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• A.H.' fiutchinson.

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X

Bulletin No. 20.

V. p. p.— 72.

U. S. DEPARTMENT OF ACzRICULTURE.

DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY.
B. T. GALL^OWAY, Chief.

PEACH LEAF CURL:

ITS NArURE AND TREATMENT

BY

TsTEAVTOlSr B. PIERCE,

lu Charge of Pacific Coast Laboratory, Santa Ana, California.

WASHINGTON:

(iO VKKNMENT PRINTIN(; OFFICE.
1 <) 0 0

DIVISION OF VEGETABLE PHYSIOLOGY AM) PATHOLOGY.

SCIENTIFIC STAFF.

B. T. Galloway, Cliiif <iJ Dirislon.
Albeut F. Woods, Assistdiil Cliicf.

as.s^)(■iates.

Ekwin F. Smith, 1'. 11. 1>()Ksktt,

Mekton B. Waite, Oscak Loew,

Newto.v B. Pierce, W.m. \. Outon,

llEHIiEHT ,1. WeIJHEK, KkNST A. BeSSEY,

M. .\. Cakleton, Fi.oKA W. Patterson,

Maucis L. Fi.oyi).*

I\ ('IIAKdlO OF l.AMOUA roIUES.

>\m!EKT v. Woods, I'lmil riii/sia/iK/i/.

Krwin 1*'. Smith, J'Imil I'tilliolni/i/.

Newton i'>. I'iickci;, I'tn-ijii- CuukI Liiliiir<ili>ri/.

Herbert .). Weisbkr, J'lant Brccdimj.

Oscar Loew, I /'l<(iii Nutrition and Ftrnicnidtion.

*I)cluilcil as lohacco cxpi-Tt, Divisiim of Soils.

till (liuitjL' of loliacco liiiiKiitalioii iiivtsligutions, Division of Soil.s.

.EITER OF TRANSMHTAl

U. 8. Dei'aktment of Acjkicultuke,
Division of Vegetable Physiology and PAXiioLOciY,

WasJungUm, D. C, February '20, IDOO.
8ik: I respectfull}' 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 reconnncnd 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 l)e controlled l)v com-
paratively simple and inexpensi^'e treatment.
Respectfully,

B. T. Galloway,

Chief of DivUloi).
Hon. James Wilson,

Secretary of Agriculture.-

3

HTTER OF SUBMITTAL

Pacific Coast Laboratory,
Santa Ana., Cal., Deconhcr 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 equalh' applicable
wherever peaches are grown.

Respectfully, Newton B, Pierce,

lu ( '/i(fr(//; of Pacific ( ''oast Laljoratorij.

Mr. B. T. CirALLOWAY,

Chief., Division <f Yajetahlc Physiology and J\ttholo</y.

5

CONTENTS.

Page.

Chapter I. — Primaky Considerations Relative to Pkacii LeaeCi-ri 11

Introduction 1 1

General characteristics t)f the disease 12

Geographic distribution 12

Origin of the disease 18

Losses from the disease 19

Chapter II.— Nature op Peach Leaf Curl 22

Physical conditions influencing the disease 22

The fungus causing the disease ;^1

Relations of the fungus to tlie host 40

Chai^er III. — History of the Treatment of Peach Leaf Cfri 46

Tlie European situation 46

1 )evelopinent of the present methods of treatment 4S

Chapter IV. — Plan of Preventive 8prav Work Condicted hv the Depart-
ment 67

Preliminary plans for the work 67

Spray work conducted in 1894 70

Spray work conducted in 1895 : 72

General consideration of sprays applied 75

CiiAi^ER V. — Influence of Sprays on the Vecjetation of the Trees 77

Saving of foliage from injury by curl 77

Comparisonsof weight and color of foliage from sprayed and unsprayed trees. SS

CJrowth of branches and leaf buds on si)rayed and unspraye(l trees 91

Tlie development of new fruit buds and fruit spurs for the year following

an attack of curl 95

Chapter VI. — Influence of Sprays on the Fruitino of the Trees 10;>

Thinning the fruit of sprayed trees ^ 108

(iathering fruit of sprayed and unsprayed trees 10(>

(■omparative quantity, quality, and cash value of fruit fioiu sprayed and

unsprayed trees 112

Comparative value of sprays in relation ti > fruit 115

Comparative size of fruit on sprayed and unsprayed trees 119

Color of sprayed and unspraj'ed fruit 1 20

Method of thinning and cost of picking peaches 121

Thinning by hand and by curl 121

Co.st of picking peaches 122

The local action of curl on foliage and fruit 122

Records of trees sprayed on one side ' 1 22

CiiAPfER VII. — Preventive Spray Work Conducted rv ()r( iiahdists 126

General consideration of the auxiliary work 126

Notes on the auxiliary experiments in Michigan 127

Notes on the auxiliary experiments in Oregon 135

Notes on tlie auxiliary experiments in California 140

Notes on the auxiliary experiments in New York, Indiana, and other

peach-growing States 144

7

8 CONTENTS.

Page.
Chapter VIII. — Preparation, Composition, and General Characters of

Tii E Sprays Used 1 46

Preparation of the copper sj^ra ys 140

Copper sulphate sohition 147

Bordeaux mixture 149

Eau celeste l'>2

Modified eau celeste l-ili

Ammoniacal copper carbonate 1 •">:>

Preparation of the sulphur sprays 154

Preparation of combined co])per and sulphur si)niys aii<l notes on other

si)rays tested 1 Hi

Bordeaux mixture and sulphur sprays combined Uil

Miscellaneous sprays 1 (il

General chaiacters of the sprays tested 1 <>-

The enduring qualities of the sprays - . . 1(>2

The corrosive action of the spi-ay s 1 (U

Advantages of discernible and indiscernible sprays Kia

Sprays adapted to use in wet and in dry localities 1 (>(>

Chapter IX. — The Application of Sprays 1()7

( ieneral accessories for winter spraying 1<)7

Nozzles suited to winter work 1 ()7

Hose and extension pipes 1 ()H

Protection of the sprayer 1 70

Pumps for various sized orchards 171

Spraying tanks 1 7r)

A])i)lying winter sprays for curl 17")

The time for winter spraying 1 7()

The manner of applying winter sprays 1 7()

Spraying where other diseases are present with curl 177

I'rune rust on the peach {Puccinla ])rinii Pers.) 177

Mildew of the peach {I'orlo.'<]))i:rr(i ii.ii/dcinillur l)e P>. ) 1 78

Brown rot of the peach {Mojiilitt friiclifffiid Pers.) 1 7S

Black spot of the jn-ach {('IddoxporiHtn (vrpoj)lilli(in Thiim.) 1 7S

Winter blight of the peach and other spot and shot-hole diseases, such

as I'liyUoxtirta nrcniniic'tstfd Berk., ('crronjxirK f/fYrwyy/.sr/.v.s-a Sacc., etc.. 170

Sooty mold of the peach 17il

Animal parasites of the j)each tree ISO

Chai-ter X. — Nati're and Soihck ok riiE Si'uavino Maiioui.m.s I'sed ISl

Cop])er sulphate IS!

Copper c-arbonate IS.!

AnuMonia 1S5

Sodium carljoiiate IS7

Sulphur i!tO

Cmai-i i:it \I. — Pi:a( II N'arietiis and Xiusery Stock in Uei.ation io Ci hi.. I;t4

( 'oiiiiiari.son of peach varieties : 1!M

Treatment of nursery stock L'tHi

Summarv l-'()2

ILIllSTRATIONS.

PLATES.

I 'use.

Plate I. Curl -infested peach slioot from Rifigs, Cal 11

II. Rlyccliuni of E.ronsais dcfmnnaii — the fungus causing peacli leaf curl . 85

III . Fruiting stages (»f Exonscus dej'ortiKiux 36

IV. Germination of the ascospores of E.rodsciix (h'/onnaiix 88

V. Terminal peach twigs infested with peach leaf curl 42

VI . Sprayed and unsprayed peach branches 42

VII. Sprayed and unsj)rayed Crawfords Late trees, Live Oak, Cal 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

XL 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 sjjrayed with Bordeaux mixture, Biggs, Cal 115

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

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

Y VI /^^e- ^' -^I^'mt^r of spraying trees on one side, Biggs, Cal "I ,^.j

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, I.,ive Oak, Cal 142

XXI. Steam sprav-cooking appliances for small orchards 158

XXII. Steam spray-cooking appliances for large orchards 1(51

XXIII. Appearance of (jrchard at close of spray work, Biggs, Cal 17(i

XXIV. Cnj)runed trees, too late for spraying 1 76

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 orcliards 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

FICUUES.

Fk;. 1. Cyclone nozzle, w'ith direct discharge and degorger 168

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

8. Heavy cyclone nozzle, with oblique discharge, I'or thick si)rays 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 pum}) for general orchard work, upright lever 178

9. Spray i)ump for general orchard work, upright lever 174

10. Pneumatic pump for general spraying 175

9

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

Leaf Curl.

H-Ii-r

DESCRIPTION OF PLATE T.

Curl-infested peach .shoot from Biggs, Cal. Leaves of tliis character are badly
infested with Exoascus deformans. The greatly broadened and distorted leaves, which
are characteristic of this disease, 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
shortened. A branch thus badly 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 been seen to spread
only a short distance beyond the parts showing the hypertrophy. (Compare with
Pis. V and VI.)

PEACH LEAF CURL: ITS NATURE AND
TREATMENT.

By Newton li. Pierce.

CHAPTER I.

PRIMARY CONSIDERATIONS RELATIVE TO PEACH LEAF CURL.

INTRODUCTION.

This bulletin has been prepared to place before the peach growers
of the United States the results of experiments conducted during- sev-
eral years past for the prevention of peach leaf curl. The losses
arising from this disease frequently' amount to several millions of dol-
lars annually, and it is believed that a wide dissemination of the results
obtained by the experiments here outlined will lead to a large saving
to the peach industry. During the progress of the Department's work
over one thousand six hundred peach growers in all peach-growing
States have ))een requested to test the preventive measur(\s here rec-
ommended. A large number have done so, and some of the more
important results of their work are also given. From conservative
data it has l)een estimated that the experimental work thus widely set
on foot l)y the Department has saved to the coiuitry in a singU^ year
the sum of three-fourths of a million dollars. This is but a fraction,
however, of what may easily be saved in the future, when all growers
have obtained a more thorough understanding of the disease and its
prevention.

The obscure views held by many growers in the past upon the true
nature of peach leaf (uu'l, and the total lack of previMitive UK^asures
up to a recent date, make it desirable to thoroughly consider the sub-
ject at this time and to record the detailed work upon which the con-
clusions reached arc l)ased. These conclusions are that peach leaf ciirl
may be prevented Avith an ease, certainty, and cheapness rarely attained
in the treatment of anj' serious disease of plants, and that there is no
longer a necessity for the losses annually sustained from it in the

United States.

11

12 PEACH lp:af cukl: its nature and tkeatment.

GENERAL CHARACTERISTICS OF THE DISEASE.

The disease of peach trees here considered is variousl}^ known in
dilterent regions and languages. In the United States it is commonl}^
know as peach leaf curl, or curl leaf of the peach; in England and
all Britisli possessions, as leaf blister, leaf curl, or curly leaf; in
France, as cloque du pecher; in Germany, as Krauselkrankheit; in
Italy, as Fillorisseraa, 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 hnifing of the trees, and the greatest
injuries are caused in wet settsons and in humid localities. The leaves
become enlarged, thickened, much curled, and distorted. As the dis-
ease progresscvs the healthful green of the foliage is changed to a yel-
lowish, sickly appearance. 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 nuich of the terminal growth may die throughout the orchard. In
severe attacks young trees are frequently killed. The second crop of
leaves, appearing on affected trees after the spring defoliation, usually
remains c()m})aratively free from curl for the rest of the season. The
amount of disease which will appear upon this later crop of foliage
depends largelj'^ upon the humidity or dryness of the atmosphere,
excessi\'e moisture favoring a continuance of the ti'ouble. The action
of the disciise upon spi'ing branches causes them to enlarge, become
curved iind distorted in various ways, and often to dry up and die.'

GEOGRAPHIC DISTRIBUTION.

IN'ucli Iciif cui'l exists in most peach-growing countries. Its distri-
Itutioii in llic I'liitcd States extends from the Gulf of Mexico to Can-
ada and Ironi tlie Atlantic to the Pacific. The cent(M-s of greatest
prevalence, and where the greatest losses are sustained from tiiis cause,
are in tiie leading ))each-growing districts bordering the Great Lakes,
e.s|)ecijilly in Michigan and w(^stern New York; in the central, north-
ern, and co:ist I'egions of California; and west of the C^ascade Moun-
tiiins in Oiegori juid Washington. Tlu^ disease is less serious, or is of
minor importance, in tlios«i peach-growing counties of New York
most distant from the lakes, in Pennsylvania, Ohio, Indiana, Illinois,
and in southern California. Still less injui'y is reported fiom New
.Jersey, Dtdawaie, Connecticut, Rhode Island, Massachusetts, Mary-

GEOGEAPHIC DISTRIBUTION. 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 widel}^ known.
Reports from Utah and Nevada are meager, but it is probal^lc 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 favoral)ly 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, being
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 A^et
practiced there.

In Europe Dr. K. Sadebeck'' records the disease from Denmark, Ger-
man}^, Austria, Switzerland, and Ital}^ He states that in central Ger-
man}^ it prevails more extensively than in the vicinity of Hamburg.*
Among the many German scientists who have written upon this

' ^Ir. L. Woolverton, secretary of the Fruit Growers' Association of Ontario, said,
in 1890, in a paper entitled, Points onPeach Growing in the Niagara District, pul)-
lished in the Annual Report of the Society for that year, pj). 50 and 57: "The peach
has its share of enemies and diseases, chief among which are the curl, curcnlio, the
borer, and the yellows. For the curl I know no remedy. It is not often severe, but
sometimes with the diseased leaves the fruit also drops." Mr. John Craig, in writing
from Ottawa under date of October 7, 1897, says, relative' to the disease in Ontario:
" It is only severely injurious here during years of unusually heavy rainfall. This
year it was very l)ad."

2 Letter of March 22, 1890, to Mr. J. M. Dobbs, U. S. Consul at Valparaiso, Chile.

^Sadebeck, Dr. R., Die para.sitischen Exoasceen. Fine Monographic, Hamburg,
189:5, p. 94.

'Sadebe(;k, Dr. R., Untersuch. iilx-rdie Pilzgattung Exoiuscus, Hamburg, 1884, p.
115.

14 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

disease luid its cause are Sadebeck/ Winter,- De Ear\^,'' von Tavel,*
Haitig/ Zopf.« Tubeuf/ Ludwig,* Sorauer,' Frank/" Kirchncr,"
Fuckel,'' and others. Winter says (1. e.) that the fungus of this
niahid}' 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 accurate!}' described 1)}^ an English gai'dener
under the name of "blight." He says:" "Under this denomination
[])light] are frequently confounded two varieties of disease materially
dillerent in their appearance, and which I shall distinguish ])y the
appellation of Mister and curl. The former is generally confined to
such peach trees as have glandular leaves, which are mostly subject
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 the}' become healthy.
The leaves so attacked are crisp, and assume a swollen, crumpled, and
succulent appeai'ance; the shoots themselves are atfected l)y it in the
same manner, and never produce either good blossom or healthy wood."
Berkeley '* has described the fungus causing this disease, and it has
been mentioned by Bennett and Murray^'' and many other English
writers. (Consult a poi)ular article on Peach Blister, by W. G. Smith,
Gardeners' Chronlde.^ Vol. IV, pp. 36, 37.)

'tSadebeck, Dr. K., see locations cited; also Einige neue Beobachtungeii uiul krit-
ische Bemerkungen iiber die lilxoascacejc, Bot. Ges., 1895, Band XIII, Heft 0.

^Winter, Dr. Georg, Die durch Pilze verursachten KninkluMtcii d(>r Knltnrge-
wiichse, Leipzig, 1878, p. 47; also Ral). Krypt. Flora, 18S5, II, p. (i.

^De Bary, Prof. A., Comparative Morjjhology and Biology of the Fungi, INIyceto-
zoa, and Bacteria, English edition, Oxford, 1887, p. 265; see also in the same volume
various other references to the arrangement and jxtsition of tiie Exoascus group.

'Tavel, Dr. V. von, Vergleicliende ^Morphologic der Pilze, Jena, 1892, pp. 55,5(5.

•^Ilartig, Dr. Robert, Lehrbuch der Baumkrankheiten, Berlin, 1889, j). 118; also
the English edition, Text-lx)ok of the Di.seases of Trees, London, 1894, j). WVl.

"'Zopf, Dr. Wilhelm, Die Pilze in mori)hologischer, phy.siologisclici', biologisclier,
und systematischer Beziehung, lireslau, 1890, pp. 2:^6,282.

'Tubeuf, Dr. Karl Ennheer von, rilauzenkrankheitcn durch Uryptogamc I'ara-
siti-n verursacht, Berlin, 1895, pp. 167-188.

''Ludwig, Dr. Friedrich, Lehrbuch der Niedcrcn Krvptoganuii, Stuttgart, 1892,
p. 205.

'•'Soraucr, Dr. Paul, ilandl)U(li der i'llau/.cukranUlicilcu, /wcitcr Tlicil, Die para-
sitiircri KranUhi-itcn, Ik-rlin, 188(), p. 278.

'"Frank, Dr. \. B., Dit; Krankheiten der IMlauzcu, l>aiid 11, Die I'ilzpanisitarcu
Krankhcilcu, I'.re.siau, 1896, pp. 24!», 250. Fdition of 1880-81, Vol. II, p. 52().

"Kirchncr, Dr. O.^kar, Di(t Krankheiten und Heschiidigungen unserer lamhvirl-
wrhaftlichen Kuiturpflanzeh, Stuttgart, 1890, j.p. ;}24, -107.

'M''u(;kel, L., Synd)ohe niy(!ologica', 1869, j). 252.

'•' See (juotation in li<'port of Miciiigan Pomological Society for 187:5, i>p. 16, 17.

" l'.erkfley, M. .1., Introduction to Cryptogamic liotany, 1857, p. 284, and Outlines
of r.rilisli Fungology, Lfindon, 1S60, pp. :)76, 444, tab. 1, lig. (i.

'' IJcniifIt, .\. W., and Murray, < Icorgc, .\ Handbook of {"ryptogamic I'.otany,
I.on<Ion, IHH9, p. :179.

GEOGRAPHIC DISTRIBUTION. 15

Tulasne,^ Prill ioux,- and others (Cours complete d'aj^riculturc, T.
XV, p. 255, art. Pechcr) have .studied this disease more or less care-
fully in France, where it often develops in a serious form. In June,
1890, the writer saw the peach trees near the Mediterranean, particu-
larly about Montpellier, in anything but a healthy condition. On the
3d of June leaf curl was l)ad, and the ends of branches were seen to
be dying in some cases. In Italy Briosi and Cavara,* Berlese,* and
Comes ^ are among those who have described this malady. The dis-
ease varies in its j)re valence tli rough 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 cause, 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 l)y Prof. P. Genardius," the disease rarely causes
any damage of importance, because of the dryness of the climate, and
for this reason, he states, no treatment has been tried. In Austria-
Hungary the situation respecting leaf curl is iiuich the same as in
Italy. Dr. Johaim BoUc, 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 appears some years with great intensity and causes great
damage. In Koumania 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 man}^ vears. He states that Roumania has in the region
of the lower Danube almost a steppe climate — in sunnner ver}" 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 1(P 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 teiuperature, when

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

■' rrillieux, Ed., Bull, de la Soc. Bot. do France, 1872, T. XIX, pp. 227-280; Conipt.
Rend. 3; also Maladies des Plantes Afrricoles, Paris, 1895, T. I, pp. 394-400.

* Briosi-, G., and Cavara, F., Fungi Parassiti d. Plan te Colt i v. od Utili, essice., delin.
e descr., 1891, fasc. 5, No. 104.

' Bcrlese, A. N., I Parassiti Vegetali d. Piante Coltiv. o Utili, Milano, 189.o, j)p.
124-126.

•''Conies, O., Crittogamia Agraria, Napoli, 1891, pp. 1(53, 165-167, 549.

« Letter dated Athens, Sept. 12, 1895.

1<> PEACH LEAF CURL: ITS MATURE A>'D TREATMENT.

the development of the fuiitru.s liegin.s. .so that in Juno all leaves at the
ends of the young branches are curled and deformed and perhaps all
the blossom buds fall off. If the more developed leaves at the l)a.se of
the 3'oung 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 prolxibly also throughout
Algeria and other peach-growing portions of 'the continent. Profes.sor
^lacOwan. 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, Xatal. in writing to the Cape
Colon}' agricultural department under date of October 81, 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 leaf curl
than New Zealand. Mr. W. M. Maskell, of "Wellington, writes as
follows : * ■■ The curly blight has ])een for many years prevalent in this
country — so nuich so that whereas in the early days peaches were exceed-
ingly luxuriant and fine, they have dwindled to comparatively very
sn)all and poor trees and in many i)arts of the eolony almost di«'d out.
In the last two or three years the people have been advised to emi)loy
remedies, and have done so to sonic extent, so that thcic is a marked
improvement in the j)each orchards. * * '^ I can myself recollect,
early in the sixties, when the most sj)lendid peaches used to grow
wild in the warm iiortheiii distiicts. wheic now scarcely a tree is
seen; and thecui"ly blight has been a dicadful curse all over the colony."

Australians r«'p(»rt peacii leaf curl among their serious plant dis-
eases. In South Australia it "has been known (jiiite twenty years."'*
and })rol>ably longer, and occasions consi(leral)le losses in seasons
favoring it. The situation is much the same in New South ^\'ale>.

' MacOwan, Prof. P., Agricultural Journal, puhlishtMl by the department of
a>;ri«'ultnn' of CajK- CVdony, 1H92, Vol. V, pp. 2.">2, 2n:i.

- Ix'tter<lat<'<l Cape Town, Oct. 2<i, ISit.").

' Ajjriculfiiral .lournal, ('a|K.' Colony, Vol. VI, No. 2.3, j). 4.'i1.

Matter (lafe<l \Vclliii>j;t<.ii, New Ziahiiid, I)c'ceniUT24, l.S«».'i.

^()l>s«TvationH of .Mr. \. Molineiix, jiencnil secretary for the atrrienltural l>iinaii
of South .\uftralia, l«'tt«T <late<l .\<lelai<le, Fel)niary 11, ISW.5.

GEOGRAPHIC DISTRIBUTION. 17

Prof. N. A. Cobb,^ pathologist for the agricultural department of that
colony, has described the malady quite fully, and although he 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 industr}-. * * * j 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 jSIr. D. McAlpine," pathologist for Victoria, among the
specified diseases in the vegetable diseases bill, recently passed in that
colony. Mr. Mc Alpine 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. Mc Alpine adds: "The disease is distributed all
over the colon3^ In the cooler districts it is generally more severe
than in the northern and warmer districts, and it is generally 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. Mij^abe,^ of the Sapporo Agricultural
College. He writes that Exoascus deformans 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 dou))t of its existence from the
time of the first introduction of American peach trees, al)out 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 be attacked to some
extent during these few}' ears. American varieties are now most seriously
affected, and many persons have been obliged to cut down their trees
on account of the disease. Respectiiig the distril)ution throughout
Japan, Professor Mij'abe sa3'S : ''As to the rest of Hokkaido [the
northern island] I found the fungus in 1890 at ]VIombetsu, a farming
village on Volcano Bay, settled about twenty-seven j-ears ago ))}' the
people from Sendai. I could not tell wiiether the peach trees culti-
vated there were of American or Japanese origin. In Honsiu, or

' Cobb, Prof. N. A., paper in tiie Agricultural Gazette, 1892, Vol. Ill, pp. 1001-1004.
'' Letters dated Melbourne, Australia, July 14, 1896, and Oct. 12, 1897.
* Letter dated Sapi)oro, Hokkaido, Japan, ]^ov. 22, 1897.
19093— No. 20 2

18 PEACH LEAF CUKL'. ITS NATURE AND TREATMENT.

Main Island, the peueh curl seems to be prevalent only in the northern
provinces, * * * i sent letters of inquirj^ relating to this question
to the g-raduates of our colleg-e, 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 ever}" tree is more or less attacked b}' the fungus. T 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 Prof essor
Miyabe that the disease had not been seen there b}' 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 i)cach-almond. The
exceptions to this, where the disease has been noted on tlie ])lum,
almond, etc., are rare, and not sufficiently luimerousor general to mate-
rially allect 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 troul)le. 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 ]n-o))ably its
source rathei- than the near-l)y continental coast. I'n Australia, how-
ever, this may properly be questioned, for, as already mentioned, Mr.

' Ix'tt<'r from Aufinftus Whitt', Esq., forwardi'd April 8, KSilti, throiifrh tlic kiinlm-SM
of Mr. KufuH S. Ka«tlack, tlii'ii U. S. Deputy Con.sul-(Jeneral at Sliungliai. Cliiiia.
Mr. Wliitc! sayH, in concludiiif^ his Htatciiietits, that tlio Chinew, i«;noraiit of I he us(.
of tfie knife in pruning;, trust solely to an animal inspection of the trees at the lime
the l)ios.soms set, when they carefully pick off all excess of fruit, and with it all
»liHeaH«;(l leaves, etc., but allow these to fall to the ^,'round ami remain under the
trees to rot or reprodiun; the plague, as natun; thinks best.

LOSSES FROM THE DISEASE. 19

George Ncilson, 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 countr}' would be
doubtful. Its European origin, however, may not be improba])lc.

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 d(^sira])le 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 ahnond, that none of the many Avidel}^
cultivated varieties of the almond in California, either of local or for-
eign origin, are 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 affected, 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 lift}^ varieties of seedling almonds examined by
the writer none has thus far shown the disease.

LOSSES FR03I 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 ])y the growers themselves, as the nature and action
of the disease are misunderstood b}" 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 partiid crop, the grower has l)ut
little ground for an opinion as to what the yield would have been had
curl not prevailed, hence the estimates of losses made b}^ growers are
frequently \'ery 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 nearh^ alwa3's too
low.

By preventing the disease upon a portion of the trees of an orch-
ard the amount of injur\' sustained })y the untreated trees has been
determined most accurately by direct comparison. Such comparative
work has now been conducted for several years in man}' of the leading
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
1898, there were 251, living in 35 peach-growing States and Terri-
tories, who stated whether or not their orchards were affected ])y curl.

20 TEACH LEAF CURL: ITS NATURE AND TREATMENT.

Sixty-three per cent of these (158 g-rower.s) reported that their
orchard.s were affected, and 37 per cent (93 growers) reported that
their trees had not been troubled by it. Of the 158 whose trees
were atiected, 66 per cent (101 growers), or about 12 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 Pacitic. 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 l)e 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, Maryland,
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 sustained by the 12 per cent of the growers
reporting losses is given in the replies in various ways. Some
growei-s have reduced their loss to dollars and cents; others have indi-
cated the loss in percentage of crop; while still others have used some
term, such as "slight" loss, '' small" loss, etc., as a repl}^ to the
inquiry. In estimating the true loss sustained by these growers a
uniform system has been adopted. Where the loss has ])een stated in
dollars the amount has been recorded as given. Where the loss is given
in percentage of crop the cash loss has l)een determined from the basis
used by the United States Census Bureau in determining the \alue 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 i-epoi't of the grower was indefinite, the statement being that the
loss was small, it has been placed at ^2.50 per acre, which amounts to
about 2i cents per tree as usually planted. It is ijrohable that this
is iiMich below the average loss in such cases, as a loss so small as
this would usually escaj)!' notice. Tn all the caiculacions in these esti-
mat<'s an efl'ort is made not to o\'en:ite the loss. T1h>sc calculations
ga\-e a loss to the gi-owers averaging >:^1(>.1»5 per acre for the aci'cage
r('port('<l as sullcring from the disease, or 12 ))(>r c(Mit of the full aresi.
This IS (•(|iii\alcrit to about !i^l.t)(» per acre foi' the entire acreage", or
about 1 cents \)vr tree. At first thought this may seem high, t)ut this
is more ajjpaicnt than real. If one l(»-acr(M)rchar(l loses its cro}) from
curl, valued at $150 ])cr aci-c. the loss amounts to ^1. .■"><»(). There may
lie ;'>2 other oi'chards of K) acres each all about this orchai'd where not
a [)each is lost, yet the average for such a district is the same as that
Htat<'<l. Tins is peilia|t> a clearer manner of putting the matter than

LOSSES FROM THE DISEASE. 21

by placing an average loss for all orchards. The loss may ))e viewed
in still anotlun* manner. If an orchardist has grown peaches for 82
years and lost only one crop during that time from leaf curl his loss
for the third of a century will average 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 ])e far too low.

If the preceding calculations and statements are accepted as fairly
representing the situation throughout the country, the annual losses
fi'om 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 507,786 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 12 per cent sustained some loss from the disease.

Most of the orchards included in the 12 per cent sustained only a
slight loss, but a very small percentage sustained a heav}^ loss, some-
times amounting to the entire crop. The average loss for the 12 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 507,786, the loss should be calculated
upon 12 per cent of this, or 213,219 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 groat injury 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 fruit
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 1898, when the investigation of this disease was undertaken
by the writer, a vovy large amount of correspondence has been con-
duct(Kl with peach growers in all parts of the Union who have sus-
taiiied 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 l)ecn drawir upon in the above esti-
mates, as it might ])e 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 tlu^ circular letter, the basis of tlu^ estimates, which was
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 th(^ country where curl is scarce
than from the more affected portions.

CHAPTER II.

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
plnsiologv. (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 cui'l has long been
known as a parasitic fungus, Exoascus (Jcforinanx (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 influiMices as tem-
perature, the humidity of the soil and atmosphere, and others. Such
facts were foreshadowed by the theories advanced by p(>ach grow(M's
as to the cause of the disease. Many growers have considered peach
leaf curl as tiie direct result of excessive moisture and low tem-
perature or sudden changes, and as these physical conditions cer-
tainly have an important bearing upon the injurious de\ elopment of
the disease, they are considered together with the direct relations of
the parasite to its host. However, too nuich 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 conti'ol of tin; fungus has been found practicable, simple, and inex-
pcnsivi!.

I'llVSICAI, CONDniONS INFLIiKNCIM! TIIK DISKASK.

Tlx' influences of temi)erature, humidity, situation, soil, etc., upon leaf
curl are often so well marked that they have frecpiently and in fact<iuit(»
generally been mistaken for the active cause of the dis(>ase. Indeed a
Nci'v large ])ercentage of peach growers have maintained, to within the
past ten or fifteen years, that sudden changes of tiMuperature occuning
in conjunction with west w«>ather are the solo cause of the curling and
22

PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 28

loss of foliage. Notwithstaiidino- the nunil)er 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
firmly believe that leaf curl is due to uncontrollable climatic influences
that they would not consider other explanations, bcMng 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 respecting the
conditions under which leaf curl develops most severely, a circular of
inquiry was addressed to several hundred orchardists in November,
181);:>. 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 difference, 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 w^ere 104 replies. Of these, 78
stated that peach trees were most affected in wet seasons, 8 that the}"
were most affected in dr}^ seasons, and 18 that there was no difference.
Here again is seen a marked agreement in the replies, a great majority
of the growers 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 sa3'S that irJten the combined
effects of tJie physical eiwironment are uiifavorahle to the host, hut not so
or are even favorable to the parasite, 'wefind the dtseaxe axKuinhxj a more
or less j^ronoimced epidemic chara,cter. He is not here speaking of curl,
but the statement holds perfectly true for that disease. A cold, w^et
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 transpiration, due to lowered temperature
and saturated atmosphere, soon results in the tissues of the plant being
suffused Avith water. "'The stomata," as Ward puts tt, ''are nearly

^Wanl, Prof. W. Marshall, The Relations between Host and Parasite in Certain
Diseases of Plants, Croonian Lecture, IVoc. Roy. Soc, 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 arc thoroughly saturated with water and
aqueous vapor, respectiveh', 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 absorljed 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 partialh'^ blocked ven-
tilation system have for a consequence a depression of respiratory
activity and the absorption of oxygen genei-alh'."' 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
leaves. "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 Ijecome
relatively thinner than usual, as well as watery, because the ill-nourished
protoplasm does not add to the substance of the walls in proport^pn.
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
ec^ually as good for J'J.rod.scus defoi'man.'t as for other forms. In speak-
ing of these conditions in relation to a fungus known as Botrijtis^ Pro-
fessor Ward gives some generalizations equally applicable to Kiy>ai<cu.'<
(h'forrnans in its relation to curl. He says that just those external
climatic conditions which are disturbing the well-l)eing of the green
host plant are either favorable to the fungi considered or, at any rat^,
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 80-^ C. and higher, and althougli we still want information as to
details, experiments have shown that the mycelia flourish at tempera-
tures considerably below the o])timum for higher plants. Moreover.
light, so indispensable for the carbon assimilation of the green host,
is al)solutely 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 intei'ference
with the normal performance of \arious correlate(l functions, as we
have seen, and rendei- the plant tender in all respects, are distinctly
favoi"al)le to the <le\ clopment of these fungi; conse(|uently the \ cry
set of external circumstances which make tin; host plant least al)lc to

PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 25

withstand the entry and devastation of a parasitic fungus like Boti'i/tis^
at the same time favor the development of the fungus itself."

The writer thinks, as the result of observations in the field, that
Exoascus deformans is favored in both its entrance and spread within
its host by the conditions which have just been considered. It is a
widely observed fact that leaf curl usually develops sparingly in a
uniformly warm and dry spring, and it is also noticed that where
infection has occurred a return of warm, dr}^ 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 spaces 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 likel}' to run more than a short and feelile
course. Soil and elevation are here considered with atmospheric con-
ditions, for it is found that on the same farm a difference of elevation
or soil moisture may determine the degree of virulence 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 afl'ected 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 is no difl'erence. While the majority claiming that trees
on low land are most afi'ected 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 be most
affected on high land, hence is sufficient to establish confidence in its
reliability, even if it were not indorsed by man}' published statements
to the same eflect.

Mr. Thomas A. Sharpe, superintendent of the experiment farm at
Agassiz, British Columbia, has made several comparative I'eports on
the action of peach leaf curl on trees planted in the valley and upon
the more elevated bench lands of the farm. A few brief statements
from these reports should be of value in connection with the above
statements.^ In 1892, Mr. Sharpe says, the peach trees sutt'ered from
a severe attack of leaf curl. "Only .5 varieties of those planted m
the valley escaped" the disease. "The trees planted on the bench
lands did not sufler so much, and appeared to recover much more
rapidly than those in the valley" (1. c, p. 278). In 1898, it is said,

' See rei)()rts of oxi)eriiuei)tal farms, Ottawa, Canada, for the years indicated.

