges the spray at an angle 
of about 45^ with a line leading directly froni the sprayer. This 
gives the nozzle the advantages of both the lateral and direct dis- 
charge. The work of either of these types (figs. 1, 2, and 3) may be 
accomplished with this angular discharge. 

Makers of cyclone nozzles of all kinds are usually able to supply 
the discharge plates of the nozzles separately, and this is convenient 
for the grower, where the original discharge plates have been worn 
out. The separate discharge plates usually sell at 25 cents each. 

HOSE AND EXTENSION PIPES. 

Rubber hose of good quality is most satisfactory for ail kinds of 
spray work. The strongest and best hose will usually prove cheapest 
if properly cared for. All hose should be 
thoroughly washed, both inside 
and outside, at the close of each 
day's work, and it should be 
well scrubbed, washed, and dried 
when the spray work is com- 
pleted, and stored in a uniformly ^o- ^.-wire^xtended suction 
cool, dark, and medium dry place. 

Practice varies somewhat as to the internal diameter of 
hose used. One-half inch is perhaps the most common size. 
The external diameter of the hose should not be so small 
nor its flexibility so great that it will easily kink and twist 
upon itself. Hose which does this is a constant source of 
annoyance, causing loss of time and often endangering itself. 
Where possible, it is best to have all lines of discharge hose 
leading from the pump pass from the back end of the wagon, 
between two short stakes, one at each corner. With such 
an arrangement there is little danger of its being caught in 
the wheels or run over by them. Many lines of hose are 
injured or destroyed in this way. The stakes at the back 
comers of the wagon also serve as a means of winding up 
the hose preparatory to going to or from the orchard. 

Couplings for connecting 1, 2, 3, or 4 lines of hone with 
the pump may usually be obtained from responsible hard- 
ware firms, or through them from the manufacturers of the 
pumps used. The more common hose couplings are nearly 
always in stock at such hardware houses. 

For most pumps it is well to supply wire-extended suc- 
tion hose (fig. 4r). Some styles have the spiral wire coil 
within the interior; others have it embedded in the rubber. 
When the metallic spiral is exposed to the spray in the interior of 
the hose it should be of brass, if possible, to enable it to withstand 
the corrosive action of the sprays. 



170 PEACH LEAF CURL: ITS NATUBE AND TREATMENT. 

Brass suction pipe strainers for attachment to the end of the pipe 
may be had of different forms. They are necessar}' when the end of 
the suction pipe is simply lowered into the spray tank or when it rests 
upon the bottom of the tank. 

The extension pipes used by different growers vary. Some adopt 
conmion three-eighths or one-fourth inch iron tubing, while others 
obtain the bamboo-covered extensions, which latter contain one-fourth 
inch pipe. The essentials of an extension pipe are a brass coupling for 
connecting the hose, a good brass stopcock for controlling the flow of 
spray, a metallic pipe of suflScient length (which should be determined 
by the height of the trees to be sprayed), and upon the end of the pipe 
a thread and shoulder for the attachment of the nozzle and the recep- 
tion of a washer. The ordinary length of extension pipes is 8 or 10 f eet^ 
but where trees are large a 12-foot pipe may be needed. Either of 
these lengths are now obtainable from dealers in spraying supplies 
in the form of bamboo extensions (fig. 5). There are advantages in 
the bamboo extension pipes over uncovered iron tubing. Where hot 
sulphur sprays are used the bamboo cover prevents the hands from 
feeling the heat, and where cold sprays are applied in very cold weather 
the bare, wet pipe is liable to chill or even freeze to the hand. The 
greater size of the extension pipe which is covered by bamboo also 
adds to the ease with which the pipe may be held and turned in the 
hands. 

PROTBCmON OP THE SPRAYER. 

The nature of spray work makes it unpleasant for the workman, but 
much of this inconvenience arises from an incomplete or improper 
preparation for the work. Men who would not care to work in a 
rain storai without suitable covering are often improperly protected 
against the similar or worse conditions prevailing when they are spray- 
ing. In the spraying of large orchards it has been learned that one of 
the most suitable coverings for men who are applying sprays is a sail- 
or's oilskin suit and sou'wester. This covering is light, impervious to 
wind and water, and is not as liable to crack as rubber clothing. What- 
ever form of head covering may be chosen it should be soft, so as pot 
to be interfered with by limbs, and it should extend in front to pro- 
tect the eyes and behind to protect the neck. It is always desirable to 
protect the hands with long rubber gloves, and these can usually be 
obtained from or through druggists. In selecting such goods, how- 
ever, it is well to learn how long they have been held in stock by the 
dealer, and if they have been kept for more than a year it is best to 
order new ones from the manufacturer, as such goods soon rot when 
held in stock. Besides, new stock is no more expensive than old, and 
it will frequently endure twice as much use. Numbers 11 or 12 are 
usually about the right sizes for ordinary hands. Most wear can be 



SPRAY PUMPS. 



171 



obtained from gloves which are large for the hands, and in such the 
hands are not as apt to perspire. Where rubber gloves are not obtain- 
able the hands may be greatly protected and kept soft by rubbing them 
thoroughly, as often as necessary, with a piece of beef suet. 

If corrosive sprays are to be applied, such as the simple solution of 
copper sulphate, eau celeste, etc., it may be found necessary to protect 
the eyes. For this purpose ordinary clear glass goggles may- be used, 
or the sprayer may provide himself with mica goggles of large size, 
such as are worn in some portions of the country by men employed 
about thrashing machines. Both the glass and the mica goggles may 
be usually purchased through druggists. 



PUMPS FOR VARIOUS SIZED ORCHARDS. 

The selection of a good spray pump is advisable. The difference 
between the first cost of a poor pump and that of a good one is little, 
while the difference in the ex- 
pense of spraying an orchard 
with a i)oor and a good pump is 
apt to be considerable. 

There are some features which 
every spray pump should possess. 
It should be furnished with an air 
chamber for the regulation of the 
flow, and the wearing parts should 
be of brass or brass lined. It 
should be strong and work easily, 
be supplied with means for firm 
attachment, and have capacity 
sufficient to maintain the required 
pressure without undue rapidity 
of stroke. 

Pumps for small orchards 
should be capable of throwing 
two good sprays. Such pumps, 
suited for attachment to the top 
or side of barrels, or to other raised tanks or foundations, are shown 
in figs. 6 and 7. These pumps are supplied with air chambers and are 
of sufficient capacity for ordinary orchard spraying. Each has a con- 
nection for a small pipe leading down from the discharge pipe to the 
bottom of the barrel or tank. By opening a stopcock in the pipe a 
stream may be forced back into the tank close to the end of the suction 
pipe, thus serving to free the suction from deposit and to agitate the 
spray. These pumps can be obtained with brass-lined cylinders. 
The stroke is upward and downward. (See also PI. XXVI.) 




Fig. 6.— Spmy pump for use on l>arrel or t&nk. 



172 PEACH LEAF CURL*. ITS NATURE AND TREATMENT. 

For orchards of iiiodiuin to large .size it is better to obtain more 
powerful pumps — those capable of throwing four strong sprays. The 
pumps shown in figs. 8, 9, and 10 are admirably suited for this class 
of work. Pumps of the type shown in fig. 8 are used in the 1,600- 
acre Rio Bonito orchard. In this orchard one man pumps for four 
men spraying (Pis. XXVII and XXVIII). In many portions of 
California the pneumatic pump, shown in fig. 10, is a favorite. It has 
been used extensively in the spraying of orange groves where the 
trees are large and where high pressure is necessary to throw the 
spray to their tops. The pumps shown in tigs. 8 and 9 have peipen- 




FiG. 7. — Spray pump for use on barrel or tank. 

dicular levers, thus avoiding the bending or stooping motion of the 
operator. The levers of each of the three st\'^les shown are long, and 
both the strength and capacity of the pump is suflScient. The style 
of pumps, both for small and large orchards, to which attention is here 
called, will be found figured and listed in catalogues usually to be 
found in the hands of leading hardware dealers. 

Within the past few years leading orchardists and others have 
tested, with varying success, the application of different motive 
powers to the operation of spray pumps. Steam and gasoline engines 
have received most attention for this purpose. Many of the power 



SPRAY PUMPS. 



173 



spi-ayers as now constructed are heavy, cumbersome affairs, which 
could never be of practical value in everyday orchard work. Of the 
luachines or descriptions of the same which have come to the writer's 
attention, none have thus far appeared better adapted to pitictical and 
continuous orchard work than one in use at San Diego. This machine 
was planned and constructed for Mr. H. R. Gunnis, of San Diego, 
and has seen pi*actical service for several years. It has been more 
or less changed and perfected from time to time, such improvements 
being made as have seemed best from experience gained in actual and 
extensive orchard work. This machine, as first called to the attention 
of the writer by Mr. Gunnis in the early part of Julv, 1895, is illus- 
trated in PI. XXIX. The 
photograph from which this 
plate was made was taken 
while the machine was being 
used in spraying a young 
orchard near Santa Barbara. 
In reference to the changes 
made since this photograph 
was taken, Mr. Gunnis writes: 

^'The changes made in the 
machine since I corresponded 
with you regarding it in 1895 
consist in the addition of a 
rotary supply pump and the 
use of a tender cart for haul- 
ing the material to the machine 
instead of having to shut down 
and go to the material every 
time the tank is emptied." 
Mr. Gunnis further says, 
under date of March 10, 
1899: "The machine is still 
in constant use, and I can still say, as 1 wrote you over three years 
ago, that it has developed no defects whatever. Some of the parts 
wore out from actual service and have been replaced, but no changes 
have been made in its construction. * * * The use of the supply 
pump and tender increases the capacity of the outfit 25 or 30 per cent, 
especially in large orchards. In very small places it can also be used 
economically bj^ two men, both spraying, as a good, steady team can 
soon be taught to move and stop at the word. In this case it is not 
necessary to use the tender." 

While it is believed that the machine which Mr. Gunnis has built 
and operated is superior to any other of its class, I am informed that 
the gentleman contemplates still further improvements. In regard 




Fig. 8.— Spray pump for general orchard work, upright 
leviT. 



174 



PEACH LEAF CURL*. ITS NATURE AND TREATMENT. 



to these changes Mr. Gunnia says that he is now building from nis 
own designs, and has almost completed, a small gasoline engine of 3 to 
4 horsepower, weighing less than 200 pounds. This engine is intended 
for use with a spraying machine embodying ail the features of his old 
apparatus, but lighter and more compact He also has plans under 
way for a self-propelling machine, in which the extra power required 
will not cost half of what it does to feed a team, and which can be 
much more easily controlled. 




FiQ. 9.— Spray pump for general orchard work, upright lever. 

PI. XXX shows the right and left sides of Mr. Gunnis s sprayer 
as it appeared after the addition of the rotaiy pump for filling the 
spray tank. A detailed description of this machine was prepared by 
Mr. Gunnis and published in the Yearbook of the Department for 
18i)6 (pages 73 and 74), in an article by L. O. Howard, on the use of 
steam apparatus for spraying. Those wishing more complete details 
may refer to Mr. Gunnis direct, to whom the writer is indebted for 
the illustrations and facts here given. 



THE APPLICATION OP 8PEAYS. 



175 



SPRAYING TANKS. 



A great variety of forms and sizes of spray tanks are in use. For 
small orchards, scarcely anything better could be desired than large 
oak barrels holding 60 to 80 gallons. These may be swung upon 
wheels separately if desired, but the most convenient way is to place 
them firmly in a one or two horse wagon. Large tanks, well hooped, 
are also very suitable for large orchards. Casks of this kind, holding 
300 gallons, may easily be placed in the bottom of a two-horse wagon, 
leaving abundant room for placing and operating the heavy hand 
pump. Such casks are shown in Pis. XXVII and XXVIII. The 
manner of securing the tank by placing side timbers inside of the 
wagon bolsters is shown in PI. XXII, 
as is also the stirring stick which 
projects from a square hole in the 
top of the cask. 