26 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

the t'lU'l leaf in the peach and nectarine trees was worse than it had
ever been l)efore, the Malta being the only variety that was entirely
healthy on level laud. The varieties received from England and
planted on the level land were just as l)adly affected as the others.
The tii'st and second l)ench orchards suffered alike with those on the
level gi'ound. but the orchard highest up, at an elevation of SOO 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 1890. "as heretofore, the trees on the upper bench(^s, both
nectarine and peach, escaped the curl leaf entirely" (1. c, p. 4A9).
Again, it is said that "the peach crop on the level land this year [in
1898J 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 l)ench 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 thej' were recorded by a single ol^server on one farm
and during successive years and epidemics of curl, and they are in
perfect harmony with the experience of a majority of the growers
whose views are presented above.

The soil may exert its influence b}' 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 commoidy 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 temporary excessive humidity of the atmos-
phere upon leaf curl, which has already been considered, there are
other atmosphei'ic influences and relations of importance, which depend
upon the local or general ge()grai)hic, topogra])hic. and climatic fea-
tures of couiiti-y. Some of these more i)r()iniiient atmospheric
influences may here b(^ brietly considered, together with their most
l)r()bal)le causes.

Proximity to large bodies of water, whether salt or fresh, greatly
favois the development of curl. The cause fortiiis clearly rests in the
I'esuiting greater humidity and lower temperature of the atmosphere.
Plants grow iiig in a constantly humid atmos[)here luuc normally more
Huc<-ulent and tender tissues than those gi-owing in a drier legion. The
reasons for this ha\'e already l)een allu(le<l to for special castas of
(sxti't'ine atm()S[)herie humidity and lowered temixTatui'e. Near large

PHYSICAL CONDITIOTSTS INFLUENCING THE DISEASE. 27

bodies of water spring fogs couimonly 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 nmch more
humid than in an inland region. Instances of the influi^iice 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 liay 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 temperature is
high, transpiration may proceed normally even in the neighl^orhood of
large bodies of water, and curl may not commonly prevail.

In contrast to the influences of large Ijodies of water are those of
neighboring dr}^ 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 aftecting the general and perma-
nent prevalence of curl over extensive regions is the normal annual
rainfall. Comparisons of this kind umst be made, however, between
regions of approximately similar temperature. Under such condi-
tions it may be said that the general animal 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 temperature 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 CUKL: ITS NATDEE AND TREATMENT.

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

In the following remarks on this subject I have left out of consid-
eration the temporary influence of exceptional seasons and, as far as
possible, the special influence of local features. The subject should
be viewed from the broad field above pointed out. In southern C'ali-
fornia leaf curl is not recognized as a generally prevalent and serious
trouble, but there is evidence which shows that its prevalence increases
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 Los Angeles, which is not far from the mountains. In
the San Joaquin Valle}' 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, !♦ inches at Fresno,
11 inches at Merced, and 11 inches at Stockton, reaches 20 inches at
Sacramento, about which center curl is quite prevalent. The average
rainfall at Oakland is 23 inches, and curl is ([uite trou))lesome there.
In the Sacramento Vallej' curl is frequently ([uite pre^•alent, and the
rainfall varies from 20 inches at Sacramento and Chico to 31 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 becomes decidedly more prevalent and injurious
at the west of the Cascade Mountains, and increases as Portland is
approached. The rainfall is 35 inches at Koseburg, 1(5 inches at
Alban}', and !*.> inches at Portland. From Albany to Portland the
peach industry has been greatly injur<>d by curl, and on its account
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 spit(> of the
humidity of tin; climate. In the Patent Oftice Report for 1855, p.
298, there is a statement of the situation in Polk and ^Marion comities
from 1852 to 1855. This statement was from Mr. Amos Harry, of
FaiiM \'idlev, Polk County, Oreg., and is of special interest in this
connection. Mr. Harry says: "The peach in this county has been
attectcd with a disease known as the 'curled leaf,' which threatens to
destroy the trees. It made its ai)p(>ai-ance at Mill Creek, in Marion
County, in 1852, and extended considerably on that side of tli(> rixcr
(Willamette River) in 1853, but had reached most parts of tho valley
in 1S51-55. Some trees seem to escape it much more than others, but
if tlu' malady irici-cascs for two years to come as it has foi* two ])ast, 1
fear we shall conif entirely short of this delicious t'l-uit. Some think
It is owing to cold, wet w<'ather. and reconnnend shortening all the
limbs as a remedy, and some experiments seem to taxor this id(>a.
Others think it i> produced by an insect, and that no icniedy will save
the tree- iird<» it can l»e applied to llie whole siiit'ace of the leaves."

PHYSICAL CONDITIONS INFLUENCING THE DISEASE. 29

The rainfall at Portland, as already said, is 41> inches, and eurl is com-
monly prevalent and severe. At Umatilla, east of the Cascade jMoiui-
tains, l)ut 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 beino' nuich less
prevalent and of secondary importance. This shows that it is not the
distance north and the consecjuent lower temperature which makes curl
more severe at Portland than at Los Angeles for instance, T)ut that it is
the excess of rainfall, for at the east 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, the general prevalence of curl
and its injurious action being one of the chief reasons. The rainfall
is 50 inches at Seattle and 56 inches at Ol3"mpia. 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 neighl)oring
sections on the east side of the Cascades and near Ellensburg, where
this rainfall is taken, are noted for their extent, thrift, and general
health, and curl is not a serious trouble. This case is parallel with
that of Portland, already considered. The rainfall at the west of the
mountains is 60 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 ])v the
Washington Board of Horticulture as one of the horticultural indus-
tries, but in the latter region the peach is a leading fruit, ))eing
extensiveh' and successfully grown. The winter temperature east of
the mountains should range fully as low Avhere 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, Novem})er, 1893, Mr. T. C. Staj'ton, of Queen Anne, makes some
statements which bear directly on the matter here considered and are
of nuich interest as resulting from personal observation. After speak-
ing of the conditions in Maryland, Mr. Stay ton sa3's: ''I was in
Washington State during the months of April, May, June, etc., this
year, and I find they can not grow peach trees west of the Cascade
Mountains or in western Washington, as that part of the State is
called, as that is a ver}' wet part of our country.'' He adds that this
was especially true in 1893, and continues: "Ahout 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, ])ut over in eastern Washington
I did not notice any curl leaf, the climate being dry."

'For a full and accurate account of the rainfall conditions i)revailin<i on the
Pacific coast, see Report of the Rainfall on the Pat-ilic Slope for from Two to Forty
Years, Washington, 1889; also other reports of the Weather Bureau.

30 PEACH LEAF OFRL: ITS NATURE AND TREATMENT.

Peach leaf curl appears to be more prevalent in late than in early
springs. This is probabl}^ 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 question 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 heavj^ dews on curl was also sub-
mitted to the orchardists, and the views expressed in their replies
exhil)it 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 che(;ked 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 ])ut little
influence upon the tissues of the leaf. It might seem that dew would
ha^■e a dii'ect 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 held or in the laboratory. In regions having little
cloudy weather, with exceptionally clear skj^, as in manj' portions of
th(^ Southwest, the heat of the soil radiates rapidly aftei- sunset. In
such sections of the country the days are hot and the nights cool or
cold in comparison, the range of temperature between night and day
))eing often considerable. In such regions dew is conmion ;uid often
heavy, but it is here that least curl occurs.

Relative to the action of dew on the germination of the spores of
Kxod.HciiH <lA'f(yniianH^ it may be said that something more than dew is
required for such germination. The writer has tested this matter
most thoroughly, not oidy with dew, l)ut with many forms of culture
nicdiii at various temperatures and with varying supplies of oxygen.
Hrcfcld has also shown that moisture alone is not sufficient for germi-
nation, h<' having utterly Failed to induce germination in a single instance
after months of work with cidture media in li(|uid I'oi-ni. l')udding of
the spores is easy to obtain in all li(|uids, and is more iilmndant and
continuous in suitable noniishing cultures than in dew oi' rain water.
I'Ml'tv-eighl growci-s i'ej)lied to an in(|uiiy on this suljjeet, 47 stating
that llic disease is no worse after a s(>,ries of hca\ \ dews, 7 (iiat it
is W(^-s<!, and I that no dill'crcncc was obseived.

THE DIRECT CAUSE OF PEACH LEAF CURL. 31

THE FUNGUS CAUSING THE DISEASE.

The fungus causing peach leaf curl, now known as Exoas<yus defonnans
(Berk.) Fuckel, is a member of the subfamil}' of fungi known as
Exoascem. The Exoamea'. are low or simple Asco)itycete>i^ or fungi liear-
ing their spores in cases or asci.

The classification of the Eroaxcen', which now la^vs 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 directl}^ concerns
us at this time, as it is to this genus {Exoascus) that the peach curl
fungus belongs, as well as numerous other species injurious to horti-
culture. In considering this genus Sadebeck ^ has grouped thirty 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 iimer tissues of the axial organs.

a. The development of the hymenium occurs only in the floral leaves of the '
host i)lant. Eight species.

h. The development of the hymenium occurs only in the foliage leaves of the
host plant. Seven species, including E. dcfonnaui^.^

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 l)uds of the liost plant and develops only
subcuticularly in the leaves.

'Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, p. 43.
Sadebeck recognizes five genera in the Exuasccrv, which he arranges and character-
izes in the following manner:

EXOASCEjE : Ascoinycetes whose asci are not xinited in a fruit body.

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

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

2. Maymmclld Sadebeck. Parasitic. Asci with more than four spores; usually
conidia formations in the ascus. Oidia and chlamydospores wanting.

B. The asci take their origin fi'om a more or less loose hymenium.

3. Ascocortk'inm Bref. Saprophytic on bark. The ascus layers are arranged in a
loose hymenium upon the mycelium.

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

5. Exodscufi Fuckel. Parasitic. With i)erennial mycelium. In the formation of
the asci no differentiations of material appear. The subcuticular mycelium changes
directly to ascogenous (xdls. Causing sprout deformations.

■^Sade])eck, Dr. R., Einige neue Beol)achtungen und kritisclie IJemerkungen iil)er
die Exoascaceaj, pp. 277,278, reprint from den Ber. d. deutsch. hot. Ges., 1895,
Bd. XIII.

"Dr. von Derschau has described the occasional fruiting of E.mnxrus tfrformans in
the blossoms of the peach. The figures given by this author do not show the nor-
mal development of ascogenous cells in the blossoms which are so conunon in the
leaf Vjlade of the peach. His figures show the asci as arising from lateral l)ranches
of a continuous mycelial hypiia, and this mycelium is situateil beneath the epidermal
cells instead of between the cuticle and t-pideruiis (Landw. Jahrb., Berlin, 1897, pp.
897-901, and Table XLI).

32 PEACH LEAF CURL: ITS NATUEE AND TREATMENT.

ti. The develoimu'iit of the hynienimu occurs only in the Horal leaves of the host
plant. Three sjiecies.

h. The develoiiiuent of the hynieniuni oix-nrs only upon tlie foHajre leaves. Ten
species.

c. The resting mycelium extends intercellularly in the deformations of the leaves.
One siiecies.

It may be seen under A 7) of this arrang-enient that Kromcus defor-
m<in>< is said to possess perennial mycelium, inhabiting the inner tis-
sues of the axial organs, and that the development of the hymenium
occurs only in the foliage leaves of the host plant. As will be seen in
another part of this l)ulletin, it is perhaps a perennial nature of the
mycelium of E. deformans which makes it difficult to thoroughly rid
an orchard of curl by means of spray treatment, but this matter
requires further careful consideration.

The synonymy of Exoascus deformans (Berk.) Fuckel has been
given b}' numerous writers. Sadebeck^ gives it as follows:

Aacomyces deformarnf Berk. Intro, to Cryptogamic Botany, 1857, \i. 284.

AscoKporiiDn (h'foDiiauH Berk. Outlines, 1860, p. 449.

T(q}hrhm deformans Tul. Ann. Sci. Nat., 1866, V. Ser., t. 5., p. 128.

Exoascus deformans Fuckel. («) Persicx Fuck. Symbola? Micolog., 1869, }>. 252.

This fungus has been very commonly observed and frc(j[uently
desci'ibed ])v ])otanists 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 centur3\ The peculiar behavior of peach foliage under its action
has })een observed by horticulturists, however, for a nnich longer
time. The disease was well descri})ed in England in the early part of
the present century.

In spite of the very conmion appearance of Exoasous deformmis
upon peach foliage in peach-growing countries, the descriptive litera-
ture relating to its life history is not free from conflicting statements.
Several species of Exoasceo} have been confounded with this species
in some instances, and subseqiuMit writers have perpetiiat(>d the
confusion.

Some eai'liei' wi'itrrs believed this species inhabits a considerable
lunnbci" of host plants, tluis resulting in tlu^ (lescrij)ti()ii and disti'ibu-
tioii of sciveral distinct species as Exod.scu.'^ dcfornttiits. To avoid such
confusion it would 1)c best to confine remarks upon this species to the
fungus as it develo])s upon the peacli {Pnimi.s perslca L.). which if
ii(»1 its only host, is certainly its most coiiunon one.

At least two modes of infection of the peach 1 i'C(> by Exiklscu.^
dij'oriiKiiis ai'c said to exist (1) by means of perennial mycelium,
and (2) by means of the s))<)rcs of the fungus.

SadebecU ' is authority for the stat(Mncnt, that the niyceliiini winters
o\er in the youngest poilionsof the one-yeaioid Inanchesof the host

'Sadeheck, i)r. II., Dif parasilisclicn I'lxoasceeii, llamlmig, ls;i;'>, p. 53.
^Jdeni, I.e.

THE IlSrFECTION OF THE HOST. 33

plant, and may be seen in the primary cortex, in the medulla, and in
the medullar}^ rays of the first shoots of each period of \egetation,
but has not been o])served 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 b}^ De Bary ''' can not be cited 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 leav^es from the shoots of the previous
summer, has probably considerabh^ retarded the progress of prevent-
ive treatment. Pathologists have thought it improbable that any
considerable amovmt of disease could be prevented after a tree Avas
once generally aflected, 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.
Assmning the mycelium to be perennial, he says that the curing of the
disease might be aimed at through cutting back of the diseased branches
and the prevention through <|uick 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 industr3^

^Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, pp. 24-28. — Das
perennirende Mycel der Exoascus- Arteii.

'■'De Bary, A., Com. Mor. and Biol, of the Fungi, Mycetozoa, and Bacteria, Eng-
lish edition, 1887, p. 26(5.

•'rrillieux, Ed., Bui. de la soc. hot. de France, 1872, T. XIX, p. 2m

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

^Winter, Dr. Georg, Die durch Pilze verursachten Kranklieiten der Kulturge-
wilchse, Leipzig, 1878, ]>. 47.

«Cobb, Dr. N. A., Tlie Agricultural (iazette, Sydney, New Soutli Wales, IS92, Vol.
Ill, pp. 1001-1004.

19093— No. 20 3

34 PEACH LEAF CURL". ITS NATURE AND TREATMENT.

Relative to the use of fungicides the same writer sa^'s: "These
treatments are of doubtful value as far as the curl is concerned, and
were it not that they are viseful 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 uncelium is responsible for the major portion
of the spring infection of the tree. The writings of others to the
same 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 place
except under exceptionally favorable conditions. Our experiments
have demonstrated that as high as 98 per cent of infections may be
prevented b}^ 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 pei'ennial mycelium exists,
aJid it seeuis probable that the infections by this means luay 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 hi))ernating mycelium, which certainly would be
unusual and scarceh' 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 tlie tree
are i)revented by a single spraying suggests that at least such ])ei-cent-
ag(? of the infections is by means of spores.

The mycelium of Kroa.sciis difoi'iiKinx as found in the ])(>acii. shows
great differences in the form and appearance of its hyplne. These
differences depend ui)on the stage of development of the funglis and
the various functions of the mycelium. Th(> writer recognizes three
types of hyphte, which may he teinied vegetative, distributive, and
fruiting.

'I'he vegetative hypha* are found most connnonly in the leaf ])ai(>n-
chyma, but are also met with in the leaf stalk and cortical ])ai'eiichyma
{*f l)adly diseased and distorted l)i'anches. These hyphic may l>e most
distinctly seen, and ar«> most highly developed, in infested leaves which
have not yet foi'ined the hyiueniuni of ascogenous cells, but in which
the parasite has been present a sutKcient time to (Mitirely altei- the
(•hara<-ter of the palisade tissue and caus<' the loss of the chlorophyll.
In the leaf l)lade the palisade tissue first shows the serious action of

BULL. 20, DIV. VEQ. PHYS. a PATH., U. S. OEPT. AGRICULTURE.

MrCELIUM OF EXOASOUS DCPORMANS, THE FUNOUS 0AU8INQ PEACH LEAF CURL.

A.ll<,niik I'll, Mil, ll,illli,>„i„

DESCRIPTION OF PLATE II.

Mycelium uf Exua-scus deformans (600/1) . Figs. 1 and 2, normal vegetative hypha?,
as ff)imd in the leaf parenchyma, showing characteristic septation, modes of branch-
ing, etc. ; figs. 3, 4, and 5, usual type of distributive hypha^ found in swollen branches
in the cortical parenchyma and medulla; figs. 6, 7, 8, and 9, fruiting hyphie, show^-
ing successive stages in the development of ascogenous cells from the subcuticular
mycelium (6) to the half-formed ascogenous cells (9). (See PL III for further stages
in the development of the ascogenous cells and asci. )

THE MYCELIUM OF THE FUNGUS. 35

the vegetative hyphae, which are usually found somewhat later among
the cells of the spongy parenchjMiia, 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 hj^phae is
ver}^ irregular, and their elements, or cell members, are often of dif-
ferent size, length, and shape. The cells vary greatl}" 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 hj^phje
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 hyphte 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 l)eing 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 l)ut closed. These peculiar septa are
remarkal)ly 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
hyphre are shown in PI. II, tigs. 1 and 2, of this bulletin. The hypha?
there shown were carefully separated from the leaf parenchyma and
drawn under the camera. The vegetative hyphre of the l)ranch are
much like those of the leaf, and have been seen most commonly among
the looser parenchj^ma cells of the cortex just exterior to the bast fiber
bundles. Thus far they have never l)een found by the writer in the
caml)ial tissues. Sadebeck states that the mycelium has been found in
the pith and medullary rays.

The distributive hyphae 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 al)undance in
the pith. They are occasionally found in groups of several hypha^ but
slightly separated from each other and following a course parallel to
the longitudinal axis of the shoot. The cells composing these hypha?
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 hypha^ have l)een followed for some
little distance in the swollen portions of the peach twig, and the name
has been given them from their apparent function of spreading the
fungus in the branch. Such hypha- bi-anch ])y bifurcation, the branches
commonly assuming a course parallel to the parent hvpha and the
direction of the peach limb.

36 PEACH LEAF CUELt ITS NATUKE AND TREATMENT.

The fruiting hyphse have been seen to arise in Exoasaus deforma/ns
from the vegetativ^e hyphse after the latter have become well developed
in the parenchyma of the leaf. Large, well-nourished vegetative
hypha? commonly develop just below the epidermal cells of the upper
leaf surface.^ From these hyphse arise branches which penetrate
between the cells of the epidermis, and press themselves between the
epidermis and the cuticle. Such hyphje may be seen both in section
and surface view. These subcuticular hyphaj now branch freeh', 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 hj'phre. By opening and following these channels the
mycelium assumes the outlines of a quite uniform network l)eneath the
cuticle. While this manner of following the line of juncture of adjoin-
ing epidermal cells with the cuticle is conmion, it is not invariably the
practice of the fungus, cases occurring where apparently no such
agreement exists. Series of straight and parallel hyphje, at regular
distances apart, are sometimes met Avith beneath the cuticle as the
precursors of the hj^menial layer. These send off lateral branches on
either side, which ])y enlarging, branching, and curving eventually
occupy most of the surface of the epidermis between the main hypha\
It is probable that the path followed by the first subcuticular hypha?
depends largely upon the firmness with which the cuticle is attached
to the epidermal cells, and which ma}' largch' 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 groAvth, the
hypha' could naturally pursue a more direct course beneath the cuti-
cle than under contrar}' conditions. After the esta])lishment of a
much-))raiiched filamentous ni^twork of subcuticular hyplnv. the cells
of which are usually slender, of medium length, thin-walled, and of
comparative!}' uniform diameter (PI. II, fig. 6), these cells begin to
distend, and are shortened ])V 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 th(! fact that Winter's statement that "the asci break throujili tiie lower
si<l(; of the leaf" does not hold jiood for the peach (Kryp. Flora, Asco., p. <>, and
Krank. Kultur-dewiichse, I^'ipzijr, 1878, p. 47). Winter is not alone in statinji that
thea.«<i of K. ih/oniKinxurm'im the luider .surface of the leaves. Robinson says: "The
asci are borne on both sides of the leaf, l)nt in greater luunbers upon the lower sur-
face" (Koltinson, I?. 1>., Notes on the; (Jenus Taphrina, Ann. Bot., Nov., 1887, Vol. 1,
No. 11, J). H)8). Atkinson also says: "The asci are developed on both surfaces of the
leaf" (Atkinson, (Jeo. F., I>eaf Curl and I'luni PiK-kets, ('ornell Ajrr. Kxp. Sta. I?ull.
No. 7.'{, 1894, p. .'{25). These and other like statements have probably arisen from a
Htudy of other foliap- than that of the j)each, and of other species of Exoaaciis, and
qave been i)er[>etMat<'<l thnm^'h iiisullicient reference to nature.

DESCRIPTION OK IM.ATK TIT.

Fruitiiifi stages of Kni<(xciti< deformans. F'igs. I to 11^ (fiOO/l), various stages and
conrlitions of the asci and ascospores of t!u' fungus. Fig. 14, section of peach leaf,
showing sul)epi<leriiial and suV)cuticular myccliuiii, the latter already jiartially dif-
ferentiated into a.'^cogenous cells. Fig. 15, section of peacli leaf showing three suc-
cessive stages in the formation of the asci from the ascogenous cells: a, the i)ushing
of the ascogenous cells; //, the ascus nearly full-formed, but with the contents still
connected with the ascogenous cell; <•, the asci separated by a sejitum from the ascog-
enous cell, wliich now forms the stalk cell of the ascus. Figs. 1() to 20 (tiOD/l), the
first stages in the formation of the asci from the ascogenous cells, the latter being
rui)tured above and the asci pushing ui>ward. Fig. 21, the pushing of a forming
ascus tlirough the leaf cuticle (()00/l). Figs. 22 to 27 (600/1), various stages in the
fonnation of ascogenous cells from subcuticular mycelium. (P'or several early stages
in this process see PI. II, figs, (i to 0). Figs. 28 to 30 (000/1) show fully developed
asc(jgenous cells as seen from above.

BULL. 20, DIV. VEQ. PHYS. & PATH., U. S. DEPT. AGRICULTURE.

PLATE in.

NVwt.in II Picni- ;«1 iwit H':l

FRUITING STAGES OF EXOASCUS DEFORMANS.

i.llurn< r».l.iil>. Ka

THE FEtTlTlNG 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
lobes eventually tilling, 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 'ascooonous
cells is formed (PI. II, fig. 9; PI. Ill, %s. 23, 24, 25, 26, and 27). At
this time the cells become well rounded and heavv-walled, and thev
may or may not become loosened and separated^ from each otheT
(PI. Ill, tigs. 28-30). These are now the fullv 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
hypha' 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 ])lade 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
cell. 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
cell.

38 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

In view of these facts, it seems possible that the asoogiMious cells
may be capable of enduring, under especiall}^ 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 ))lade and petiole
of the leaf and upon the blossom, and a vegetative mycelium is found
growing thriftily in the swollen branches, there seems to be no good
reason why the parasite may not fi'uit upon the infected twigs.

The perpendicular growth of the developing asci in the leaf soon rup-
tures or pierces the cuticle, and where largo 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,
fig. 21). The contents of the forming ascus are finel}^ 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,
tig. 15). When fully developed the asci are usually broader at the top
than at the base, and often somewhat clavate in form. A series of asci
measured \aried in length from 3-1: to -i-i /<, the average being 38 M '■, the
width of the asci ranged from 10 to 12 yw, and the height of the stalk
cells varied from 8 to 13 ;^, the average l)eing slightly over 10 m (PI-
III, tigs. 1-18).

The formation of the ascospores in Exoascus deforrrums has not been
carefully studied by th(^ writer. Sadebec^k has shown, however, for E.
turg'iduH^ that mitotic nuclear division occurs in the ascus in connec-
tion with spore foi'mation (Untersuch. iiber die Pilzgattuiig Exoas-
cus, Hamburg, 1884, PI. Ill, tig. 20). The ascospores devek)ped in
the asci of E. deformans varj^ in number from 3 to 8, the latter being
the full and typical numl)er. When matures they are surrounded l)v a
moderately tirm 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 (^uite spherical. Fresh ascospores sometimes show distinct
nuclear phenomena. This has been obscu'ved with spores still within
the ascus, 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 (PI. IV, tigs. I, 2, 3, 4, and 10).
Th(^ average; length of the ascospores measuivd was T/f /<, the length
vaiying from <> to 9 a*, and the average width was (>,•',, /<. varying from
5 to 7 }i. The ascospores escape from the ascus through an ajjical I'up-
tuic of the latter.

(icrmiriation of the ascospores has been observiMl by the writci" to
pi'oce(;d in two ways: (1) \\\ means of budding or conidia formation;
(2) by nutans of stocky germ (iil»t's. often one branched and rcsiMnbling
promycelia.

DESCRIPTION OF PLATE IV.

Germination of tiie ascosporet- an<l conidia of Kroascus deformans. Figs. 1 to 12
(al-KJut 800/1), a.scof?ix)res, of whifli five show nuclear phenomena and several are
budding. Figs. 13 to 21 (800/1 j, thin-walled conidia, several of which are ]»roducing
hu<1s; tlie remaining spores, uniuniilK're<l, show various modes of proiiiycdium
f<jnuation or mycelial germination.

JLL. 20, DIV. VEG. PHYS. St PATH., U. S. DEPT. AGFUCULTUBE.

N'pwttiri H.l'ifuc lui.iint del

GERMINATION* OF THE SPORES OF EXOASOUS DEFORMANS.

A. Hum, *- <■« Liili B.illhiiurv.

1

GERMINATION OF THE SPORES. 39

Budding- of the ascospores occur.s 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 lieen seen. Budding occurs most commonh" at one end
of the ascospore, but occasionalh^ lateral buds are observed. In the
earh' 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 Peroiiosporece. The successive primary conidia bud-
ding- from an ascospore ma}' 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 of primary conidial budding can no longer take place the empty
ascospore may or ma}^ 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 (primar}', secondary, tertiary, etc.)
when grown in pure water, are each smaller than the preceding, and
the conidia are considerabh' elongated in form, sometimes almost
cylindrical. The walls of the conidia are more delicate than those of
the parent 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 Inidding process for considerable periods of time,
as in the yeasts (Saccharomyces). Whether the conidia of Exoascus
defoivnans 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 Exoascus
defornuuhs, 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
cxtremit}', 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 tosquinstii^ 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 promj'celium, is connected with the spore by a verj'^ narrow and
short tube, with straight and ])arallel walls. The same mode of con-
nection is also observable in the formation of the bud conidia, and

40 PEACH LEAF CURL: ITS NATUEE AND TREATMENT.

ivininds one of the .sterigmatti bearino- the sporangia of P]nii(>j>hi}t(>r(i
hifextaiix.

Thus far efforts to induce tilamentous gerniiiiation of the bud eonidia
or of the ascospores of ExoancuH defonnmis in culture media have
proved unsuccessful. Brefeld has worked with this problem for
months, and the writer has frequentl}' attempted to ol)tain this form
of germination.' Budding occurs, as alreadj^ indicated, quit(^ readily
in various luitrient 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 m^^celial germination have
.shown that this germination occurred under natural conditions upon
the peach leaf, the germinated spores l)eing transferred from the leaf
to the culture^ in preparing the latter. It may be added here that the
))ud eonidia are also formed in vast numbers upon the surface of the
infested leaf after the maturing of the ascospores. It i-; largely these
eonidia which give the infested leaf the marked white appearance
conmionly observed at the height of the disease. The leaf appears as
if covered with flour or a heavy white bloom.

RELATIONS OF THP: FITNGUS TO THE HOST.

Under a previous heading in this chapter the physical conditions
which influence the serious development of peach leaf curl liave been
considered in accordance with the light which we now have relative to
such influences, and there remain to l)e taken up at this time the more
intimate and direct relations of the host and parasite. These relations
includ(> the action of the fungus upon the cell contents, the cell walls,
and the cellular tissues of the host; the pi'obal)le mode of infection and
the spread of the parasite within the tissues; the wintering of the
fungu.s upon the tree; etc.

'A very considerable number of cultural experiments have been tried. The cul-
tureH oi asco.sporeH and eonidia liave been subjected to temperatures nnich below tlie
freeziiifr i)oint and to various degrees of heat in the thermostat. Sudden changes of
tcmjK'rature have l)een tried. Increased and diminished amoimtsof o.xygen, as con-
trasted with that of the normal atmosphere, have been tested. Even a chamber tilled
witli nearly ])ure oxygen has produced no ai)parent effect. Water from various
sources, such as rain water, dew, ice water, distilled water, tap water, et(;., has been
testcfl. Solutions of tlie various sugars, malt extract, sterilized beer, plum extract,
etc., were tried. Hanging drop cultures of various nutrient media and plate cultures
of potato-peptone-sugar gelatin have not shown germination. Drojjs of variou-
nutrient solutions placed upon newly forming leaves dissected from unopened peacii
buds and thes(! lield in moist chambers have given oidy negative results. The same
is true for peach i)itH brought near to germination and the cotyledons treated with a
weak solution of diastase, the spores jilaced between theui and held at various tem-
I)(Tatur<'s in moist ehamlM'rs. Sections of such cotyledons with spores placed upon
them were also prepared in moist ciiambers. A brief treatment <>f tiie spores with
ellii-r was tested without bringing about germination.

I'rillieiix states that attempts to artilicially infect the leaves or shoots luivc not
thus far succerde.i (>hil. .1. I'lantes Agr., Vol. 1, p. :{!«>).

RELATIONS OF THE FUNGUS TO THE HOST. 41

As al ready indicated, the writer's work witli sprays seemed to siiow 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, H5 to !t8 per
cent of the spring infections could be prevented ])y a single spraying,
and this was actually accomplished where the spraying was done with
sufficient thoroughness. It is believed by the writer, however, that
these percentages wnll vary within moderate limits iji diti'erent locali-
ties, with different varieties, and in different seasons. The following
observations will explain these views.

The mycelium of diseased leaves is found to l)e comKH-tcKl through
the leaf petiole with the nwcelium of the infected limb. From the
writings of Sadebeck and many others it might ])e supposed that the
leaves were infected from the perennial mycelium in a majority of
cases, and that the mycelium met with in the petiole of the leaf origi-
nated from the perennial mycelium of the ])ranch. That such spring
infection really 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 e^^e. A macroscopic examination of diseased and
swollen branches will show that the enlarged parts may extend upward
or downward along the branch from the ])ase 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 })ranch
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
remem))ered, however, that this mycelium, 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 B.'nton's observations, to
be hereinafter considered, but the writer is scarcely prepared to admit
the large percentage of spring infections arising from new myc(>lium
entering the branch which the observations of that writer schmu to
imply. ^ The microscope shows that the hyph.v whicli ])ass away from

'Pacilic- Knral Press, Aug. 2, 1890, p. 88.

42 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

the ba.se of tlie leaf petiole gradually deer(>ase in ininibers as they
recede from the leaves, and the}' appear to l)e wholly lost at a short
distance from the point of entrance into the shoot. As a rule, little or
no niyccliuinhas been found extendino- more than 1 or 2 inches })e3'ond
a point where external macroscopic evidence of disease exists.

The preceding facts lead to the belief that where mycelial infection
of foliage takes plac(^ from the branch it is usually done in the spring
from hypha^ 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 nn'celium
which succeeds in accomplishing spring infection, is comparatively
rare. Badly infested and swollen branches are apt to die and dry out,
tluis 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 l)ranches very rarely exceed 2 to 3 per cent of the total num-
ber of ))uds upon the tree. Most branches appear to suffer from the
disease only in an indirect manner, that is, by the fall of attected
foliage. It seems probable to the writer, therefore, that the swollen
})ranches, in which the swelling is apparent to the eye, constitute the
trne and almost exclusive home of the perennial mycelium, and there-
fore supply the only possible source of spring infection by the win-
tering hyphai, and consequently the only source of infection not
(•ontrollal)le by sprays. This is in harmony with the results of wide-
spread orchard treatment. All ))ut 2 to 3 per cent of infections have
been prevented by a single spraying. (See the results of work on
half-s])rayed trees.) That such spraying did not prevent the si)read
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 hav(>
become infested, the treatment is inefl'ective and the disease will con-
tiruie to develop and both foliage and crop may be lost. It is not the
checking of the spread of the my('(>liuin fioni tiie bi-ancli to the new
leaves, therefoi-e, that results from spraying, but the i)r(>v(Mition of the
early spore infections from without; and as all but 2 to 3 ])er cent of
the year's infections may he thus prevented, all of such infection^
UHist be considei'ed as arising from s])oj'es.

Tln" limitation of tlie peremiial myceliiun of Krod.^cu.^ <h'f<>nriaiis to
the swollen l)raM(hes or branch parts, as here held, is in harmony with
ohser\('<l facts respecting other species of Kxodxcciv. It is not under-
stood, foi- instance, that trees developing witches' brooms are infested
in all their Inanches, but that the branch-infesting mycelium is limited
in its clistribution to those centei-s which develop the al»normal uuilti-
plication of shoots, the swellings and other external manifestations
of (lis(!ase. (See I'ls. I,\'.and \' I. and descripl ions, in connection with

DESCEIPTION OF PT.ATE 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 internodes. It is in shoots of this char-
acter that the mycelium is found, and its extent is nearly coincident, so far as
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 o i)er cent of
the buds of a tree. Specimens were collected at Santa Ana in the sjjHng of 1S99 and
photographed natural size. (Compare with Pis. 1 and VI.)

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

Plate V.

Peach Twigs and Leaves Affected by Curl.

'I'Ik' (iistrihutivc iiiyct'liuiii of tlic fuuf,'us is louiid in .-uch swolk'ii branchc't

DESCRIPTION OF PLATE VI.