Rectangular plank tanks are used 
by some, but it is generally found 
more difficult to keep them from 
leaking than in the case of casks, 
where the hoops may be tightened 
at will. Numerous spray carts, bar- 
rel attachments, etc., are illustrated 
in E. G. Lodeman\s work on The 
Spraying of Plants. 

The use of iron tanks is rare, and 
is hardly to be advised for general 
spray work, owing to the corrosive 
action of many sprays. For special 
sprays, as the kerosene emulsion, 
such tanks may, however, be safely 
employed. 

All spray tanks should be arranged 
in such a manner as to be easily 
cleaned, especially where Bordeaux mixture or the sulphur sprays are 
to be used, and they should be provided with some means for stirring 
or agitating the spray. The entrance to all suction pipes should be 
f^uarded with fine brass wire screen. It is well to wash the tanks out 
thoroughly at least once a day. 




Fia 10.— Pneumatic pmnp for general 
spraying. 



APPLYING WINTER SPRAYS FOR CURL. 



A study of the many experiments conducted by the growers and 
described in this bulletin will give much information relative to the 
proper time for applying sprays for the control of curl. A presenta 
tion of a few general principles involved may, however, be properly 
made in this place. 



176 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



THE TIME 1^)R WINTER SPRAYING. 



The proper time for the application of winter sprays for the control 
of peach leaf curl depends very largely upon the conditions of climate, 
season, and situation of the orchard. The object to he attained is to 
prevent the fungus from infecting the first growth of spring. It has 
become apparent from the many and widely separated experiments 
which are here described that nearl}^ if not all this infection result 
from the spores of the fungus, which are present upon the tree and 
not, as formerly supposed, from a perennial mycelium, and it natui 
ally follows that these spores are to be destroyed or their germination 
prevented if the new growth is to be kept exempt from curl. When 
a spore is about to germinate or has just begun to germinate, its mem- 
branes are most tender and susceptible to fungicides. That most of 
the spores of Exoohcus defaj'mans enter upon the stage of germina- 
tion at or about the time of the pushing of the first leaf buds in the 
spring admits of little doubt. That is the time when the tissues of the 
peach leaf are most tender, and when their infection by curl is actually 
known to take place. 

The preceding facts indicate that the time when the fungicide i;s apt 
to do the greatest good is just before or at the time of the earliest push- 
ing of the peach leaf buds. The spra}- should be everywhere present 
upon the trees just prior to the beginning of growth. To obtain this 
object it should be applied from one to three weeks before growth 
begins. This time may usually be determined by carefully watch- 
ing the fruit buds, which show signs of swelling some time before 
they open. When thev first l^egin to swell, the spray ma}" be at once 
applied (Pis. XXIII, XXIV, and XXV). 

This plan relates to regions of moderate rainfall, where a single 
thorough spraying, with sprays sufficiently strong and active, will 
prove sufficient. In regions of heavy precipitation more spray should 
be applied to the trees. It should be stronger and have greater adher- 
ing qualities, or else more than one spraying during the winter will be 
required to give the best results. If two sprayings are given, it is 
better to apply both to the dormant tree than to delay the second 
treatment till the leaf buds have opened The first spraying may be 
given in the fall or a few weeks before the second. 

THE MANNER OF APPLYING WINTER SPRAYS. 

The source of infection of the spring foliag of the peach by the 
fungus of leaf curl is local — i. e., it is to be found upon every portion 
of the tree. This fact is sufficient to shov that any portions of the 
tree not reached by the spray will be as subjec to the disease as if no 
spraying had been done. It thus becomes apparent that very thorough 
work is essential to the genenil control of the disease upon the tree. 



DESCRIPTION OF PLATE XXIH. 

This plate shows the condition of the trees in the experiment block of the Rio 
Bonito orchard at the close of the spray work in the spring of 1896. The row of 
trees at the left has been sprayed; that at the right has been left unsprayed for com- 
parison. The first 10 trees on the left have been treated with a spray containing a 
moderate amount of lime; the second 10 in the same row were treated with a spray 
containing more lime, and they are much whiter than those in the foreground. 
P2ach row of 10 sprayed trees on the left and the corresponding row of 10 unsprayed 
trees on the right constituted an experiment. The uniformity in the size of the trees 
in these experiments is here shown to advantage. It should be noted that the buds 
are still closed, while the spraying is completed. 



Bull. 20. Div. Veg. Phys. 8c Path., U. S. Dept. of Agriculture. 



Plate XXIII. 





DESCRIPTION OF PLATE XXIV. 

A portion of the Ix)vell trees in the Rio Bonito orchard left unpruned until too 
late to spray, many of the flowers being already open. This plate should be com- 
pared with PI. XXV, which shows how the orchard should be pruned before 8i>ray- 
ing, and als^o with PI. XXIII, which shows how far bud development may ordinarily 
be allowed to advance in the spring up to the time the spray work is completed. 



Bull. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. 



Plate XXIV. 



§ 8 




DESCRIPTION OF PLATE .XXV. 

A properly pruned portion of the Rio Bonito orchard, which has develoi)ed too 
far for the best results of spraying. Spraying should be completed by the time the 
buds have developed as far as those shown in PL XXIII. 



Bull. 20. Div. Veg. Phyt. & Path., U. S. Oept. of Agriculture. 



Plate XXV. 




SPRAYING WHERE SEVERAL DISEASES ARE PRESENT. 177 

Thorough spray work requires that the sprays be applied in as calm 
weather as possible. Wind greatly retards and lowers the class of 
work done. Sprays should likewise not be applied when the twigs or 
limbs of the trees are covered by frost, snow, or sleet, or by the water 
of rains, dew, or heavy fogs. To avoid the presence of hanging drops 
of dew upon the limbs, it is frequently necessary to delay spraying 
until late in the morning. Such delay is preferable to the application 
of spray to the dripping trees. When the twigs are dry the spray 
dries where it strikes, and succeeding dews or showers, if the latter 
are not too heavy, will not wash off the spray to a very injurious 
extent. 

If the sprayer is provided with suitable extension pipe and nozzle 
with lateral discharge, the work of spraying peach trees of ordinary 
size nmy be rapidly and easily done. The cone of spray is first turned 
upward under the base of one of the main limbs of the tree and the 
pipe moved so that the spray passes outward toward the end of the 
limb, spitiying the entire under surface of the limb from base to tip. 
The sides and top of the limb are now sprayed, together with all of 
its terminal branches and twigs. Each main limb of the tree is treated 
in like manner, the sprayer passing about the tree as the work is com- 
pleted. The habit of actively moving the nozzle back and forth while 
at work will soon be acquired by the workman desirous of doing good 
work, and by this means the most uniform spraying is accomplished. 

SPRAYING WHERE OTHER DISEASES ARE PRESENT WITH CURL. 

There are many peach diseases which may coexist upon the tree 
with curl. Many of these are amenable, in whole or in part, to treat- 
ment adapted to the control of curl, but in some cases where two or 
more are present it may be advisable to make slight alterations in the 
treatment. The following notes on some of the more conmion dis- 
eases may prove of value. 

PRUNE BUST ON THE PEACH {Puccifiia pruni TeTB.) . 

It is a fact which does not appear to be generally known that prune 
rust infests the tender branches of the peach as well as its leaves. 
This has been found especially true in young trees. Spore clusters are 
found upon the young shoots before growth begins in the spring, 
showing that the disease winters over by means of spores produced 
upon and remaining attached to the bmnches, as well as by the spores 
produced upon the leaves and scattered over the tree. Where the 
trees are suffering from rust it is therefore apparent that a thorough 
winter treatment is required to clean the tree and prevent the spring 
infection, hence such spraying is recommended for the control of both 
curl and rust, though the full control of the latter disease is very 
19093— No. 20 12 



178 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

difficult and will, at best, l>c necessarily followed by several summer 
treatments. There can be little doubt, however, that a thorough 
winter spraying will prevent a greater portion of the injurj' from nist 
than any single spraying applied at a later date, as it gives a practi- 
cally clean tree at the opening of the season of growth. Winter 
sprays for the control of rust must be strong; but sununer spra3\s if 
strong should be positively neutral and noncorrosive, as peach foliage 
is exceedingly tender. 

MILDEW OP THE PEACH (Podosplissra oxyooarUhx De B.). 

Peach mildew is widely distributed in the United States and in 
Europe. The fungus causing it attacks the leaves, fruit, and tender 
branches in the early part ot the sunuuer. The branches serve f or 
the wintering over of the spores, thus aiding in supplying the source 
of spring infection. Winter treatment of the trees, with either the 
copper or sulphur spi*ays, will largely limit this spring infection, 
but later treatment with weak sprays will often be necessary for full 
control. 

BROWN ROT OP THE PEACH {MonUia frudigena V&TB,) . 

Brown rot of the peach has become one of the woi*st fungous dis- 
eases of the peach over large portions of the United States. It is 
quite general throughout most peach-growing sections of the East, 
and has become well established in the Pacific Northwest. It has been 
shown by Erwin F. Smith that the fungus winters over in the disea.'^ed 
branches and in the dried fruit adhering to the tree. These facts 
point to a thorough winter spraying with active fungicides as one of 
the first steps required in its treatment. Smnmer sprayings will also 
be required, and even when thoroughly followed up, the disease will 
prove hard to control. Too much stress can not be laid, however, 
upon the necessity of disinfecting the dormant tree as perfectly sis 
possible by thorough winter treatment. 

BLACK SPOT OP THE PEACH {Clado9porlum (wrpophUum TXmm.j , 

This disease, which produces black spots upon the peach, is well 
known in many portions of the United States and in Europe, and in 
the East and South, especially in Texas, it has become quite trou])le- 
some. In some parts of Europe it has been known as a true epiphy- 
totic. Whether this Cladosporium infests the branches the writer 
can not say, but it appears not improbable that such is true, or in any 
case that the spores probably find winter lodgment upon the tree itself. 
Black spot has been controlled in Texas by the use of the copper 
sprays, and there seems no reason to doubt that the winter treatment 
of the infected trees would largely tend to disinfect them and materi- 
ally reduce the summer development of the disease. 



SPBAYIWG WHERE 8EVEBAL DISEASES ARE PRESENT. 179 

WINTER BLIGHT OP THE PBAC^H AND OTHER SPOT AND SHOT-HOLE DISEASES, SUCH AS 

PhyllosiicUicircmmfcissa hmiK^f Cercospara circumscmasACCj etc. 

In the Northwest, on the Pacific coast, there are several diseases of 
the peach not generally known throughout the East, and also several 
other diseases common to both sections of the country. These troubles 
are generally known as leaf spot or shot-hole diseases. One very 
widely distributed disease is that produced by CercoHpora ciraiimnGWHa 
Sacc, but one of the most troublesome diseases of this class that 
oc*curs in California and Oregon, is induced by a fungus not yet fully 
studied, which infests the tender and bearing branches and appears to 
begin its vegetative activity some time prior to the blooming of the 
tree in the spring. On account of the habit of the fungus to grow in 
the dormant or semidormant branches of the tree, the disease is termed 
by the writer the winter hligJd of the peach. It is one of those dis- 
eases which destroys the most valuable young growth of the tree, i. e., 
the shoots which are low and suited to the production of the finest 
fruit. This disease, in common with another quite prevalent on the 
Pacific coast and which is probably induced by a Coryneinn^ does 
most damage in the more humid localities. Both do their more serious 
work so early, as is also true of peach leaf curl, that summer spraying 
would have but little effect toward their control. Both induce gum- 
luasis of the affected branches, as is true of the action of many fungi, 
and is a well-marked result of the presence of Coryneuin hyerlnckll 
Ond. Winter blight has already been successfully treated with the 
winter sprays, and it is l)elieved that such spraying is sufficient for its 
control, provided the work be done thoroughly and repeated each year. 

There is no doubt that the winter treatment of the peach for curl is 
properly and essentially the first step for the control of any of the 
above-mentioned diseases. Too much can not be said in favor of this 
treatment, which disinfects the trees before vegetative growth begins. 
The striking thoroughness of such disinfection work may be seen 
from the records given below. 

SOOTY MOLD OF THE PEACH. 

When the Department spraying experiments began in the Rio 
Bonito orchard, there was everywhere present on the trunks, inner 
limbs, and older bark of the experiment trees a fungous "smut,'" or 
''sooty mold," giving the Iwirk a black appearance when closely 
examined. Of the 58 rows included in this block, 35 were sprayed, 
as before stated, prior to March 10, and 23 left unsprayed for com- 
paiison. On August 10, 5 months after the spraying was completed, 
all but 4 rows were examined for the presence of soot}' mold, with the 
following result: 

Sprayed rows showing no sooty mold August 10: Nos. 1, 3, 6, 7, 10, 
12, 13, 15, 16, 18, 19, 21, 22, 25, 27, 28, 33, 35, 3(5, 38, 39, 41, 45, 47, 48, 50, 
51, 54, 66, and 57 — total, 30 rows. 



180 PEACH LKAF CURL: ITS NATUBE AND TREATKENT. 

Sprayed rows showing: a trace of sooty mold: Nos. 42 and M (r»ul- 
phide of potassium wsu^ applied to row 42 and simple milk of lime to 
row 44) — total, 2 rows. 

Unsprayed rows showing the prcjsenoe of sooty mold upon the tree;? 
August 10: Nos. 2, 5, 8, 11, 14, 17, 20, 23, 26,^29, 34, 37, 40, 4:^, 4*s 
49, 52, 55, and 58— total, 19 rows. 

Unsprayed trees showing no sooty mold, none. 

Rows sprayed in 1894, but not sprayed in 1895: No. 4, no mold 
apparent; No. 24, some mold present; No. 53, a little mold present- 
total, 3 rows. 

Rows for which no notes on sooty mold were obtained: Nos. 9, 30, 
31, and 32— tot&l, 4 rows. 

The above notes show that records of the sooty mold were obtained 
from 32 rows of sprayed trees 5 months after treatment. Of the.<»\ 
30 rows showed no sooty mold, while 2 showed a very little. Neither 
of these exceptional rows was sprayed with a generally recognized 
fungicide. On the other hand, of the 19 unsprayed rows examined, 
all showed sooty mold. The record for rows sprayed in 1894 but left 
unsprayed in 1895, shows that the trees had but little mold upon them 
17 months after spraying. 

The preceding facts show the disinfecting value of a single winter 
spraying, even where the whole tree surface is covered with fungoas 
mycelium and spores. 

ANIMAL PARASITES OP THB PEACH TREE. 

Among the insect pests of the peach tree now prevalent in manv 
parts of the United States, the San Jos6 scale {Aspidiotic^ jpernk'liNfHJ^ 
Com.) is probably the most injurious. This pest, as is already well 
known on the Pacific coast, can be controlled by winter spraying with 
the sulphur sprays considered in this bulletin. Where the insect is 
known to be present, the strongest of these sprays described should be 
used, and it would be well to apply it somewhat earlier in the spring 
than where weaker sprays are used. 

All leaf -eating insects depositing winter eggs upon the tree may 
be largely controlled by the winter use of sulphur sprays. There 
is also a mite {Phytoptm sp. ?) infesting the peach leaver in Califor- 
nia, which the writer believes may be destroyed in this manner, 
from the fact that experiments conducted in 1895 in the Sacramento 
Valley showed that the same line of treatment is effexjtive in the 
destruction of a related mite {Phytoptua pyri Sor.) upon the pear. 

Mr. William N. Runyon, of Courtland, Cal., makes the following 
statement respecting the peach moth, which may also prove of value 
to growers suffering from this pest: ''Incidentally I would state that 
experience shows that peach trees sprayed with lime, sulphur, and 
salt are not subject to the attacks of the larva of the peach moth. 
Some growers claim a saving of 90 per cent of affected fruit." 



CHAPTER X. 

NATURE AND SOURCE OF THE SPRAYING MATERIALS USED. 

The following notes on the chemicals for sprays are presented for 
the general information of the fruit grower. The facts given are 
those which every sprayer should understand. 

' Spraying is frequently retarded or prevented owing to a want of 
information relative to the nature, sources of supply, or true value of 
the chemicals required. A grower uninformed upon the last-named 
point is often at the mercy of local druggists or other dealers. For 
example, copper carbonate can be made by the grower himself at from 
13 to 14 cents per pound, and ammonia of 26° strength may be pur- 
chased at about 60 cents per gallon, while local prices have been 
known to range as high as f 1 per pound for copper carbonate and 
11.50 per gallon for ammonia, Which makes it impossible to undertake 
spray work. The writer has found the same conditions prevailing in 
respect to prices for sulphur, which is used very largely in the sulphur 
sprays and for the treatment of mildew. In some cases the prices 
asked by dealers in the East have been 400 or 500 per cent higher 
than growers have for years been paying in California. It can 
not be expected that the sulphur sprays will be generally used in the 
East under such conditions. 

COPPER SULPHATE (formula CuS045HgO). 

Of all fungicides thus far known, copper sulphate is the most 
important. It is commonly known as blue vitriol or bluestone in the 
United States. Its foreign names are largely equivalents of these 
terms, although the Germans also apply the name of copper vitriol 
{Kupferrvitriol). 

When pure, copper sulphate crystallizes in large, blue, triclinic 
prisms. It contains about 25.3 per cent of copper, and dissolves in 
four parts of cold water and two parts of boiling water. 

The presence of iron is indicated by a greeniish color of the crystals 
or at the surface of a watery solution when exposed to the air. A 
solution of pure copper sulphate should be blue. The presence of a 
small amount of iron, which commonly occurs when copper sulphate 
is manufactured as a by-product in modern smelting works, does not 
necessarily detract from it^ value as a fungicide, while this by-product 

X8l 



182 PEACH LEAF CURL! ITS NATURE AND TREATMENT. 

may often be purchased at a somewhat lower figure than a purer 
article. Spraying tests have been made by the writer for the com- 
parison of pure commercial bluestone with that obtained as a by-prod- 
uct of smelting works, and which contained a considerable amount of 
iron, and the results showed that the latter article contained fully hs 
great fungicidal value as the former. 

The manufacture of copper sulphate is carried on at a considerable 
number of establishments in the United States, and various processes 
are followed. A large amount of this chemical is also imported, 
chiefly from England. 

Bluestone is prepared by dissolving cupric oxide in sulphuric acid, 
or by oxidizing the sulphide of copper, the latter being the cheaper 
process. Mr. Alfred Kapp, a gentleman who has enjoyed a wide 
experience, has kindly supplied the following facts respecting the 
manufacture of copper sulphate by a leading smelting firm of the 
Pacific coast. He states that the copp>er is mainly derived from mattes 
produced in the blast furnaces, and, secondly, from an acid solution 
of sulphate of copper resulting from the precipitation of silver by 
metallic copper out of a sulphate solution. To bring the copper in the 
different mattes jn solution they are first crushed and pulverized to 
about one-thirty-second of an inch or finer, and subjected to a roasting 
process by which the sulphur is nearly all oxidized. The roasted 
matte contains the copper as oxide and partly as sulphate, with a small 
amount still as sulphide. This material is pulverized once more and 
fed into lead-lined leaching tanks, where the acid copper sulphate 
solution is added, and, if necessary, sulphuric acid. The whole mass 
is heated by stream running through lead pipes. The copper oxide 
and the copper sulphate in the roast is thus brought in solution as a 
sulphate. About 80 per cent of the copper contained in the matters is 
thus leached out. The resulting solution, of course, is not a neutral 
one, but still contains an excess of free sulphuric acid. This solution 
is transferred to other lead-lined tjinks, containing, suspended from 
wooden sticks, strips of lead about 3 inches wide, the central portion 
of which is bent downward between the sticks so as to form a loop, 
which is held by the ends of the lead strips l>eing bent over the sticks. 
The copper sulphate when run down to these crystallizing tanks is 
about 86^' to 44^ B. During the cooling process, which take^ about 
four to seven days, the copper sulphate, or rather part of it, separates 
out of the solution as blue crystals, which are deposited upon the 
strips of lead. These crystals are dried and packed in barrels ready 
for the market. This, Mr. Rapp adds, is the general way in which 
bluestone is made the world over, except that they have at the works 
considered, in addition to the copper in the mattes, the acid copper 
sulphate solution from a silver refinery. 



NATURE AND SOURCE OF 8PRAYING MATERIALS. 183 

Water draining from copper mines sometimes carries copper sulphate 
in solution, in which case the crystals are procured by evaporating the 
excess of water. Barrels of copper sulphate weigh from 300 to 600 
pounds. 

The manufacturer's price of copper sulphate will depend largely 
upon the price of copper and sulphuric acid — two leading constituents, 
as they are sold in the market — and upon supply and demand. The 
cost to the manufacturer will not, however, necessarily depend upon 
the miarket value of copper and acid, for one or both may be obtained 
by him as by-products in other regular and profitable lines of manu- 
facture, such as the smelting of gold and silver ores, etc.^ 

COPPER CARBONATE. 

Copper carbonate -as usually prepared shows the following formula: 
CuCOj. CuHgOg. It is widely used in the preparation of ammoni- 
acal copper carbonate sprays, and is especially well adapted to the 
treatment of maturing fruit where subject to fungous diseases. As 
commonly sold on the market, the carbonate of copper is green and 
finely granular or powdery. It contains about 57.4 per cent of cop- 
per. Native minerals of similar composition occur, such as malachite 
and azurite. 

Copper carbonate is manufactured by a number of firms in the 
LTnited States, but much less extensively than the sulphate. In most 
c-ases it is prepared by adding to a solution of copper sulphate an 
excess of sodium carbonate (sal soda) in solution. This gives a floc- 
culent mixture of pale blue color, afterwards changing to green. 
Heating makes the precipitate more granular. 

Owing to the difficulty of obtaining carbonate of copper in smaller 
towns, as well as the high price usually charged for it, the Depart- 
ment has usually recommended that the fruit growers prepare it. 
The following instructions for this work were published by the writer 
in a circular sent to the peach growers of the country in 1894—95: In 
a barrel dissolve 6 pounds of copper sulphate in 4 gallons of hot 

^ Owing to the somewhat enhanced value of copper at this time (March, 1899) , the 
wholesale price of copper sulphate has advanced . San Francisco prod ucers quote copper 
sulphate in barrels, f. o. b., at 5^ cents, and carload lots at 5 cents per pound; Omaha 
<|uotations are, by the ton or carload, 5i cente; one New York firm quotes 5} cente 
by the barrel or ton and 5J cents by the carload, and a second firm quotes 6 cents by 
the l)arrel, 5^^^^ cents by the ton, and 5 J cents by the carload; Denver quotations are 
Scents by the barrel, 5} cents by the ton, and 5J cents by the carload; Cleveland 
quotes 6 cents per pound m any quantity; one Phila<lelphia finn quotes 6 cents by 
the barrel, 5i cents by the ton, and 5i cents by the carload, and a second firm quotes 
5} cents by the barrel, SJ cents by the ton, and ^i cents by the carload; Baltimore 
quotes 5} cents by the barrel, 5i cents by the ton, and 5 J cents by the carload; Great 
Falls, Mont., quotes 4| cents per pound in carload lots and 5 cents i)er pound for less 
than carload lots, etc. 