Sprayed and unsprayed 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 l)ranches show the typical and conunon effects of curl. Hypertrophy of
the branch is not shown, and it is probable 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 infected by the fungus in 1893, when the orchard suffered severely
from curl, and had the branches at thi' left not been sprayed before the leaf buds
oj)ened in the sjjring of 1895, they would have been in the same condition as those
at the riglit of the plate. (Compare with Pis. I, V^, and VII.)

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

Plate VI

Ml

CONCLUSIONS REGARDING SPRING INFECTIONS. 43

tlio present remarks on infested and noninfestcd 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
formed buds; (2) that most of the infected leaves fall off without
infecting- the branch which bears them; (3) that the mycelium of badly
C ^ased leaves sometimes infects the branch through the leaf petiole;
(4) that such mycelium 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 possibl}^ infect one
or two adjoining buds; (5) that badly infested branches usuallv die
during the year, while in comparatively few instances they may sup-
port a living mycelium capable of inducing spring infection of opening-
buds; (()) that most infected branches show by external hypertrophy
the presence of the parasite, which mav 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 nwcelium wintering in an
active state, although the results of spraying in many parts of the
country, continued for several years, have shown the variation in
these respects to be contined within comparatively narrow limits.

The direct infection of the peach leaf by means of the spores of
Exoasc'us deform an s 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 earl}' 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
EvoaacuH tosqulnetii^ in which species the germ tube creeps for a short
distance on the leaf surface, and then enters a stoma, nuich as in the
germination of the conidium of Phytophthora omnivora.

The major portion of the spring infection of foliage occurs while
the latter is 3'oung 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 ])e expected when external influences are such
that transpiration is rai)id and normal. The longer or siiorter course
of the disease in spring may be said to depen<l largely, therefore, upon
the greater or less susceptibility of the tissues of the host, mostly

44 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

resultiiio- from atmospheric influences. The injury which the fungus
may do after infection is also dependent, where development of the
funous has not progressed too far, upon a very nice bahmce of the
atmospheric conditions. Newly infected leaves may he g;reatly
distorted and fall at an early date, or they may be only slightly
injured l)y the fungus, according to the atmospheric conditions prevail-
ing and their influence toward softening or hardening the tissues and
moistening the intercellular spaces of the host. A few days favorable
to the drying and toughening of the parenchyma of the infested Leaf
may entirel}' check the spread of the fungus. The action of the
myceliiun of E. deformanH upon the tissues of the leaf and branch of
the peach has been widely remarked. The hypertrophies of peach
branches, due to this parasite, are as striking and characteristic as are
the witches' brooms caused on other hosts by various Exoascece. In
tiie case of the peach, however, there is rarely if ever any increase
noted in the number of shoots, as upon the cherr}', the hypertrophy
manifesting itself in enlargements and twistings of the infested
branch. There is often a great reduction in the length of the infested
portion of the shoot and a shortening of the internodes, so that the
approximated and enlarged leaves give a tufted orphaned appearance
to the shoot. An examination of transverse sections of such enlarged
shoots shows that the enlargement is due to a great increase in the
mmi})ei- of cells of the cortical parenchyma, and frequently an entire
separation of such cells into a network or series of chainlike cells.
The stiucture of the infested parenchyma is altered, the cells being
enlarged and much more angular than normally, while the thickness
of the tissue from the ])ast ti])ers to the epidermis is freciuently eight
or ten times as great as usual. The parenchyma cells lose the chloro-
])hyll and all matter which the eye can detect, IxH'oming (juite trans-
pai'cnt. The cell walls vary nuicli more in thickn(>ss tiian normally,
some of them l)eing heavier and others lighter than in healthy cells.
Tratisverse and longitudijial sections of swollen peach twigs show that
the pith cells are greatly injured along the course of the infesting
mycelium. The location of the mycelium may often l)e detected by
treating transvei'se sections with Bismark l)r()wn, tiie infested nu^dul-
lary tissue taking less stain than that not harboring the fungus. The
walls of the healthy cells of the medulla become reddish brown, while
(hose of the infested tissue assume scarcely more than a light yellow
or yellowish brown. The cells of the infested tissue are also much
more angular and irregular than those in which the mycelium does
not exist, while in some instances the cells c()lla]>se.

The action of /'/. (leforiiuni^ on the tissues of the peach leaf has been
(considered by ditterent writers, as rrillieux,' Knowles," and others.

'IVilli<Mix, Ivl., Mai. <1. riantcs y\frr., Vol. II, pp. :«M-4nO; also Bull, dc la S..c.
i'.ot. .Ic France, 1872, T. \IX, Coiiii). KcikI. d'Sri., :{, pp. 227-2;'.0.
M\nowl(H, Kttu L., r.ol. (ia/,., 1KK7, V<il. Xil, pp. 21()-21H, with plau.

ACTION OF THE FUNGUS ON THE LEAF TISSUES. 45

The badly infested leaves become greatly increased in thickness and
breadth and the weight is often much increased above the normal, the
tissues become stiffened in a coriaceous or cartilaginous manner, the
cell walls become greatly thickened, and the cells become more com-
pressed. The cells of the palisade tissue are increased in size and
number, and suffer an entire loss of chlorophyll, as in the case of the
cortical parenchyma of the branch. The walls of the epidermal cells
become considerably thickened and the multiplication of the paren-
chyma cells on either side of the midrib causes a pronounced gather-
ing and distortion of these tissues. As the midrib does not elongate
in proportion to the increased extent of the parenchyma, it acts as a
gathering string passing through the leaf from end to end, and the
parenchyma becomes folded upon itself. The increase in the number
of cells occurs more extensively among the palisade tissue of the upper
half of the leaf than among the cells of the spongy parenchyma of the
under leaf surface; hence the majority of l)adly diseased leaves are
convex above and concave ])elow. though this appearance is often lost
sight of, owing to the number and variety of folds w^hich the leaf blade
assumes.

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 ma}' 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 papei' on peach leaf curl, pre-
pared in 1872, describes the fungus £lwascus defo/'//tans and its action
on the tissues of its host.^ He states that the fruiting fungus should
1)6 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 bj^ the
cutting off and burning of diseased branches. In 1878 Winter"^ stated
that the only way to prevent this disinise is to destroy the fungus by
carefully removing the affected leaves, and by protecting the trees from
rain during the unfolding of the leaves, as rain favors the spread of the
l)ai-asite. Tlie same year Felix von Thiimen wrote of E.roascvs pruni^
the fungus causing plum pockets and closely related to E.v(><(KCut< defor-
vimis of the peach,'* l)ut 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 affected trees.* In 1880-81 Frank, in the
second volume of the first edition of his work on plant diseases, rec-
ominends the cutting back of tlie twigs as a cure for leaf curl, and the
(|ui<k removal of the diseased leaves for prevention.'*

1 n 1886 the well-known work of Sorauer on plant diseases* appeared.
'i'hc treatment recommended l)y tiiis author is somewhat similar to
that recommended Ijy Frank. He says, in speaking in a geniM-al way

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

^Winter, Dr. (Jeorg, Krankheiten der Knitnrgcwiichse, Leipzig, 1878, p. 47.

"Thumeu, Felix von, Die Pilze und Pockcii iuif Wein und Ohst, Berlin, 1878, 111,
I'migi Poiiii(;oli, pp. 88, 8J).

'Tliiimen, Felix von, DielH'k:imi)fun^'dcr I'ilzkniiiklicifcii nnscn'rKiiltin-jrt-wiichse,
N'ienna, 188(), p. 71.

'•{•"riiiik, Dr. A. 1'.., Die K nitiklicilfii dcr I'llanzcii, I?rcsl:\n, ISSO-Sl, Tlicil II,

!'• ■'•-•■'•
'■■ Soraiii-i, Dr. I'aiil, I lan<ll)ucli <ler I'lluiizenkrunklieiten, second (.'ditiuii, riicil II,

p. 2SI.

40

HISTORY OF TREATMENT. 47

of the Exoascem^ that it has been proved that the mycelium winters
over in the youngest parts of the shoots and in the buds, and he
reconmiends 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 alread}' present in the axial organs, it is advised that all
of the }■ oung 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 off 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 })ranches, 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 Exoascece among
those maladies which should be combated by the removal of the
diseased living plants and plant parts (pp. 8(5, 87). The second edition
of Frank's work on plant diseases appeared in 1896, fifteen 3^ears
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 ITnitcd States and in Aus-
tralia. The recommendations for cutting awa}" 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 hardh' 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 impractica])le 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 1891, in his work on vege-
table parasites, Berlese recommends for this disease in Italy the use

'Hartig, Dr. Robert, Lehrhuch der Baumkrankheiton, Berlin, 18S9, pp. 118,119.

2 Idem, The Diseases of Trees, London, 1894, pp. 132, 133.

* Kirchner, Dr. Oscar, Die Krankheiten nnd Beschiidigungen iinKercr landwirt-
schaftlichen Kulturpfianzen, Stuttgart, 1890, p. 324.

■'Comes, Dr. O., Crittogamia Agraria, Naples, 1891, Vol. T, j)p. 1()7, 168.

^Tiibenf, Dr. Karl Freiherr von, Pflanzenkrankheitcn dnrrh kryptoganie Para-
siten verursacht, Berlin, 189.5, pp. 86, 87, and 184.

•'Frank, Dr. A. B., Die Krankheiten der IMlanzen, second c<lition, Breslau,
1896, Bd. II, pp. 249, 250.

■'Ehrenfels, J. M. Ritter von, Ueber die Krankheiten und Verletzungen der
Frucht- oder Gartenbtiume, 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 mycelium of the parasite winters over under the
cortex of the liranches/

In France, in 1895, Prillieux published the first volume of a work
on plant diseases, devoting seA^eral pages to the consideration of peacn
leaf curl.' In this work the recommendations for treatment appear-
ing in his paper in 1872 are not given, but instead it is statecC 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 are 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 grasped 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 celeste 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 above authors in their erroneous description of the fruiting habits
of the parasite.

DEVELOPMENT OF THE TKESENT 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 Avas first practiced in California, being intro-
duc(Hl ])y the winter application of sprays for the destruction of the
San Jose scale {^Aapldlotus perniciosus). 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-

' IVtIcsc, a. X., I Para-SHiti Vogotali ilcllc Tiantc^ Coltivati^ o TTtili, prefaci' datul
ls<)4, i>i). 124-126.

■' rrillicux, EfL, Mai. d. Planten Agr., I'arin, ]8«)5-<»7, i-p. :{!l4-4()().

' Weisz, .1. E., Die HfliiidiichHton Kraiikheik'ii hiihitit Fold-, Obft-, Cicuuiw- mid
Garten-Gewachse, Miinchen, 1898, p. 45.

HISTORY OF TREATMENT. ' 49

phur were combined ^yy boiling-, and still later a caustic spray contain-
ing lime was tested. All the above chemicals, 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 spra}' containing much larger quantities of sulphur Avas being
used, and proved of much greater power, both as a fungicide and insecti-
cide. This was a spra}' 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 history 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 spra}' 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 spra}' 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.
Thomas, of Visalia, agree in placing its first use as a spray in the year
1880 or 1881. The writer is informed 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 b}^ a Dr. Rowe, and offi-
cialh" 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 Jose 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 spra}^
on Mr. Covell's 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, 1881, 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-
eases of plants. (See Revue Horticole, 1852, p. 168, and Gardeners'
Chronicle, 1852, p. 419.)

1 Pacific Rural Press, July 29, 1899, p. 68.

^Letters from I. H. Thomas, Visalia, Cal., Sept. 6, 1899; \. W. :\IotlK'ral, Han-
ford, Cal., Sept. 0, 1899; and A. T. Covell, Woodbridge, Cal., Oct. 13, 1899.
19093— No. 20 4

50 PEACH LEAF CURL! 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 nuich 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 hy curl. In a
report by Mr. W. G..Klee, who inspected the orchards iii many counties
of California from Juh' to September, 1886, it is stated that in Alamedii
County the cultivation of peaches must be confined to such varieties as
are very little subject to leaf curl; in Santa Cruz County, that "peaches,
of course, are subject to curl}' leaf, and can not, as a general thing, be
considered profitable;" and that in the Santa Rosa Valle}^ the peach is
"of course subject to curU" leaf."^

As peach leaf curl was quite prevalent throughout California in
1880-85, and as a large number of peach growers treated their dor-
mant trees with fungicidal sprat's 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 3'ear
1885 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 ni}' attention. Trees
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 trees
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 ])est 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, 188(), Kept. CJal. .State Bd. H(jrt., 1885-86, pp. 344, 347, 34!t, 350.

'■'Letter dated Vinalia, Cal., Sept. 6, 1899.

"L. c, p. 347.

M>etters dated Santa Clara, Cal., Sei)t. 1 and 10, 1899.

'^ It may be noted that whale oil soaj) was thus u.sed by Mr. Block with success
against curl in 1885 and 1880. Prof. L. K. Taft, in a letter dated A^'ricultural College,
Mi(;h., Aug.'31, 1899, says that he had gocxl re.'^ults in the treatment of curl witli
linu'water, lye, and whale oil soaj). (See al.«o records of «'Xi)crimctits by the writer
with milk of lime, etc.) Mr. F. M. Webster rei)orts uatisfactory 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 3'ear, 188G,
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 l)light had previously caused all
the leaves to fall from ever}^ 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 spra}^
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,
as 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, I have l)een unable to get further details of
this early work with copper sulphate, as Mr. Runyon is no longer
living.^

In Noveml)er, 1888, Mr. W. (1. Klee stated at the Chico meeting of
the California State Board of Horticulture, that an experienced and suc-
cessful fruit grower in San Jose 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 since 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 doruiant, 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 Avriting of his past
spray work, he states that his trees had not ))een 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 1 used it, but I
continue to apply it to my trees once a yeaj' to prevent leaf curl." He
further states that this wash nuist be applied when the buds are dor-
mant, and that it is generally applied in February in his section.

oil soap (South Australian Journal of Agriculture, March, 1899, Vol. II, No. 8, p. 630) ;
see also the results reported by Henry Rofkar and W. Y. Latham & Son, of Catawha
Island, 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.

-Ihid., 1887-88, p. 9?,.

^Rept. Cal. State Bd. Hort., 1889, j). 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 ]\Iedford, Oreg., who Avas 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 destro3'ing the San Jose or pernicious scale, and gener-
ally on onh" 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 1890.
The summer use of these sprays had been tested in Australia, and
probal)lv 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 w(;re answered at length, the literature on Exoascius deformans
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 recounnendations for treatment were nec-
essarily inadequate, and were based upon the then accepted views
respecting the strict ])erennial nature of the mycelium of the fungus,
and the consecjuent difficulty of controlling the parasite hy 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 int(>rest. vV sununai-y of his results was
published in August, 18iH).' Three copper sprays were tested, the
amnion iacal (•()[)per carbonate, l)asic copper acetate solution, and Bor-
deaux mixture. The ammoniacal copper (■arb()nat(^ was applied on
Febi'uaiy 28, 1890, before tiie opening of the huds. All three of the
sprays mentioned were also tested soon aftei' the leaves started. The
results demonstrated that winter treatment of the trees with tlie saUs
of copper will cflectively conti'ol the diseas(>, ])ut that sunnner treat-
ment will not control it, and also that infection of the spring growtli
by perennial mycelium was the exception and not the rule with this
disease facts of the utmost practical imi)ortance for the orchardist.
Mr. Benton's studies likewise led him to the view that the mycelium,
pa.ssing from infected leaves to the stem, is able to infect new foliage

•racilic Rural IVcsh, Auu;. 2, 1890.

HISTORY OF TREATMENT. 53

by following' close ])ohind tlio growing- point of the stem. His observa-
tions seemed to point to this young mycelium, resulting from the tirst
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 onl}^ 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 3^ears' 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
correct. 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
in 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 November 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 conmiit-
tee for their experiments." Mr. Smith, of this coumiittee, informed

54 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

the wi-iti'i- that their work was ])ased largvly upon that of Vrui. K. S.
Cxoti' on Fusichidiuni.'

The spray work Avas begun in »Iuly, 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. Trescowtiiick.
and were treated with Bordeaux mixture. In the block was one
peach tree, which was spraj^ed when the apricots were treated. This
tree had suffered severel^^ from curl, so much so, in fact, that it had
not borne for four or live years, ])ut after spraying it yielded eight
cases of fruit of 50 pounds each, or 400 pounds, the curl being almost
entirely prevented. Mr. Smith writes, respecting this Avork, that
when applying Bordeaux mixture from Juh' 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 memliers of the committee w^ere 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 whs continued the following season, and some contrasts
obtained on the place of Messrs. Sidney Smith & Son, of Yaluml)a, 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 ver}^ 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^he other side, where spra\'-
ing had not been done, was a Idock 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, w^as inspected l)y 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
tiie ai)ricot and peach trees having been sprayed. One peach tree had
been si)i'ayed on ordy one side with the Bordeaux mixture, and on this
side the foliage was clean and healthy, while on the unsprayed side it
was curled. "Ilei-e again," says th(> rejjorter of this examination,
"■was absolutely <'onclusive evidence of the preventive effect of spray-
ing for curl leaf."

In the United States, in 1892, tiie use of both the sulphur andcopixM-
sprays on dormant trees was nuich mon^ common. The control ol
curl was a new discovery to several growers who had not heard oi
the ])ublish(!d ("xperimcMits. Mi'. George Woolsey, of lone, ('al., had
been considerably troubled by ashot-hole fungusall'ecting jjcach twigs
a conunon li'ouble in the northern })<)rtion of the State. A bundle of
the uffecttnl twii'-s was sent to Professor W'oodwortli. of Berkeley, who

'l,ctl.T ihitcd AnK!i.«ton, Snutli Aiislruliii, Fch. II, 1S})5.
-'Ix'ttcr .lalc<l Aii^'iistoii, Soiitli AuhI rnliii, Apr. (>, ISitf).

HISTORY OF TREATMENT. 55

advised the use of Bordeaux mixture; but as this fungus is active in
the spring before the trees leaf out, Mr. Woolse}' 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. Sjdvester, 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 experiment he selected a row of
10 trees, spraying 5 and leaving 5 unsprayed for comparison. He
states that the 5 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. Sj'lvester 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 spraj^ed and unspra3^ed trees was well marked, the
unsprayed trees being much affected hj 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 1885. By
1892 the San Jose 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 remed}^ was used to destro}' the San Jose 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 hespra^'ed his peach

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

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

56 PEACH LEAF CFKL! ITS NATURE AND TREATMENT.

trees in 1892.' He says he used a spra}^ 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 East, 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 absoluteh' negative
results, except the arsenites, which injured ))oth 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 ver}' little of late j^ears. 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 ))y 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 on(^ application, othei's were sprayed two, three, and four times.
It was noticed, the trees spra} ed in April with either copper sulphate
or Bordeaux mixture had no curled leaves, while unspra3'ed trees iind
those that were not sprayed until June or July were seriously injured
by leaf curl.

''From the marked dilierence in the injury from the leaf curl to
the sprayed and unsprayed trees, I felt very confident that the disease
could ])(' held in check to a large extent by the use of fungicides, and
in writing Bulletin 92, in December, 1892 (published in March, 1S1>;5),
I make the statement that ' it is ([uite certain that the disease can be,
to some ext(>nt, hiild in check b}' their use,' in referring to the effect

' lA-tU-TH dated Medford, Oreg., Dec. 14, 1894.

M>-tt«T dated Ridjicly, Md., Feb. IT), 1895.

•'I/-lt«T<liit<'d Iloffinan, Ta., Mar. 18, IWt.'i.

Matter dated Agricidtiiral College, Mich., .\iig. :;i, ISiH).

HISTORY OF TREATMENT. 57

of fungicides in preventing- the development of leaf curl on peach
trees. "

It would seem that the work in Australia, as well as that of the pre-
ceding ten years in California, had not come under the notice of Pro-
fessor Taf t at the time of his observations in 1892, and that the same
was true at the close of the succeeding j^ear's experiments. In his
article on curl, published in the American Agriculturist for February,
1894, he saj^s,^ 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 ])v the previous
winter's spra3^s. The orchard was that of Mr. W. H. Campbell, of
Yuba City, and was at once examined b}^ 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 Jose
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 spra3'ed
for San Jose 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 Jose 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 ])lockof Crawfords 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. riu\so inarkt>d 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 spraved as high as 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 unspraved trees, as well as those spraj'ed
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 T)lock were loaded with fruit and in full leaf,
while the trees sprayed only to the forks of the limbs were nearl}' 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 fui'ther 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 lielief.*

Mr. AVilliam N. Runyon, of Courtland, Cal., treated a large acreage of
peach trees with lime, sulphur, and salt in the winter of 1892-93. He
states that the trees sprayed once while dormant were practically free
from cuil, while trees of the same variety not sprayed were badly
aiS'ected.^ He also gives an observation of interest in connection
with the habits of the fungus, and one since indorsed ])y the writer,
that is, that the disease "will not spread from an unsprayed to a sprayed
tree." In letters from Mr. Runyon'' relative to this work, he
remarks that although he had heaid that a mixture of lime, sulphur,
and salt was beneficial in controlling curl, \u\ had no idea that the result
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 50 three year
old nectarine trees stood in rows adjoining about a dozen full-grown
trees of the same variet}'^ that had shown curl for years. The young
trees, not having shown any scale, were left unsprayed, and weiv a
niass of curl, while the old trees, which were given the regular treat-
ment, wen^ almost entiivly fi'ee. In this orchard about <)0 acres of
peach trees were also sprayed, the work being done about the 1st of

'For further n<>t<'s and tsihnlatcd ri'conlH of soiiio of this work of (lie Hj)riii<r of
W.y.i tli(! reader is referred t(t Cliajjter VII under Notes on the Auxiliary Kxperi-
iiieut.H ill (California.

'■' AiiHwer to eiri-ular letter of Nov. 25, 1H93.

' Ix'ttern dated ( 'oiirtlaiid, Cal., Jan. .".I, and >hir. K, l.S<)4.

HISTORY OF TREATMENT. 59

Fehriiarv, and 4-0 acres of young trees left unspruyed. In the Santa
Clara Valley the sulphur spraA's were in general use by the leading
gi'owers in 1893. Mr. A. B. Elder, of Santa Clara, writes, in reply
to a circular letter of November 25 of that year, that this spray is
giving good satisfaction for the control of curl and "is used by large
growers of peaches.'' Mr. John Rock, of Niles, Alameda 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 Carmel
Valley, near Old Monterey, with the express pui'pose 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, Amador County, Cal., spra^^ed
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 spra3'ed 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 spra\' was a combination of the sulphur spra}^
with copper sulphate, although the former Avas 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 sprays made by the writer, pp. 84, 86, 117, 118.

60 PEACH LEAF CURL I ITS NATURE AND TREATMENT.

hv throe applications of amnioniat'al ooppor carbonate after the appear-
ance of the foliage. He had better success, however, from aninioniacal
copper carbonate applied in late winter, before the swelling of the
buds, followed ])y three applications of a weaker solution upon the
foliage. ••This.'' he says, "was a complete success.""

In Michig-an the work in 1893 was verj^ satisfactory. Mr. Charles
Youngreen, of Whitehall, sprayed one row of peach trees before they
leafed out in the spring. He states^ that not one of the sprayed trees
showed curl, while the unsprayed trees were all affected. The follow-
ing year he sprayed the entire orchard and not a tree suffered from
the disease. At Shelby. Oceana County, several growers sprayed
with Bordeaux mixture with good success. Mr. R. Morrill, of Benton
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 lirst 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.

Prof essor Taf t 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 experimiMits, and in the fall of 1892 had a
immbcr of peach trees sprayed with a solution of copper sulphate
(1 pound in 25 gallons), and in a similar experiment 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 ])een 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
ticated 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 Bull(;tins 103 and 104 of the Stjition. On June 14, 1893, I gave the
results, up to that time, at th(^ meeting of the State Ilorticultui'al
Society."

The orchai-ds of the Michigan Agricultural Experiment Station at
South IIa\'cn, in charge of Mr. T, T. Lyon, had suffered se\'erely from
curl in ls9<). ISDI. and 1892.' Mr. Lyon sa^'s, respecting the spray

' l^'ttcr diil«'.l Wliitcliiill, Mich., Sept. 6, 1899.

■' Ii<'iit. .Midi. Stut(! llort. Hov.., W.V.i, p. OH.

M>-tt<T elated A);ri(;nitural Colici^iS Midi., Aug. :U), ISiH).

♦Hee Repta. Mich. Hurt. Soc, 1890, p. 144; 1891, p. 228; 1892, pp. KJO, Kil.

HISTOKY OF TREATMENT. 61

work done in the winter of 1892-93,^ that as the apparent result of
the fall and .spring- spra3dngs, 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 particular 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
progress, 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 different parts of the United States."
The circular reached many of the leading peach growers of Michi-
gan. During the winter, that of 1893-91:, plans for the testing of
winter sprays for the control of curl were undertaken by growers, at
ihe request of this Department, at Whitehall, Albion, Ganges, Beulah,
Riverside, Benton Harbor, St. Joseph, Kalamazoo, Covert, Hawk-
head, South Haven, Ludington, Shelby, Douglas, Millgrove, Custer,
Amber, Mears, Hart, Gobleville, Ortonville, Monterey, Fenville,
Saugatuck, Allegan, Way land, 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. Each 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 number 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., Dee. 16, 1897.

=• Paper read at Shelby, June 14, 189.3, Kept. Mieh. llort. Soe., 189:5, pp. 66, 67, and
79; article in Allegan Gazette, July 1, 1893; Mich. Kxp. Sta. Bull. No. 104, j). 64; pub.
Feb., 1894; American Agriculturist, Feb., 1894, pj). 71, 72.

* Ludington (Mich.) Appeal, issue of July 20, 1893, quoted by ShcUjy Sentinel, etc.

62 PEACH LEAB' CURL: ITS NATURE AND TREATMENT.

wero .sent to a number of orchardists in the peach-growing centers
of Ohio in the winter of 1893-94. During this and the succeeding
wintei" over tifty orchardists, located in twenty-live 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 of
unsprayed or control trees being left for comparison with the trees to
t)e treated with each spray to be tested. The object in thus planning
the work Avas the same as for that in Michigan and elsewhere — that is,
to obtain such striking contrasts between sprayed and unspraj^ed trees
that they would form long-remembered Object lessons for all who
should chance to see them.

The spray work of the Ohio Agricultural Experiment Station after
1800 was quite extensive; but the treatment of peach leaf curl is not
mentioned in the bulletins on orchard spraying pul)lished by tliat
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. .1.
Green spra\'ed 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 tlie season of 1884," during which and in 1895
•'thei'c was some effect noticeable." He says further, in this connec-
tion: ''I am aware that other work in this direction had been done
before 1 commenced, because I received my suggestions from some
other source, but I can not now recall the particular case." (Letter
dated September 30, 1899.)

L'l^on these results obtained liy Professor Green, and supported l)y
the work of Benton in California and Taft in Michigan, were based
the subse(|U(Mit experiments of Prof. A. D. Selhy in the orchard of
William Miller, of Gypsum, Ohio. '^ These experiments were begun,
accoiding to Professor Selby, in April, 1895,'' but no results with
Icjif curl wei'e ol)tained until 189(5.' as in 1895 theiv was no difference
between sj)i-aye(l and unsprayed trees in the amount of curl developing,
it being so insignificant as to be without evident effect. The curl
which <le\-el()])ed in l<S!>«t enabled Mr. Selby to obtain some contrasts
l)et\veeii sprayed and uns])raye<l trees, but these contrasts were not as

Mircci), W. .t., The Si)rayii)K <>f Orchards, Ohio A<rr. Kxj). Stii. I5nh No. n, Dec,
l«91, Vol. IV, Hccoiid series; Bui. No. 48, Vah., 189:{, p. 12; and a letter from Tro-
1('s«or (ireei), dated Wooster, Ohio, Sej)t. ;W, 1899.

■'letter from Prof. A. D. Selhy, dated Wooster, Ohio, Sept. i:'., lS<t!».

^I>. c; also Ohio Agr. Kxp. Kta. Bill. No. 92, March, 1898, pp. 2:57-24r).

'()hio Aur. Exj). Sta. Bill. No. 92, March, 1898 j). 245; also Thirtieth Aim. Kept.
Ohio Slate llorl. Soc., pp. 87.

HISTOKY OF TREATMENT. 63

marked as the^^ would have been had the disease developed seriously.^
As it was light in 1895 and 1896, no gain in fruit was shown b}'
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 Avas 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 l)eing
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 orchardists
in over twenty of the peach-growing centers, and b}^ means of care-
fully prepared circulars. Among others, Mr. W. T. Mann, of Barkers,
undertook spra}' 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 thew^ork of Mr. Henry Lutts, of Youngstown,
for the spring of 1894; and Mr. A. D. Tripp, of North Ridgeway,
reports excellent results from his work.

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

''Ohio Agr. Exp. Sta. Bull. No. 104, March, 1899, p. 210; also Kept. Oliio State
Hort. Soc, 1898, p. 13.

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

64 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

A ])ulletin of the Cornell Agricultural Experiment Station, by
Georo-e F. Atkinson.^ which appeared in September, 18W, treats of leaf
curl and plum pockets. Respecting the treatment of leaf curl, ]Mr.
Atkinson says that some experiments had been made in various places
bv 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 cheeked 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 an}'
tield work of the station , and may have arisen from Mr. Atkinson's under-
standing of the perennial habits of the fungus causing the disease.
Th(>re seems to have })ecn no winter spraying for curl by the Cornell
Station before the spring of 1898, and the results then obtained aVe 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 In' B. M. Duggar and H. P. Gould. The
results of this work are given in a ])ulletin by Mr. Duggar, published
in February, 1899.'

The ctiorts to control peach leaf curl by winter sprays in Canada,
so far as concerns the work of the Canadian Government, appear l(
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 110 — only 5 escaped leaf curl, and the attack
was severe.'' In the r(>port for 1893 it is said that leaf curl was worse
that year than ever before. Of alxiut 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 ])e stated h(n'e, however, that the work done was too late to
hav(^ given good results had curl developed, and that it did not properly
constitute a prevcuitive s])raying. Whether this late spraying was
owing to the nature of the season, or wlietlier it was supposed tlisit
siicli f icatincnt would control the disease, is not known to the writer.

' Atkinw^n, Geo. F., I^af Curl and Plum Pocketa, Cornell Agr. Exp. Sta. Bull.
No. 7:5, Sci)t., 1H94, pp. :i24-32(;.

M)uwiir, n. M., Virdrh Ia-hI Curl, etc., ("onicll .V^r. Kxp. .-l.^. Bull. No. 1(>4, Keh.,
1S!)'.», pp. :{77-:W4.

"Kept. Kxji. KartiiH, ]H<I2, p. 27K.

M{cpt. Kx|). FarniH, iHiC!, pp. :{42, :U:i.

Mic'i)!. K\\>. FaniiH, lHii4, p. 404.

HISTORY 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
had very little curl, and made a very strong and 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 greatlj- 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 unfavoral)le
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 Avork on peaches in
1894 was planned to prevent the rotting of fruit 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 3'ear no con-
clusive results were obtained. Later work, I am informed by Mr.
Craig, has given more conclusive and satisfactory results.* The vari-
able results reported in Bulletin No. 1, second series, leads the writer
to wonder, however, if the early spray work Avas done with sufficient
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 spraj's for
the control of curl on the Pacific coast began in the spring of 1893.
In the fall of that A'ear 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.
''Kept. 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. 35-37; Central Exp.
Farm, Dept. of Agr., Ottawa, Canada, Sept., 1898.
6 Letter dated Ottawa, Oct. 7, 1897.
'Canadian Horticulturist, Jan., 1899, i)p. 18-20.
19093— No. 20 5

66 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

1803-94. 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 spra3nng 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 given
in Chapter VII, and the facts gathered and experiments conducted under
the direct charge of the writer in 1893, 1894, and 1895 are detailed in
full in other portions of this bulletin, and require no discussion here.

CHAPTKR IV.

PLAN OF PREVENTIVE SPRAY WORK CONDUCTED BY THE

DEPARTMENT.

PRELIMINARY PLANS 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 Jose scale {Aspldlotiis per-
niciosus)^ 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 1893. The facts thus obtained were
of much value, but the general lack of accurate knowledge respecting
})oth 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 experiments. The first, which had been planned before the sending
out of the circular, was to bo 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 alread^'^ 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 Valle}', 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

G7

68 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

thousand dollars, having been largely lost in 1893. After a l)rief
correspondence Mr. Ditzler kindly offered 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 tiner 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 nearh' 600 trees at the southwest corner of a -It »-acre block
of Lo veils, 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 live years, were 25 feet apart each way, and had
grown so vigorously that l^efore pruning the branches met l^etween
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 8i acres in extent. At the south of these Lovells is
an ahuond 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 U> trees wide from east to west,
and 29 trees long from north to south. Each cross row of 10 trees was
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 driveway being row 29. On the west of the driveway the
south row was 30, the second row 31, etc., the north roAV beting 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 })e fixed more clearly in the mind b}' the diagram on page »)!>.

This diagram, in addition to showing the arrangement of the rows,
as already described, is plaimed to i-c))resent and distinguish the
i-ows which were to be treated with sprays from those wliicli were to
be hift untreated as check or control trees in each experiment. 'I'lie
trees of the rows to be ti-eated are rei)r(>sented l)y a star (*) and the
treses to be, left uiisprayed are shown by a (Circle (^), with the exceptions
to be noted. It may thus be s(>en that each row of 10 trees iiitciided
lor trcatnicnt lias at its side 10 untreated trees as a cIhm-U or control
row. With the e.\ce])tion of rows 29 and 58 each control row serv(>s
for comparison with two s|)ra\('d rows, one on either sid(>. This
method (»f <ont rastiiig each conti-ol I'ow with a sjn'ayed row on either
side admitted of the plainiing of )>S experiments in the block of 5S
rows, each c\p(>riment comprising 20 trees K) s])i'mv«'(I and lo
unsprayed. in two immediately adjoining and parallel rows.

PLANS FOR SPRAY WORK,

C^{)

After locating and numbering each of th(>. 38 experiments to be
tested the block was carefully examined to determine if any of the
trees were missing 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 fact is shown by a cipher (0) in the place of the

North.