184 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

water. In another wooden vessel dissolve 7 pounds of washing 
or sal soda, in 2 gallons of hot water. The soda should be clear 
(translucent), and not white and powdery, as it appears when air slaked. 
When cool, pour the soda solution slowly into the copper solution. 
As soon as bubbles cease to rise fill the barrel with water, stir thor- 
oughly, and allow the mixture to stand over night to settle. The 
next day siphon off all the clear liquid from the top with a piece of 
hose, fill the barrel with water, stir thoroughly, and allow it to stand a 
second night. Siphon off the clear liquid the second day, fill the bar- 
rel with water, stir, and siphon off the clear liquid once more the 
third day. Now pour the wet sediment from the barrel into a crock 
or other earthen dish, strain out the excess of water through a cloth, 
and dry slowly in an open oven, stirring occasionally, if necessary, to 
prevent overheating. Prepared in this manner there should be 
obtained, if none of the sediment in the barrel be lost, about 2.65 
pounds of carbonate of copper. 

Owing most probably to the comparatively limited sale of carbonate 
of copper, the market price has been and still remains too high. It 
can rarely be obtained for less than 30 to 40 cents per pound, which is 
from two to three times the cost to the grower when it is prepared at 
home. This condition reacts upon the manufacturer by causing 
the grower to make his own carbonate, the market never feeling his 
demand. With fungicides which the grower is unable to prepare the 
conditions are different. His needs increase the demand in the market, 
and increased demand tends ultimately to lower prices. 

The cost of copper carbonate when prepared by the grower will 
depend upon the cost of copper sulphate and sal soda. Quotations of 
March and April, 1899, placed copper sulphate at 5 cents per pound 
by the barrel and sal soda at j% of a cent per pound in like quan- 
tity. At these rates the grower should be able to prepare the car- 
bonate of copper at about 12.3 cents per pound. Quotations on larger 
lots of sal soda and copper sulphate placed the price at ^V of a ^^^ 
and 4i cents per pound, respectively. At these prices the raw mate- 
rials for a pound of copper carbonate would cost about 11.8 cents. 
These facts show that wholesale druggists and manufacturing chemists 
could place the carbonate upon the market at 15 or 20 cents per pound 
and still make a good profit, even when buying their sodium carbonate 
and copper sulphate in the open market. If we go a step farther 
back, however, we may see that the first cost of copper carbonate can 
be greatly reduced below any figures here given. Ten-elevenths of 
the cost is seen to depend upon the price of copper sulphate, and the 
first cost of this latter depends upon the cost to the manufacturer of 
sulphuric acid and copper. Both of these articles may be produced 
as by-products of modern smelting processes. A firm at Blacksburg, 
S. C, informs the writer that they employ gold-bearing pyrites for 
the manufacture of sulphuric acid, the sulphur fumes being driven 



KATURE AND SOURCE OF SPRAYING MATERIALS. 185 

off with heat and condensed in lead chambers in the usaal way. The 
acid, the firm states, pays the expenses, hence the gold collected is a 
by-product with them. For the same purpose sulphur may be obtained 
by heat from several kinds of pyrites — that is, from the sulphides of 
copper and iron. As already shown in the notes on copper sulphate, 
copper for the production of this chemical may be derived largely 
from the mattes of silver smelting works. In view of the fact that 
both the copper and sulphur of copper sulphate may be obtained as 
by-products in the extensive gold and silver smelting works, the first 
cost of this chemical can certainly be placed at a figure admitting of 
the manufacture of copper carbonate at a very low cost It could 
probably be placed on the market to-day by the leading smelting 
companies at 15 cents per pound and still leave a liberal profit on 
first cost. It is to be hoped that this matter will be looked into by 
some of the larger smelting firms, and that the carbonate of copper 
may soon be had on the market at prices which are not prohibitive to 
its purchase by the horticulturists of the country.* 

AMMONIA {formula NH,). 

\ Ammonia is of gaseous nature and strongly alkaline in reaction. 
It is readily taken up or dissolved in water, in which form it is used in 
preparing the ammoniacal copper carbonate, eau celeste, and modified 
eau celeste — three of the more impoilant copper sprays. A strong 
solution of ammonia may be commonly had on the market or from the 
manufacturers. Such a solution contains, by weight, about 28 per 
cant of ammonia gas, and is sold as 26^ ammonia, as shown by Baum^'s 
h3'drometer test. A weaker solution is often prepared by druggists 
and is sold as ammonia water, or aqua ammonia. This often contains 
no more than 10 per cent of ammonia gas, and is obtained by reducing 
the stronger article with water. It is scarcely necessary to add that 
there is no economy in buying this dilute liquid. The price is apt to 
be out of proportion to the strength, and if quantities are to be shipped 
long distances there is a needless increase of freight, owing to the 



*The following quotations on copper carbonate were received March, 1899: St. 
Louis quotes 10-pound lots at 27 J cents per pound, 100-pound lots at 25 cents per 
pound, and 1,000-pound lots at 23 cents per pound, f. o. b.; one Philadelphia firm 
quotes 10-pound lots at 23 cents per pound, 100-pound lots at 22 cents per pound, 
1,000-pound lots at 21 cents per pound, f. o. b., and a second house quotes 28 cents per 
pound for ordinary quantities and 21 cents per pound by the barrel; New York 
quotes 10-pound lots at 35 cents per pound, 100-pound lots at 28 cents per pound, and 
1,000-pound lots at 22 cents per pound f . o. b. ; Boston quotes 10-pound lots at 20 cents 
per pound, 100-pound lots at 18 cents per pound, and 1,000-pound lots at 16 cents per 
pound. 

The writer invites attention to the great variation in quotations from different 
centera of trade. It is satisfactory to note that quotations just received from Boston 
indorse the view already expressed, that carbonate of copper can be place<i upon the 
market at about 15 cents per pound and leave a sufiicient profit to the manufacturer. 



186 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

added percentage of water. It is always desirable to specify the 
strength of the ammonia solution when obtaining quotations. 

Plants and animals furnish the main sources of commercial ammonia. 
In each case the ammonia is obtained through the decomposition or 
destructive distillation of the organic matter. Mr. Mallinckrodt, of 
the Mallinckrodt Chemical Works, of St. Louis, and president of the 
Pacific Ammonia and Chemical Company, states that there are, as 
already indicated, but two prime sources from which aqua ammonia is 
obtained, viz, ''bone liquor," obtained an a by-product in the manu- 
facture of bone coal, and "gas liquor," obtained from the scrubbing 
of gas in works for the manufacture of coal gas. A similar source is 
also found in the making of coke. It is further stated that ammonia 
is obtained from bone liquor almost exclusively in the form of sulphate 
of ammonia, often of crude quality, which is used in the manufacture 
of fertilizei's. Gras liquor is partly worked into a sulphate of superior 
qualit}'^, but mostly into aqua ammonia, by what is called the direct 
process. It is redistilled and aqua ammonia made therefrom. Aqua 
ammonia obtained from this source is largely used in the manufacture 
of ice and for other technical purposes. Obtained in this way, it is 
said to be the cheapest article of good qualitj^ that can be supplied. 

A crude concentrated ammoniacal liquor is also largely made ])y 
concentrating gas liquor without purification. This concentration is 
carried on mainly at smaller works for the purpose of transporting the 
liquors in a more concentrated form, to save the expense of freight, to 
works where crude liquor is redistilled and inanufactured into pure 
aqua ammonia. The concentrated liquor is, however, also largely used 
in the preparation of nitrate of ammonia, which is used in the manu- 
facture of powder, but most largely in the manufacture of soda ash. 
This crude liquor contains, besides a small amount of free ammonia 
(NH3), a considerable amount of carbonate, sulphide, cyanides, and 
other ammonia salts, together with tarry and empyreumatic matter 
resulting from the destructive distillation of coal. The strength of 
this liquor can not be made greater than 15 to 20 per cent, and it is 
doubtful if it could be advanbigeously used as a substitute for aqua 
ammonia in the preparation of sprays. The ammoniacal liquors obtained 
in the manufacture of coal gas are entirely a by-product. 

As the gas works of the United States have been largely supplanting 
coal gas with water gas, in the manufacture of which ammonia is not 
obtained, the quantity of ammonia produced in the country has been 
steadily d<»creasing, and the demand is being supplied principally from 
England. Both aqua ammonia and anhydrous ammonia are made 
largely from imported sulphate of ammonia, and very large quantities 
of the imported article are also consumed in the manufacture of 
fertilisers. ' 



^San Francisco' H quotation on ammonia water of 26° hydrometer test, in drums of 
about 750 pounds, f. o. b., is 7 J cents per pound. 



NATURE AND SOURCE OF SPRAYING . MATERIALS. 187 

SODIUM CARBONATE {formvla NajjCOj.lOH^O). 

Sodium carbonate, sal soda, or washing soda is used in making car- 
bonate of copper from the sulphate of copper and in preparing the 
modified eau celeste. As obtained in the market it is in colorless, 
monoclinic ciystals, showing a strongly alkaline reaction to litmus 
paper. When exposed to the air much of the water of crystallization 
is lost from the crystals, which rapidly effloresce or slake to a white 
powder. When perfect, nearly two-thirds of the crystals, by weight, 
is water. 

Carbonate of soda dissolves in 1.6 parts of water at 50^ F. and in 
0.2 part of boiling water. When a solution of sal soda is added to 
the solution of cx>pper sulphate in making copper carbonate, or to any 
other acid solution, a decided effervescence takes place, so that in 
making the copper carbonate the two solutions used should be united 
slowly or they may overflow the containing vessels. The more com- 
mon impurities found in sodium carbonate are sodium chloride 
(common salt) and sodium sulphate (Glauber's salt). These impurities 
are due to the source and manner of manufacture of the sal soda, but 
are not usually present in the latter in sufficient amount to require 
attention in the spraj^ work being considered. 

The sources of sodium carbonate are somewhat numerous, but the 
commercial supply of to-day is derived mainly from conmion salt or 
from natural deposits of the carbonate. In nearly all arid countries 
carbonate of soda is frequently found in the soil in such quantitie.s as 
to be injurious to vegetation. West of the Missouri River large accumu- 
lations of the different soluble salt<^ of the soil are frequently met 
with. In the East such accumulations are prevented by the greater 
rainfall, the salts l)eing eventually washed from the soil and carried to 
the sea, but in the West the}' often coat the ground, appeiiring white 
or black, and are known as "" alkali beds," owing to the frequent pres- 
enile of strongly alkaline salts, such as sal soda. The most abundant 
fonstituentfe of these deposits are sodium sulphate, sodium chloride, 
and sodium carbonate. The sodium chloride and sodium carbonate are, 
when in excess, so injurious to vegetation as to constitute a leading 
l)ane of the horticulturist of the western half of the United States. In 
the great plateau region between the Rocky Mountains and the Sierra 
Nevada and Cascade mnges are vast stretches of alkaline soils, the 
soluble salts of which accuuuilat<^ in lakes and along water courses 
through the drainage of the winter rains. During the long, dry sum- 
mer these waters evaporate to a considerable extent, leaving the salts 
deposited along the margins of the lakes and rivers.^ In some cases 
these deposits of alkali are composted largely of sodium carbonate, and 
in several instances, after passing through a simple purifying process, 

* These deposits are very well shown in the illustmtiouH of Bull. No. 14, Division 
of Soils, U. S. Dept. of Agr. 



188 PEACH LEAF CURL: 1T8 NATURE AND TREATMENT. 

this salt is obtained in a quite pure state, the original deposits contain- 
ing as high as 90 per eent of sal soda. This latter is obtained from 
the soda lakes of South America, Egypt, etc., as well as from those of 
the United States. There are several such soda lakes in Wyoming, 
Nevada, and California. Large amounts of sal soda are crystallized 
from crude carbonate of soda obtained from Soda Lake, near Bagtown^ 
Nev. This lake is known as Big Soda Lake, to distinguish it from a 
smaller soda lake near by. The lake is a beautiful sheet of water, lying 
in a depression of the desert, the water being abput 150 feet in depth at 
the deepest point. It is very close to the old emigrant road running 
from the sink of the Humboldt River to Carson River. The separa- 
tion of carbonate of soda from the waters of this lake is largely by 
solar evaporation. In the fall the salts deposited are taken up, washed, 
passed through a furnace, and shipped in sacks to San Francisco, where 
the soda is refined and bleached for various uses. The principal uses 
on the Pacific coast are in glass-making and boi'ax-making. It is 
stated that sal soda obtained as hero described is practically a pure 
article, though the natural color is somewhat yellow or brownish. It 
is genei-ally useful, except as a fancy article for the retail trade. For 
such purposes it nmst be bleached with chloride of lime, after which 
it presents beautiful crystals. 

There is also a large plant in operation at Owens Lake, Cal., get- 
ting out carbonate of soda from the waters for the Pacific market. 
This product, with that alK>ve described, is nearly equal in strength 
and purity to the eastern and the imported product, so much so that 
consumers are safe in using the western product, if desired. All or 
most sodas (carbonates) found on the Pacific coast proper are in the 
form of sesquicarbonates, and are often so much contaminated with 
sulphates and chlorides that much expense is entailed in their separa- 
tion, and they are therefore of little value as sources of supply. 

The second great commercial source of sal soda is common salt. 
The salt deposits of the country are vast and inexhaustible in quantity. 
The Onondaga Salt Group of the Upper Silurian alone underlies 
much of the large extent of country, as well as the Great Lakes, situ- 
ated between Salina, N. Y., and Green Bay, Wis. At certain points 
the salt deposits of this group are known to exceed 100 feet in thick- 
ness. The deposit is tapped by wells at Warsaw, N. Y., in western 
Ontario, in eastern and in western Michigan, and elsewhere. The rock 
salt of western Michigan is 20 to 80 feet in thickness, and is reached at 
a depth of 1,800 to 2,200 feet. Other large salt deposits are found in 
Kansas and in numerous other portions of the country. 

Sal soda is manufactured from salt on a commercial scale according 
to two leading processes. The older of these is known as the Leblanc 
process, and has been extensively employed in England and through- 
out Europe. It involves two steps in the manufacture, (1) the conver- 



NATURE AND SOURCE OF SPRAYING MATERIALS. 189 

sion of salt into sodium sulphate, and (2) the decomposition of sodium 
sulphate and its conversion into sodium carbonate. The first opera- 
tion is known as the ''salt-cake" process, and the second as the ''soda- 
ash" process. The first step is carried out by the application of sul- 
phuric acid to the salt and the decomposition of both in a furnace, the 
double decomposition resulting in the formation of hydrochloric acid 
and sodium sulphate. The hydrochloric acid is condensed and pre- 
served, while the salt is converted by heat into a hard cake of acid 
sodium sulphate. There is usually in this cake, however, more or less 
unaltered sodium chloride. In the second step the salt cake is pul- 
verized and mixed with an equal weight of pulverized limestone or 
chalk and half its weight of tine coal. This mixture is heated to 
fusion in a furnace, being constantly stirred or revolved. The com- 
bustion of the coal under the heat which is maintained seems to con- 
vert the sodium sulphate into sodium sulphide, and the decomposition 
of the sodium sulphide and limestone, with the interchange of ele- 
ments, produces calcium sulphide and sodium carbonate. The resulting 
mass is cooled in iron receivers, broken up finely, and digested in tepid 
water. The alkali dissolves and leaves the insoluble impurities. The 
sodium solution is evaporated, and when dry the mass is calcined with 
one-fourth its weight of sawdust, to more fully convert the alkali into 
carbonate. This product — the soda ash of commerce — is again dis- 
solved in hot water, and the solution filtered and allowed to cool. As 
the solution cools the carbonate of soda is deposited in large, trans- 
parent crystals, such as are supplied to the ti*ade. Soda ash was 
formerly largely imported from England, but in the last few years has 
been made in the United States to a very large extent. The dissolv- 
ing of the soda ash and the crystallizing of the sal soda is carried on 
extensivel}'^ by firms not manufacturers of the ash. A St. Louis fijrm 
states that they crj'stallize the solution of soda ash in tanks holding about 
8,0(X) pounds each. After the crystallization has progressed sufficiently, 
which takes from ten to fourteen days, according to the temperature of 
the weather, the mother lye, which contains all the impurities, is 
drawn oflf and the sal soda is then broken, dried, and packed in barrels. 
It is stated that a newer process is to crystallize the solution in small 
tanks, holding perhaps 200 pounds. In this small quantity the liquid 
crystallizes in a very short time, say over night, but does not give any 
mother lye, and consequently no impurities are removed. 

A system entirely different from the Leblanc process is in use in the 
United States in some of the leading salt regions and has come very 
largely into use in Europe. It is known as the ammonia soda process, 
or the Solvay process. It consists in decomposing a solution of com- 
mon salt with ammonium bicarbonate, whereby the greater part of 
the sodium is precipitated as bicarbonate, while the ammonia remains 
in solution as ammonium chloride. This latter salt is heated with 



190 PEACH LEAF CURLt ITS NATURE AND TREATMENT. 

lime to li})orate ammouia, which Ls then reconverted into bicarbonate 
by the carbonic acid evolved in the conversion of the sodium bicar- 
tx)nate into monooarbonate by heat. The ammonium bicarbonate thus 
reproduced is employed to decompose fresh portions of sodium chlo- 
ride, so that the proce^is is made continuous/ 

SULPHUR {symbol S). 

The value of sulphur as a fungicide, insecticide, and germicide nas 
been known for many veal's. Its use in a powdered state has been 
long followed in hothouses and vineyards, and ife application in the 
treatment of parasitic skin diseases of man and the lower aniuials, and 
in the control of fermentation in fruits and wines is equally well 
known. In connection with potash and soda it has been applied to 
the treatment of fungous diseases in the fonn of sulphide^s of these 
bases. 

The recent marked use of sulphur in preparing sulphide of lime for 
the spniying of trees is believed to have been first suggested in Cali- 
fornia, the idea coming, it is thought, from the use of sulphur in a 
similar form as a dip to kill scjil) mites on sheep. The spi-aying of 
trees infested by scale insects was a natural application of its known 
insecticidal qualities to the needs of the orchard. In combination with 
lime and salt it is now very widely used on the Pacific coast. These 
chemicals are boiled together for a considerable time, and result in the 
formation of one or more of the sulphides of calcium in liquid form. 
While the value of this spray is well established in regions west of the 
Rocky Mountains, its introduction in the East has been slow, though 
it is almost certain to have a wide application in that section in coming 
years, when the full importjince of winter spraying for the control of 
insect pests and fungous diseases is more fulh'^ appreciated. This is 
more especially true where both of these classes of diseases occur at 
one time on the same host plant. 

Sulphur is obtainable in the market in several forms and degrees of 
purity. The forms most common are known as brimstone, the flour 
of sulphur, and flowers of sulphur. Brimstone is sulphur in the solid 
form, flour of sulphur is ground brimstone, and flowers of sulphur is 
sulphur which has been sublimed. Common brimstone is the cheapest 
form on the market, flour of sulphur stands next in price, while 
flowers of sulphur c^omos still higher. The purity of any of these 

^ QiiotatioiiH on sal .««oda were receivetl as follows during March and April, 1899: 
San Francisco quotes 50-sack lots at 60 cents per 100 pounds, lO-barrel lote at 
70 cents ix?r 100 ix>unds, and smaller quantities at 75 centa per 100 pounds; Loe 
Angeles (juotes by the barrel $1.25 per 100 pounds, and by the car in sacks |1 jjer 
100 jKyunds; St. Louis (|uotes by the car load in Imrrels 55 cents per 100 jwunds; 
New York quotes, f. o. b. Syracuse, in jobl>ing lots, Imrrels of 375 pounds, 40 cents 
per 100 pounds; FairiK)rt, N. Y., quotes 50 cents per 100 pounds, f. o. b. 



NATURE AND SOURCE OF SPRAYING MATERIALS. 191 

forms is usually sufficiently high for the use of the horticulturist. 
Brimstone and flour of sulphur are usually about 98 per cent pure, 
while flowers of sulphur is almost entirely pure. Brimstone weighs 
most, flour of sulphur less, and flowers of sulphur least for a like 
bulk. 

The horticulturist uses sulphur in all the above-named forms, brim- 
stone l)eing employed for bleaching fruit, nuts, etc., while flour and 
flowers of sulphur are used in field work for the control of insect and 
fungous pests. A simple mode by which one may test the purity of 
sulphur is to weigh out any desired amount and then dry and burn 
it; the weight of the remaining incombustible portion, added to the 
amount of weight lost in drying, determines the amount of impurities. 

The sources of the sulphur supply of the United States are numer- 
oiLs and varied. A large amount of crude sulphur is imported, 
although much of the sulphur now used in the production of copper 
sulphate, sulphuric acid, and various other chemicals is obtained in 
the United States through the decomposition of several native metallic 
sulphides, such as the sulphides of iron and copper, which are known 
as iron and copper pyrites. It has been estimated that the amount of 
sulphur consumed in the United States in 1892 was 243,154 tons. The 
sources of this sulphur were as follows: 

From 100,721 tons of imported brimstone (98 per cent) 98,707 tons. 

From 1,825 tons of domestic brimstone (98 per cent) 1,787 tons. 

From 210,000 tonvS of imported pyrites (43 per cent) 90,300 tons. 

From 119,000 t-ons of domestic pyrites (44 per cent) 52,360 tons. 

At the present time the amount used is probably much greater than in 
18H2. 

Great deposits of native sulphur are found in many foreign coun- 
tries and in various portions, of the United States. Most of the 
natural deposits occur in past or present mountain regions, and are 
of volcanic origin. ''The exhalations of volcanoes include, as a rule, 
sulphurous acid (SOg) and sulphureted hydrogen (H^S), which two 
gases, if moist, readily decompose each other into water and sulphur, 
a circumstance which accounts for the constant occurrence of sulphur 
in all volcanic districts." It is estimated that 5,000, (X)0 tons of sulphur 
exist in one deposit in Japan. The deposits of Sicily are famed the 
world over, and 400 distinct workings are said to exist in that island. 
In central Sicily, at Assoro, Imera, Villarosa, and elsewhere, large 
amounts of brimstone, in the form of short truncated pyramids, are 
commonly seen piled near the railroad stations, as wood is piled in the 
United States. These large blocks, probably weighing 100 jx)unds each, 
are brought to the i-ailroad on the backs of donkeys driven down from 
the mines in the mountains in long trains. Large refineries, devoted 
to the refining of such brimstone, are located at Catjmia. The annual 
output of sulphur in Sicily is said to exceed 300,000 tons, and the present 



192 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

importation of the United States from Sicily is about 120,000 tons. 
The richer sulphur ores of Sicily run from 30 to 40 per cent of sul- 
phur. A considerable quantity is also imported from Japan. 

The leading nativ^e sulphur deposits of the United States are located 
in Nevada, Utah, California, Wyoming, and Louisiana. While the 
amount of sulphur ore in the country is inexhaustible, the writer is 
informed by a New York dealer that not to exceed 3,000 tons are 
mined here annually, which, of couree, does not include the amount 
extracted from pyrites. Respecting the Utah sulphur mines, which 
are located in the foothills of the Wasatch Mountains and in Beaver 
County, about,200 miles from Salt Lake City, the writer has received 
the following interesting data from Mr. C. F. G. Meyer, of St. Louis: 
The sulphur supply at these Utah mines is practically unlimited, and 
the price of the product is governed entirely by foreign markets. 
The sulphur is found in an immense bed, the ore beginning at the sur- 
face of the earth and extending down to unknown depths. This ore is 
of a very soft character, containing sand, gypsum, and gravel, and 
has from 15 to 95 per cent sulphur. The profitable ore is mined 
through open cuts and hauled on a tramway to smelters. The smelters 
are cast-iron retorts and hold a ton of ore. Each charge is her- 
metically sealed and the retort is subjected to 40 atmospheres of steam 
pressure. UnSer this heat the sulphur percolates, in the shape of 
liquid sulphur, through the foreign matter into a pot below, from which 
it is drawn off and passes into a distilling vat for the purpose of per- 
mitting all foreign substance to settle to the bottom of the tank; thence 
it is drawn off into wooden molds, holding about 200 pounds, and 
allowed to cool, after which it b passed through a grinding process 
in an attrition mill. The product obtained by the above process is about 
99 per cent pure, and forms the flour of sulphur, which is extensively 
used, as already indicated. For obtaining what is commonly known 
as flowers of sulphur, which is chemically pure, the ground sulphur is 
passed through a resubliming vapor process. 