West. 3

56

*

*

*

*

5

*

*

*

*

*

*

*

*

*

*

*

*

*

* *

55

o

o

o

°

°

°

°

o

o

o

°

°

°

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°

°

°

o o

54

*

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*

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*

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* *

53

*

*

*

*

*

*

*

*

6

*

*

*

*

*

*

*

*

*

* *

52

o

o

o

°

o

o

o

o

°

o

o

o

o

o

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o

°

°

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51

*

*

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*

*

*

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*

*

*

*

*

*

* *

50

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

* *

49

"

°

°

°

°

o

o

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°

°

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°

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48

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47

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*

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* *

46

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45

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44

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*

*

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*

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*

*

*

*

*

*

*

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* *

43

o

o

o

o

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o

o

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°

o

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42

*

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*

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*

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*

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*

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*

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*

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*

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*

* *

41

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

4

* *

40

o

o

°

o

°

o

o

o

o

o

o

°

o

°

o

°

°

°

o o

39

*

*

*

*

*

0

0

*

*

*

*

*

*

*

*

*

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*

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38

*

*

*

*

*

*

*

*

*

*

*

*

*

4:

*

*

*

*

* *

37

o

°

o

°

o

°

o

o

o

o

o

°

o

°

o

°

o

°

o o

36

*

*

*

*

*

*

*

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*

*

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35

*

*

*

*

o

*

+

6

*

*

*

*

*

*

*

*

*

*

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34

o

o

°

°

°

°

o

o

o

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33

*

*

*

*

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8

*

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8

*

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32

*

*

*

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*

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31

°

°

o

°

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*

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10

9

8

7

6

5

4

3

■>

1

10

9

8

7

0

5

4

3

2 1

■ —

— Tree immbi-rs.

— '

- —

— Tree numbers

24§
23

* Sprayed in 1894 and 1895, except wliere noted.

"^ Unsprayed in 1894 and 1895.

§ Sprayed in 1894 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-tenths perfect, 5 that it was ilve-tenths

70

PEACH LEAF CURL: 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 b}' the trees of each row are first divided b}^ 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 51 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 W'ORK CONDUCTED IN 1894.

The spray tests conducted in the Rio Bonito orchard in 1894
included the application of sprays prepared according to 88 diflFerent
formula, making 38 distinct experiments. Each experiment included
two adjoining rows of 10 trees each, one sprayed and the other
unspra\Ted for comparison. Of these 38 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 th(; formula or fornmhe used in each case.

Table l.—ShuwinythefonmilKof the sprays applied in 1894, dates of opplicaiion, and

rows treated.

Row No.

Date of
spraying,

Feb. 20

Feb. 24
/Ki'b. l(i
\\'\-\>. 28

l'\'b. 23
Feb. 24

Feb. 23
/Feb. 20
\Mur. a

Feb. 24
Feb. 13

Feb. 13
/Feb. 2(J
\Mar. 6

Formulae for 45 gallons of spray.

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

Control row.
10 lbs. Mil|plHir. 'JD lbs. linu", 7 lb.<!. .salt.
10 lbs. sulphur, 2(1 ll)s. liiiu-, 7 lbs. salt.
.') U><f. sulphur, U) lbs. linic, 3 lbs, salt.

Cdiilrol row.
5 lbs. sulphur, 10 lbs. lime, 3 lbs. .salt.
l.-> lbs. sulphur. 30 lbs. lime.

Cunt rill row.
10 lbs. siilphur, 20 lbs. lime.
10 ll>s. sulohur, 20 lbs. lime.
f) lbs. .sulphur, 10 lbs. lime.

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

Control row.
20 lbs. lime.

45 lbs. .milt (hot).

46 lbs. salt (hot).

SPRAY WORK OF 1894.

71

Table 1. — Showing the formula; of the sprays applied in 1894, dates of application, and

rows treated — Continued.

Date of
spraying.

Formulse for 45 gallons of spray.

18

Feb. 26

19

Feb. 27

20

21.

/Feb. 16-
IFeb. 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

Feb. 2

33

/...do...
\Mar. 2

34

35

Mar. 3

36

Feb. 27

37

38

Feb. 26

39

/Feb. 1
iFeb. 28

40

41

Feb. 23

42

/Feb. 14
\Mar. 3

43

44

Feb. 24

45

Feb. 27

46

47

/Feb. 14

48

\Mar. 3
/Feb. 14

49

50

Feb. 14

51

52

Mar. 3

53

/Feb. 14

54

\Mar. 6
Feb. 27

55

56

Mar. 6

57

do

58

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 lbs. 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, 5 lbs. lime.

Control row.

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

Control row.

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

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

Control row.

5 oz. copper carbonate, 3 lbs. ammonia.
5 oz. copper carbonate, 3 lbs. ammonia.
5 oz. copper carbonate, 3 lbs. ammonia.

Control row.

5 lbs. copper sulphate, 10 lbs. lime.

6 pints spray .solution.
6 pints spray .solution.

Control row.
6 lb.s. copper sulphate, 15 lbs. lime.
3 lbs. copper sulphate, 15 lbs. 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.
5 lbs. sulphur, 5 lbs. lime.

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

Control row.
8 pints .spray solution, 2 lbs. copper sulphate, 10 lbs. lime.
5 lbs. sulphur, 15 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
spring advanced, however, it became evident that the disease would
not appear to any serious extent in that portion of the State that sea-
son, 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 181M 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 1895 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 1895 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 spra}^ 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 observing 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 row,
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 0 make two experiments. These illustrations will be sufficient,
as the entire block, with the exception of the three rows jil ready
noted, was treated according to the same general plan.

In considering the application of sprays in the experiments of ISIh"),
the nature of the sprays used, the fonnuhe according to which tlu>y
were prepared, the location of the rows treated, and the dates of a])i)li-
cati(Mi, as well us the location of the control rows for comparison, are
set foi-th in the table- which follows. That the I'eader may better grasp
the nature of all treatments which each row had received the previous
year, the formula' foi- the s])rays applied in 1S94 ai-e jjlaced at the left
of the treatment ifix en the same rows in 1895.

SPRAY WORK OF 1895.

73

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74

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

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GENERAL CONSIDERATION 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, ])ut, 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 spraj^s Avere 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 Jose scale, and that a spray com-
bining both fungicidal and insecticidal properties would often prove
of greater value than one the action of Avhich 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
Jose scale, this spray, together with various modifications, was tested
and compared (rows 1, 8, and 0). 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 T, 9, 10,
12, 16, 51, and 57). The lime and salt were tested together (row 13),
and the lime was tested separately (row 14). The trial of a strong
salt solution was made the previous 3'ear (row 16), but as it injured
the foliage somewhat it was omitted in 1895. Other modifications
of the sulphur spray were prepared l)}^ 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 alread}' 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 30), as was the modified eau celeste, composed of
copper sulphate, sal soda, and ammonia (rows 35 and 39), 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 potas.sium combined with milk of lime (rows 42 and 48).

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 unspra3'ed 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 spra}^-
ings in 1894 with a hot saponified solution of sulphide of potassium.

Bull. 20, Div. Veg. Pnys. & Patn.. U. S. Dept. of Agriculture.

Plate VII.

O £

I- £

$ -

DESCRIPTION OF PLATE VII.

Sprayed and im.^prayed Crawfords Late trees in the orchard of Mr. A. D. Cutis,
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 curi. (See records of fruit of sprayed 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 FKOM INJURY BY CURL.

(PI. VII.)

The etfectivenoss of the winter tsprays discussed in the previous chap-
ter in saving- the foliage of peach trees from injury by peach leaf curl
has})een carefully considered. The relative importance of this matter
appears from the fact that it is the injury from the loss of foliage which
is responsible for the ultimate loss of the fruit. The spray work
alread}" mentioned was completed, in iSlto, about the close of the first
week in March. From this time on the flowers opened rapidh^, 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 spra^^ed 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. BadW diseased leaves were considered as those
seeming to have sufiicient 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 spra3's, 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, so far as

could be told, with ee[ual force to all rows.

77

<8 PEACH LEAF CURL: ITS NATURE AXD TREATMENT.

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. — Eslimaled percentage of diseased leaves on trees April ^3 and 23, 1895.

Row No.

Percentage of diseased leaves estimated
Apr. 22 and 23, 1895, on tree No.—

Average
per cent
of dis-
eased
leaves

per

tree in

sprayed

rows.

Average
per pent
of dis-
eased
leaves

per

tree in

control

rows.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

1

10
90
30
70
80
40
20
75
30
30
80
25
-10
80

5
16
80
25

8
80

7

8
82
80

8
80
17
20
85

8
85
25
10
90
20
25
75
50
27
78

9

r)0

85
13
14
85
70
30
90

:«

30
85
85
17
85
30
26
5)0

15

15

10
85
40
80
85
50
30
85
42
40
85
35
40
78
13
45
85
40
16
90
26
9
&5
85
18
90
21
30
90
15
85
35
10
90
20
10
75
35

10
&5
35
85
80
40
25
75
25
35
85
34
45
75
16
37
87
29
25
90
17
16
85
85
27
90
21
26
90
10
90
30
5
90
12
15
75
25

10
90
30
85
90
45
35
70
27
27
85
50
50
76
16
31
78
32
•2Z
90
10

9
80
85
15
85
15
24
87
15
85
30
10
85
10
10
75
19
15
80
18
65
85
35
11
90
70
38
80
42
30
85
85
20
80

9
20
87

15
90
30
80
85
35
30
70
25
23
85
45
35
77

9
20
65
40
35
90
11
10
85
80

9

a5

24
30
87
15
80
30
10
90
8
15
65
17
20
75
18
55
87
31
18
85
70
30
87
45
35
80
85
15
85
20
18
88

15
85
30
80
90
40
30
75
29
30
80
50
50
80
12
20
80
31
20
90
10
10
80
85
11
85
26
31
90
15
85
35
10
90
15
20
60
25
15
80
23
60
85
28
12
80
75
40

a5

43
22
85
85
15
85
18
16
90

20
&5
25
85
90
»5
35
80
47
27
80
45
60
80
11
30
82
35
23
90
10

15
85
20
80
85
30
30
80
45
36
80
47
35
80
13
25
90
60
36
90
9

13.5

2

90 90

87.5

3

35
80
80
60
25
85
34
32
90
47
45
80
11
35
90
30
15
90
11
10
85
80
12
80
20
21
90
5
80
35
10
90
15
15
75
45
35
85
14
45
80
27
12
85
70
40
87
40
26
80
80
10
75
22
31
89

35
80
85
40
25
80
46
40
90
15
55
78
8
30

a5

33
13
90
16
15
80
80
12
85
17
21
90
15
85
30
10
85
15
10
70
40
18
80
12
50
80
16
12
90
60
40
85
40
28
80
80
11
80
30
31
85

31.0
080.5

4

5 . .

as.o

6

41.5
28.5

8

77.5

9

35.0
32.0

10

11

84.0

12

39.3
45.5

1.3

14 . .

78.1

15

11.4
28.9

16

17 ....

82. 2

18

is. 5

21.4

19

20 .

8>t. 0

21

i2.7
10.7

22

12 , 8
90 85
S5 i 80

23

83.7

24

(i82. 5
13.7

25

15
90
23
15
88
20
80
35
10
90
12
12
65
24
15
85
13
55

a5

30
12

a5

75
28

as

35

:V)
a5

80
16
82
19
15
90

10

85
17
19
90
15

a5

30
5
a5
10
10
65
10
18
78
17
60
85
25
13

a5

75
42'

as

33
28
80

as

18
87
13
11
88

26

as. 5

27

20.1
2:^.7

28 .

29

88.7

30

13.3

31

81.0

32

3i.5
9.0

33

34

a8.5

35 ....

i.3.7
14.2

37

70.0

29.0
20.3

39

80
13

82
90

80.3

41 .

15.7
55.0

55 55

85 : 88

43

84.5

30
12
90
50
38
85
50
25
80
80
12
80
25
32
90

30
10
80
&5
37

a5

45
32
80

a5

12
85
22
21

85

26.5
12.6

45 .

as. 5

47 .

68.0
36.3

49

85. 1

40. 8
29.1

51

82. 1)

53

(laS.O
14.6

55

82.4

20.8
22. 1

57 . .

88.2

aKuw8 apraycd in 1894. but left uusiprayed in 1895.

SAVING OF FOLIAGE. 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 In^ the trees of the sprayed
rows, divided by the number of spraA^ed rows in the block, shows the
average amount of disease in the sprayed rows to have been 26.2 per
cent. Evidently this average is much above the percentage of disease
shown at that date hy 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 63 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-
ticall}'^ 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 generalh" 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 alread}^ fallen. To avoid this difiiculty 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 twent}^ t3'^pical trees studied,
to determine the per cent of perfect foliage upon it, taking* the amount
which should l)e upon the tree at that date, if no disease existed, as
100 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 l>lock. 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 foliage on the sprayed and unsprayed trees May
9, 1895, as compared with the amount a healthy tree should have at that date.

1

2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
2o
26
27
28,
29
30
31
32
3;}
34
35
36
37
38
39
40
II
42
43
44
45
46
47
4H,
19
;')0
51
52
53,
{>!

•'i*;,

57,

')8,

Percentage of healthy foliage eompared
with the amount the tree should have,
estimated May 9, 1895.

Tree No. —

1.

2.

3.

4.

5.

6.

92

93

93

92

94

95

9

10

12

9

15

10

90

85

80

82

m

85

15

8

15

10

15

20

10

12

12

10

18

15

85

65

87

80

85

60

95

a5

90

85

83

84

10

i;

13

9

12

10

88

75

87

80

90

80

90

SO

88

8;:

90

82

9

8

10

20

11

20

92

80

«8

85

80

80

87

87

75

85

65

86

«

10

15

10

20

i;5

95

89

95

90

90

88

92

65

80

80

80

v-

20

11

12

10

8

16

92

85

90

85

88

86

90

8,5

90

91

85

85

10

9

9

8

9

10

97

95

97

89

92

99

96

%

96

90

90

98

8

10

14

10

8

10

8

9

11

9

9

9

89

90

92

85

88

87

10

10

9

8

10

12

91

92

97

87

92

91

87

88

96

88

85

92

9

10

12

10

8

13

%

95

92

91

90

96

11

18

20

20

15

22

65

50

55

60

65

45

92

92

94

94

90

90

9

9

16

20

16

14

86

90

88

92

92

90

65

80

85

90

75

SO

10

13

10

12

15

15

65

45

68

70

70

75

73

82

93

(c)

(0

92

15

10

10

12

10

12

93

92

95

85

85

80

45

25

45

28

45

50

10

12

15

10

15

18

78

75

80

55

65

55

89-

89

80

90

90

95

11

16

13

15

25

20

40

40

40

45

28

45

70

75

55

70

65

50

9

10

20

18

20

15

70

65

50

60

40

50

80

70

75

70

70

65

9

10

10

10

18

12

20

15

18

8

15

15

85

87

90

70

82

85

9

14

10

9

15

15

85

80

70

75

65

<K)

70

83

6r>

60

75

87

H

10

11

10

12

12

7. 8. 9. 10.

Average
per cent

of
health}-
leave.s
per tree

in

sprayed

rows.

92.3

84.7
a 14. 8

76.8
85.4

83.1
86.4

81.0
79.6

90.0
82.0

84.7
83.2

95.9
94.6

a9.4
89.8

91.2
89.3

52.5
91.9

91.8
78.2

70.3
83.4

87.0
41.6

58.8
86.7

38.8
58.0

67.0
68.5

a 14. 8
82.2

75.8
74.8

Average
per cent

of

healthy

leaves

per tree

in control

rows.

Gain in
leaves of
sprayed
trees "over
average
of all con-
trol trees,
expressed

in
percent.

10.1
'u.5

'u'.i
'ii'.h'

iis'
"i6."7

"i2.'2

12.2

9.7

14.2
"u'.8

'i'i's
'ii.h'
'ib.h'
14.' i'
'13.0
ii's
'io.'-y

549

13

488
554

536
554

620
509

689
528

549
537

634
624
639

688

698
684

302
CM

603
499

438
639

666
219

350
656

197
344

336
424

13

629

480
473

a Trees sprayed in 189-1, but un.sprayed in 1896.
/) Gain of^ control row over row sprayed in 1S9I.

(Tree missing.

TliP, conipiirison of .some of tho jronoriil fact.s brouf'-lit out in thrcsti-
niatcs of foliajrc April 23 and 23 jind ]Ma\' 1), l«i>5, .shows the progress
of the di.sea.se durinj^ 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,
1895.

Average per cent of disease on the trees of all control rows

83.6
26.2

82.0

86.9

Average per cent of disease on the trees of all spra ved rows

21 2

Average per cent of disease on the trees of the three rows sprayed in 1S94, but
left unspraved in 1895 ! . .

87 0

These comparisons show 3.3 per cent more diseased foliage on the
control trees May 9 than April 22. The percentage of foliage of the
sprayed trees showing disease had decreased, however, 5 per cent. Of
the total foliage of the trees sprayed in 1894. but left unsprayed in
1895, 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 unspraj-ed trees was still increasing just prior to the
second estimate. The second estimate may thus be considered as taken
before anj^ of the trees had begun to recover from the effects of the
disease. The time of maximum contrast was the true time to make
the estimates, and it is believed the date of this second estimate was
certainlv not too late to fully comply with this requirement. This
belief was substantiated b}^ 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.

Before considering the action of individual sprays in saving the
foliage from curl, the following comparisons are given of the action
of the classes of spra3^s used:

T.VBLK 7. — Percentage of healthy foliage on trees differently sprayed.

Percentages of healthy foliage shown by trees sprayed with
different cla.sses of .spravs. Estimated April 23 and May
9, 1895.

Average of 30 trees sprayed with sulphur, lime, and salt

Average of 70 trees si)rayi>d with sulpluir and lime

Average of 100 trees sprayed with the two preceding sulphur
sprays

Average of 90 trees sprayed with Bordeaux mi.xture

Average of 20 trees sprayed with eau celeste

Average of 20 trees sprayed with modified eau celeste

Average of 130 trees sprayed with the three preceding copper
sprays

Average of 20 trees sprayed with ammoniacal copper car-
bonate

19093— No. 20 6

71.4
69.3

70.3
86.2
83.3
83.0

84.2

69.8

84.6
80.0

82.3
89.6
91.7
87.6

89. 6

13.2
10.7

12.0
3.4

8.4
4.6

5.4

CQ -. M >-;

8.4

82 PEACH LEAF CURL: ITS MATURE AND TREATMENT.

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

Percentages of healthy foliage shown by trees sprayed \rith
different classes of spravs. Estimated April 23 and May
9, 1895.

iC>,J1.1 '^■■'~

^ so^^.g

Average of

and lime

Average of

Average of

lime
Average of
Average of

lime
Average of
Average of

30 trees spraved with copper sulphate, sulphur,
(a) ".

10 trees sprayed with iron sulphate and lime

10 trees sprayed with iron sulphate, sulphur, and

f 10 trees sprayed with sulphide of potassium

f 20 trees sprayed -with sulphide of potassium and

10 trees sprayed with milk of lime

10 trees sprayed with milk of lime and salt.

76.3
59.2

79.2
32.0

M.3
73.5
54.5

82.0
57.0

75.8
38.8

49.8
58.8
79.5

2.2
3.4

6.8

4.5
14.7

a Compare text.

The table show.s the average of liealthy foliacife on the trees .sprayed
with the sulphur sprays (sulphur, lime, and salt, 3t_> trees: sulphur and
lime, To trees) to have been 82.3 per cent Mav 0. The average on the
trees sprayed with the leading copper sprays (Bordeau.x mi.xture. 90
trees; eau celeste, 20 trees; modified eau celeste. 20 trees) was 89.6
per cent. The average amount of healthy foliage saved on trees
spra,yed with a combination of these two holding classes of sprays
(Bordeaux mixture added to the sulphur and lime sprays. 3(> trees)
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 sulpluir
sprays. This result was a surprise, but by carefully h)oking into the
rea.son 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
averag(» of the sulphur sprays arose from including in the average the
results of tho.se sprays which contained much more sulphur than was
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 foi' this reason it Avould ])e as well to omit
this row in detennining the average saving of the combined spraj's.
The two i-emaining rows, 18 and 19, sprayed with combined spraj^s,
showed 84.7 and 83.2 per cent of healthy foliage, respectively — an
average of 83.9 per cent. The formula for each of these experiments
contjiined 5 pounds of sulphur. In the experiments with uncombined
sulphur sprays there were four formula; contjiining 5 pounds of sul-
phur each. The average per cent of saving of tiiese four experiments
was 75.3. These facts show that when the amount of sulphur was
equal there was an average gain of 8.6 per cent in healthy foliage
resulting fi-om the addition of Bordeaux mixture to the sulphur
sprays.

The average p(!rcentiige of foliage saved by the us(> of the ammo-
niacal coppci- carlionatc (2'> ti-ccs) was. May 9. r.l.k .\s tlic ammoiiiacal

SAVING OF FOLIAGE. 83

copper carbonate sprays 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 nuich less satisfactory action
than cither the copper or the sulphur sprays. The iron sulphate com-
bined with the sulphur and lime sprays showed a saving of foliage
Ma}' S< of 75.8 per cent. While this is a good showing, the beneficial
action was evidently due to the sulphur of the spra}' and not to the
iron, and the result was even below the average obtained by 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. S. 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 alread}^ 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. AVhile it is possible that the fungicidal action of
this spra}- may be somewhat higher than that of milk of lime alone,
it is perhaps more pvobable that the results 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
likeh' 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 woukl be well,
however, to repeat this test.

Some interesting fa(;ts are brought out hj the preceding ta])le 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 Ma}^ 9, it will
be seen that the percentage of healthy foliage on all trees sprayed
with the sulphur or copper spraj^s increased decidedly between th(>
two dates of estimate, as shown in the third column. On the other
hand, the action of the weaker sprays was overcome I)}' 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 CUKL: 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 by 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 arid salt in solution. It is thought, however, that the trui'
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 is
shown that the highest degree of effectiveness in saving foliage is
possessed by the cop[)er 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 etlectiveness of the latter is some-
what increased. It is also made clear that sulphide of potassium,
sulphate of iron, and several other sprays, as tested, are of secondary
\alue in this work. It should l)e noted that the average saving
o))tained from the use of the sulphur sprays is sufficiently high to well
warrant the use of these sprat's, either in combination with Bordeaux
mixture or alone, in cases where it is desired to use a spray ha\ing
both fungicidal and insecticidal (lualities.

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

Table 8. — Nature and cornpo.vlion of uprays applied.

Row

No.

(Masses and formula; of sprays applied.

Average per cent of
healthy foliage May
9, 1895.

Net gain per cent of
healthy foliage over
average per cent of
all control trees.

go

m

Ill

1

Sulphur, lime, hihI suit :

15 lbs. suli>luir, :;i) lt)s. lime, 10 lbs. salt

92.3

84.7
76.8

86.4
83.1
8.5.4
82.0
74.8
81.0
(iH. 5

78.2
84.7
83.2

iK). 0

607
649

488

564
636
,564
628
473
520
424

499
649
637

589

80

3

10 lbs. snli)hiir, 'JO ll)s. lime, 5 lbs. .salt

60

6

.') lbs snlpliur U) lbs. lime, 3 lbs. .salt

60

7

Sillpliiiriiiid lime:

60

g

10 lbs suli>linr 20 lbs lime

60

10
16

10 lbs siilplnir S lbs llnic

60

80

67

60

12

60

61

60

86

Bordciiiix iiii.xtiirc ami siilpbiir spnivs coinbiiicd :

70

18

nibs copper Kiilpliiitt' 5 lbs siiliilmr, 10 lbs lime

80

19

80

16

Bordiim.x inixtiirc:

(i lbs. coijper siilpbnic, ir> lbs. llnio

100

SAVING OF FOLIAGE.

85

Table 8. — Nature and composition of uprays applied — Continued.

Row
No.

Classes aiid l'(>runihi» of sprays applii'd.

O 0) o

>

a> o i* =0

9 X-::

3' lbs. copper sulphate, 15 lbs. lime

5 lbs. copper sulphate, 10 lbs. lime

3 lbs. copper sulphate, 10 lbs. lime

3 lbs. copper sulphate, 10 lbs. lime

5 lbs. copper sulphate, .5 lbs. lime

4 lbs. copper sulphate, h lbs. lime

3 lbs. copper sulphate, 5 lbs. lime

2 lbs. copper sulphate, 5 lbs. lime

Eau celeste :

4 lb.s. 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 snl)>hide 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 lb.s. salt

Lime :

20 lbs. lime

*91.9
87.0
85.7
82. 2
95.9
94.5
89.8
89.3

91.2
t92.2

91.8
83.4

70.3
52.5

57.0

75.8

38.8

58.0
41. G

79.5

58.8

*604
566
556
529
634
624
588
584

598
t606

603
539

438
302

336

480

197

344
219

509

350

80
100

90
SO
100
100
80
80

SO
tlOO

80
80

80
60

40

40

40

50
40

60

50

* Exceptional, see p. 87. t Outside row, next to driveway.

The above table is planned to give for each experiment the following
facts: (1) The number of the row to which *he spray was applied; (2)
the nature and amount of the ingredients used in each case; (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
(200 unsprayed trees), and which is expres.sed in per cent; (5) thrift
of uninfected leaves in color, texture, and size. The figures under
the foui-th head were obtained in the following manner: The average
percentage of healthy foliage of all the trees of each control row was
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 13.00.
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 sprayed row. This net gain was then divided by the 13.0()
per cent of the .-ontrol trees to obtain the net gain per cent of each
sprayed row. For example, take row 1 : 92.3 % — 13.06 % =79.21 %
gain; 79.21: %-^ 13. OG 7c shows tiie net gain to ht> '(;} '=007 70 of the

86 PEACH LEAF CURL*. ITS NATURE AND TREATMENT.

average amount of healthy foliage of the control trees. The fifth sub-
ject, thriftiness 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 spraj^s (rows 1, 3, and 0) 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 spraj^s. 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, 54:7 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 3(j). it is well to omit comparisons of row 30, 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 alreadj^
been noted. Rows 18 and 19, containing 3 pounds and 2 j)ounds 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 desirable proportions of copper and lime to
be used. Of the 9 experiments with Bordeaux mixture, 2 fornuihe
contained 15 pounds of lime each, 3 formula? 10 pounds each, and 4
formula' 5 pounds each.

By comparing rows 15 (0 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
liealtiiy foliage of 5.S1» per cent, 5(j() p(>r cent, and (IIU per cent, respec-
tively. Dividing these gains by the iiunibei- of pounds of copp(>r in
th<', res])ectiv<' fonnuhe, which may he fairly d()n(\ owing to tii(> nearly
e(jual amounts of coi)per contained in each, the following results will
be obtiiined:

IVr fcul.
Kow 15 (6 poniids copper Hulphate, IT) pounds lime = l ixmud copper to 2.5

poiindH lime) hIiuwh a j^aiii of foliage ])er pound of copper milphatti of i)8

Row 41 (5 poundH copfRT Hulpliate, 10 jjounds lime = l pound copjier to l'

l)OUiidH lime) hIiowh a gain of foliage per ))ound of copper sulphate of Illi

Kow 21 (5 pound.M copper nulpliate, 5 pounds lime = 1 ))ouiid copin-r to 1 pound

lime) ahowH a gain of foliage per jjounil of copper nulphate 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 number of
pounds of copper sulphate and lime are equal. The formulae contain-
ing 3 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 190
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 well 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 deWed 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
o})tained 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 ma}- properh' be omitted in these comparisons.

88 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

The results olitained hy the use of eau ceh^ste and nioditied eau
celeste were very satist'aetory. l)ut in no case Avas as hioh a percentaj^e
of foliage saved by them as in the better tests with Bordeaux mixture.
The exceptional]}' high percentage of foliage saved on row 30 with but
2 pounds of copper sulphate may be in part due to the fact that the
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.
Ry comparing the formula used on row 27 with that used on row 3o
(each containing 4 pounds of copper sulphate) it will be seen that tlie
saving of foliage was about equal with eau celeste and modified eau
celeste. Comparison of these results with those shown ])v row 22.
which was spi-ayed with Bordeaux mixture containing the same amount
of coppei". will show that the latter saved the highest percentage of
foliage.

Amnion iacal coppei carbonate gav^e less satisfactory results than the
preceding sprays, probably owing to insufficient copper. The various
results given l)y the other sprays tabulated require no special comment.

Another fact is made evident In' the preceding table. Of two
fornud* of the same class, as the Bordeaux mixtures, one containing
n)ore of the fungicide than the other, the percentage of foliage saved
for each jwund of fungicide will l)e the greater in the weaker spray.
Each of the Bordeaux mixtures used in spraying rows 21, 22, 25. and
28 contained .") pounds of lime, l)ut the amounts of copper sulphate
used were 5, 4, 8, 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 ma}' be thus shown.

Row 21: 5-poun(l formula, 6M percent saved; jut pound of c-opper sulphate, \'27
per cent.

Kow 22: 4-]»i)iind forniiila, <;24 pt-r cent saved; per ixmiid of (■oi)i)er sulphate, I'lG
per cent.

Row 25: 3-poinid formula, oSS i)er cent saved; i)er pound of copper sulphate, 19(5
per cent.

Row 28: 2-pound formula, 584 i)er cent saved; per juiimd 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 isdecreas(Hl. but a decided increase
in the percentage of foliage saved per ])()iuid of fungicide.

CO.'NIl'AKlSO.NS OK WEIGJIT AM) COLOR OF 1"0LL\(;K FROM SFRAYED AM)

UNSPRAYED TREES.

Besides the di reel loss of loaves through infection by KrodKcii.sdcfor-
iiKiiiit^ there is an indii'ect loss llii'ough the retarding of growth of such
foliag<' as has not been dii'cctly infected l)y the fungus. A limited
examination of this matter was made May 17 and is. IS!C». Two
typical trees were selected in adjoining rows, one of which had been

II. 20. Div, Veg. Phys & Pa;n,, U, S. Dept of Agncultur

Plate VIII.

COMPARATIVE WEIGHT AND COLOR OF FOLIAGE. 89

spraj'ed and the other not. These were trees No. 10 of rows 20 and
21. Tree No. 10 of row 21 was sprayed the tirst week in March, 1895,
with Bordeaux mixture (5 pounds copper sulphate, 5 pounds lime).
Tree No, 10 of row 20 had not been spraj^ed. 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 spra3^ed
tree 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 spraj^ed 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 I'equired 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 enormousl}^ 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 spraj-ed 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 unspraj^ed
trees comparative!}' 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 health}' 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 spra^vs on the thriftiness of the leaves
was especially examined. This examination was contined to such foliage
as was free from infection bv the fungus, but was extended to spra3'ed
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
spra3's, 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 -1 rows, Nos.
15, 41, 21, and 22, were all sprayed with Bordeaux mixture, containing
6 pounds, 0 pounds, 5 pounds, and -i pounds of copper sulphate,
respectively. Smaller amounts of copper sulphate did not give equally
high results.

The average results shown ])v the different classes of sprays are as
follows :

Per cent.

Sulpluir, linii', and wait {'.i rown) 67

Sulphur and lime (7 rown) 63

Bordeaux, .sulphur, and lime coudjined (3 row.s) 77

I*>ordeaux (9 rows) 90

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

Kau celei^te (2 rows) 90

Modified eau celeste (2 row.s) 80

Aiiinioniacal ('oj)per carbonate (2 rows) 70

Iron snlj)hate and lime (1 row) 40

Iron sul]»liate, sul])luir, and lime (1 row) 40

Potassium sulj)liide (1 row) 40

l'ota,«sium sulphide and lime (2 rows) 45

iJme and salt (1 row) 60 '

i.ime (1 row) TiO

Trees si)ray(!d in 1894, hut not in 1895 (3 rows) 20

("ontrol trees (19 rows) 20-

Thc i»(»i(l('!iii.\ mixture is licrc shown to give the best av»M'age results
as to thrift of foIiag(;. The (^\('('llen(•e of textur<\ color, and size of
the l(;av«!s on rows sprayed with the stronger Bordeaux mixtures
would be hard to sui'pass.

' First leaves prohahly injin<'<l by spray.

^(hw. exceptional row, showin); 40 per cent, omitted; ))erhap.s benefited by wind-
borne spray.

INFLUENCE OF SPRAYS ON THE VEGETATION OF THE TREES.

91

GROWTH OF BRANCHES AND LEAB^ BUUS ON SPRAYED AND tTNSPKAYED

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 unsprayed. 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 l)eneticial action
of the spra}^ 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 tlie results, the time being equally divided
between the 10 sprayed and the 10 unsprayed trees. Typical limbs
were measured upon ])oth the lower and upper portions of the trees,
and the length and compurati^'e liealth 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 1891 or from that which was older. The
results of this work are shown in the following table:

Table 9.

-Records of ineasurementfi of Iwalthii and diseas^ed wood on unspraijed and
sprayed trees, taken May 10-14, 1895.

Row 20, unsprayed trees.

Row 21, sprayed trees.

o

Coo

n

Length of .spring growth
of 1895^

a

o

Length of spring growth
of 1895—

Tree No.

On wood of

1894.

On wood more

than 1 year

old.

On wood of
1894.

On wood more

than 1 vear

old!

.a ■
"3

a
$

5

"3

a

-d

0!

s

Healthy.
Diseased.

£

1
w

•d

§

s

1

In.
1,422
1,614
1,364
1,304
1 , 576
1,886
1,366
1,7.58
1,986
1,912

In.
492
570
301
.557
499
298
.527
686
977
670'

In.
249
229
251
304
326
2.57
230
.516
.550
582

In.

76
219

83
234

85
182

18

.53
120

.56

In.
91
134
22
29
41
41
32

8
2

In.
674
664
592
666
702
976
998

1,068
938
982

In. In.
1,189 11
908 1 6
768 1 4
1,,580 , 6
1,100 3
1,2.59 4
1,348 4
2, 7.51 2

2,100

1,869

In.
194
494

46
330

45
325
183
195

84
220

In.
2

2

14

3

4

6

1

7 .

8

9

10

Total

16, 188

5,577

3,494

1,126

402

8,260

14,872 40

1

•> 110 1 17

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 unspraved 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 CURL: ITS NATURE AND TREATMENT.

On the unsprayod trees, prior to the middle of May, the total amount
of new growth on 16,188 inches of 189-1 Avood, including the older wood
from which this arose, was 10,599 inches. On the sprayed trees the
new growth amounted to 17,01.5 inches during the same time (two
months) on 8,260 inches of 1891 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 1891 wood and
older, while the sprayed trees had produced a growth of 21.75 inches
per foot of 1891 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 oi-chards situated Avhere the
spring growth represents the major part of that of the season, as is
true in many 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 1891 — the pushing of dormant or quiescent buds — an analysis
of the table shows a net gain by the old wood of sprayed trees of 178
per cent above the growth produced from like wood of unspraved
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 tend(!d to denude the lower limbs of 3'oung and productive
wood. This tendency of Bordeaux mixture to aid in the forcing and
active growth of dormant buds was especially well marked in the case
of a tree sprayed ver\' thoroughly on one side (6 pounds copper sul
l)hate, 1 pounds quicklime, 45 gallons of water) and left uiisprayed on
the other. From the base of the main liml)s on the sprayed side there
arose i;'. shoots from dormant buds during the first two months of
spring growth, while the unsprayed limbs produced practically none.
Th(; 1;^ shoots on flic sprayed side had made the following growth to
May 17, gi'owth beginning about the close of the first week in March:

Shoots.