Respecting any possible advantage to the horticulturist by purchas- 
ing sulphur refined in Europe in preference to that refined in the 
United States, a prominent sulphur refiner of San Francisco has kindly 
supplied the following facts: 

The sulphur refined is mostly from imported Sicilian and Japanese 
products. While there exists the remnant of a former prejudice 
against California sulphur, it should be of interest and value to know 
that there is absolutely no difference between that manufactured here 
and that manufactured in France, Italy, Denmark, and other European 
countries. Both start with the same raw material coming from Sicily, 
the same apparatus is employed, and even experienced foreigners are 
hired to refine the brimstone in the identical manner in which it is 
treated in the above places. There comes to the horticulturist no 



NATURE AND SOURCE OF SPRAYING MATERIALS. 193 

advantage, therefore, to offset the present duty of $8 per ton levied on 
the refined imported sulphur, and our agricultural population, it is 
claimed, is duped when demanding French, Italian, or other European 
refined sulphur. The same manufacturer further states that Sicily 
sulphur of 98 per cent purity is at present admitted to the United 
States duty free, and that it can be ground or sublimed in this country 
and sold at a price below the cost of the imported foreign-refined sul- 
phur. It is also said, as to the comparative value to the horticulturist 
of ground (flour) and of sublimed sulphur (flowers), that for ordinary 
purposes domestic ground or powdered sulphur, which averages less 
than 1 per cent of impurities, will answer all requirements in a wash, 
being finer than the imported, the only impurity being a neutral, 
irert volcanic ash. The sublimed sulphur, as before stated, is identical 
with the imported and contains little, if any, trace of anything but 
elementary sulphur. It is lighter in bulk and more stringy than 
ground sulphur (if examined under the microscope), but is not usually 
enough better for agricultural purposes to offset the difference in 
price. In other words, thq difference in purity percentage between 
ground sulphur and sublimed sulphur is not in any way commensu- 
rate with the difference in price, and a great saving could bo effected 
by substituting the former for the latter in ninety-nine cases out of a 
hundred. 

To these views the writer would add that the flour of sulphur is cer- 
tainly what should be used in the preparation of sprays. As to the rela- 
tive value of flour of sulphur and flowers of sulphur for powdering vines 
for mildew, there is a difference of opinion among vine growers, the 
ease with which the fumes are given off being considered of prime 
importance in the treatment of this disease.^ 

* Quotations on Bulphur in March, 1899, were afi follows: New York quotes flour 
of sulphur in 250 pound barrel lota at $2.20 per 100 pounds, 100 pound sacks at $2.15 
per 100 pounds, and car loads in barrels at $1.80 per 100 pounds, and in sacks at $1.75 
per 100 pounds, all f . o. b. A second Xew York firm quotes roll ])rimstone at $2 per 100 
pounds; flour of sulphur, heavy, at $2.20, and light at $2.25 per 100 pounds by the 
barrel; sublimed flowers of sulphur at $2. 37 J per 100 pounds, in carload lots, f. o. b.; 
roll brimstone, $1.70 per 100 pounds; flour of sulphur, heavy, 100 pound bags, $1.75; 
250 pound barrels, $1.80 per 100 pounds; light, 175 pound barrels, $1.85 per 100 
pounds; flowers of sulphur, sublimed, $2 per 100 pounds. San Francisco quotes 
powdered sulphur, sacks or barrels, by the car load at $1.50 per 100 pounds, less 
quantity at $1.60 per 100 pounds; sublimed (flowers of sulphur) , sacks or Ixirrols, 
car load lots, $1.75 per 100 pounds, less quantity, $1.85 per 100 pounds; roll, barrels 
only, $1.85 per 100 pounds; refined, barrels only (quality same as roll) , $1.75 per 100 
pounds; crude, sacks, $1.40 per 100 pounds. 
19093— No, ao 13 



CHAPTER XI. 

PEACH VARIETIES AND NURSERY STOCK IN RELATION TO CURL. 
COMPARISON OF PEACH VARIETIES. 

It is a well-known fact that certain peach varieties are less snscep 
tible to curl than otht^rs. When planting, many growers strive to 
select varieties which are known to be comparatively resistant. This 
has led nurserymen to select and grow as hardy varieties as possible, 
and such selection has resulted in cultivated varieties becoming to 
some extent more hardy than the majority of seedlings. Of 97 peach 
growers who have stated whether, in their opinion, seedling or budded 
trees are most affected by curl, 50 say that seedlings are most affected, 
19 think budded trees are affected most, and 28 growers have observed 
no difference between budded and seedling trees in this respect. 

In spite of the fact that some varieties of budded peaches are quite 
hardy, many of the finest peaches grown are much subject to curl. 
There are also varieties which are hardy in one locality and become 
very subject to the disease when grown under different conditions. 
There are, in fact, so many influences, such as season, soil, situation, 
etc., that it has been difficult to decide, except in a few cases, whether 
a variety may be fairly classed as hardy or susceptible. It is found 
by wide inquiry that a peach which is considered hardy in one portion 
of the countiy is not resistant to curl in another. The views of peach 
growers vary so widely respecting the hardiness of varieties that it has 
been thought best to s^ive the results as obtained, rather than strive to 
draw from them any final conclusions. Of a large number of growers 
who have been asked whether early or late-blooming varieties are 
most affected, 70 have expressed their views. A majority, or 42 of 
these growere, think there is no difference between early and late 
blooming varieties, 23 believe early blooming varieties most subject 
to the disease, and only 5 believe the late bloomers most affected. It 
would seem that the late blooming varieties may be less liable to 
injury, owing to the increased warmth when they push in the spring, 
but the difference is certainly not well marked. Respecting the hardi- 
ness of early or late maturing varieties, there appears to be little dif- 
ference from the replies to the circular letter. Among 79 peach 
growei-s who have expressed their views, 22 think early varieties most 
subject to the disease, 16 believe the late varieties most subject to it^ 
and 41 think there is nO difference. 
194 



PEACH VABIETIES IN RELATION TO CURL. 



195 



Besides the facts respecting the hardiness of varieties gathered by a 
circular letter addressed to the peach growers of the country in 1893, 
the following list contains such information on this subject as it has 
been possible to glean from the publications accessible to the writer.. 
In this list are tabulated 191 peach varieties and a few nectarines in 
relation to their resistance to curl. So far as possible the form of the 
glands, the season of ripening, and the adhesion of pit is shown. ^ The 
susceptibility to curl is shown in three columns — little susceptible, 
medium susceptible, and very susceptible. Every record for or against 
a variety has been obtained from a distinct source from all other 
records for that variety, and the list includes over 1,000 records. As 
a record under medium susceptible or very susceptible is against the 
variety, showing that it is subject to the disease, these two columns 
are added and the smn carried to a final column. This final column 
may thus be fairly contrasted with the first column, which gives the 
records of varieties little susceptible to curl. The entire list goes far 
to show that few varieties are practically free from curl in all locali- 
ties, and that some of the finest varieties are very susceptible to it. 
(See for example the records under Crawf ords Late, Crawf ords Early, 
Elberta, Heath Cling, Lovell, etc.) 

Tablk 43. — Edations of peach varieties to peadi leaf curl, wUh records of glands, Hme of 
ripening, ana adhesion of pit. 



No. 



Peach varietieB. 






3S 

12 




1 Aiffle de mer, Sea EagU. . 

2 Albright 

3 Alexander , 

4 Alpha 

6 Amelia 

6 Amsden 

7 Austin 

8 Beatrice 

Beers (smock) 

10 Bilyeaufl Late 

11 BishopsEarly 

12 Bonanza 

13 Boston 

14 Brandywine 

15 Brett (Mrs.) 

16 BricesEarly 

17 BriggsMay 

18 Bronson (seedling) 

19 California (cling) , 

20 Canada 

21 Cape Clingstone 

22 Cape Freestone 

23 Capo Pavie 

24 I Chairs (choice) 



11 



17 



* In some instances it is known that the form of the glands of a variety is reported 
differently by different writers, and on this account a few errors may have crept into 
the table here given, but where it has been possible to determine such questions by 
referring to several authors it has been done. Unfortunately the writer has not l3een 
able to study this matter in the orchard except for a portion of the varieties given. 



196 



PEACH LEAF CUBL: ITS NATURE AND TREATMENT. 



Table 43. — RekUiom of peach varieties to peach leaf curly wUh records of glands^ time of 
ripening, and adhesum of pit — Continued. 



No. 



64 
65 
66 
67 

68 
69 
70 
71 
72 
73 
74 
75 
76 
77 
78 
79 
80 
81 
82 
83 
84 
85 
86 
87 
88 
89 
90 
91 
92 
93 
94 
96 
96 
97 
98 
99 



Peach varieties. 



^4 
'I 






Charlotte 

Chinese (cling) 

Clemence 

Columbia 

Comet 

Cooledee (favorite).. 

Cots (cling) 

Cranes Early Yellow. 

Crawfords Early 

Crawfords Late 

Crimson Beauty 

Crocketts White , 

Crosby 

Doctor Hogg 

Downing 

Dumont 

Early Albert 

Early Juno 



Early May .. 

Early (red) Rareripe. 

Early Rivera 

Early Rose 

Early Slocomb 

Elberta 

Ellison 

Florin. 



Fords Late White. 
Foster. 



Fox (seedling) 

General Bid well ... 
George the Fourth. 

Georges Late 

Globe. 



Gold Dust 

Golden Cling 

Golden Drop 

Governor Briggs 

Governor Garlaud 

Governor Wood 

Grave Cling 

GroBso Mignonuo 

Grover Cleveland 

Hales Early 

Hales Late 

Hardy White Tuscany.. 
Hardy Yellow Tuscany. 

Heath Cling 

Heath Free 

Henrietta, Lei^ya Late . . . 

Hills Chile 

Honest Abe 

Honey Cling 

Hood Cling. 



Imperial (early) 

Indian Blood (cling; 

Ingles (seedliug) 

Ironclad 

Jacques Rareripe 

Japan Blood 

Jenny Worrell 

Jenny Worthen 

Jones (seedling) 

Kalamazoo 

Kennedy (cling) 

Keyport WTiite 

Kites Honey 

Lady Polmerston 

La Fleur 

La Grange 

Large Enrlv York, Honest John . 

Large White Cling 

Large Yellow 

Late Admirable 

Late Barnard 

Late(XU)ber 



FEAOH VABIETIES IN RELATION TO OUKL. 



197 



Table 43.— /Jeforfiarw of peach varieties to peach leaf curl, with records of glandSy time of 
ripening, and adhesion of pit — Continued. 



Xa. 


Peach varieties. 


•5 

u 
« a 


1 


1 

< 


3^ 
.2 

3 




> 




IfH) 


Late Rareripe 


T 
T 

r 


1 
1 
1 

e 


i 
C 

f 
f 






1 
1 


1 


101 


Lemon Cling 


5 
1 
2 


2 


s 


10? 


Lemon Free 




108 


Lewis Seedling 


...... 


1 
...... 

1 

13 

2 

...... 


1 


104 


Lewis Stanley 


1 


105 


Lola (ML««) 


r r 
g 

r 


1 
1 
1 


f 
I 

I 

i 




1 


106 


Lord i^almereton 


1 

1 


1 
2 


2 


107 


Lovell 


15 


108 


Lovetta White 


2 


109 


Lovetts Wonder 




1 


1 


110 


Lyons ... . ... 




1 


c 




1 


111 


Auirys Choice 




4 


2 

1 


2 


11? 


McClish 








1 


113 


McCollister 








1 




114 


McCowan (cling) .. ... 






c 
c 
c 




1 
1 
1 
1 
...... 


1 


115 


McDevitts (cling) 






2 

1 


1 
2 


2 


116 


McKevitts (cling) 






8 


117 


Millers (seedling) 






1 


118 


Moore 


g 

r 


e 
e 
1 
e 
1 
e 


f 
f 

c 

f 
f 
f 

c 

f 

c 

f 
f 

c 


...... 

1 

10 
9 
4 
3 

"**6' 

1 
2 
7 
2 


1 
5 


1 


119 


Morris White 


7 


1?0 


Mother Porter. 




1?1 


Mountain Koee 


r 


6 

11 


4 


9 


vr? 


Muir 


16 


1?3 


Newhall 




1?4 


Nichols Orange 




i 




I?.*) 


Nohlease 


B 

g 
g 

r (?) 


e 

1 
e 

1 


1 
3 

...... 


1 
30 

1 


1 


1?6 


Oldmixon Cling 


4 


1?7 


Oldmixon Free'. 


14 


1?8 


Onderdonk 


2 


1?9 


Orange Cling 


2 


130 


Oregon 




131 


Palfas 


g 
r 


e 


f 
f 




1 
2 

2 
1 


1 


13*^ 


Vo&ti'TOy South China Saucer 






2 


133 


Perkins 




i 

3 


i 


\M 


Pi<vin*»ti| I^t** , , 


r 1 


f 


3 


5 


135 


Plammer ., 


1 


136 


Pratt 


r 
g 


e 
1 


f 

f 


1 
1 






137 


President 








138 


Red Ceylon 




1 
1 


1 


139 


RedCheek 


g 1 


f 


1 
1 




I 


140 


Red Madeline 




141 


Reeds Crawford.. 


g 


e 


f 




1 

1 


1 


14? 


Hecdfi nearly Holdnn 






1 


143 


Reeves Favorite ..... 


g ! 1 


f 


2 
1 


4 


4 


144 


Reeves Golden Yellow 




145 


Reine de vergers, Orchard Queen 


r 
r 
g 

8 

g 
8 

r 


1 
e 
1 
e 
1 
e 
1 


f 
f 

c 

f 

c 

f 
f 




1 


1 


146 


Richmond .....,..., . . , 


2 
...... 

1 






147 


Roeeville Tclini?) 


1 
""2 


...... 

1 
1 

13 

1 

...... 


1 


148 


Royal Qeorgc 


1 


149 


Runvons Oranire 


8 


IfiO 


Sal lie Worrell 


1 


1f>1 


Salway 


11 


12 


25 


IfV? 


Schumacher 


1 


l'»3 


Sellers Cling 


:*'::i ■ .:: 


c 

f 

f 


5 

1 
1 

1 


1 
1 


1 


IfVI 


Sellers JYee 




8 


1P>5 


Sener , 


r 


c 




1.')6 


Shinns Rareripe : 








157 


Shlpleys (late red) 


g 


1 


f 




2 

1 
...... 


2 


1S8 


Silver Twig 






1 


1W 


Smocks Free,/^. George 


r 
r 

r 
r 

g 
r 
r 


1 
1 
1 
e 
e 
1 
1 
1 


f 
f 

f 
f 
f 
f 
f 
f 

c 

f 
f 

c 
£ 


2 
7 
8 
2 
5 


1 
8 


1 


160 


Smocks Late 


11 


161 


Snow 




16? 


Snows Orange 


4 

4 


...... 

2 


4 


163 


jpt. JO^Tl...,"^....... ,.. 


7 


164 


Steadly 


2 


165 


Stevens Rareripe 


2 
7 






166 


Stilsons 


1 
2 
10 

1 


G 


1 


167 


Strawberry Cling 




4 


168 


Stump the World, Jcntey Stump 


g 
g 

g 

r 


1 
c 

1 
1 


16 


169 


Sturtevant 


1 


170 


Summer Snow ....-, - - , 




171 


Susquehanna 




6 

1 
1 


6 


17? 


Susquehanna No. 2 


5 


4 


5 


173 


Switzerland 


g 
g 


1 
e 


£ 

£ 


1 


174 


TlUotooo (early) 


3 


2 


2 



198 PEACH LEAF OURL: ITS NATURE AKD TREATMENT. 

Table 43. — ReUUions of peach variOies to j^acii leaf carl, wUh records of glands, lime of 
ripening, and adhesion ofpU — Ck)ntinued. 



No. 



176 
176 
177 
178 
179 
180 
181 
182 
183 
1B4 
185 
186 
187 
188 
189 
190 
191 



192 
193 
194 
195 
196 
197 



Peach varieties. 



ThiasellH White 

Troths (early) 

Tuskena, TSuean Cling. 

Ulatis 

Wager 

Wards Laie Free 

Waterloo 

Wheatland (early) 

White English 

White MeTocoton 

Wilcox Cling 

Wiley . 



WilkinaClIne.... 
Willow (peach) . . 

Winters 

Wonderful 

Yellow Rareripe . 



NRCTARINm. 



Boston. 

Early Newington 

Hardwicks Seedling . 

Ijord Napier 

Rivers Orange 

Victoria 












as 

■OS 

1^ 




1 1 

n 



A digest of 98 reports on pe.ach varieties in respect to the form of 
glands, earliness or lateness of ripening, and adhesion or nonadhesion 
of the pits, as these characters may or may not be related to suscepti- 
bility to curl, is given in the following table. 

Tablb 44. — Comparative suscepfihUity of 98 peach varieties in relation to form of glands, 
earliness or lateness of ripening, and adhesion or nonadhesion of pit. 



Character of glands. 



Reniform, no varieties. 



Qlobone, 42 varieties. 
Serrate, 6 varieties. . . 



Period of ripening 
and adhesion of 
pit. 



Early., 
Late... 
Free.., 
Cling. 
Early., 
Late... 
Free... 
piing. 
Early. 
Late.., 
Free.., 
iCling. 



Number of varie- 
tie»— 



Very 
suscepti- 
ble. 



LitUc 
suscepti- 
ble. 



Total varieties- 



Very 
suscepti- 
ble. 



24 



21 



Little 
suscepti- 
ble. 



In the above table a most striking correlation appears between 
peach varieties with serrate leaves and susceptibility to curl. All 
the six varieties for which full information could be obtained are 
little susceptible, which is all the more interesting from the fact that 
the varieties with serrate leaves have long been known to be very 



PEACH VARIETIES IN RELATION TO Ot^RL. 



I9d 



subject to mildew. A list of seven such varieties for which the char- 
acters of the leaves have been obtainable is here given in conti-ast to 
the above. 

Table 45. — IaM of peaches gubject to mildew. 



Name. 



Hrig)^ May 

I>(>wning 

KHrly Anne 

Eairly Y<*rk 

Red Rareripe 

Roval George 

Ti Ilotson ' do. 



Characteristics. 



GlandH ur leaves. Kipen.<). Adhesion 



Serrate ' Early 



.do. 
.do. 
.do. 
.do. 
.do. 



I 



.do. 
.do. 
.do. 
.do. 
.do. 
.do. 



Free. 
Do. 

Free. 
Do. 
Do. 
Do. 



Some correlations of the shape and absence of leaf glands with the 
time of maturity of the fruit and the adhesiveness of the pit havo 
been compiled from over 400 varieties, and these correlations are 
shown in the table which follows. 



Table 46. — Correlatum of shape or altsence of the leaf glands of the peach with the period 
of maturity of the fruit and the adhesivenesa or rtonadhesirenei^s ofthepU. 



Early 

Late 

Free 

Cling 

Early free . . 
Late free . . . 
Early cling. 
Late cling.. 







Serrate 


Renifonn 


GloboHe 


leaves, or 


glands. 


glands. 


without 






glands. 


4C 


130 


32 


140 


50 


4 


124 


166 


32 


62 


14 


4 


35 


120 


28 


89 


46 


8 


14 


10 


4 


48 


4 


1 



This table shows that of 208 early-fruiting varieties, 4:6 have renifonn 
glands, 130 globose glands, and 32 serrate leaves; while of 194 late 
varieties, 140 have reniform glands, 50 globose glands, and 4 serrate 
leaves. In other words, of the early varieties given there are nearly 
three times as many with globose glands as with reniform glands. 
On* the other hand, of the late varieties, there are nearly three times 
as many with reniform glands as with globose glands. The table 
also shows that there are 120 early free globose to 35 early free reni- 
form varieties, while there are 89 late free reniform to 46 late free 
globose varieties. This table is given as a step in the direction of 
future investigations along this line, which appear warranted by the 
correlations found to exist between the form of glands, the date of 
maturity, the date of bloom, etc., and the little or great susceptibility of 
varieties to curl and mildew. Such facts may prove of much impor- 
tance when taken in connection with future work in originating hardy 
or otherwise desirable varieties by cross breeding. 



200 PEACH LEAF OURL: ITS NATUBE AND TREATMENT. 

The preceding records, showing the comparative susceptibility to curl 
of nearly 200 varieties of peaches, will enable the grower who contem- 
plates setting an orchard to make his choice of varieties advisedly. 
As already said, however, many superior varieties are verj' subject to 
curl, hence the practical methods of preventing it as detailed in this bul- 
letin make it possible to successfully grow the most susceptible varie- 
ties in the most unfavorable situations, so far as this disease is concerned. 
Such varieties are in fact saved to the peach industry of largo sections' 
of the country ])y means of this preventive treatment. The Elberta, 
a favorite in both the East and the West, and the Lovell, a favorite in 
California, may now l>e cultivated to any desired extent in regions 
from which they have heretofore been practically excluded by ciu:l — 
advantjiges that are certainly not the least of those arising from the 
recent work in the treatment of that disease. 

As a striking illustration of what has just been said, the following, 
contained in a letter recently received by the writer from a gentleman 
in northern California, is given: He states that the Lovell variety 
will curl in his locality so as to be of little use, if not sprayed. One of 
his neighbors, who had a small orchard of that variety, stated that he 
intended grafting the trees to some other peach, as they did so badly 
on acx'ount of curl, but our correspondent advised the winter use of 
Bordeaux mixture, cautioning the grower to spra}'^ his trees thor- 
oughly. This was done, and the trees bore a fine crop of fruit. The 
work was so satisfactory that instead of grafting over the Lovell 
variety a block of Fosters was gmf ted to the Lovell, the variety with 
which the detiiiled experiments of the writer were conducted in the 
Sacramento Valley in 1894 and 1895. 

TREATMENT OF NURSERY STOCK. 

The nursery is not only the source of the orchard, but also very 
largely the source of orchard diseases, and its health is therefore of 
common interest to the orchardist and nurseryman. Could a nursery 
l)e freed from curl, many orchards planted from it would not suffer 
from the disease for years, especially if isolated. There is little dotibt 
that curl has been largely disseminated throughout the world by 
means of nursery trees. 

It has been supposed that the main source of spring infection of 
trees was from the perennial mycelium already in the buds, and were 
this hypothesis true nurserymen could scarcely hope to procure buds 
for their seedlings which were free from this disease. The spray 
work upon curl has shown, however, that the single external applica- 
tion of a fungicide is sufficient to prevent 95 to 98 per cent of curl 
when the treatment has been thoroughly made. This appears to 
indorse the view that at least 98 per cent of the spring infections are, 
as elsewhere claimed in this bulletin, from spores upon the tree, prob- 
ably largely resting upon or within the bud scales themselves. 