].

2.

3.

4.

6.

6.

7.

8.

9.

10.

11.

12.

13.

2;!

Total

lA^ngth in inches

36

44

29

37

46

21

36

36

36

46

22

21

SC. feci 1 i

As sli(»WM by the table, the growth coining from i:! (ioriniml buds
at the base of tiic main limbs of the sprayed side of the tree during
the first two months of .spring growth amounts to 30 feet and 1 inch,

COMPAEATIVE GROWTH OF BRANCHES AND LEAF BUDS. 93

or an average of over 3H 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
spraved 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 Avood 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 181)4: 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 difference 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 following 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 two-thirds of the injuries
which may be properly assumed to be due to the infection of branches by means of
mycelium coming from diseased leaves. There would then appear 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 branches 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 tlie 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 tliis 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 spraj'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 1)ore a full crop of fruit
in 1893, while the unsprayed trees, everywhere surrounding those that
were spraA'ed, 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 unspraj^ed
trees had apparenth' 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, is
shown by the measurements recorded 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 sutficientl}' extensive to give reliable
results.

Table 10. — Gain in number of lateral shoots and spurs from old wood on sprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

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

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

8,255

2,922

0.3539

13

7,363
2,300
0. 3124

Gain in favor of spnivcd trees per cent..

The above table shows that 13 per cent more buds had pushed into
shoots and spurs on the sprayed trees, in the summer of 1893, than on
the unspra^'ed 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. Tliis was in spitt^ 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. — Gain in length of new growth in favor of sprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

Ix;nKth of old wood, inea.sured in inches, on sprayed and unsprayed trees

8,255

7,363

18, 174
2,692

16,390

1,100

20,866

17.490

2.527 2.376

Gain in ncwKrowlh iii favor of sprayed Irecs percent..

6.4

DESCRIPTION OF PLATE YIU.

Experiments at Biggs, Cal. (Unsprayed.) Looking north through the Lovell
treew from row 28 of the exi)erinient block, showing the nnsprayed trees on both
sides as they appeared May lo, 1895, in the nnsprayed orchard. These should be
contrasted with the two sprayed rows, 21 and 22, shown in I'l. IX.

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

Plate IX.

DESCEIPTION OF PLATE IX.

Experiments at Biggg, Cal. (Bordeaux mixture.) Looking east between rows 21
and 22, May 15, 1895. Row 21 was treated before blooming with 5 pounds copper
sulphate, 5 pounds lime, and 45 gallons of water, and row 22 with 4 pounds copper
sulphate, 5 pounds lime, and 45 gallons of water. Row 21 matured 4,44.3 pounds of
fruit, and row 22, 4,421 pounds, while row 20, unsprayed, just south of row 21,
matured only 648 pounds, and row 23, unsprayed, just north of row 22, matured
only 712 pounds. Row 21 set 22,164 peaches, and row 22 set 21,478, while row 20
set only 1,911, and row 23 only 2,127; or, in other words, row 21 set eleven times as
many peaches as row 20, and row 22 ten times as many as row 23 (p. 111). (Com-
pare with PI. VIII.)

COMPARATIVE 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 hudfi infaror nfspraijed trees.

Records.

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

Number of leaf buds

Average n umber of leaf bud.s to inch of wood

Gain in favor of sprayed trees per cent. .

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 lOiJ 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.

Table I'A. — (rain in niimhcr of lateral shouts a)id spurs fro))i new vood on sprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

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

18,174
640

0. 0302
109

16,390
276

0. 0168

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 Februar}", 1894, Avhile the action of the sulphur spra3^s 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 ^yith the sulphur spra3^s in the
winter of 1892-93 for the destruction of the San Jose scale {Aspidio-
tus 2)<ivn-icioHw<). The manner in which this work was done furnished
an excellent opportunity to ascertain 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 -lO-acre block of 4-year-
old Crawfords Late, had become infested with San Jose 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 CURL: ITS NATURE AND TREATMENT.

Later in the winter Mr. A. D. Cutts, one of the proprietors and the
superintendent of the orchard, had these marked trees thoroughl}^
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 Jose 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
unspra3^ed trees, which represented the major portion of this l:0-acre
orchard, were almost wholly denuded of foliage and largeh' 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 purpose 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 tliem had not ])een sprayed and had suff'erc^d considerably from the
disease. These 20 trees were all Crawfords Late, 5 j^ears 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 lim])s, 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 nu^asui'cd, were counted and the nunil)er set down. All these
new shoots, with the exception of fruit spurs 4 inches or less in lengtii,
were then measui'ed. Records were kept of the length of the new
shoots, the number of well-d(^veloped fmitl)uds, th(^ inunberof ])()()rly
developed fruit buds, and the number of leaf buds they bore. A
record of the num])er of lateral shoots and fruit spurs from the growth
of 1893 was also preserved. Th<' results of this work are brought
tog(!ther in the two tables wiiicli t'<tli()\v:

COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS.

97

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19093— No. 20-

98

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

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COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 99

111 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 kinds were produced by the new growth arising from 8,255
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
7f 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.

Table 16. — Gain in total number of fruit buds on sprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

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

8,255
23,879
2.892

71

7,363
19, 777

Average number of same to inch

2.686

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 iiiispra3'ed
trees showed that a large percentage of the fruit buds they had pro-
duced in 1893 were imperfect, many of them being so poorl}" developed
that fruit could not be expected from them. The following table shows
the average number of imperf ecth" 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 nior(> imperfect fruit liuds on the unsprayed than upon the sprayed
trees at the close of the growing season of 1893.

100

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

Tahi.e 17. — Excess of imperfectly developed fruit buds on unsprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

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

8,255
7,792
0.944

7,363

9,200

1.249

32

Average nunibtT of imperfectly developed fruit buds to inch of wood

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

Table 18.

-Gain in aril-developed fruit buds, exclusive of spurs, on sjtrayed over
unsprayed trees.

Records.

Trees.

Sprayed.

Unsprayed.

Ix-npth of old wood, measured in inches, on sprayed and unsprayed trees

8,255

12,049

1.459

7,363
8,927
1.212

Gain in favor of sprayed trees per cent. .

20

Taking the aggregate of all well-developed f I'uit l)uds, including the
spurs, at an average of 3 l)uds 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:

Tahle 19.

-Gain in spur buds and other well-developed fruit buds on sprayed over
unsprayed trees.

Records.

Lenjfth of old wood, mea.sured in inches, on sprayed and unsprayed trewf. .

AKPregate of spur buds and of other well-developed fruit buns

A veraKC iinmbcr of sjune to inch

(iain in favor of .sprayed trees per cent

Trees.

Sprayed. Unsprayed.

8, 255

lfi,087

1.919

7,363
10, 577
1.437

One of the most striking contrasts shown ]>v the data obtained in
thes(' field studies is that existing l)etween the numl)er 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 l)uds on
the spraye(l trees of 118 per cent above the numl)er produced l>y 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-

COMPARATIVE DEVELOPMENT OF FRUIT BUDS AND SPURS. 101

ducing- these fruit spurs for the following- 3'ear, while the unspra3^ed
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 ftprayed over unsprayed trees.

Records.

Trees.

Sprayed. Unsprayed.

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

Total number of spurs

Number of spur buds, estimatwl at 3 buds per spur

Average number of spurs jier inch

Average number of spur buds per inch

Gain in favor of sprayed trees per cent.

8,255
1,346
4,038
0.163
0.489
118

7,363
550
l,6ri0
0. 075
0. 224

Besides comparing the number of fruit buds produced in 1893 by
the spra3^ed and unsprayed trees, it is desirable to contrast the bud-
producing a])ilities 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 an3'thing
tending to this result ma3' prove of value. Peach leaf curl, being due
to a fungous parasite, has a tendency to do more injur3^ 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 b3^ the lower limbs of the spra3'ed 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 unspra3^ed
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 spra3"ed trees. The tabulated
figures are as follows:

Table 21. — Gain in total number of fruit buds on lower limbs of sprayed trees over those
of unsprayed trees, as compared with upper limbs of each, respectively.

Records.

Trees.

Sprayed.

Unsprayed.

10, 964
1,358

9 770

Length of spurs, estimated at 2 inches per spur

554

12,322

10,324

Length of new wood, measured in inches, on lower limbs

7,210
1,334

6,620
546

Length of spurs, estimated at 2 inches per spur

8,544

7,166

Total number of fruit buds on upper limbs

13,724
10, 155
1.114
1.189

7

11 901

7,876

1 153

1.099

Gain in favor of lower liml)s on sprayed trees per cent. .

5

Difference in favor of sprayed trees do

12

102

PEACH LEAF CURL: ITS NATURE ANr> TREATMENT.

By contrasting only the well-developed and spur fruit buds it is
learned that there was 1-1 per cent in the number of buds in favor of
the lower limbs on the sprayed trees and -i 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. — Gain in number of well-developed and spur fruit buds on the lower limbs of
sprayed over unsprayed trees, as compared with upper limbs of each, respectively.

Records.

Trees.

Sprayed.

Unsprayed.

10,964
1,358

9,770
554

Length of spur.s, estimated at 2 inches per spur

12,322

10,324

7,210
1,334

6,620
546

8,544

7,166

8,975
7,112
0.728
0. 832
14

0,340
4,237

0.614

0.591

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

4

Difference ir favor of sprayed trees — ". do —

18

CHAPTER Vl.

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

The ojonoral discussion of the spray work conducted in the Rio Bonito
orchard will be found in Chapter IV, and it is therefore not necessar}"
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
spra3'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 passed,
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 ))e to destroy the contrast in the amount of
fruit arising from the use of different formula\ This would result in
the loss of the verj^ 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 yoiuig peaches were allowed to fall upon the canvas as picked, and
the canvas was moved as necessar3^ The fruit thus thinned was
poured from the canvas into picking boxes beneath the tree from which
it was thiimed. 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 separated 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 inim])er entered with the other records of the row, and
on this basis the average numbor of small peaches per pound for the
row was determined. By nmltiplying 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

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

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 held 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. — Weif/Jit of peaches thinned from tJte sprayed Lovell peach trees in the experi-
ment block of lite Rio Bonito orcliard in the spring of 1S95. (a)

Row No.

Actual weight in pounds of thinned
peaches from trees Nos. —

Total

weight of

peaches

in row.

Number
. of
peaches

in 25
pounds.

Average
number

of
peaches

per
pound.

Total

number

of

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

peaches
per row.

1

16

16i

18

33

20i

22i

27

45

50

35

Pounds.
282}

482

19.28

5,442

2

3

27

22

15

20

221

21

30i

m

29

16

2194

550

22.00

4,829

4

.5

(i

18
17

2
25

15
11

6

7i

15
12

3

21 i
15

5
6

19

5i

164

84

121
117

486
484

19.44
19. 36

2,352

7

2,265

8.

9

36
30

21
30J

15
24

131
10

18i
17

25
25

36
40

6i
19J

6
17

204

185
2334

522
466

20. 88
18.64

3,863

10

4,352

11

12

31
23i

13

Hi

3
2

10
2i

6

18

164

n
n

19i
2i

m

34

224
54

1334
93

511
495

20. 44
19.80

2, 729

13 . . ..

1,841

14

15

82
20i

44
6

27
15

31

24
9i

40
5

45
17

23

m

29i
14

22
13

3674
121

528
496

21. 12
19.84

7,762

16

2,401

17

18

32
24

17
35

26
29

16
16

17
25

8
14

10
13

6
11

14

7

4
12

150
186

504
486

20.16
19.44

3,024

19

3,616

20 .

21

68
33

48
51

26
35

28
21

481
35

49

58

58
41

21
22

294
29

614
60

4374
385

484
472

19.36

18.88

H,470

22

7,269

23

24

25

42

20

22

18

28

21

37

38

43

51

320

449

17.96

5, 747

26

27

34

18

34
21

35
32

11

29

14
31

35
33

30
34

22
30

21
63

23
50

259
341

495
421

19.80
16.84

5, 128

28

5,742

29

30

55

49

42

43

60

43

41

35

70

86

524

487

19. 48

10,208

31

32

31

47

15
51

18
34

20
40

22
22

18
39

27
33

8
29

159
381

514
483

20. 50
19.32

3,269

33

39

47

7,361

34

35

62
23

03
35

23
14

io'

57
11

42
31

46
26

.57
31

54

28

62
46

466
255

r.22
480

20. H8
19. 20

9,730

36

4,896

37

38

16
40

6
26

C
39

8

10

22
37

26
34

17
29

15
34

25
27

150
266

.553
547

22. 12
21.88

3, 318

39

5,820

41

54

52

27

24

26

12

27

8

36

'28

293

508

20. 32

5,953

42 .

43

44

6
26

8
23

11
21

5
11

6
22

36
196

537
504

21.48
20. 16

773

45

17

20

16

27

14

3, 961

47 . .

48

7

6

3

5

8

4

33

511

20. 44

676

49 .

50

61

15

22

8

12

11

12

12

13

18

17

140

533

21.32

2,985

62

fA

54

30

31

44

18

17

27

30

21

36

17

274

rm

20. 32

5,668

55

60

22
21

-10
35

41
16

IH
20

17
11

27
19

30
20

21
29

36
82

17
37

272
240

520
647

20. 80
21.88

5,658

57

6,251

58

<i For jtliit of orchard sec p. 69; for s]>niys applied see j). 73.

THINNING THE FRUIT OF SPRAYED TREES.

105

By referring to the above table it will be seen that only those rows
which were sprayed in the spring of 1895 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 unsatisfactor}^ spraj^s, in which cases the fruit
fell from disease. The table shows the weight of thinned peaches j^er
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 num])er of peaches, the reduction being made according to the
method already described. Comparison 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 different methods which it Was necessary to employ in obtain-
ing the figures shown in the two tables.

Table 24. — Number of peaches thinned from the sprayed Lovell peach trees in the experi-
ment block of the Rio Bonito orchard in the spring of 1895. (a)

Row

Number of peaches

thinned from sprayed trees Nos

-

Total.

No.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

1

289

318

347

636

390

434

521

868

964

675

5,442

2

3

594

484

330

440

495

462

671

363

638

352

4,829

4

5

6

350
329

39

484

292
213

117
145

292
232

58
184

418
290

97
116

369
106

321
165

2,353

7

2,264

8

9

752
559

438
569

313
447

282
186

386
317

522
466

752
746

136
363

125
317

157
382

3,863

10

4,352

11

12

634
465

266

287

61
40

204
50

123
356

337
267

31
148

399
50

215
09

460
109

2,730

13

1,842

14

15

1,732
407

929
119

570
298

655
69

507

188

845
99

950
337

486
347

623

278

465
258

7,762

16

2,400

17

18

045
467

343

080

524
564

323
311

343

486

161
272

202
253

121
214

282
136

81
233

3,025

19

3,616

20 .

21

1,316
023

929
963

503
661

542
396

939
661

949
1,095

1,123
774

407
415

571
548

1,191
1,133

8,470

22

7,269

23

24

25

754

359

395

323

503

377

665

682

772

916

5,746

26

27

673
303

673
354

693
539

218
488

277
522

693
656

594
573

436
505

416
1,061

455

842

5,128

28

29

6,743

30

1,071

955

818

838

1,169

838

799

682

i,364

1,675

10, 209

31

32...

637
908

308
985

370
657

411
773

452
425

370
753

555
638

164
560

3,267

33

753

908

7,360

34

35..^

36

1,295
442

1,315
672

480
269

""i92'

1,190
211

877
595

960
499

1,190
595

1,128
538

1,295

883

9,730
4,896

37

38

332

875

133
569

133

853

177

221

487
810

575
744

376
635

332

744

653
691

3,319

39

5, 821

40

41

1,097

1,057

549

488

528

244

549

163

711

569

5,955

42

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

106

PEACH LEAF CUKL: ITS NATURE AND TREATMENT.

Table 24. — Number of peaches thinned from the sprayed Lovcll peach trees in the experi-
ment block of tlie Jiio Bonito orchard in the spring of 1895 — Continued.

How

Number of peaches thinned from sprayed trees Nos.—

Total.

No.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

43

■

44

129
504

172
464

23G
423

107
222

129
444

773

45

343

403

323

544

282

3, 952

46

47

48

143

123

61

102

1G4

82

675

49

50

51

320

469

171

256

235

256

256

277

384

362

2,986

52

53

54

610

691

894

366

345

549

610

427

732

345

5,569

55

56

458
459

832
766

915
350

374
438

354
241

562
416

624
438

437
635

749
700

354
810

5,659

57

5,253

58

t

■■■ 1

i

1

GATHERING FRUIT OF SPRAYED AND UNSPRAYED TREES.

The fruit of the Lovell variety ripened rapidl}^ in the Sacramento
Valley after the middle of August, 1895. On the experiment trees a
large portion of the crop was sufficiently 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 >^erk was completed
before the 1st of September. The fruit was gathered at two pick-
ings, the second picking beginning shortl}^ after the close of the first.
The crop was marketed in three ways:

(1) All pcu'fect peaches abovt^ a standard siz(^ adopted l)y the can-
neries, and sufficiently firm to ])ear shipment by rail from Biggs to
Oakland, Cal., a distance of about 110 miles, were sokl to a firm at
the latter point at $30.80 per ton, f. o. b. cars at Biggs., This fruit
comi)rised a])out 51 p(>r 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 ship])(>d to
a cannery at (^hico, Cal., a distance of about 80 miles. This fruit
brought $80 per ton, f. o. b. cars at Biggs. It comprised about 80
per cent of the yield of the experiment block.

(3) Such fruit as was below cannery size, ovei'mature, or impcM'fect
in any ivspect was sent to the diying ground to be dried. In the cal-
culations of the present work this fi'uit is valued at tiiree-fourths of a
cent \n\Y [)()un(l in the green stat(>. This is less than the etjuivalent of
dried fruit was worth at the time of curing after allowing for the cost
of drying. 'Ilie fruit sent to the drying ground rcpi'csiMited about 10
per cent of the yi(^ld of the experiment block.

The work of gathering, weighing, and grading (he ciop of lh(>
(^\p(M"iment rows was cai'efully systematized. As before shown, the
expciiincnl block was 2<» frees wide from east (o west, and through
tlir cciitci' from north to south a (lri\('wa\ was made, so that the rows

Bull. 20, D,v. Veg Phys & Patn. U S. Dept of Agr,.u.tur

Plate X.

DESCRIPTION OF PLATE X.

Experiments at Biggs, Cal. (Bordeaux mixture.) Fruit gathered from row 15 of
the experiment block of the Rio Bonito orchard in the summer of 1895. The formula
for the spray used on this row was 6 pounds copper sulphate, 15 pounds quicklime,
45 gallons of water. The 10 trees of the row matured 4,351 pounds of tine peaches,
which ^re shown in the picking boxes. The trees of the adjoining unsprayed row.
No. 14, bore only 928 pounds. The value of the fruit matured on row 15 was $60.02;
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 G19 per cent.

GATHEKING FRUIT OF SPRAYED AND UNSPRAYED TREES. 107

on either side were 10 trees long from east to west. One picker was
assigned 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 sufficiently 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 cmploj^ed 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 ])earing 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
boxes. 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 l)oxes
of several trees of the row. The number of peaches in this 100 pounds
of fruit was then ascertained by counting, the numbcn- ))eing recorded
with the other data for the row. The fruit of all the experiment rows
was weighed and the average size of the peaches determined In^ 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 cannery, one for a Chico can-
nery, and a third class for drying. These tliree classes constituted

108

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

really Ijiit two (jualities of fruit — a first quality for canning, and a
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 difl'erent 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 Lovell trees of the experiment
block of the Rio Bonito orchard, gailiered in the fall of 1895.

Row No.

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

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

75

51

164

69

42

190

88

93

259

216

65

229

232

121

492

157

133

383

251

61

426

3fU

22

65

380

70

345

109

89

121

71

74

75

267

29

271

275

71

166

192

55

357

112

56

241

324

99

438

524

80

50

236

121

400

385

36

198

152

139

142
122
140
129

36
193
139

22
162
332

30
111
200
114
538
303

55
322
365
110
470
539

88

65
386

71
438
573

98
237
127
132
159

94
237
129

69
140
330

65
274
128
108
246
296

64
139
137

61
214
277
126

62
449

97
314
277

99

207
137
147

31

56
175
169

11
202

89

86
191

70
109
253

87

52
242
144
109
405
257

54

48
180

16
116
298

64
258
134
252
401

53

27
166

147

54
157

57

73
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

118
111
179
120
140

97
183
151
248
240
107
154
203
114
474
216
119
233
304

27
431
556

95

52
424

62
425
489

90
219
179
218
373
148
491
354

84
234
384

49
200
145

45

262

90
289

87
159
212
180
115
233
249
114
247
209

91
573
451

58
296
245

32
617
469

75

48
565
109
.513
489

33
296
111
209

190
140
241

74
100
212
222

39
234
297

41
168
187
114
340
235

89
144
201

22
2.52
324

38

56
459

90
290
379

95
318
199
298

180
165
200

69

64
237
169

53
153
407
106
240
145

47
453
291

44
288
189

23
343
332
105

24
285

49
200
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
29-1

92
268
327

51

140

48

49

34

66
204
110

16
121
169

70
147

77

32
273
198

21
119
180

.59
427
340

53

90
430

45
217
379

40
342
215
243
208
146
448
310
143
403
414
222
400
211

84
220
286

53
228
181

32
:{.50
310
132

5-1
285

94
.50^1
471

52

Pounds.
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
3,116
4, 120

576
2,615
1,5,52
2,282
3,189
1, 102
4,034
2,()81
1,125
2,4.52
2,804

936
3,464
1,924

6.55
1,742
3,288

727
1,572
1,347

695
2,114
2,W1
1,067

753
3,797
1,024
3.298
3.412

859

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

Pounds.
157

2.

106

3

168.7

4

75.6

5.

81

6

181.3

7

170.8

8

56.8

9

210.1

10

255.3

11.

83.3

12

208.2

13

167.6

14.. . .

84.4

15

422.7

16

234.8

17..

71.5

18

260.9

19

259. 4

20

57.4

21

430.7

22

427.5

23

67.2

24

54.7

25

377.1

26

65.8

27

311.6

28

313
29

188
71

177

412.6

29

57.6

30

261.5

31... .

155.2

32

228.2

33

283 , 271
87 ' 128
393 1 291
298 ' 213
80 96
246 91
283 1 154

428 1 429
79 ; 133
597 590
365 ' 3(k5
127 1 163
284 341
439 461
53 47

325.4

34

110. 2

35

469

36

268.1

37

112.6

38

245.2

39

850.5

40

1*5
412
287

92
171
328

52
130

97

77
250
26-J
162
140
337

123
2(W
176

8.5
150
220

87
149
155

91
284
330

99

68
457
l(i6

\m

400
64

59
451
157

32

69
430
179

32

93.6

41

410
223

97
139
413

42
105

305
119

28
231
363

73
169

346.4

42

192.4

43

65.5

44

163 70 164

174.2

45

222
107
118
106
95

510 324

90 56

228 116

117 79

78 1 60

328. 8

46

72.7

47

157.2

48

182 1 142

8(; : 41

118 229

251 193

25 (A

44 73

392 408

137 67

244 :{81

313 3'.»9

83 46

134. 7

49

r)9. 5

50

147 ' 107 120
263 1 247 207
135 147 84
lft5 54 ; 63
443 311 1 421

HO 45 1.53
415 294 181
359 ' 254 2«2

92 1 86 195

211.4

51

261. 1

62

100. 7

53

78.4

64

379. 7

,%

9:1
336

102. 4

66

347. 1

67

3:i0

341.2

68

91

hf).«

GATHERING FRUIT OF SPRAYED AND UNSPRAYED 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
fruit 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.

Table 26. — Weight of peaches of second picking from the Lovell trees of the experiment
block of the Rio Bonito orchard, gathered in the fall of 1895.

Row No.

Weight of fruit, in pounds, gathered at second
picking trom trees Nos. —

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

54
25
79
12

121

6

124

41
12
33
44
13
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
3S
30
IS
26
63
IS
15
14
12
22
6
7

14
13
5
53
S
2
4
.....

16
39

168
68

187
51
37
43

140
20
66
90
31
54
55
18
38
58
9
30
17
18
33
80
12
13
70

"5i'

62

5

385

148

210

218

57

80

53

44

37

29

23

100

25

22

32

33

14

.....

5
10

Pounds.

1,242

343

1,109

255

236

452

517

107

357

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

393

245

424

439

173

566

198

84

265

203

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.S
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

Pounds.
124 2

2

36 1

3.

151

"ei'

83
120

88
45
12
20

110 9

4

26

5

23.6
45 2

6

49
00
11
31
29

7
11
23
19
33
20
11
23
10

7

12
11

6

6
23

5

8
9

10
16
10
5
12
13
6
6
11

'"io'

6
3

8
28

109

31

27

82

76

31

41

35

8

7

11

5

10

""is"

" "'is'

"is'
"28"

7

51 7

8

10 7

9

14
16
11

96
19

"87'

35 7

10

41 5

11

36 6

12

13

15 5

13

21

"is"

IS
11

"ie'

15
13
19

"'s'

23

18 4

14

8 4

15

12 4

16

15 2

17..

4 3

18

14
"'5'

9 1

19

31
22

14

4
12

11

11 S

20

7 4

21

13 6

22. . ..

14 6

23

13

7
5
24
6

"is'

29

"ie"

4

24.

6
11

5 2

26

28

32

21 7

26

1 4

27

9
19
3
191
107
145
192
62
2.51
75
31
62
142
32
103
73

"'is'

16
12
11

8

10

28

17
5
201
27
10
3

13 7

29 . ..

1
295
33
150
212
62
63
119

"so'

108
30

149

23

9

60

18

'267'
85
81
126

12
199
103
113
104

2 6

30

270

40

200

113

8

89

6

12

23

26

15

47

21

7

16

19

3

10

11

5

4

12

138
27

107
14
13
35

"'g'
24
23

141
23
30
19
6
94
72
24

"il'

439

193

90

81

14

146

""si'

30

252 6

31

78 6

32

113 6

33

34

110.4
22 2

35

36

37

"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
55
18
17
30

97.6
39.3
24 5

38

42 4

39 .

54 8

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'

S3

"25'
6
5
11
15
6

56 6

42

19 8

43

14
43

"24"

8 4

44

26 5

45

20 3

46 ..

4 7

47

9
IS
17

10 2

48

30
10
14
25
6
9
17
16
27

9 2

49

6 1

50...

5 5

51

11
9
10
92
11
32

9 1

52

6.4

53

7
19

"2i'
4

"is'

4 9

54...

34

20 6

55

7 5

56

3
1

13
.....

""ie"

9 7

57

""26"

26
6

9.1

58

4.3

110

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

The total jield 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 wcifjht uf peaches of first and second pickings gathered from the Lovell
trees of the experiment block of the Rio Bonito orchard in tlie fall of 1895. (a)

Row No.

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

1.

6.

9.

10. Total.

1
2
3
4
.')
6
7.
8.
9
10
11
12
13
14
15
16,
17
18
19
20
21
22
23
24
25,
26,
27,
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
5:i
54
55
56
57
58

129

76
243

81

42
239
148
104
290
245

72
240
255
140
525
177
144
406
261

68
438
395

28

71
403

75
345
313

29
458
111
377
396

95
482
304

92
269
309
150
459
308

99
187
347

55
140
108

82
254
276
162
147
3.56

93
339
331

91

230

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
168
236

99
160
155

91
284
330

99

(18
478
170
361
418

(^4

183
134
173
173

49
2.53
238

30
188
357

35
111
221
114
556
321

66
322
381
125
483
558

88

65
414

71
446
573

99
532
160
282
371
156
300
248

(i9
220
438

95
423
151
117
306
314

64
148
155

78
214
288
135

72
.541
108
346
277

340
236
298

70
146
197
197

11
216
105

97
191

70
117
253

87

52
256
144
109
410
257

67

48
180

16
116
298

64
525
219
333
527

53

186
82
243

259

54
308

57
134
311
301

39
314
238

83
304
184

47
474
298

88
341
362

54
498
544

62

43
4.58

19
166
417

65
524
176
325
2.53
107
593
199
242
336

107
499
1.57

46
206
222
107
118
136
105
161
288
141
114
460

96
442
359

92

69
430
179

32

70
534

90
228
117

78
107
247
147

54
311

45
294
254

86

245
111

267
165
152
117
183
151
248
327
107
167
203
114
474
216
119
233
364

27
431
556

95

52
424

62
425
489
102
418
282
331
477
148
543
369
111
261
451

74
262
183

58
205
341

63
148

94

73
130
220

96

75
47()
171
198
312
195

394
115

315

91
159
321
211
142
315
325
145
288
244

99
580
462

63
296
259

36
629
469

82

53
589
115
513
489

33
434
138
316
442

92
632
365
135
308
462

53
425
236
104
154
430

44
111
182

95
118
251

43

44
402
137
244
313
109

302
181
403
100
100
222
222

52
234
'297

69
168
187
127
340
263

89
144
212

22
252
324

38

74
488

96
306
379

95
459
222
328
448
139
684
437
187
341
475

47
326
124

40
210
389

82
178
154

43
239
203

66

82
426

93
381
425

52

422
232
308
103

87
275
199

71
179
530
184
255
159

59
475
297

51
302
202

28
396
340
107

28
285

52
222
460

25
675
408
389
468
141
570
315
138
305
369
114
335
•299

52
213
359
103
215
157

79
306
314
100

90
328

92
281
327

62

308
116.
236

85
103
247
250

36
187
259
101
201
132

50
311
256

30
149
197

77
460
426

65
109
500

45
268
441

51
727
363
453
426
203
528
363
187
440
443
245
500
236
106
258
319

67
228
181

32
356
315
142

54
285

94
504
487

52

2,812
1,350
2,796

996
1,046
2, 265
2,225

675
2,458
2,968

969
2,103
1,860

928
4,3.51

2, .500
7.58

2,700
2,712

648
4,443
4,421

712

599
3,988

672
3,216
4,263

602
5,141
2,338
3,418
4, 271
1,324
4,874
3,074
1,370
2,876
3,243
1,109
4,030
2, 122

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, .VKi
902

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

A.s idi'ciuly said, after the weight of fruit for each tree of ii row had
been ascertjiined and recorded, the number of peaches in 100 pounds
of this fruit was determined by coiniting. From several picking
boxes of fruit, coming fiom diU'ereiit ti'ees of the row, was weighed
out 100 pounds of peaches fairly representing th(^ fruit of the row.
The jx'aches of this 100 pounds wer(» then carefully co\uited and the
nunihri- recorded. This was done both foi the tirst and second pick-

GATHERING FRUIT OF SPRAYED AND UNSVRAYED TREES, 111

ings !ind 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 hrst and
second pickings:

Table 28. — Number of peaches per 100 pounds; weight, of fruit gathered; and number of
peaches thinned, gathered, and set by the trees of each row in tlie experiment bhcJ: of the Rio
Bonito orchard in 1895. (a)

Nmnber of

peaches in 100

pounds.

259
295
285
300
303
278
280
282
288
282
292
283
293
306
309
294
296
300
289
290
308
320
296
292
284
280
276
291
277
292
304
294
291
290
325
285
282
282
289
300
284
303
293
309
309
303
2«9
308
292
287
299
303
300
306
295
293
•298
282

317

310

335

323

324

326

322

323

313

316

321

312

6 324

362

317

6 327

6 339

6 340

6 332

6 314

6 362

6 344

6 356

6 368

6 354

6 360

6 370

6 360

313

326

311

335

330

345

332

330

330

328

312

339

335

6 304

337

346

6 330

356

6 324

6 312

6 366

6 356

6 336

6 325

6 352

6 334

6 384

6 370

6 360

Pounds of
fruit —

1,570
1,007
1,687

741

810
1,813
1,708

568
2,101
2, 653

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
3,116
4,126

576
2,615
1,552
2,282
3,189
1,102
4,034
2,681
1,125
2, 452
2,804

936
3,464
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

CO

1,242

343

1,109

255

236

452

517

107

357

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

393

245

424

439

173

566

198

84

265

203

47

102

92

61

55

91

64

47

266

75

92

91

43

Number of
peaches gath-
ered at —

4, 066
2,971
4,808
2,-223
2,454
5,040
4,782
1,602
6, 051
7,199
2,432
5,538
4,911
2,583

13, 061
6,903
2,116
7, 827
7,496
1,665

13, 266

13, 680
1,989
1,597

10,710
1,842
8,600

12,006
1,596
7,636
4,718
6,709
9,280
3, 196

13,111
7, 641
3,173
6,915
8,104
2,808
9,838
5, 830
1,919
5, 383

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

11,619
3,021
9, 663

10,168
2,422

cc

3, 577

1,087

3,438

854

762

1,464

l,68f,

345

1,153

1,299

430

469

574

272

449

482

140

308

401

246

427

529

138

185

799

50

360

507

94

7,906

2,562

3,533

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

153

936

250

353

337

155

Number of
peaches —

7,643
4, 058
8,246
3,077
3,216
6,504
6,467
1,947
7, 204
8, 498
2, S{i2
6,007
5, 485
2, 855

13,510
7,385
2, 256
8,135
7,897
1,911

13, 693

14,209
2, 127
1,782

11,509
1,892
8,960

12, 513
1,090

15, 542
7,280

10, 242

12,905
3,929

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

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

10, 862
2, 358
4,906
4,447
2, 219
6,268
8,221
3,448
2,412

12, 555
3,271

10,016

10,505
2,577

OS:

u o

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

5,747

5,128
5, 742

10, 208

3,269
7,360

9,730
4,896

3,318
5,821

5,953

773
3,951

675

2, 985

5, 568

5, 659
5, 251

13, 085
4,058

13,075
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, 163

21,478
2,127
1,782

17, 256
1,892

14,088

18, 255
1,690

25, 750
7,280

13,51]

20, 265
3,929

25, 739

13,841'
3,982

11, 632

15, 365
3, 348

17, 710
6,493
2,174
7,049

14,813
2, 358
4,906
5, 122
2,219
6,268

11,206
3,448
2,412

18. 123
3,271

15, 675

15, 7.56
2,577

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

9.0
10
10

9. 5
10
10

Average
number of
peaches set

per tree.

1,308

1,307

886
873

1,107
1,285

929
733

2, 127
979

1,116
1, 151

2,216
2, 148

1,726

1,409
1,825

2, 575

1,351
2,068

2,993
1,384

1,103
1,921

1,771
649

705
1,481

491
512

627
1,120

1,812

1,6.50
1,576

o For plat of orchard sec p. 69; for sprays applied sec p. 73.