TREATJ£ENT OF NURSEKY STOCK. 201 

The facts given are sufficient to warrant some general considera- 
tions and recommendations: 

(1) The trees from which buds are to be selected should be thoroughly 
sprayed with strong copper sprays before the buds are removed. (2) 
Where the last year's branches are removed as a whole, the buds to be 
cut out while budding is in progress in the nursery, the bud-bearing 
shoots should be thoroughly dipped once or twice in a well-made Bor- 
deaux mixture before being taken to the nursery.* (3) After the nurs- 
ery trees are budded they should be sprayed with Bordeaux mix- 
ture, no portion of the tree or newly inserted bud being omitted. This 
treatment should be repeated as often as found advisable, and the more 
thorough the better, especially after the removal of the seedling top. 

The writer feels that these recommendations are for the best inter- 
ests of the nurseryman, as well as the prospective purchaser. The 
Bordeaux mixture will not only prevent the injurious action of the 
disease^ but will increase the diameter and height of the trees more 
than sufficient to warrant the outlay, and will make them in every way 
more valuable to the nurseryman and orchardist.' 

Messrs. Dressel Bros., proprietors of the Hart Nurseries, Hart, 
Mich., sprayed their peach nursery in the spring of 1894 with Bor- 
deaux mixture. They reported good success from this work in the 
control of curl. In the spring of 1895 they undertook an experiment 
with the use of 5 pounds of copper sulphate, 10 pounds of lime, and 45 
gallons of water, this experiment including 110,000 nursery peach trees 
one year old and of several varieties. The sprayed trees were treated 
twice, the first spraying being done April 1 and the second April 16. 
On July 21 the foliage of sprayed and unsprayed trees was estimated, 
and it was found that while none of the leaves had fallen from the 
sprayed trees, 16 per cent had fallen from those unsprayed. There 
were 100,000 sprayed trees and 10,000 unsprayed trees in this 
experiment. ^ 

Dressel Bros, state respecting this experiment that they considered 
the work very successful, that their nursery stock showed good 
results, and that the work would be continued. The sprayed stock 
showed an increase in height. In 1897 they again treated their trees, 

^Thia is a matter calling for careful and detailed experiments. It should be com- 
paratively easy to dip such shoots one, two, three, or four times, and to have the 
buds from sach. shoots inserted in seedling trees of separate nursery rows. By such 
method a record could be kept of the number of trees showing curl upon the push- 
ing of the first leaves. In this manner much could be learned about the disease, and 
a standard could be determined for the treatment of the shoots to be used as the 
Bource of buds. 

'In relation to the added size and weight of sprayed over unsprayed nursery trees, 
tiie reader is referred to Bull. No. 7, Division of V^^table Pathology, U. S. Dept of 
Agr., 1894. This bulletin relates to the effect of spraying with fungicides on the 
growth of nursery stock. 



202 PEACH LEAF OUKL: ITS NATURE AND TREATMENT. 

leaving unspray ed trees for comparison . The trees of the sprayed block, 
it is stated, were very nice and straight and made a good growth, and 
there was no curl, it being hard to find a leaf affected, while growth 
started well and continued thrifty throughout the season. The 
unsprayed trees on the other hand curled so badly that many were 
crooked and stunted, not attaining the height of the sprayed trees 
within a foot, and a good many were worthless. The treated trees 
were sprayed twice in the month of March, 1897. They note that 
Bordeaux mixture, to do its work properly, should be on the trees 
for seven or eight days without rain. 

SUMMARY. 

(1) Peach leaf curl haa a world-wide distribution, occurring in every 
region in which the peach is grown. In humid localities it is a leading 
hindrance to peach culture, and in portions of the Pacific coast States 
it has greatly limited the extent of the industry. 

(2) The orchard losses from peach leaf curl vary from a small amount 
of fruit to the entire crop, while in many instances young trees are 
killed. The national losses from this disease will amount to $3,000,000 
annually. 

(3) Curl Is caused byaparasitic fungus known as iSooa«en^<ii^/J>rm««w, 
the ravages of which are largely dependent upon the atmospheric con- 
ditions prevailing while the tree« are leafing out. Rains and cold 
weather at that time tend to increase the severity of the trouble by 
favoring the growth of the parasite and interfering with the proper 
functions of the host. For these reasons orchards near large bodies of 
water and in low or damp situations are more subject to curl than 
those in dry regions or in elevated situations. 

(4) Most of the spring infections of peach leaves are due to the 
spores of the fungus and not to a perennial mycelium, as formerly 
held, hence the efficacy of spmys. 

(5) Curl was first successfully treated in California during the period 
from 1880 to 1885, the success depending upon the application of 
fungicides to the dormant trees. The disease was not successfully 
treated in Europe for ten years after its prevention in the United 
States. 

(6) The copper sprays are now found to be more effective than the 
sulphur or other sprays first used. Of the various sprays experi- 
mented with, Bordeaux mixture, in the proportion of 6 pounds copper 
sulphate, 5 pounds lime, and 45 gallons of water, gave the best results, 
the equal weights of the copper sulphate and lime being most effective 
when the mixture is applied shortly before the opening of the blossom 
buds. When it is desired to increase the durability of a spray by 
increasing the proportion of lime, the application should be made 
earlier or equal proportions of copper and lime should be maintained. 



flUMMARY. 203 

The total saving of foliage increases with the increase of copper sul- 
phate when the amount of lime remains constant, but the average 
saving per pound of copper sulphate decreases with the increase of 
copper used. 

(7) In the treatment of peach leaf curl, from 95 to 98 per cent of the 
spring foliage was saved by spraying. A net gain of 600 per cent in 
foliage over that retained by adjoining unsprayed trees resulted in the 
ease of several different sprays. Bordeaux mixture when applied to 
the dormant tree increased the weight and starch-producing power 
of the leaves, and the sprayed trees showed a great gain over the 
unsprayed in the number and quality of the fruit buds they produced 
for the following year, the gain in the number of spur buds being over 
100 per cent in some cases. The lower limbs of sprayed trees showed 
a marked gain over those of unsprayed trees as compared with the 
tipper limbs in both the number of fruit buds and lateral shoots they 
produced. 

(8) The average value of the fruit per tree in rows treated with the 
most effective Bordeaux mixture i-anged as high as $6. 20 above that per 
tree in adjoining untreated rows, or the equivalent of a net gain of 
1427.80 per acre where trees are planted 25 by 25 feet. Over 1,000 per 
cent net gain in the fruit set has resulted in the use of some of the 
more eflfective sprays. 

(9) The trees should be sprayed each season, as the experiments 
proved that treatment one season will not prevent the disease the 
following year. Spraying should also be done even though the trees 
may not be expected to bear, as the loss of the crop of leaves is shown 
to result in as great a drain upon the trees as does the maturing of 
one-half to two-thirds of a crop of fruit. 

(10) The work demonstrates that peach leaf curl may be cheaply 
and easily prevented in California, in western Oregon and Washington, 
and along the east shore of Lake Michigan, where curl causes great 
loss, as well as in all other peach-growing sections of the United States. 

(11) The copper and lime sprays are less injurious to the trees than 
those composed of sulphur and lime. The use of lime in winter sprays 
has proven an advantage in enabling the workmen to see their work 
and complete it with greater thoroughness than would otherwise be 
possible. A proportional increase of both lime and copper sulphate 
is recommended for wet regions, and for very wet localities a second 
winter spraying is advised. 

(12) Cyclone nozzles with lateral or diagonal discharge are best 
adapted to the work. 

(13) The proper time for winter spraying and the number of appli- 
cations depend to some extent on the locality, season, etc., but active 
sprays are likely to do most good if applied from one to three weeks 
before the opening of the blossoms in spring. The proper time to 



204 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 

apply sprays for the prevention of curl is in dry, calm weather, and 
during the middle of the day, in order to avoid dew or frost upon the 
limbs as much as possible. 

(14) Of nearly 200 peach and nectarine varieties considered with a 
view of determining their comparative susceptibility to curl, it was 
found that very few were wholly free from the disease and that some 
were very subject to it. Some of the choicest varieties, as the Elberta 
and Lovell, are seriously affected, but it has been demonstrated that a 
single winter treatment will prevent the disease upon even these varie- 
ties. It may be thus fairly claimed that the spraying methods recom- 
mended will save to the peach industry some of its finest varieties, as 
well as result in the saving of foliage and crops already indicated. 






^^^^^^^ 



DESdillTION OF PLATE XXVI. 

A suitable outfit for spraying small orchards. One horse, two men, and a boy 
spniy two trees at a time. This scene represents the experimental spraying outfit 
used by the writer in the Rio Bonito orchard. 



Bull. 20, Div. Veg. Phys. 8c Path., U. S. Dept. of Agriculture. 



Plate XXVI. 




^ju :ser fy 



c. 



.'o r ' ' 



- r ' 



• I)RS(^RIPTI()N OF I'l.ATK XXVII. 

Spraying 4 trtn^H at a time, with 5 men and 2 horses. There is here used a 300- 
gallon Hpray tank and long-lever ((iould), braHs-lined piston pump, which ha« 
sufficient CAjwu^ty to supply 4 nozzles, 1 nuin pumping. The horses are protected 
by means of gunny sack covers. The Chinest^ hats in use furnish gmxl protection 
to the eyes and neck, but are t(M> stiff for the most convenient work umU'r limbs. 



Bull. 20, Div. Veg. Phys. Sc Path., U. S. Dept. of Agriculture. 



Plate XXVII. 




OF TWLM 



TTNIVERSITY 



^ 



DESCRIPTION OF PLATE XXVIII. 

Regular winter spray work in the Rio Bonito orchard. Eight trees are here 
being sprayed at one time, with 10 jnen and 4 horses. The trees being treated are 
well advanced, the buds being much swollen, although not yet open. If work is 
thoroughly done at this stage of bud development the results will commonly prove 
satisfactory; but an active spray should be used, such as the eau celeste, or Bordeaux 
mixture with a low percentage of lime and high percentage of copper sulphate. 
Such sprays should not be applied, however, after the opening of the blossoms. 
Earlier spraying is better, the chemicals in such cases doing less harm to the tree and 
having a longer time to reach all spores that endanger the new growth. 



Bull. 20, Div. V«2. Phys. Sc Path., U. S. Dept of Agriculture. 



Plate XXVIII. 





%,••; 
'"^v 



K 



\. 















— ^. 



\ 



V. . 



DESCRIPTION OF PLATE XXIX. 

A power Hprayer in \im in a young orchani at Santa Barbara, Cal. This sprayer 
was Iniilt by the Union (iaH Engine Ck)nipany, San Francisco. 



Bull. 20. Div. Veg. Phys. 8c Path., U. S. Dept. of Agriculture. 



Plate XXIX. 







•\ ' 



^^, OF 



DESCRIPTION OF PLATE XXX. 

Views of the right and left sides of the Gunnie power sprayer of San Di^o, C^l. 
This sprayer is one of the lightest, most compact, and most practical power sprayers 
in use for general orchard work. It supplies 2 or 4 lines of hose, as may be desired. 
A tender is commonly used to carry the spraying materials to the orchard, where an 
extra rotary pump, worked by the same power as the spray pump, rapidly transfers 
the spray to the tank of the spray wagon. Such an outfit is adapted to extensive 
orchard work. Mr. H. R. (Tunnis, San Di^o, Cal., is the ow^nerand operator of this 
mat;hine. 



Bull. 20. Div. Veg. Phys. & Path., U. S. Dept. of Agriculture. 



Plate XXX. 






■'l ^ 





Right and Left Views of Power Sprayer, San Diego, Cal. 



or TMlt 

"O'N'IVrjHsiTY 



1 V 



p 



\day resep 

\ ^: desk from wbi 



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