6 Number calculated from a less weight than 100 i)ounds, usually from .50 pounds

112 PEACH LEAF CURL! ITS NATURE AND TREATMENT.

Following the figures in the above table which .show the number of
peaches in 100 pounds of fruit are those giving the num})er of pounds
of fruit gathered at the first and second pickings. From tliese four
columns of figures has been calculated the number of peaches gathered
from the trees of each row of the block for ))oth 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 firmly 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.

COMPARATIVE QUANTITY, QUALITY, AND CASH VALUE OF FRUIT FROM
SPRAYED AND UNSPRAYED TREES.

(Pis. XlandXII.)

The actual yield in pounds of peaches, the (quality, and the ca.sh
value of the fruit produced by the sprayed and unspra^'cd 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 read(>r will compare the average value of the fruit produced l)y
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
po.ssil)le gains resulting from thorough spraying may be ol)tained. In
studying this table, it should be remembered that the results shown
were obtained from the use of 35 different formuhv 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
.spiays as those used upon rows 21, 22, or others of the better-yielding
rows of the block.

DESCRIPTION OF PLATP: XL

Experiments at Biggs, Cal. (Sulj)hur, lime, and salt.) Looking west between rows
2 and 3, May 14, 1895. Itow 2 was unsprayed; row 3 was sprayed before blooming
with 15 i)()unds sulphur, 20 pounds lime, 5 pounds salt, and 45 gallons of water.
The average value of fruit matured per tree in row 2 was !fl.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 i)eaches set by the trees of both rows, of 210 per cent (p. 117).

Bull. 20, Div. Veg. Pnys. & Path., U. S. Dept. of Agncultute.

Plate XI.

= $

DESCRIPTION OF PLATE XII.

Experiments at Biggs, Cal. (Sulphur and liuie.) Looking west ])et\veen rows 5)
and 10, INIay 14, 1895. Botli rows were sprayed before blooming. Row 9 was treated
with 10 iiounds sulphur, 20 pounds lime, and 45 gallons of water, and row 10 with
10 pounds suljihur, 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 13.35, 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 njw 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 PI. XI.)

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

Plate XII.

COMPARATIVE QUANTITY, QUALITY, AND VALUE OF FRUIT. 113

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19093— No. 20-

HtN<N6)e^C^OIiMC^INiM

114

PEACH LEAF CURL: 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 between 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) .

5u;l. 20, Div. Veg. Phys. & Path., U. S. Dept. of Agriculture.

Plate XIV.

DESCRIPTION OF PLATE XIV.

Experiments at Biggs, Cal. (Eau celeste.) Looking west ])etween rows 26 and 27,
May 11, 1895. Row 26 unsprayed; row 27 sprayed })efore blooming with 4 pounds cop-
per sulphate, 3 pints ammonia, and 45 gallons of water. Average value of friiit
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).

Bu I. 20, Div. Veg. Phys & Path., U. S. Dept. of Agncultuie.

Plate XV.

DESCRIPTION OF PLATE XV.

Experiments at Biggs, Gal. (Modified eau celeste.) Looking east between rows
34 and 35, May 14, 1895. Eow 34 unsprayed; row 35 sprayed before l)lo()niing
with 4 pounds copper sulphate, 5 pounds sal soda, 3 pints ammonia, and 45 gallons
of water. The average value of fruit matured per tree in row 34 was $1.84; in row 35,
$8.05. The spray used on row 35 showed a net gain over row 34, as determined by
the comparative value of the peaches set by the trees of both rows, of 608 per cent
(p. 118).

INFLUENCE OF SPEAYS ON THE FKUITING OP THE TREES. 115

COMPARATIVE VALUE OF SPRAYS IN RELATION TO FKUIT.

(Pis. XIII, 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 quantit}- of fruit is
concerned, shoidd 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 carr}'^ 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
fruit 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 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

It has 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 (juality when
matured. By dividing this sum by the number of trees in the row
the average 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, the}^ 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 reasons
the figures for the difl'erent 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 quantit}' 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 b}' the cash
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 ma}- be seen
that in row 30, sprayed, the average calculated value of all fruit set
per tree would have been when matured $12.63; in row 31, unsprayed,
$3.13. 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 $9.11) 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 208
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.

COMPARATIVE VALUE OF SPRAYS IN RELATION TO FRUIT. 117

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118

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

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INFLUENCE OF SPRAYS ON THE FRUITING 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 peaches per tree, would yield larger fruit than the
sprayed trees, which had to mature 919.2 peaches per tree; in other
words, that the increased number of peaches upon sprayed over
unspra3'ed trees would, to a considerable extent, be counterbalanced
by an increase in the size of the fruit on the lightl}" loaded unspra3^ed
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 ta])le
has been compiled from the facts in hand upon this matter. It is
shoAvn in this table that the fruit from the sprayed trees averaged
for the whole block (315.3 trees) 299.0311: 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
roWoo per cent, or only al)out ^oVg of 1 per cent. This amounts to
nothing from a practical standpoint.

Table 31.-

-Size of fruit on sprayed and unsprayed trees as determined by the average
number of peaches per 100 pounds.

Num-
ber

of
trees

in
block

Fruit

produced

by all trees

of block.

Average
production

Average number of
peaches—

Proportion-
ate
percentage

Aver-
age
num-
ber of
peacbes
per 100
pounds
per
tree.

Average

per-
centage
of gain

per tree.

Per
100 pounds.

Per tree.

yield
of trees.

in size
of fruit
on un-
sprayed
trees over
that of
sprayed
trees.

First
pick-
ing.

Sec-
ond
pick-
ing.

First
pick-
ing.

Sec-
ond
pick-
ing.

First
pick-
ing.

Sec-
ond
pick-
ing.

First
pick-
ing.

Sec-
ond
pick-
ing.

First
pick-
ing.

Sec-
ond
pick-
ing.

Sprayed

Unsprayed

:m5.S
228.9

Lhs.
95,094

19,035

Lbs.
14,. 504

3,257

U)S.
275. 4

83.2

Lbs.
42

14.2

293.2
293.6

337.4
330.8

S07.5
244. 3

141.7
47

86.8
85.4

13.2
14.6

299. 0344
299.0312

106

100000

per cent,

or about

1

1000

of 1 per

cent.

It should not be understood by the above that a crop of 950 peaches
draws no more heavily upon a tree than a crop of 300 peaches when
other conditions are equal. All observation tends to show that such
is not the case. A tree too heavil}' loaded will often produce

120 PEACH LEAF CURL". ITS NATURE AND TREATMENT.

much smaller fruit than a properly thinned tree, even upon exceed-
ingl}^ 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 65C 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 3(M) peaches, as were
the sprayed trees in maturing 950 peaches. If this had not been the
case, the unspraj^ed 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 sucli a year
would be equivalent to draining them of much vitality, oven though
they failed to show this drain in the reduction of wood or fruit buds
for the ensuing year. But it has already ])een shown that a marked
reduction in the number and (|uality 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 ver}' 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 Lov(;ll is ecjual to the drain upon the
tree brought about in maturing two-thirds of a crop, the loss of the
foliage upon a somiresistant 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 tln^ loss in the
reduced vigoi- of his trees, the reduced weight and size of his fruit,
and the added drain upon his soil.

("()L()1{ OF Sl'KAYKI) AM) IJNSl'KAY KD KUIIT.

The Lovcll |)c!i(li is normally a fruit of line color, but uiulcr the
action of certain of the sprays used its color was greatly heightened.
In ol)scr\ing this action of the sprays no color scale was used, but the
marked Inightcning on cei'tain spi-ayed rows was too distinct to be
mistaken bv the most careless obserxcr. This heightening ot" color

METHOD OF THINNING 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 luisprayed 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 ])e 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 advanced by certain peach growers and requiring con-
sideration is that a moderate spraying under ordinar}^ conditions is
sufficient. B}^ 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 l)egins is too uncertain a method to warrant the indorsement of
practical growers. All 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 })ortion 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 CURL: ITS NATURE AND TREATMENT.

the fruit is for the most part nourished by the foliage of the l)ranch
which bears it. and hence if tlie disease is not equally distributed the
foliage will be unequall}" distributed and the fruit unequally nourished.
One portion of a tree may have an excess of fruit, even to the break-
ing of lim])s. 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 thiiming, 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 largel}^ toward the ends of the limbs.

The statements here made respecting the local action of the disease
and the local nourishing 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 section of this chapter.

COST OF I'ICKINO PEACHES.

When considering the picking and sorting of peaches from sprayed
and unspra3'ed 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 contrast to this the cost
of picking and sorting the fruit of the unsprayed trees just north of
the experiment })lock, in the sunnner of 18!>."). was $8 pei- ton. This
was on account of the scattered condition of the fruit on these trees,
which were affected b}- curl in the spring like the control trees of the
experiment block. This cost pen- ton was calculated with wages at ^1
per day, the men ))oarding themselves, and where one sorter to five
pickers was employed. We have how a difference of $2 per ton in the
cost of picking and sorting fruit from sprayed and uns})rayed tives.
This added expense on unsprayed trees arises, of course, thi'ough the
necessity of picking over a greater expanse of tree and orchard surface
to ol)tain a given amount of fruit. It is l)elieved that in this single
item of picking the fruit enough is sav(>d to more than cover the expense
of spraying the trees and thinning the fruit.

TIIK I-OCAl. ACTION OK ("Ulil, ON FOIJAiiK AM) FKUn'.

UHCDEtDS Ol' TUERS SI'KAVEI) ON ONE SIDE.

The study of the liahits of /Cr/xiscu.s tlt^fn/-//t<//i.s iu\d its inllucncc upoJi
its host led to the following imcstigation into the localization of (he
parasite upon llie ti-ee and its local ratliei' than general eU'ects.

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

Plate XVI

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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
denuded the unsprayed half at the left.

LOCAL ACTION OF CURL ON FOLIAGE AND FRUIT.

123

Just north of the experiment block, 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 effort 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 spra}"
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 shortlj'^
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 spi-ayed and
unsprayed sides of the 6 trees used in the experiment. The following
table shows the results of these estimates:

Table 32. — Folitiye hMfroin ^pnoji'd tind unaprayed Jialve-9 of trees.

Percentage of leaves which fell from-

Trees treated

with Bordeaux

mixture, (a)

Tree No.—

Trees treated

with sulphur

spray. (6)

Tree No.—

1.

2.

X

4.

5.

6.

2
92

4
92

G
90

18

85

15

85

15

85

Sprayed half ..
Unsprayed hal.

a Foliage estimated May 18, 1895.

6 Foliage estimated May 10, 1895.

On Ma}" 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 liml)s 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
3 per cent of the leaves curled at all on the spraj^ed 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 95 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 aie not curled are small and light
in color. The foliage upon both lower and upper limbs is badly affected.

124

PEACH LEAF CFRL: ITS NATURE AND TREATMENT.

What little growth there is which is thus far free from curl is termi-
nal— very little healthy or comparatively health}' 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 spraj-ed 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 th(^ spra}' 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 could 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 unspraN'ed 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. — Ykld of sprayed and utisprayed Iialven of trees.

Bordeaux mixture,
tree No. —

Sulphur sprav, tree
Ko —

Pounds of fruit gathered from —

Spniyod half

riisjiruycd lialf

Number of luaclius gathered from —

Sprayed lialf

Unsprayed half

284.8
14.3

718
40

361.6
50.6

1,064
147

286.7
25.3

836
74

112.2
48.6

303
132

189.3
80.4

450
220

64.6
35.3

172
94

By the preceding ta])le 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 ap[)eared to have no influence whatever over
th(i sprayed limbs of the other side, as th(^ 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 peach(>s as any in the orchaid. On the
other hand, the; full and healthy covering of foliage on tlie sprayed side
of the trecap])ears to have had no beneficial infhience over the diseased
side. Had it liad any well-niai'ked l)eneficial inlluence the fruit of the
unspraNcd lialf would haxc l)een retained, which wa.s not (lie cas(\
The same local action of the disease, and the same local nouiishing
influence due to the assiniilati\e action of (he heallhv foliauc ina\ be

DESCRTPTTOX OK TLATE XVTI.

Tliis plate shows the condition of one of the trees sprayed on one side at th{' time
of ])icking the fruit. The leaves have l)eeu cut away with prnninjij shears to enable
the i)hotograph to show the fruit upon the sjjrayed half (right side) of the tree, and
the absence of fruit upon the unsprayed half (left side). The sprayed half matured
284.8 pounds of the finest peaclies; the unsprayed half matured only 14.3 i)ounds.
Over 1,100 peaches w'ere thinned from the sprayed half of this tree to enable the
limbs to bear 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, also compare
with Pis. XVI, XVIII, and XIX.)

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

Plate XVII.

DESCRIPTION OF I'LATE XVTII.

Peaches gathered from the tree sprayed on one si(lt> shown in the preceding plate.
The fruit shown on the two drying trays 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 con^j)artment were all that matured on
the unsprayed half of the same tree. The sj)rayed half hore 718 peaches, weighing
284.8 pounds; the unsi)rayed half hore oidy 40 i)eaches, weighing 14.8 jwunds.
(Compare with Pis. XVI, XVTI. an.l XIX.) "

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

Plate XVIII.

l

v^*

V „-

^-

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"P 1

K-

t

t^ w ^^ «* »^ _ ^ _ , .

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DERCRIPTION OF PLATE XIX.

This is a photograph of a limb of the sprayed half of the tree shown in Pis. XVI
and XVII, after the removal of the leaves with pruning shears. A good idea of the
size and perfection of this fruit maj^ be obtained from the plate. The color was
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 Chap-
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.

LOCAL ACTION OF CURL ON FOLIAGE AND FRUIT. 125

seen in the condition of the foliage and crop on the sprayed and
unspra}' ed sides of the other trees inchided 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 rather 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
PI. XIX. The fruit gathered from the sprayed and unsprayed halves
of tree 1 is likewise shown in PI. 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 spi*ayed 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 noneff'ectiveness of the sprays recommended, in controlling curl
under the various conditions of variety, situation, soil, temperature,
atmospheric humidity, seasonal variations, etc., existing in the man 3"
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 efficienc}' 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, whic;h was begun in
the fall of 1893, correspondence was opened with over 1,(300 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 suppljnng the
spray formuhe 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 <;ondu(;ting 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 introductor}- ex])(>rimcntal work
is large and is constantly iiurreasing. In fact, the spraying of p(>ach
tre(!S for curl has become very general in many of the peach-growing
c(!nt<;rs of the United States where the disease prevails.
126

AUXILIAKY WORK. 127

Of the reports which have been received of work conducted by the
growers, 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 reports will be given from the lake shore fruit
belt of Michigan, from, the Willamette Valle}^, 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 carefully tabulated, in as compact form as
possible.

NOTES ON THE AUXILIARY EXPERIMENTS IN MICHIGAN.

A very 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 heartil}^ into
the work, the result being that at present a very large number of
orchardists are annually spra3"ing for curl in that region. The work
conducted by Mr. Hawley involved the testing of a number of spraj^s
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 1891 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 NATURE AND TREATMENT.

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AUXILIARY 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 b}^ 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
shortly 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 could 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
spraying 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 large 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.

Experiment 2:

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
connection 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.

Experiment 3:

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
seems 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.

Experiment 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 C,
and was well done, and the trees now look fine.
1901)3— No. 20 y

130 PEA.CH LEAF CURL: ITS NATURE AND TREATMENT.

October 1, 1894. — The results of this experiment are rather disappointing, as I was
led to believe when I made the estimate of the loss of foliage in Jmie that tlie results
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.

Ejj>erimeni ,5:

June 23, 1894. — The first spraying of this lot was followed by ten hours' rain, the last
spraying by good weather. The treated trees present 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 l)e seen half a mile away.

Octol)er 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 imtreated trees,
but what pleases me most is the very great difference in ajipearance of the trees now.
Those that were treated have made double the growth this season tliat the untreated
hrees 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 this
date less difference to be noted between the treated and untreated trees than in any
other experiment.

Octol)er 1, 1894. — This experiment has resulted about as I thought it would, from
the appearance of the trees in June. 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 U'st results. The untreated trees look as though a bliglit had
struck them, api)earing 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 ))ranch, of (tourse, got sprayed
when the tree was Hpraye<l with which it mingles, and it is as full of leaves and fruit
as tlie treated tree, while the balance of the tree to which it l)elongs is bare of leaves
and fruit.

()cto})er 1, 1894. — The final results of this experiment have proved what I exiR^cted.
Tliere is a greater difference in yield than in any other exi)erinient, while the differ-
ence in ajipearance l)etween 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 lx!en very heavy iK'arers, and consecjuently have
not attained a very large size. They were never very badly affected by leaf curl till
thia year.

AUXILIARY WORK.

131

In the eight experiments described l)}^ Mr. Hawley the percentages
of net gain in fruit of the sprayed trees over the uusprayed were as
follows:

Table 35. — Percentages of net gain in fruit shown in eight spraying experiinents conducted
by Mr. Smith Hawley, of Ludington, Mich.

Experiment No.

Formula.a

Net gain.

Per cent.

191

•16

174

41

Experiment No.

Formula.

Net gain.

1

A

6. .

C

Per cent.
35

9

C

6

A

49

S

B * . ...

B

24

^

B and C . .

8

C

1,424

a See table 34.

Owing to the fact that Mr. Hawlej^'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 6 is pro})ably 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 spraj^ed 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 1)0 per cent of their leaves from curl, while those of the former
experiments lost only 50 per cent. The same evidence is given b}^ the
fruit. The unspraj^ed trees of experiment 8 bore only 3.7 pounds of
fruit per tree, while the unsprayed trees of experiments 2, 4, and 5
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. Hawle}^ was that containing 5 pounds of
copper sulphate, 5 pounds of quicklime, and 45 gallons of water. This
is especiall}' interesting from the fact that this spray also gave the
best results among the 35 formula 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
the following table:

132 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

Table 36. — Experiment No. 9, conducted by Mr. Smith Hawley.

Row
No.

Formula
used.

Variety of trees.

Age of
trees.

Num-
ber of
trees.

Date of .spraying.

Total
yield of
" fruit.

Net gain of
fruit over

yield of \m-
sprayed
trees.

1

A

Hills Chile

rears.
5
5
5
5

6
6
6
6

April 12

Unsprayed

February 8

January 19

Pounds.
270
63
306
189

Per cent.
328

2

do

3 .

C

....do

354

4

A

...do

200

The preceding experiment shows that Mr. 'Hawley obtained from
his Hills Chile trees a net gain in fruit of 85-1- per cent b}' spraying
with the Bordeaux mixture (formula (-), 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 spraj^'^ will act
more quickly than the sulphur sprays, on which account the latter
should be allowed somewhat more time for a(;tion 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 liuds and new growth.

The following are Mr. Hawley's notes on this experiment :

E.vperimeni. 9:

June 23, 1894. — This experiment, althougli on a small scale, lias been very inter-
sting and instructive, and has been noted and admired by all who saw it. The
reea stand on a slope, and a person standing on the opposite slope, only a few rods
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.

Octol)er 1, 1894. — The contrast between the treated and untreated trees is very
great as regards yield of fruit, and the contrast in the trees them.selves at this date is
(juite as remarkable. The treated trees look fresh and healthy and have made a fine
growth, while the untreated trees look sickly and have mad(^ very little growth,
looking, in fac;t, a year or tw(^ younger, as regards size, tliuii tiic others.

Late in the season of 1894 Mr. Hawley tested the sulphur and copper
sprays to ascertain the comparatixc action of the sani(> upon buds
which were considerably swolh'n. lie h>iinic(l tliat the sulphur si)ray
injured the buds to such an extent as to reduce the yield, while it
prevented curl. The copper spray, however, prevented cuil and gave
a decided increase in yield, lie tliiis icaclies Die conclusion that
foi'mula A is more injurious to buds than t'oniuda ('. While this is
ti'ue if the spray is apj)lied at loo late a date, it may l»e safely applied
at an earlier date. It should als(; !)»• nienti()ne(i that (he sul|)hur sprays

AUXILIARY 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 already 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 liut 8 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.

-Experimental work conducted hy Mr. George Lannin, of SoutJi Haven, Mich.,
in the spring and summer of 1895.

[Nature of soil, sandy.]

-= a

Formuloe for

-15 gallons of

water.

Variety of trees.

Age
of

trees.

Number

of
trees —

Date of —

Percentage
of leaves
lost by —

Date
when
loss of
leaves
was
esti-
mated.

Fruit

produced

by—

O o

o

p.

First
spray-
ing.

Second
spray-
ing.

CO

0)

;-<

'O

0)

S'
p.
a

t3

V

1

1

02

01

P.

a

flO lbs. sul-

]

years.

Lbs.

Lbs.

1

) phur, 20 lbs.
) lime, 5 lbs.
(, salt.

parnard

(1

10

10

Apr. 10

May 17

20

40

July 10

1,200

830

2

5 lbs. copper
sulphate, 10
lbs. lime.

Hills Chile

(1

10

10

...do..

June2r)

15

35

...do..

1,300

(500

3

(2 lbs. copper
1 sulphate, ;!
I pts. ammo-
l nia.

Ulales Early ....

IJ

10

10

...do..

...do..

20

40

...do..

1,7(50

080

4

[5 oz. copper
1 carbonate, 3
j pts. ammo-
[ nia.

Crawfords Late.

(;

10 10

...do..

.Tune 8

10

30

...do..

1,800

700

The spray formula? tested by Mr. Lannin were not included in the
work of Mr. Hawley, and are therefore characterized as Formula? D,
E, F, and G. As Mr. Lannin sprayed different v'arieties of peach trees
with 4 formulae, the experiments can not l)e compared with one another

134

PEACH LEAF CUKL: ITS NATURE AND TREATMENT.

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 1.57 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 unspra3^ed 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
carl)onate, 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 jdeld 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 88. — Experimental work conducted by Mr. F. N. Chesehru, of South Ilavai, Mich.,

in the spring of 1894.

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

Formula.

fl5 lbs. sulphur
I^Olbs. liiiK'....

10 lbs. salt

loo gal. water . .

Number of

Per cent of

trees—

be

leaves lost by—

•/

o

o

a;

0/

2
a.

-O

i2

d

>■.

Of

■a

>-.

'o
to

s

0.

a

3i

a

<

02

o

«

«j

0

Vcurn.
1

1 "

m

38

Mar. 7

•20

80

Date
when

loss of

leaves
wius esti-
mated.

Mr. J. F. Taylor, of Douglas, Mich., reported favorably upon the
spray work conducted by him in 1894. He used three different spmys,
treating 50 trees with (!ach, and leaving a lik(^ luunbcr unsprayed
for comparison. The formula' used wert^ those designated as A, B, and
C, in th(; spray work of Mr. Smith Hawloy. Mr. Taylor says, in regard
to his work:

Tlw hlosHorii I)ii(1h liail hwoUcii Homowhat when I iK'^ii'i H])rayin>i, but tlu- U'uf hiulH
vviTC! fiuiU; (loriiiiint. Foriiiiila ;\ was used on March 2(1, Formula 15 on April (i, and
Formula (; on .Xprii 20. HloHHoms be^an to open on tlie la-^t dayn of Ai)ril, and by
the (iih of May trees were well covered with bloom. The tree.M sprayed were (5 years

AUXILIARY WORK. 135

old, and of the following varieties: St. John, Barnards 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 as
any of them.^

After the trees were in full l(;af I invited neighboring fruit men to go through the
orchard and note the conditions of the trees sprayed and misprayed. They found
the foliage of trees that had been sprayed almost fr(« from curl, while the imsprayed
trees were badly curled. * * * The misprayed 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 number unsprayed for
comparison. The crop from the sprayed trees Avas 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 an 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. "^

NOTES 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 the same formula that waa found very satisfactory by Mr. Smith Hawley,
at Ludington, Mich., and by the writer in the Sacramento Valley.

^ There are thousands <jf such peach orchards in the peach districts of the United
States. To those who are interested in the renewal of yomig and bearing wood upon
lower limbs and upon old trees, the writer would refer to the data presented in Chap-
ter V of this })u]letin, wliere the influence of sprays on the vegetation of trees haa
been quite fully considered.

136 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

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

The great rainfall Avhich 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 facts,
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 189-1: 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 ]\lr. ]\1. O.
Lownsdale. of Lafayette, Oreg. This gentleman conducted very
extensive spraying tests according to plans supplied hy the Depart-
ment, both in 1891 and 1895, 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 ga^e 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 j'ou herewith my report of experiments for the prevention of peach leaf
curl for the reason of 1895, to which 1 de^^ire to add a few' words u{)on the status of
the peach industry in the Northwest.

Peach {rrowing has been abandoned to a great extent in the Ayillamette Valley
because of the attacks of the shot-hole fungits and leaf curl. (Irowers have not
understood the causes of their tn^ubles, and liave attributed them to peculiar climatic
condition.*, or have grouped them under tlie indefinite term blight; but now that the
nature of these fungous troubles is ])etter understood, and the remedies suggested
have proved so efficacious, it seems that the abandonment of the industry mav have
l)een premature. The success of the i)reliminary experiments has restored the con-
fidence of orchardists in a great measure, and as it becomes widely known that our
fungoTis troubles can be controlled, increased attention will be given to peach
growing.

Kxperiments through a .series of four years on a block of (J acres of Early Char-
lotte ))eaclR's indicate that it may be j)ossible to prevent these destructive fungi
from getting a footlwjld in an orchard. This block of trees, which was i)laiitcd in
dormant bud, has received an annual treatment in October and two treatments eacli
spring with the ammoniacal cojiper carbonate, with the excei)tion of the si)ring of
]HUr>, when your modified Bordeaux was apjtlied. Neitiier leaf curl nor sliot-liole
fungus has develoi)ed in this block. A faircroj)of fruit was harvested this sununer —
tlie fourth from the bud — and the trees are healthy and have grown luxuriantly. If
intending jilanters wtmld select perfectly healthy trees — (Mther yearling or dormant
buds — and would give them one treatment in autumn, jis the Department has sug-
gested, in addition to the sjjring treatment for leaf curl, it is i>robab]e that lu-acli
growing would again })ecome pro(ital)le in the Willamette Valley. I am convinced
that if the edicacy of the niodilicd I'xirdcaiix iiiixtiirc for the coMtnil of leaf curl
hid been known live years ago tlif industry umild have been liourishing to-day, for

AUXILIARY WORK. 137

with the treatment for leaf curl, which adds so much vigor aud sturdiness 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 difh-
cult for the great shot-hole wave to sweep over our orchards as it did in 1893 and
1894.

The (juality 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 attemj^t 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 fimgous
attacks will be widely adopted.

The spra}" work conducted b}^ Mr. Lownsdale in the spring of 1894
involved the sprajdng of some 1,700 3'oung trees and the testing of
10 spray formulae. 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. All the spray
formulae prepared by him were for 15 gallons of water:

Thirty acres of peach trees were devoted to experimental work under your direc-
tion. These trees were Crawfords Earl}- and Earh- Charlotte (a seedling from the
Crawfords Early) . In addition to these tests 10 acres were left wholly untreated
as a block check against the main experiments. All these trees were 3 years old,
and 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 work 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 of the sprayed trees, while 60 per cent of
the foliage of the untreated controls was affected.

Formula B (5 pomids sulphur, 10 pomids 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, while 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 pomids 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 ))adly affected that they scarcely survived the sunmier.

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 clieck trees. About 5 per cent of curl developed on treated trees,
while the check row was very badly injured.

Fornmla J (4 pounds copper sulphate, 5 pounds sal soda, 3 pints 26° anmionia) was
appliccl 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.

138 PEACH LEAF CURL! ITS NATURE AND TREATMENT.

Formula K (5 pounds sulphur, 15 pounds lime) was applied ^larch 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 foliage of the treated trees, while the check rows
were, as in the previous year, a mass of curled leaves and twisted V)ranches. 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 18 and
again March 21 to 262 trees, with 7 check rows interspersed through the l)lock. Less
than one-fourth of 1 per cent of curl appeared on the treated trees of this test, while
the check rows were almost destroyed by the disease. The greater ])ortion 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 anmioniacal copper carbonate, Formula M (5 ounces copper carbonate, 3 pints
26"^ ammonia) , was applied March 22 to 210 trees, 2 check rows oi 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 j)re-
served them, the previous year, and I feared a change.

All my treated trees have grown satisfactorily this year, ))ut the 10-acre check
block of untreated trees was so nearly destroyed by curl that all the trees will be
dug up. Several hundred are dead, and of the remainder I think no tree has had a
growth of 12 inches.

It will be .seen from Mr. Lownsdale's report of the work in 1894
that several of the sprays used gave most excellent results. On May
18 of that year he wrote:

Curl ha.s 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 (Fonnula J) is also giving good results, as is the 5 pounds
of sulphur and 15 pounds of lime; but I believe 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 ])e obtained from Mr.
Lownsdale's expcirimcnts in 1894, as the trees were yet too small,
arrano-ements were made for the testing of some of the more valuable
spravs in the spring of I8t>5. The experiments of 1895 siiow the gain
in both foliage ajid fruit, though the yield was low, resulting from the
u.se of 5 sprays — 1 sulphur and 4 copi)er. The expcu'iments were con-
fined to the Crawfords Early variety, and in each experiment the trees
received two sprayings in March. All trees were 4 years old, Imt
rather small. Mr. Lownsdale's data on this work arc })i'cscnted in
th(! followinLf tiiMc:

AUXILIARY WORK.

139

Table 39. — Experimental work conducted by Mr. M. 0. Lownsdale, of Lafayette, Orey.,
in the spring and summer of 1895.

[Variety of trees, Crawfords Early; nature of soil, red hill.]

Formulse for 45
gallons of water.

[10 lbs. snlphur . . .

20 lbs. lime

[5 lbs. salt

[5 lbs. copper sul
phate

10 lbs. lime

['2 lbs. copper sul-
phate

1 3 pts. ammonia. . .

|5 oz. copper car-
bonate

[3 pts. ammonia..

[5 lbs. copper .sul-
phate

15 lbs. lime

Age

of

trees,

Yrs.

Number
of

trees.

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-

Perct.
10

Tr i-
fling.

Per ct.
35

35

30

30

40

Date
when loss
of
leaves
was esti-
mated.

June IS
....do...
....do...
....do...
....do...

Fruit pro-
duced by—

Lbs.
346

480

807

1,264

1,048

Lbs.
187

62

193

But few comments upon the preceding table are required. It makes
the fact perfectly evident that two spring- sprayings are sufficient to
almost absolutel)^ control leaf curl in the Willamette Valley. In a
letter written June 25, 1895, Mr. Lownsdale says:

Peach leaf curl 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
sprays with lime, 10 and 15 pounds, and copper sulphate, 5 pounds, were an abso-
lute success. Lime in the amount of 15 pounds gives the best results, there l)eing 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 find 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 intermedi-
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 unspra3^ed 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.
Unfortunateh', frost killed the buds, and no comparison of fruit was
possible, but it is safe to say that the fall of 90 per cent of the leaves
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 trees
sprayed with the bluestone mixture look the best of any in the
orchard."

Mr. Bennett used the 5-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 with this work is,
however, that the variety treated was the El])erta, which is probabh'
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 jul)ilant over the success. 1 have reported only the
Elherta variety, as it was one of that kind which I left unsprayed. I am more than
pleased with the results, and can say tliat a good trial is all that any man needs who
has the welfare of his orchard at heart (his poeketbook 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 those
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 tlie tree,
nearly hah" of wliich packed 56 peaclies to the l)ox. 1 sprayed 75 Wheatland trees
witli the same sncicess as far as leaf curl is concerned. They are fine, liealtliy trees
n(jw, and bore a good crop this season. They have been bad about curling, l)ut I
left an Klberta l)ecause that variety is the worst to curl, and if si)raying 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
compai'ison. The fonnuhi used by Mr. Olwell was 1 5 pounds of sulpliur,
30 pounds of lime, and 1<) pounds of salt to (!0 gallons of watei-. Ilis
trees were 5 years old, growing in black, loamy soil. They were
sprayed Mar(rh 10. The sprayed trees did not lose any foliage from
dis«!ase, while the control trees lost 25 per cent. The fruit records
were not r('i)()ited.

NOTES ON THE AUXIMAllY KXTEKIMENTS IN (CALIFORNIA.

Besides th(^ experiinciilid work conducted by the writer in lh(> Sac-
ramento Valley in the years l!S!>4 and !S!)5, a coiisidcriibic number of
groweis assisted in canying on experiments in dillerent portions of

AUXILIARY 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 reports is one
from Mr. A. D. Cutts, of Live Oak, Sutter County. The work was
carried out in the winter of 189ii-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 spra}' was not used in 189B for the
control of leaf curl, but was applied for the purpose of destro^ang the
San Jos^ scale, which was gaining a foothold in the orchard. The
trees infested by scale were scattered through a 40-acrc 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 15 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 lirst, second, and
third quality peaches. The same facts are given for an equal num-
ber of neighboring unsprayed trees for comparison.

Table 40. — Experimental vjork conducted by Mr. A. D. Cvtts, of Live Oak, Cal., in the
spring and summer of 1893.

[Crawfords Late, 4 years old.]

Sprayed trees.

Unsprayed

trees.

Total pounds of—

Number of —

Total pounds o

f—

Number of —

>,

X

^

^_

>>

x

j^

>.

j,_.

^

ai

ci m

Ci 72

cS

C3

cS x

03 Ji

tree.

3*J

3<J

S-^

%Z

P*i

0^2

3*;

3 aj

3 CD

^a

^d

■ii;

^ cS

-S 03

'C as

•,S

■Oil

^i^

Jj CS

-r,^

-o^

u

m 1>

S a)

c^

m 0)

C <"

t

o

u^

c ft

••-■

o

oft

E

J5

S

1

E

CO

.a

Eh

s

1

156

115

32

9

276

96

29

41

23

12

6

102

56

56

2

226
180
119
180
176
279
55
126

189
145
100
146
154
225
38
106

20
28
13
25
17
34
12
15

17
7
6
9
5

20
5
5

735
615
385
605
568
815
148
367

126

no

70
138

86
161

60

65

130
45
54
60
32

139
30
27

2
1

2
1

4
3

3

4

5

2

2

5

6

7

1
3
8

'""?,'

1
3

8

8

9

18

Total.

1,497

1,218

196

83

4,514

902

546

58

31

21

6

120

79

56

The average yield of fruit of the sprayed trees given in the table
was 16(5.22 pounds per tree, while the average yield of the unsprayed
trees was but 6. -14 pounds. This represents a gain in fruit by the

142 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

sprayed trees above the yield of the unsprayed trees of 2-4.8 times the
jdeld of the latter. In other words, there was a gain in 3'ield of 2,481
per cent from spraying-. Much valuable information was also supplied
b}' Mr. Cutts in relation to the preparation and application of sprays,
and the writer has considered these subjects in other portions of the
bvdletin. Some of the more striking photographs of spraj'ed and
unspraj^ed 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. Gaylord, of Auburn, Placer County. This experiment was
made in the spring of 1895. 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
unspraj-ed nectarines curled so badly that they bore no fruit at all,
while the 4 sprayed trees jdelded 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 i)erfectly satisfactory. I sprayed some peach and some
nectarine trees, both with jrood results. One nectarine tree si)rayed has not a curled
leaf, while one of the same kind, a])out 15 feet from it, which was not sprayed, has
lost nearly all its leaves. The contrast is so great that it would be worth while to
have them photographed. A neighbor, Mr. G. P. Dixon, used formula .S (2 pounds
copi>er 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. Gaylord also states that no heaves were lost from the peach trees
sprayed, while all of the leaves curled on the unsprayed trees of the
remainfler 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 lim(% 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.

Ml'. VV^oolsey gives some notes respecting the work in the s])ring of

1895, as follows:

A block of about 200 trees, Salways 12 to 15 years old, on well-drained soil, and
500SalwayH4 years old, atijoining, I did not spray, thinking they were curl i)roof.
I regret 1 did not si)ray them. * * * The leaves are dropping, as well as a large
percentage of the fruit. 1 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. Cuttf>,
Live Oak. The tree at the right was sprayed in February, 1893, with lime, sulphur,
and salt; the trees at the left were untreated. See "Notes on anxiliary experi-
ments in California," for a full account of the work at Liveoak. (Photojjraphetl
in May, 189:5, after most of the disea.sed leaves had fallen from the unsprayed trees.
Compart' witli Pi. VII.)

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

Plate XX.

AUXILIARY WORK. 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 jjortion of the fruit. The adjoining sprayed trees of this tender variety
are all right (no cnrl) 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 peacli 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 jieach and apricot trees. I say nearly all; for, time press-
ing, I foimd I would not get over all the peaches, so to save what I considered the
most valuable portion, viz, the young lower growth, I liad that sprayed and left the
tops unsprayed. The season w^as 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-
ment 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 formulae, 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. Ho sprayed GOO trees, 3 years old,
of the Hales Earlj^, 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 unspraj^ed
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
3^ears a formula for Bordeaux mixture which gave the writer exceed-
ingly good 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: "I 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 spray in the experiment
block at the Rio Bonito orchard, in the summer of 1895.

1-14 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

NOTES ON THE AUXILIARY EXPERIMENTS IX NEW YORK, INDIANA, AND
OTHER PEACH-GROWING STATES.

Much experimental work for the control of leaf curl has hoeu under-
taken at the suggestion of the Department ))y the peacli growers of
New York, Indiana, Illinois, Ohio, Kentucky, Maryland, Penn.sylva-
nia, Georgia, Tennessee, North Carolina, Arkansas, Missouri, Kansas,
and other peach-growing States not already considered in this bulletin.
For instance, SO prominent peach growers of various peach-growing
centers of New York were given full instructions for the control of
curl in the winters of 1893-01: and 1891—05, and requested to report their
work, Avhich in a luimber of instances Avas carefulh' done. The same
is true of 51: growers 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 arc full}' 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 ]\I. Cravens, of Madison, Ind., i-eported almost a])solute
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 pi-r cent. Mr. Cravens states in a letter
accompanying his report that he sprayed separate rows through his
orcliard which were sufficiently far apart not to have the spray affc^ct
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 Api'il 0, 1804, and left 25 trees at their side
without spraying for comparsion. On May 28 only 42 diseased heaves
were found on the 25 sprayed trees, while as high as 40 per c(>nt of
curled foliage was i)resent 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 28
only 51> curled leaves had developed on thc^ entire 25 sprjiyed trees,
whih; 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 tiiat among the
50 trees treated not one showed an appr(>cial)le amount of disease,
while all through the orchard trees weic badly aflecti'd, was to him
veiy satisfactory evidence of tiie value of the licatmeiit, es[)eciully 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 189-1:, 1895, and 1896 he made the spray tests on peach trees
for leaf curl which had been suggested by the writer, and says he
is 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 Ridgewa}^ N. Y. , states in his report of
spray work for curl that he treated 208 trees and left 320 trees
unspra3^ed. 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 66 to the basket. From 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 OF

THE SPRAYS USED.

PREPARATION OF THE COPPER SPRAYS.

It is not the intention to consider in this place the man}^ forms of
copper spra} s 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 f ormukie 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 carefulh^
studied. Several other formuhe 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 formulfe 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 formula?. Each formula is that used with
45 gallons of water, except the first for Bordeaux mixture, which was
with 48 gallons.

Table 41. — Copper spraya applied for the coiilrol of peach leaf curl.

Copper sulphate solution:

*4 j)otindH copper sulphate, 45f;;allons -water.

*2 pounds copper sulphate, 45 fralloiis water.
Bordeaux mixture:

t24 pounds copper sulphate, 45 pounds lime.

*6 fiounds copper sulphate, 15 pounds lime.

t 5 pounds copper sulphate, 15 pounds lime.

*'i i)Ounds <;opper sulphate, 15 pounds lime.

to pounds copi)er sulpliat-e, 10 ])ounds lime.

*5 pounds copj)er sulphate, 10 pounds lime.

*3 i)Ounds copper sulpliate, 10 pounds lime.

*5 poiHids c(tpper sulphate, 5 pounds lime.

*4 pounds copp(>r sulphate, 5 pounds lime.

*:i pounds coi)per sulphate, 5 pounds lime.

* Prepared and tested l)y the writer, aiid in many cases also tested by jrrowei-s.
t Chosen and tested ])y >;rower.

t Recommended hy the writer, hut tested hy the growers.
14(j

PREPAKATION OF THE COPPER SPRAYS. 147

Bordeaux mixture — Continued.

*2 pounds copper sulphate, 5 pounds lime.

*6 jjounds coi)per sulpliate, 4 pounds lime.

*6 pounds copper sulpliat(>, 3 pounds lime.

* 3 pounds copper sulphate, 2 pounds lime.
Eau celeste:

*4 pounds copper sulphate, 8 pints ammonia (26°).

*2 poiuids copper sulphate, 3 pints ammonia (26°).
Modified eau celeste:

*4 jiounds copper sulphate, 5 ])ounds sal soda, 3 pints ammonia (26°).

*2 pounds copper sulphate, 3 pounds sal soda, 2 pints ammonia (26°).
Ammoniacal copjier carbonate:

*5 ounces copper carbonate, 3 pints ammonia (26°) .

*3 omices copper carbonate, 2 pints ammonia (26°) .

* Prepared and tested l)y the writer, and in many cases also tested ])y growers.

The preparation of the copper sprays containing- different chemical
constituents will bo considered in the order in which they appear in
the preceding- list.

COPPER SULPHATK SOLUTION.

Copper sulphate (CUSO4.5H2O), 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 ])y 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 spraj^s, 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 CURI/. 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 60
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 l)arrel 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 nux}" 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 chenucal
near the top of the water. If this can be done, the heavier copper
solution will settle to the bottom of the l)arrel, leaving the purer
water to continue th<' 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 ma}' 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, sacks,
f raj^ed staves, and stirring sticks, the less trouble the spra3'"er 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 ])askct 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 l)e open at the top, with strong 1-inch slats across the ])ottom,
the latter to be set one-fourth inch apart. If the ])ox be fitted with
a strong hoop bail it may be suspended in the barrel l)y placing a stick
through the bail and across the top of the barrel. As a rule, how-
ever, the writvr has found it sufficient to place the copper sulphate
directly in the bottom of a good oak barrel, tilling tlie 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 woi-k is sufficient to dissolve
many pounds of copper sulphate in this maimer. With three or four
good barrels one man can thus keep a large spraying gang supplied
with material, if the water l»e convenient. It is always an advantage
to place tli(! copper in water in the bai'rels over night, when i)()ssible,
as sufficient material is thus easily made ready in the morning for a
half day's spraying. It is jin advantage to strain all water before the
(•<)])per sulpiiate is added, as afterwards oidiiiary strainers are liabU^
to be injured by the acid, and, as lu'fore stat(>d, the use of cloth
straiiiei's is not advisable.

The «^yes and liands sliould be protectiHl as nuicii as possible from

PREPAKATION OF THE COPPER SPRAYS. 149

injury by 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 alread}^ 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, otherwise the
last dipped out will be vevj much stronger than that coming from the
top, and consequentl}^ the work will be inaccurate and often very
unsatisf actor}' ; 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 MIXTURE.

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 rules for measuring square and round tanks and casks may i)rove
of value in this connection:

Circular cistemn. — Multiply the square of the diameter in feet by the depth in feet
and the product by 5| for the contents in gallons.

Circular cai^ks or harrek. — 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
naay 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 7j%%, 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 b}^ 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 haA*ing great value as a general fungicide,
and, as alread}^ 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 mixture 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 Avork. (8) The lime of Bordeaux mixture causes the spray
to become visible upon the trees sprayed, and Avhile 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 summers 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 Avinter, is claimed to retard the develop-
ment of the buds. The unsprayed trees absorb more heat, which
causes the ])udH to swell during Avarm days in Avinter, thus making
them liable to injury from su])se(juent cold.''

The methods of preparing Bordeaux mixture for large and small
orchards may vary according to the ro([uircments and faciliti«>s of tlu'

' Ivfulemun, E. (i., Tlui Si)ruyin>^ of Plant.M, ]\[ac'iuillaii & Vn., 1890.

'Kaircliild, D. (i., Bordeaux Mixture as a Fungicide, Bull. No. 6, Division of Vege-
tiihle Pathology, U. S. Ik'pt. of Agr.

» Wliitt<-n, J. C, WinU'r Protection of the Peach, Mo. Agr. Exp. Sta. Bull. No. 38.
Sf)nie of the conclunioiiH from the work f)f Mr. Whitten are: Whitening the twigs and
VnidH by Hprayiiig tlictii with whitewa.«h is the iiiont i)roniising method of winter ])ro-
tection tried at the Misaouri Station; wliitcticd l.ud.s remained practically dormant

PREPARATIOISr OF THE COPPER SPRAYS. 151

growers, but the general principles involved remain the same. AvS a
common example, the manner of preparing the 5-pound formula will
be described: In a 45 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 15 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 118 and
119, 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 loassed the winter safely, and only
20 per cent of unwhitened buds jjassed the winter imharmed. 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 c(juntry where the buds are liable
to winter injury. A fall spraying may also be a decided advantage in such situations
in addition to the early spring spraying for curl.

See also on this subject the January nmnber 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,
tlie 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 water, 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 j)our off the mixture
carefully. If a red precipitate is found at tliel)ottom of the cup, the mixture requires
more milk of lime, which sliould be addcil until no smjh 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 spra}'. In nearly all the for-
mulae 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 l)est quality. There is no economy in using
poor lime, and air-slaked lime should neyer 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 yery 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 consistency
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 pve-
vent drying out. If the Bordeaux mixture is then to be made, cold
water should ])e added to the lime J^utty, 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 s])ray is to be applied.
When making Boi-deaux mixture wooden vessels should be used, as
l)arrels, half ))arrels, tanks, etc.

For peach leaf curl the amount of copper sulphate and lime to ])e
used to 45 gallons of water will vary according to the views of tiie
growei-, after making a study of the results obtained from the diti'erent
foi'inulic tested in the present series of experiments.

KAU CKIJOSTK.

The pr(;parati()n of can celeste is veiy siMipl(\ To each 2 })ounds
of copper sulphat(! dissolved in <> oi- S gallons ol" water add .'5 pints of
strong ammonia, stir thoroughly, mimI dilute to 4^> gallons. 'I'lie stock

PEEPAEATION OF THE COPPER SPRAYS. 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 spraying outfit.

MODIFIED EAT 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 nearl}^ 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 maj^ 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 use 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 kss satis-
factory than several of the other copper spraj^s.

The manner of preparing this spray is simple. Place 5 ounces of
copper carbonate in the bottom of a 3-gallon crock. From a 2-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, read}" 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 spra}" of any desired strength.

The copper carbonate used in the preparation of the present spraj^
is frequently not obtainable in quantity at the drug stoi-es in smaller
towns. It is also frequently the case that druggists in sucli places
charge two or three and s(mietimes four or five times as nuich as it is
worth, making the ultimate cost of tlie spray Ixnoiid the reach of the

154 PEACH LEAF CFRL: ITS NATURE AND TREATMENT.

grower. For this reii:?on the writer gives, on page 1S3 of this bulletin,
a simple way of preparing the copper carbonate on the fann at a
minimum figure.^

PREPAKATIOX OF THE SrXPHTTB SPRATS.

While the use of copper sulphate as a base for sprays intended for
the control of fungous diseai:es is veiy genei"al. there are special dis-
eases or combinations of diseases which may be more cheaply, and
often more successfully, treated with sulphur in the fonu 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
sidphur possesses valuable insecticidal qualities, and many of the scale
insects and mite diseases of our fiiiit trees may be readily 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 Jose scale on the Pacific coast has been by sulphur
sprays. This scale is 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 ciu'l. when the tree is dormant. It
has already been shown in this bulletin that such a winter treatment
of the peach tree with sulphur spi-ays will also control peach leaf curl.
For this reason, and the fact that the San Jose 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 scoui'ge over much of the Ea<-t and in the Pacific Northwest.

As in the ca.se of copper sulphate sprays, it has also been found
that the sulphur sprays may be most satisfactorily prepared by com-

' In view of the work of ifr. C. L. Penny, published in Bulletin 22 of the Delaware
Agr. Exp. .Sta., 1893, the amount of water recommended to Ije added l>efore the strong
ammonia water i.< ])oureil ujxm tliecarl)onateof copper is nmch greater than formerly
used by the Department. Mr. Penny conducted a somewhat extended series of
experiments to a.«certain the s^olubility of copper carlx)nate in ammonia gas as it is
contalne^l in ammonia water of different strengths. He found that a given amount
of ammonia gas in a weak s<dutionof ammonia water dissolves more copj)er than the
same amount of gas in a strong sohition. A given weight of ammonia gas in a 2 to 4
per cent .S4jlution of anmionia 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 I'ent
ammonia water will dissolve its own weight or more of copi>er carl>onate. On tlie
other hand, tlie aumionia gas in a 10 per cent sohition of ammonia water will dis-
solve but 60 i>er cent of its weight of copi>er carlxmate, and anmionia gas in a 20 per
cent solution diss<jlvea only alx)ut 3.5 jK'r cent of its weight of copjx^r. Furthermore,
the ammonia ga.s containe*! in ammonia water of U-ss than 2 jH'r cent stn-ngth rapidly
loueti its power to dissolve copi>cr <-arlN>nat«.' jis tlie .-roiutiuu is weakened.

PREPAKATION OF THE SULPHUR SPRAYS. 155

bining sulphur with lime. Salt has also been used in connex^tiou with
these sprays in several f ormulse.

In the following table are shown the various formulae 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 the control of peach leaf curl.

* 15 pounds sulphur, 30 poundn lime, 10 pounds salt, 60 gallons water.

* 10 pounds sulphur, 20 poiuids lime, 10 pounds salt, 60 gallons water.
1 15 pounds sulphur, 30 pounds lime, 10 pounds salt.

* 10 pounds suljjhur, 20 pounds lime, 10 pounds salt.
1 10 poinids sulphur, 20 pounds lime, 5 pounds salt.

* 5 pounds sulphur, 10 pounds lime, 5 pounds salt.

1 5 pounds sulphur, 10 pounds lime, 3 pounds salt.
1 15 pounds sulphur, 30 pounds lime.

1 10 jjounds sulphur, 20 pounds lime.
1 10 pounds sulphur, 8 pounds lime.

1 6 pounds sulphur, 4 pounds lime.
1 5 pounds sulphur, 15 pounds lime.
1 5 pounds sulphur, 10 pomids lime.
1 5 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 sprays 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 CUKL: ITS NATUEE AND TREATMENT.

spra}' 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 hj the formula. The spray maj^ 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 effective
and easier to apph" 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 many 3^ears.
In the series of experiments here described, however, an effort has
been made to ascertain if salt is necessary in this spray, and also
whether there is any disadvantage in uniting all of the lime and sul-
phur at tirst. 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 different times with those prepared 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 the
omission of salt, and further, that all of the lime and sulphur })e united
and reduced with boiling water before the cooking ])egiiis in all cases
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 the}' may be boiled
much more uniformly, more easily, and oftentimes better in l)arrels or
wooden tanks hy using live steam as the source of heat. These facts
are widely recognized on the Pacific coast, and the knowledge is put
into practice })y some of the leading fruit growers, many of whom
have established special steam cooking plants for ])reparing and hand-
ling the sulphur sprays. Some of these spray-crooking appliances are
on ([uite an extensive scale and others more limited, Ix'iiig adapted to
the needs or facilities of the growers. As the sulj)hur 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
particulai'Iy intended for winter a])plic:iti()n to all d(>ciduous trees and
are known to be of marked value l)oth as insecticides and fiuigicides, the
more; improved methods of preparing them Avill b(> of general interest
to orchaiflists. and several are her(> given. Thre(> tyjx's of cooking
plants are described: (i) One ada])ted to the needs of an orchard of 10
acTes, (2) one suited to the needs of an oicliaid of loo acres, and (3)

PREPARATION 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 spra}^ is boiling in the ))arrel. 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 l)eing 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.
Where 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 ma}' 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, w hile the third
is filled with l)oiling water for use in slaking lime, filling the barrels
after the sulphur is added, and reducing the spra}- 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 ma}-^ be sent to the orchard about once an
hour, after allowing each lot two hours of constant boiling. In pre-
paring the spray for ])oiling, 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 ver}^ 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 re(|uired 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 off 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 CURL*. ITS NATURE AND TREATMENT.

spray required b}' the formula, and this is then drawn oti'. Before a
new charge of spray materials is placed in the ])arrel, the latter should
be removed from beneath the steam pipe and cleaned. Convenient
boilers suited to boiling one or more barrels of spray are show n in the
illustrations given. (PI. XXI.)

For orchards of 100 acres the boiling of sprays in l)arrels i.s 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, ])uilt 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 each
end to hold the head in place, and in addition the planks arc nailed
together with -iO'* cut nails. Each 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 by 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 otf 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 l^-inch pipe leads to near the
ends of the tanks. This is coimected with a transverse 1 -inch horizontal
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.
Til rough each side of that portion of the 1-inch pipe which extends
along the inside of the bottom of each tank arc drilled 0 small holes
for the escape of the steam into the tanks. In the pij)e leading to
<'ach tank is placed a glolx' valve for separately controlling or ])rcvcnt-
ing the liow of steam to each of the tanks. A\'licii a (aide of spray is
ready to go to the orchard, the spray is run into another taidc situated
on a low truck wagon, the tru(^k IxMiig first driven under the end of
the ))oilitig taid< which is to be empti<'d. The low truck with (he
spray is then di-iven (o the spi'ay tatiks in the oichard, and (iu> spray
is punijx'd from the truck (ank (o the spray (ank, wi(h<)ut delaying
the work of (he spi'iiyei-s. Thesj)ray is strained (wice, lirs( when <h-awn
oil from (he boilino- \jits tlirouuh (lie faucet, and second when it is

DESCRIPTION OF PLATE XXI.

Steam spray-cooking applianoe!* for small orchards. Figs. 1 and 3 show boilers snited
to cooking sprays in 1 to 3 barrel lots; fig. 2 shows a boiler connected with a tank in
which larger <]uantities of spray may he lx)iled at one time. These cooking appli-
ances are well adaj)ted to use in ten-acre orchards (p. 157). (Compare with PI.
XXII. j

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

Plate XXI.

PREPAKATION OF THE SULPHUR SPRAYS. 159

piiinpod from the truck tank into the spra^v 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 da}'', 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 600 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 orchard. The water for preparing sprays at this
orchard is obtained from a well and is forced b}" 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
fiUed. 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 boiling tank 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-
ing 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 CUKLI ITS NATURE AND TREATMENT.

are closed. Along l)oth 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 b}- means of a glo])e valve
in the steam supph' pipe, the valve being conveniently placed for the
workman at the tank. Broad l)oard covers are made for covering the
whole tank when the boiling is in progress. As in the cas(> 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 sufficienth' 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
spra3\ When it is desired to till 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 pipe
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 su])ply are
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 foi'm a vacuum, soon causes a combined
stream of hot spra}' and cold water 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, HUing the 800-gallon stoi'age tank with
spray of the required strength, the strength of the spray in the boil-
ing tiink Ix'ing dou])le'that re(|uired. This work is accomplished ])y a
careful adjustment of tla^ inflow of steam, spray, and water to the
injector, the storage tank being filled without the necessity of lifting
a pound of spray T)V 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 otheiwise become
too high for efficient work. When the storage tank is full, steam is
turned into the pi})es situated at its bottom, and the s])ray is again
heated to the boiling ])oint and kept very hot until drawn ofl' into,a
spray tank and taken to tiie orchard. The facility with wiiich a plant
<;f Ihis description may l)(^ ojx'i'ated will depend to (luitc^an extent u])()n
the nature and capacity of the boiler used foi" generating steam. The
njore easily steam can bo generated and the greater ca})acity for steam
which the boiler possesses the better for the work.

Bull. 20, Div. Veg. Pnys. & Path., U. S. Dept. of Agticultur

Plate XXI

Steam Spray-cooking Appliances for Large Orchards.

DESCRIPTION OF PLATE XXII.

Fig. 1 shows i^ulphur, lime, and salt spray-cooking aiipliances used on tlie Rio Bonito
Raneho. The lieavy 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"\vhich steam is issuing. This rectangular vat, described on yrnge 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 filled from the cooking vat by means of a steam
injector, described on pJige 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,
standmg 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 corner stakes at the back of the wagon. These stakes serve to prevent
the hose from falling beneath the wheels, as all lines of hose extend from the rear of
the wagon when in use in the orchard.

PREPARATION OF COMBINED COPPER AND 8ULPHUR SPRAYS. 161

By referring' to PI. XXII and the descriptions of tigures the
reader may obtain a good idea of the arrangement of this extensive
spray cooking pUint, as well as of the ])oiler supplying steam.

PREPARATION OF COMBINED COPPER AND SULPHUR SPRAYS AND NOTES ON
OTHER SPRAYS TESTED.

For many years the use of coml)ined copper and sulphur sprays has
t)een practiced ])y peach growers in Oregon, and as they have reported
good results the writer prepared the following four fornuihe of this
character for the control of curl.

BORnEAUX MIXTURE AND StTLPIIUK SPRAYS f'OMniN J':i).

The formula of the combined Bordeaux mixture and sulphur
sprays tested are given in the following list:

Lifit of ftuJpJnrr >f}>raiis cotnliincd irllli llordeanx mixture.

8 poundy ('()])per sulphate, 10 pounds sulphur, 20 pounds lime.
.S pounds copper sulphate, 10 pounds sulphur, 10 pounds lime.
'?> pounds copper sulphate, 5 pounds sulphur, 10 jumnds lime.
2 pounds copper sulphate, •"> pounds sulphur, 10 pounds lime.

In preparing these combined sprays, which were found somewhat
moi'e effective in the control of peach leaf curl than the sulphur sprays
alone, the Bordeaux mixture was added to the fully prepared sulphur
spra3^ A portion of the lime given in the formula was reserved for
making the Bordeaux mixture, while the remainder of the lime was
C(nnbined and boiled with the sulphur in the manner already described.
When the sulphur spray had ])een placed in the spray tank, the Bor-
deaux mixture, which had been freshly prepared from the copper
sulphate and the remainder of the lim(\ was added, and after thorough
mixing was at once applii^l to tlie trees. The luiion of the yeliow
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 sam(> class of nozzles.

MISCICI.I.ANKOIS srUAVS.

A large number of sprays not includcnl 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 spra^^s, 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 potassimn,
applied in various strengths in li(iuid form, and the union of this sul-
phide of potassium with milk of linu^ was also testinl. Iron sulphate,
1901)3— No. 20 11

162 PEACH LEAF CURL: ITS NATURE 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 consideral)le fungi-
cidal action, none of them gave results which would warrant their
substitution for the spra3'^s alread}' considered in previous chapters,
and hence it is unnecessar}^ 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 unsuital)le for various classes of work, and to these it
may be well to allude.

THE ENDURING QUALITIES OF THE SPRAYS.

In the worK here described careful notes were made on the enduring
or weathering (lualities of the sprays tested.

During the last week in April and first week in March, 181)5, 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 shown. 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 appearance of the sprays upon the trees, after five months' weather-
ing, may be grouped under the following four heads or classes:

(1) Sprays showing ([uite distinctly upon the trees on August 10.

(2) Sprays moderately evident on August 10.

(3) Sprays little evident on August 10.
(I) Sprays not observal)le on August 1<».

The sprays classed under the first head, were those applied to rows 1,
3, 7, 9, 13, 15, 18, 19, 21, 22, 25, 33, 3(1, 41, U, 45, 50, 54, 56, and 57;
under the second head, those ui)plied to rows 0, 10, 12, 16, 2S, 42, 48,
and 5L; under the tiiird head, those applied to rows 27 and 35; and
under the fourtli head, those applied to rows 30, 32, 38, 39, and 47.
By refeniiig to page 73 the reader will find a table giving the fonnuhv
for sprays applied to each of the rows nani<>d, and an examination of
these fonnuhi' will l)ring out the following facts: All the sprays

GENERAL CHARACTEES OF THE SPRAYS TESTED. 163

included under the first two headings contain lime, while those under
headings 3 and i contain none; all formuhe 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 spra3^s 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:

WeatJier-resistlng qualities of sprays.

30 pounds lime in formula, class 1, rows 1 f and 71-

20 pounds lime in formula, class 1, rows 3t, 9t, ISf, 36t*, and 44°.

15 pounds lime in formula, class 1, rows 15*, 33*, and 57t.

10 pounds lime in formula, class 1, rows ISf*, 19t*, 41*, 45*, SOft, 54*, and 56ttt;

class 2, rows 6t, 12t, and 48t°.
8 pounds lime in formula, class 2, row lOj.
5 pounds lime in formula, class 1, rows 21*, 22*, 25*; class 2, rows 28*, 42t°, and

51t.
4 pounds lime in formula, class 2, row 16t.
No lime in formula, cla-^s 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.

ft Iron sulj)hate and lime.

tttlron 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 thev are without lime, the eye can
not detect their presence in man}^ cases where it ispo.ssible the chemi-
cals may realh^ be present in effecti\e quantity, and it is therefore
apparent that the value of such a list is largely of a comparative
nature among those sprays containing more or less lime in various
combinations.

The general facts appear to })c, as already indicated, that the copper
sprays are more enduring than the sulphur sprays, considering pound

164 PEACH LEAF CUKL: ITS NATURE AND TEEATMENT.

for pound of lime in their composition, and also that the amount of
lime may be 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 pi'oved of
poorer weathering quality than is desirable in a given climate, the cop-
per should be increased as well as the lime when greater resistance 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 CORROSIVE ACTION OF THE SPRAVS.

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 spra3\s upon peach trees, which are known to be
among the most tender deciduous fruit trees commonly 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 comparatively early in the dormant period, say four weeks
earl ier than the copper sprays. Sprays having not more than 1 0 pounds
of sulphur to 45 gallons of spray may be used with little danger up
to within four weeks of the swelling of the ])uds.

There is no danger of injuring twigs or l)uds with th(^ copper s])ra3's if
properly prepared and applied before the l)uds have opeiuHl. Well-
made Bord<>aux mixtui'emay be used e\'(>n as latx^ as the opening of the
first blossom l)U(ls. Tlie annnoniacal copper carbonate may also b(> safely
used to a late (hite. and both may l)e again applied, if desired, after the
trees ha\'e passed out of bloom. The simple solution of coj^per sul-
phate and the eau celeste may be safelv used to within a \ve(>k of the
opening of peach ))u(ls, but they should never ])e used upon the foliage
of tiie tree. Modifi«>(l (>au celeste is less corrosive than the eau celeste,
and may ))e used until th(^ first buds ))egin 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 ])each.

The injurious action of the sulphur si)rays wIkmi combined with Bor-
deaux mixtun^ is fairly to be compared with the action of (h(> sulphur
sprays alone when containing e(|ual amounts of suli)hur.

The spi-ay composed of iron sulphate and lime is more a|)l to in jur(>
tender shoots and buds than the Bordeaux mixtuii'. •md such a spray
can not be recommended for use upon foliage.

GENERAL CHARACTEKS OF THE SPRAYS TESTED. 165

Milk of lime appears to be practicall}^ harmle.ss 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.

ADVANTAGES OP 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 arc decidedly
advantageous for all winter work, those leaving no sucb 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 difference
between success and failure in the work.

Some recent experiments in applying whitewash or spra3's contain-
ing large amounts of lime have tended to show that the opening of the
buds may be somewhat retarded b}^ 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 dormant condition somewhat later than would otherwise l)e the case.
Whether this will prove of enough ihiportance 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. (Pl."^ XXIII.)

In the summer treatment of trees and plants having fruit approach-
ing maturity, the use of clear spra3^s is often most to be recommended.
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 siunmer work up to a date when the fruit is approaching maturity,
and then to adopt the anmioniacal copper carbonate. The time at
which the sunnner 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. 18-20. See further remarks on this subject on p. 150.

166 PEACH LEAF CURL! ITS NATURE AND TREATMENT.

Bordeaux mixture could be used upon fruit luitil a later date in the
summer than it eould 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 IX WET AND IX DRY LOCALITIES.

Little can be said on this subject that has not been previously
touched 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 formulae contain. For instance, the relative proportions of
copper sulphate and lime being maintained, a Bordeaux mixture
which contains lU pounds of lime to -io 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-
sar}', 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 Avill not l)e found desira))le to reduce the copper below the
e(iui\ alcnt of 1 pound of copper for each pound of lim(>. and a higher
prcjportion 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 g-reat
increas-e 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
spraj^er. 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 rotar}" 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 enjo3^ed
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 Jose, Cal.,
and now bearing the name of that town, is perhaps better adapted to
long-distanc(^ 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 ma}" take place through the
temporary expansion of the opening in the plate.

The cyclone nozzles are now made by many manufacturers in different
portions of the country, and may be obtained through any first-class

167

168

PEACH LEAF CUKL: ITS NATURE AND TEEATMENT.

l-ICi. 1.— C'vi-1 Jliu iio/.zU

with direct dischargo
and degorgcr, for thin
sprays.

hardware dealer 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
1 )e done ^vith less waste of spray when nozzles having
a lateral discharge are employed. The reasons for
this are evident. Donuant deciduous trees are but
a skeleton or framework, presenting to the sprayer
hut 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 pass through the limbs of the tree and fall upon
the ground, whik^ 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
liml) surface which will be reached by the use of a given
amount of spray. The nozzle having lateral discharge
can also ])e handk'd to nuich greater advantage than the
nozzle Avith direct discharge. B}' turning the extension
pipe which l)ears the nozzl(>. the conc> of spray may be

directed upward, downward, or laterally upon
the limbs as desired. This has proven of great
advantage in doing thorough work.

The ordinary lateral discharge cyclone nozzles
aie suitabk' for use with most of the copper
sprays. For use with the sulphur sprays or
Bordeaux mixture containing a large amount of
lime, tlie connnon X'ermorel or cycloiu' nozzle* is
lather too liglit and the opening. too small. In
Califoi Ilia a sj)ecial form of nozzle is in use for
theapplicationof such s})iays (tig. ;5). This nozzle
is mjuiufactuicd in San Francisco, and may be
obtained from the leading hardware linns of that
city. The iioz/.h' i> of the cyclone pattern, liut is much larger, iieavier,
and strongei" than the ordinary tyju'of cyclone or Vermorel. The dis-
charge opening is of sulficient size to allow of the use of thick sprays,
and the (lisciiai'ge plate is heavy enough to withstand much wear from
corrosive fluids. A l'a<'t of prime iiiiMoilancc. howcNcr. lor the work

Fig. 2.— Cyclone
nozzli', with
lateral dis-
chargi", for
thin si)rays.

Fir;. 3. —Heavy cycluiic no/.
zlu.withohlifiucdischurge.
for thick .spruy.s.

GENERAL ACCESSORIES FOR WINTER SPRAYING,

169

being- considered, is that the nozzle diseliarg-es the spray at an angle
of about 45° Avith a line leading* directly from the spraA'er. 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
aceomplished 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 AXI> EXTENSION I'lI'ES.

Fig. 4. — Wirc-cxtuiidcd surtioii
hose.

Ru])ber hose of good ({uality is most satisfactory for all kinds of
spray work. The strongest and best hose will usually pro\'e cheapest
if properly cared for. All hose should he
thoroughh' washed, l)otli insid(>
and outside, at the close of each
day's work, and it shoidd ])e
Avell scrubbed, washed, and dried
when the spray work is com-
pleted, and stored in a luuformly
cool, dark, and medium dry place.

Practice varies somewhat as to the internal diameter of
hose used. One-half inch is perhaps the most connuon size.
The external diameter of the hose should not be so small
nor its flexibility so great that it will easily kink and tAvist
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 tlie pump pass from the back (md of the wagon,
between two short stakes, one at each corner. AVith such
an arrangement there is little danger of its being caught in
the Avheels or run over by them. Manj^ lines of hose are
injured or destroyed in this Avay. The stakes at the back
corners of the Avagon also serA^e as a means of winding up
the hose preparatory to going to or from the orchard.

Couplings for connecting 1, 2, 8, or 4 lines of hose Avith
the pump nuiA' usually be obtained from responsible hard-
ware firms, or through them from the manufacturers of the
])umps used. The more connnon hose couplings are nearly
always in stock at such hardware houses.

For most pumps it is well to supply wire-extended suc-
tion hose (tig. tt). 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, Jto enable it to Avithstand
the corrosive action of the sprays.

170 TEACH LEAF CURL*. ITS NATUKE AND TREATMENT.

Brass suction pipe strainers for attachment to the end of the pipe
may be had of different forms. They are necessary when the end of
the suction pipe is simply lowered into the spra}" tank or when it rests
upon the bottom of the tank.

The extension pipes used by different growers vary. Some adopt
common three-eigiiths 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 sufficient 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 th'e nozzle and the recep-
tion of a washer. The ordinary length of extension pipes is 8 or 10 feet,
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 verj^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 b}' bamboo also
adds to the ease with which the pipe may be held and turned in the
hands.

PROTECTION OF 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 storm without suitable covering are often improperl}' protected
against the similar or worse conditions prevailing when they are spray-
ing. In the spraying of hirge orchards it has Ix'on U^arned that one of
the most suitable (-overings for men who are applying sprays is a sail-
or's oilskin suit and sou'wester. This covering is light, impervious to
w'ind and water, and is not as liable to crack as rubber clothing. AVliat-
e\'cr form of head covering ma}' be chosen it should be soft, so as not
to ])e interfered with by limbs, and it should extend in front to pro-
tect the eyes and Ix^hind to ])rotect 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
deaha-, and if they have been k(>,pt for more than a year it is Ix'st to
orrlci- new ones from the manufacturer, as such goods soon lot wIumi
held in stock. Besid(;s, new stock is no more ex])ensive than old, and
it will fre(nu'ntly endure twice as much use. Numbers 11 or 12 are
usuallv altout the ri<rht siz(;s for ordiiiuiN hands. Most wvav c:in be

SPKAY 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 spra3^s 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 ordinar}'^ 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 FOE 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 poor 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 capacit}" 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 th(;
spray. These pumps can be obtained with brass-lined cylinders.
The stroke is upward and downward. (See also PI. XXVI.)

Fig. ('). — Si)rny piinii) for use on harrol or tank.

172

PEACH LEAF CUKLI ITS NATURE AND TREATMENT.

For orchiuds of niediuin to larg-o .size it is better to obtain more
powerful pumps — those eapul)le of throwing- four strong- sprays. The
pumps shown in tigs. 8, 9, and 10 are admirably suited for this class
of work. Pumps of the tj'^pe shown in fig. 8 are used in the 1,600-
acre Kio Bonito orchard. In this orchard one man pumps for four
men spra^ying (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 Avhere the
trees are large and where high pressure is necessary to throw the
spra}' to their tops. The pumps shown in ligs. 8 and 9 have perpen-

Fic. 7. — Spray jmini) for use (in liiirrcl nr lank.

dicuLii- levers, thus avoiding the IxMiding or stooping motion of the
()|)ci:itor. Tlie levers of each of the three styles shown an' long, and
bolli the sti-engtli and eapaeity of llie ]nuu\) is sullieient. 'ilie style
of j»um])s, both foi" small and large orchards, to which attention is here
called, will be found figured and listed in catalogues usually to be
foiuid in the hands of leading hardwafe dealei's.

Within the past few years leading orchai'dists and others have
tested, with varying success, the application of ditterent motive
])oweis to the opeiiition of spiav pumps. Steam and gasoline engines
ha\e i-eeei\ed nio-l attention for thi> purpose. Many of the power

SPKAY PUMPS.

173

spra3^ers as now constructed are heav}', ciimbersonK^ affairs, which
could never be of practical value in everyday orchard work. Of the
machines or descriptions of the same which have come to the writer's
attention, none have thus far appeared bettcT adapted to practical 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 practical 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 l)y Mr. Gunnis in the early part of July. 180.5, 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 haid-
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,
1890: ''The machine is still
in constant use, and I can still Hii}\ as I wrote you over three y<>ars
ago, that it has developed no defects whatever. Sonu^ of the parts
wore out from actual service and have been replaced, but no changes
have l)een 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 1)V two m(ni, 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. (nmnis has built
and operated is superior to any other of its class, I am informed that
the gentleman contemplates still further iniprovements. In regard

Flo. 8.-

Spray pnmp for g-oncral orohard wnv'k, nprisht
lever.

174 PEACH LEAF CUKL: ITS NATUEE AND TEEATMENT.

to these chang-e.s Mr. Giinnis saj's that he is now building from nis
own designs, and has ahnost completed, a small gasoline engine of 3 to
4 horsepower, weighing less than 200 pounds. This engine is intended
for use with a spraA'ing machine embod^'ing all 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.

Fig. 9. — Spray pump for general f)rchiir<l work, upright lever.

PI. XXX shows the right and left sides of Mr. Gunnis s sprayer
as it appeariid after the addition of the rotary pump for tilling the
spray tank. A detiiiled description of this machine was prepared by
Ml', (hinnis and ])iiblished in the Yearl)ook of tlie r)ej)artment for
IS'.MJ (pages 73 and 74), in an article liy L. O. Howard, on the use of
steam apparatus foi- spraying. Those wishing more complete details
may refer to Mr. (iuiinis direct, to whom tin- w liter is indel)ted for
the illustrations and facts here yi\i'ii.

THE APPLICATION OF SPRAYS.

175

SPKAYING TANKS.

A great variety of forms and sizes of spray tanks are in use. For
small orchards, scarcel}" anything better could be desired than large
oak barrels holding 60 to 80 gallons. These may be swung upon
wheels separateh' 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 easih" 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 timl)ers inside of the
wagon bolsters is shown in PL XXII,
as is also the stirring stick which
projects from a square hole in the
top of the cask.

Rectangular plank tanks arc 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 safeh'
employed.

All spray tanks should be arranged
in such a manner as to be easily
cleaned, especially where Bordeaux mixture or the sulphur spraj's are
to ))e used, and the}^ should be provided with some means for stirring
or agitating the spray. The entrance to all suction pipes should be
guarded with fine brass wire screen. It is well to ^vash the tanks out
thoroughh' at least once a day.

Fig 10. — PuL-uiiuitie pump for Kwicral
spraj-ing.

APPLYING WINTER SPRAYS FOR CURL.

A study of the many experiments conducted by the growers and
described in this bulletin will give much infonuation relative to the
proper time for apph' ing sprays for the control of curl. A presenta-
tion of a few general principles involved may, liowever, ])e j)roperly
made in this place.

IVC) PEACH LEAF CURL: ITS NATT^RE AND TREATMENT.

rriE TIME I'OU WIXTEli .SPKAYIXG.

The proper tini(> for the application of winter sprays for the control
of peach loaf curl depends ver}- largely upon the conditions of climate,
season, and situation of the orchard. The object to be attained is to
prevent the fungus from infecting the first growth of spring. It has
become apparent from the man}' and widely separated experiments
which are here described that nearh' 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 natur
alh" follows that these spores are to ])e 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 Exoancm^ deformans 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 tliat the time whiMi the fuiigici(K^ is apt
to do the greatest good is just before or at the tim(> of the earliest push-
ing of the peach leaf buds. The spray should l)e evcnywhere 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 timc^ b(»fore
the}' open. When they first begin to swell, the spray may 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
l)e applied to the trees. It should l)e strongei- and have greater adher-
ing ((ualities, or else more than one spraying during the winter will be
required to give the best results. If two sprayings are gixen. it is
better to apply both to the dormant tree than to delay the second
treatment till the leaf l)uds have openinl The first spraying may be
given in the fall or a few weeks before the second.

THE .MANNEIi ()!•' A I'I'I.YI \( 1 WINTEU SI>I!AVS.

The source of infection of the spring foliag of the ]>each by th(>
fungus of leaf cuil is local — i. e., it is to be found upon every portion
of the tree. This fact is suliicient to shov that any portions of the
tree not I'cached b\- the s])ray will be as subj(>c to the disease as if no
sj)rM\ ing li:i<l liccn done. It tlnis becomes :il)i);irent llial \vv\ tJioi'ough
woi'l< i-~ e<>enli:d Id the gcneiid control of the dise;ise upon the I re(\

DESCRIPTION OF PLATE XXIII.

This plate ."hows tlio condition of tlio trees in the experiment hlock of the Rio
Bonito orchard at the close of tlie spray work in the spring of 1895. 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.
Each 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 tlui trees
in these experiments is liere shown to advantage. It should l)e noted that the buds
are still closed, while the spraying is completed.

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

Plate XXI

I)?:8CRIPTI0N OF I'LATK XXIV.

A portkjii of tlie LovrH trees in the Rio Bonito orchard left unprnned until too
late to Hpray, many of the flowers being already open. This plate should be com-
pared with ri. XXV, which shows how the orchard should be pruned before si)i-ay-
ing, and also 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.

W rn
c m

— >

~ rn

'4f r .J.

Ai?*

-^"-*t^

^^f

.a**"*^! 1,

i.V-.

DESCRIPTIOX DF PLATE XXV.

A properly pruned ])ortion of the Rio Bonito orchard, wliit-li lias developed too
far for the lK>st res^ults of spraying. Spraying should be eonipleted by the time the
buds have developed as far aa those shown in PI. XXIII.

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

Plate XXV.

S O

SPEAYING WHERE SEVEEAL 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 oil' the spray to a very injurious
extent.

If the sprayer is provided with suitable extension pipe and nozzle
with lateral discharge, the work of spra3'ing peach trees of ordinary
size ma}^ be rapidl}^ 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, spraying 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 mny 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 common dis-
eases may prove of value.

PRUNE RUST ON THE PEACH {Puccittia pvuni Ters.) .

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 3^oung 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 branches, as well as b}'^ 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
10093— No. 20 12

178 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

difficult and will, at best, be necessarily followed by several summer
treatments. There can be little doubt, however, that a thorough
winter spraying will prevent a greater portion of the injury from rust
than an}^ 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 summer sprays if
strong should be positively neutral and noncorrosive, as peach foliage
is exceedingly tender.

MILDEW OF THE PEACH {Podosplisera oxyaxianthx De B.).

Peach mildew is widely distributed in the United States and m
Europe. The fungus causing it attacks the leaves, fruit, and tender
branches in the early part of the summer. The branches serve for
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 sprays, will largely limit this spring infection,
but later treatment wnth weak sprays will often ])e necessarv for full
control.

BKowx ROT OF THE PEACH {MoniUa fructigena Teis.) .

Brown rot of the peach has become one of the worst 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 diseased
branches and in the dried fruit adhering to the tree. These facts
point to a thorough winter spra3"ing with active fungicides as one of
the first steps required in its treatment. Summer spra3'ings 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 necessitj' of disinfecting the dormant tree as perfectly as
possible by thorough winter treatment.

BLACK SPOT OF THE PEACH {Clodosporium carpophilum Thiim.y .

This disease, which produces black spots upon the peach, is well
known in many portions of the United States and in Europe, and in
th(! East and South, especialh' in Texas, it has l>ecome (juite tr()ul)le-
some. In some parts of Europe it has been known as a true epiphy-
totic. Whether this Cladosporium infests the ])ranches the writer
can not say, but it appears not improbal)le 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 copp(>r
sprays, and there seems no reason t<^ doubt that the winter treatment
of th(! infected trees would largel}' tend to disinfect (hem and materi-
ally reduce the summer development of tlu^ disease.

SPRAYING WHERE SEVERAL DISEASES ARE PRESENT. 179

WINTER BLIGHT OF THE PEACH AND OTHER SPOT AND SHOT-HOLE DISEASES, SUCH AS

Phyllosticta circumscissa berk., Cercospora circumscissa sacc, 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 countr3^ These troubles
are generally known as leaf spot or shot-hole diseases. One very
widely distriliuted disease is that produced b}^ Cercospora cirmiinscissa
Sacc, but one of the most troublesome diseases of this class that
occurs in California and Oregon, is induced b}^ 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 white/' Might 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 Coryneum^ 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 eflfect toward their control. Both induce gum-
mosis of the affected branches, as is true of the action of many fungi,
and is a well-marked result of the presence of Coryneum hyerlnckti
Ond. Winter blight has already been successfully treated with the
winter spraj^s, and it is believed that such spraying is sufficient for its
control, provided the work be done thoroughl}^ and repeated each 3^ear.

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 jArOLD OF THE PEACH.

When the Department spra3dng experiments beg-an in the Rio
Bonito orchard, there was ever}" where present on the trunks, inner
limbs, and older bark of the experiment trees a fungous "smut," or
"sooty mold," giving the bark 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-
parison. On August 10, 5 months after the spraying was completed,
all but it rows were examined for the presence of sooty mold, with the
following result:

Spraj^ed 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, 30, 38, 39, 41, 45, 47, 48, 50,
51, 54, 56, and 57 — total, 30 rows.

180 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

Sprayed rows showino- a trace of sooty mold: Nos. 42 and 44 (sul-
phide of potassium was applied to row 42 and simple milk of lime to
row 44) — total, 2 rows.

Unsprayed rows showing the presence of sooty mold upon the trees
August 10: Nos. 2, 5, 8, 11, 14, IT, 20, 23, 20/29, 34, 37, 40, 43, 46,
49, 52, 55, and 58 — total, 19 rows,

Unspraj'^ed 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 o>)fained: Nos. 9, 30,
31, and 32 — total, 4 rows.

The above notes show that records of the sooty mold were obtained
from 32 rows of spra^^ed trees 5 months after treatment. Of these,
30 rows showed no sooty mold, while 2 showed a verj' little. Neither
of these exceptional rows was sprayed with a generally recognized
fungicide. On the other hand, of the 19 unspra3^ed rows examined,
all showed sooty mold. The record for rows sprayed in 1894 but left
unspra}' ed in 1895, shows that the trees had but little mold upon them
17 months after spraying.

The preceding facts show the disinfecting >'alue of a single winter
spraying, qxgu where the whole tree sui;face is covered with fungous
mycelium and spores.

ANIMAL PARASITES OP THK PEACH TREE.

Among the insect pests of the peach tree now prevalent in many
parts of the United States, the San Jose scale {Asj>ldlotus jperniciosm
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 shoidd 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 {Phytoptus sp. ?) infesting the peach leaves in Califor-
nia, which the writer believes may be destroyed in this manner,
lioni the fact that experiments conducted in 1895 in the Sacramento
Viillcy showed that the same line of treatment is effective in the
destruction of a related mite {I^/iytojAua pyri Sor.) upon the pear.

Mr. William N. Runyon, of Courtland, Cal., makes the following
statvuKMit r<'s])e( ting tlu^ pcMicli moth, which may also prove of value
to growers sull'ciirig from this pest: ''Incidentally 1 would stat(» that
experience shows that peach trees sprayed with lime, sulpiiui'. and
salt are not siihjcct to the attacks of tiie larva of the i)each moth.
Somt! groivers claim a saving of IM) per cent of allected 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 00 cents per gallon, while local prices have been
known to range as high as $1 per pound for copper carbonate and
$1.50 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 ver}^ largel}: 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 (fonuula CuS0^5H20).

Of all fungicides thus far known, copper sulphate is the most
important. It is commoidy known as l)lue vitriol or bluestone in the
United States. Its foreign names arc largely equivalents of these
terms, although the Germans also apply the name of copper vitriol
( Klip few itr ioT) .

When pure, copper sulphate crj^stallizcs 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 greenish 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 its value as a fungicide, while this by-product

181

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 b}" 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 as
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,
chietly from England.

Bluestone is prepared by dissolving cupric oxide in sulphuric acid,
or b}' oxidizing the sulphide of copper, the latter being the cheaper
process. Mr. Alfred Rapp, a gentleman who has enjoyed a wide
experience, has kindl}^ supplied the following facts respecting the
manufacture of copper sulphate b}^ a leading smelting firm of the
Pacific coast. He states that the copper is mainly derived from mattes
produced in the blast furnaces, and, sec^ondl3^ from an acid solution
of sulphate of copper resulting from the precipitation of sih^er by
metallic copper out of a sulphate solution. To bring the copper in the
different mattes in solution they are first crushed and pulverized to
ai)out one-thirty -second of an inch or finer, and subjected to a roasting
process by which the sulphur is nearlj^ all oxidized. The roasted
matte contains the copper as oxide and partl}^ as sulphate, with a small
amount still as sulphide. This material is pulverized once more and
f(^d into lead-lined leaching tanks, where the acid copjx'r sulphate
solution is added, and, if necessary, sidphuric acid. The whole mass
is heated by steam running through lead pipes. The copper oxide
and the copper sulphate in the roast is thus l)r<)ught in solution as a
sulphate. A})out 80 per cent of the copper contained in the mattes is
thus leached out. The resulting solution, of course, is not a neutral
one, })ut still contains an excess of free sulphiiric acid. This solution
is transf(!rred to other lead-lined tanks, containing, suspended from
wooden sticks, strips of lead about 3 inches wide, the central portion
of which is lient downward between the sticks so as to form a loop,
which is held by the ends of the lead strips being l)ent over the sticks.
The copjx'i- sul|)hat«' when run down to tiiese crystallizing tanks is
about y>i') to 44 li. During tiie cooling ])rocess, which takes a])Out
four to sev(;n days, th(^ copper sulphate, or ratiiei- })art of it, separates
out (jf the sohition as ])lue crystals, which are deposited upon th(>
strips of lead. These crystals are dried and ])acl<ed in barrels ready
for th(! market. This, Mr. Rapp adds, is the g(Mieral way in which
bluestone is made the world o\-cr, except that they haxc at the woi'ks
considci'cd. in addition to the copper in the mattes, the acid copper
sulphate solution from a silver relinci\ .

NATURE AND SOURCE OF SPRAYING 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 the}^ are sold in the market — and upon supply and demand. The
cost to the manufacturer will not, however, necessarily depend upon
the market 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
United States, but much less extensively than the sulphate. In most
cases 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 usuall}^ 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 189-1-95: 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
wholes-jale price of copper sulphate hasadvanced. San Francisco producers quote copper
sulphate in barrels, f. o. b., at 5^ cents, and carload lots at 5 cents per pound; Omaha
quotations are, by the ton or carload, 5^ cents; one New York firm quotes 5| cents
by the barrel or ton and 5^ cents by the carload, and a second firm quotes 6 cents by
the barrel, Sf'o cents by the ton, and 5| cents by the carload; Denver quotations are
6 cents by the barrel, 5| cents by the ton, and 5|- cents by the carload ; Cleveland
quotes 6 cents per pound in any quantity; one Philadelphia firm quotes 6 cents by
the barrel, 5|- cents by the ton, and 5| cents by the carload, and a second firm quotes
5| cents by the barrel, 5j cents by the ton, and 5| cents by the carload; Baltimore
quotes 5| cents by the barrel, SJ cents by the ton, and 5^ cents by the carload; Great
Falls, Mont., quotes 4| cents per pound in carload lots and 5 cents per pound for less
than carload lots, etc.

18-4 PEACH LEAF CUKL: ITS NATURE AISTD 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 slowh' 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 slowlv 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 rarel}' 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 unal)le 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 sulpliat(> at 5 cents per pound
by the l)arrel and sal soda at 1*0 of a cent per pound in like (|uan-
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 -^\- of a cent
and 4rf 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 tlu^ market at 15 or 2(> cents per pound
and still make a good profit, even when l)uying their sodium carl)onate
and copper sidi)hate in the open market. If we go a step farther
))ack, h()wev(;r, we may see that the Hi-st cost of co^jper carbonate can
be greatly reduced Ix'low 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 hitter depends ui)()ii the cost to the nianufacturcM- of
sulj)huric acid and copper. Both of these articles may l)e produced
aw by-])roducts of modern smelting processes. A lirni at Blacksburg,
S. C. informs the wi'iter that they employ gold-bearing i)y rites for
the manufactun; of sulphuric acid, the sulphui- fumes l)eing driven

NATURE AND SOURCE OF SPRAYING MATERIALS. 185

off with heat and condensed in lead chambers in the usual wa}'. 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 ma}^ he 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
ma}^ soon be had on the market at prices which are not prohibitive to
its purchase by the horticulturists of the country.^

AMMONIA (ybrmt/Z(2 NH 3).

\ 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 important 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
cent of ammonia gas, and is sold as 26° ammonia, as shown by Baume's
hj^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 272 cents per pound, 100-pound lots at 25 cents per
pound, and 1,000-pound lots at 23 centa 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 85 cents per pound, 100-pound lots at 28 cents per pound, and
1,000-pound lots at 22 cents per pound f . 0. b. ;" Boston quotes 10-j>ound 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
centers of trade. It is satisfactory to note that quotations just received from Boston
indorse the view already expressed, that carbonate of copper can be placed upon the
market at about 15 cents per pound and leave a sufficient 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 annuals furnish the main sources of conunercial anunonia.
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 as a by-product in the manu-
facture of bone coal, and "gas liquor,'' obtained from the scrub]:)ing
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 l)one liquor almost exclusively in the form of sulphate
of ammonia, often of crude quality, which is used in the manufacture
of fertilizers. Gas liquor is partly worked into a sulphate of superior
quality, but mostly into aciua 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. 01)tained in this way. it is
said to be the cheapest article of good quality that can be supplied.

A crude concentrated ammoniacal licjuor 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 maiuifactured into pure
aqua ammonia. The concentrated li([uor is, hoM'ever, also largely used
in the preparation of nitrate of ammonia, which is used in the manu-
facture of powder, Ijut most largely in the manufacture of soda ash.
This crude liquor contains, besides a small amount of free anmionia
(NHg), a considerable amount of carbonate, sulphide, cj'anides, 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 })e advantageously used as a sul)stitute for aqua
anunonia in the preparation of spi-ays. The anunoniacal liquors obtained
in the manufacture of coal gas are entirely a by-product.

As th(; gas works of the United States have been largely supplanting
coal gas with water gas, in the maiuifacture of which anunonia is not
ol)taiii('d, the <|uantity of anunonia ])ro(luce(l in the country has been
steadily (Icci'casing, and the (IcniiiiKl is hciiig sui)plied piMncipally from
England. Hoth aqua anunonia and anhydrous ammonia are made
largely fioin imported sulphate of ammonia, and very large (|uantities
of tin; iinpoited article ar<' also consnnied in the manufactnre of
ffitilizerH.'

'San i'"ruiiciMC()'H (inolatioii on anmioniii water of 2(i° liyilroiiictcr Ic.'^t, in drnniH of
about ToO i»oiuniH, f. o. I)., i.M 7\ ccnt.s per jujund.

NATURE AND SOURCE OF SPRAYING MATERIALS. 187

SODIUM CARBONATE {formula Na^COj-lOHjO).

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 crj^stals, showing a strongly alkaline reaction to litmus
paper. When exposed to the air much of the water of cr3^stallization
is lost from the crystals, which rapidly effloresce or slake to a white
powder. When perfect, nearly two-thirds of the cr^'stals, l)}- weight,
is water.

Carbonate of soda dissolves in 1.6 parts of water at 59° F. and in
0.2 part of boiling water. When a solution of sal soda is added to
the solution of copper 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 spray work being considered.

The sources of sodium carbonate are somewhat numerous, but the
commercial supply of to-day is derived mainly from connnon salt or
from natural deposits of the carbonate. In nearly all arid countries
carbonate of soda is frequently found in the soil in such quantities as
to be injurious to vegetation . West of the Missouri River large accumu-
lations of the different soluble salts of the soil are frequently met
with. In the East such accumulations are prevented by the greater
rainfall, the salts being eventually washed from the soil and carried to
the sea, but in the West they often coat the ground, appearing white
or black, and are known as "" alkali beds," owing to the frequent pres-
ence of strongly alkaline salts, such as sal soda. The most a])undant
constituents of these deposits are sodium sulphate, sodium chloride,
and sodium carbonate. The sodium chloride and sodiiun carbonate are,
when in excess, so injurious to vegetation as to constitute a leading
bane of the horticulturist of the western half of the United States. In
the great plateau region between the Rock}' Mountains and the Sierra
Nevada and Cascade ranges are vast stretches of alkaline soils, the
soluble salts of which accumulate 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 composed largely of sodium car])onate, and
in several instances, after passing through a simple purifying process,

^ These deposits are very well shown in the illustrations of Bull. No. 14, Division
of Soils, U. S. Dept. of Agr.

188 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

this salt is obtained in a quite pure state, the original deposits contain-
ing as high as 90 per cent 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 cr3"staUized
from crude carbonate of soda obtained from Soda Lake, near Ragtown,
Nev. This lake is known as Big Soda Lake, to distinguish it from a
smaller soda lake near b}' . The lake is a beautiful sheet of water, l3'ing
in a depression of the desert, the water being about 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 relined and bleached for various uses. The principal uses
on the Pacific coast are in glass-making and borax-making. It is
stated that sal soda obtained as here described is practically a pure
article, though the natural color is somewhat yellow or brownish. It
is generally useful, except as a fancy article for the retail trade. For
such purposes it must be bleached with chloride of lime, after which
it presents l)eautif ul f rystals.

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 above descri])cd, is nearh' 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 (carl)onates) found on the Pacific coast proper are in the
form of sesquicarl)oiiutes, and are often so much contaminated with
sulphates and chlorides that much expense is entailed in their separa-
tion, and they are therefore of littk^ value as sources of suppl}'.

The second great connnercial source of sal soda is common salt.
The salt deposits of the country are vast and inexhaustible in quantit}\
The Onondaga Salt Group of the Upper Silurian alone underlies
much of tiic large extent of countr}', as well as the (ireat Lakes, situ-
ated ])etween 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 tapj)ed 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 'M) feet in thickness, and is reached at
a depth of 1,800 to 2,200 feet. Other large salt (le])osits are found in
Kansas ;ind in numerous other portions of the country.

Sal soda is manufactured from salt on a commercial scale according
to two leading j)roces,ses. The older of these is known as the L(»blanc
])rocess, and has been extensively employed in England and through-
out Kurope. It involves two steps in th(> maiuifacture, (i) the conver-

NATURE AND SOUKCE 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 hj^drochloric acid
and sodium sulphate. The h3^drochloric 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 fine 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 trade. 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 i-s carried on
extensivel}^ by firms not manufacturers of the ash. A St. Louis firm
states that the}^ crystallize the solution of soda ash in tanks holding about
8,000 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 off 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
largel}^ into use in Europe. It is known as the ammonia soda process,
or the Solva)'^ 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 CURL'. ITS NATURE AND TREATMENT.

lime to liberate ammonia, which is then reconverted into bicarbonate
by the carbonic acid evolved in the conversion of the sodium bicar-
bonate into monocarbonate by heat. The ammonium bicarbonate thus
reproduced is employed to decompose fresh portions of sodium chlo-
ride, so that the process is made continuous.^

SULPHUR {symhol S).

The value of sulphur as a fungicide, insecticide, and germicide nas
been known for many years. Its use in a powdered state has been
long followed in hothouses and vineyards, and its application in the
treatment of parasitic skin diseases of man and the lower animals, 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 form of sulphides of these
bases.

The recent marked use of sulphur in preparing sulphide of lime for
the spraying 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 scab mites on sheep. The spraying 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 wideh" 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 importance of winter spraying for the control of
insect pests and fungous diseases is more fullj'^ 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 comes still higher. The purity of any of these

' QiiotatioriH on Hal soda were received as follows during March and April, 1899:
San Francisco (juotcs 50-sack lota at 60 cents per 100 pounds, 10-barrel lots at
70 cent« per 100 pounds, and smaller quantities at 75 cents per 100 pounds; 1^)8
Angeles (piotes by the barrel $1.25 per 100 pounds, and by the car in sacks %\ jkt
100 pounds; St. Louis (juotes by the car load in l)arrels 55 cent.s jM'r 100 ])()un<ls;
New York (jiiotcs, f. o. I>. Syracuse, in jobbing IoUj, barrels of ;?75 jxiuiuls, 40 tvnta
per 100 pounds; Fair^iort, N. Y., quotes 50 ccnt.s 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 being employed for bleaching fruit, nuts, etc., while flour and
flowers of sulphur are used in fi.eld work for the control of insect and
fungous pest5. A simple mode by which one may test the purity of
sulphur is to weigh out any desired amount and then dr}-^ 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-
ous and A'aried. 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 p3a'ites. It has been estimated that the amount of
sulphur consumed in the United States in 1892 was 243,151 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 tons of imported pyrites (43 per cent) 90,300 tons.

From 119,000 tons of domestic pyrites (-l-i per cent) 52,360 tons.

At the present time the amount used is probably much greater than in
1892.

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 (SO^) and sulphureted hydrogen (H^S), which two
gases, if moist, readil}^ 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 5,000,000 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 Sicil}^, 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, probabl}^ weighing 100 pounds each,
are brought to the railroad 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 Catania. The aimual
outputof sulphur in Sicily is said to exceed 300,000 tons, and the present

192 PEACH LEAF CUKL: ITS NATURE AND TREATMENT.

importation of the United States from Sicil}" is about 120,000 tons.
The richer sulphur ores of Sicily run from 30 to 10 per cent of sul-
phur. A considerable quantity is also imported from Japan.

The leading native sulphur deposits of the United States are located
in Nevada, Utah, California, Wyoming, and Louisiana. AVhile 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 course, 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 b}' 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 10 atmospheres of steam
pressure. Under this heat the sulphur percolates, in the shape of
licjuid 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 taidv; thence
it is drawn off into wooden molds, holding about 200 pounds, and
allowed to cool, after which it is 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 ])v 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 al)solutely no difl'erencc between that maiuifactui'cd here
and that manufactured in France, Italy, Denmark, and other European
countries. Both start with tin; same raw material coming from Sicily,
tlu; sanu! apparatus is employed, and even experienced foreigners are
hired to refine the brimstone in the identical maimer in which it is
treated in the above places. There comes to the horticidturist no

NATUKE 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 onlv impurity being a neutral,
inert 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, the difference in purity percentage between
ground sulphur and sublimed sulphur is not in any wa}^ commensu-
rate with the difference in price, and a great saving could be 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 difl'erence 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 sulphur in March, 1899, were as follows: New York quotes flour
of sulphur in 250 pound barrel lots 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 New York firm quotes roll l)riinstone 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 $2.87i per 100 pound.s, 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 i)ounds, less
(juantity at $1.60 per 100 pounds; sublimed (flowers of sulphur), sacks or barrels,
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.

lyoya— No. 20 — 13

CHAPTER XI.

PEACH VARIETIES AND NURSERY STOCK IN RELATION TO CURL.
COMPARISON OF PEACH VARIETIES.

It is a woll-known fact that certain peach varieties are less suscep
tiblc to curl than other.s. When planting-, many g-rowers 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 Imdded 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 liecome
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 country 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 give the results as obtained, rather than strive to
draw from them any final conclusions. Of a hirge 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 growers, 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 l^loomers most affected. It
would .seem that the late l)looming 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 hite maturing varieties, there appears to be little dif-
ferenc^e from the replies to the circular letter. Among 79 peach
growers who have expressed their views, 22 think early varieties most
.subject to the disease, 10 believe the late varieties most subject to it,
and 41 think there is uo difference.
1U4

PEACH VAEIETIES IN RELATION TO CURL.

195

Besides the facts respecting- tiie 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,
mediiun 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 sum 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 arc 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. — Relations of peach varieties to peach leaf curl, with records of glands, time of
ripening, and adhesion ofj)it.

No.

Peach varieties.

"o

u

4) .

O

s

•c .

II

o

i

03

c

o

ft

s .
3

o

ft
&

1

r
g
?
r
r

r
r
r
g
g
r

e

1
e
e
e
e
1
e
1
1
c
1

f
f
f
c

f

f

c

f
f

c

f
f

......

18
2

""s

1

1

0

Albriglit

S

11

6

17

■1

"S

2
5

1

......

......

3
4

2

fi

Amsden.. T

7

7

1

8

Beatrice

2

9

4

......

1

1

2

2
2

6

10

6

n

Bishops Early

12

3

3

IS

Boston

11

g

1

1
e
e

1

f

c

2
1
1
4

1

....„

1
2

3

15

Brett (Mrs.) . ..

1

Ifi

1

17

r

f
f

c
c
c

f

4
1

7

1«

1

]y

California (cling)

2

■>()

g

c

4
......

■21
22
23
21

1
1

1

1

Chairs (choice)

r

1

f

2

2

^lu some instances it ia 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 lias been possible to determine such (luestions by
referring to several authors it has been done. Unfortunately the writer has not l)een
able to study this matter in the orchard except for a portion of the varieties given.

196

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

Table 43. — Jiekilions ofpeadi varieties to peach leaf curl, villi records of glandu, time of
ripening, and adhesion of pit — Continued.

No.

Peach varieties.

0
u

O' on*

u

5

.£■

"^ ti

0
§

<

0
0

H

0

6

1

>

ii

■§>. .

5 c 0

V5

Charlotte

4

......

3
10

3

12

Vfi

r
r
r
r
S

1
1

1

1

e

c

f
f
f
f

c

f~

Clemence

?R

......

2

1

""'i

1

1
1
5

X

'^

Com et

?X)

81

Cots (cling)

3''

e
e

1

'i
1

29
10

1

S'^

g
J?
r
r
r
r

25

18

26
27

51
45

8-1

Crawfords Late

S=)

Crimson Beauty

Sfi

Crocketts White

1

1
1

......

1

S7

Crosbv

1

S«!

81

Do\^'ning

1

40

Dumont

r

e
c
c
e
e
e
e
e
e
]
e
1
c
1
1
e
1
c

1

41

Early Albert

1
1
1

1

4''

l'

4S

Earlv May

1

44

Earl V (red) Knrcripe

r

1
1

4t

3

7
1
1
30
1

10

46

1

47

Earlv Slocumb

1

48
4<<

Elberta

r
r

1

-'-VI

5
2

35
3

fiO

Flori n

*)!

5?

1
7

1
3
1

i

2

f)''

10

fS'^

Fox (seedling)

1

54

General Bidwell

2
2

i

i
2
3
3

1

6

5=)

George the Fourth

K

2

•16

Georges Late

4

57
58

Globe

Gold Dust

{?

6
1

59

Golden Cling 1

2

60

Golden Drop ■.

Governor Briggs

r

1
e
c

4
1
1

61

...

ff>

m

Governor \\ oo<l 1

1

1

64

Grave Cling

1
1

6t

S

c

1
c

1

-

3

13

5

66

Grover Cleveland

2

67

68

Hales Early

g

11
1

4

1

17
1

6<t

Hurdv ^\ hite Tuscany

2

70

Hard V Yellow Tuscany

:.::;::::::

4
4

5

2

71

Heath Cling

r

1

3

1

24

1

27

7?

Heath Free

2

7S

r
r

1
1
c

74

Hills Chile

5
1

7

12

1

7';

Honey Cling

2

1
1

1

78

r

1"

1

70

Iiinian Blood (cling)

Ingles (seedling)

9

80

1
1

1
1
1
1
2
1
1
1

81

Ironclad !

;:;;;:;:;::i:: ::

82

.lacques Kareripe

.laiian Bloofl

r

1

3
1

3
1

Kl

.Icnny Worrell 1

85

.Jenny \\ orthen

r

R
r

e

1
e

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

86

.Jones (seedling)

87

KH

8<t

<Kt

K iles Honey

............

......

5
2

8

1
2
8

1

2

\)1

Ivudy I'alnierslon

r
r

1

1

2

1

2

S*?.

La Fleur

2

%\

Iji Grunge

6

<M

Ijirge Karl v York, Jltmcst John

8

K

0

1

G
1

4
2

6

•I;')

6

1N°>

Ijirge Yellow

1

«7

r

1
1

1

2

«ts

I.iite BiiriiMnl

1

2

10

yj

Lute October

1

PEACH VARIETIES IN RELATION TO CURL.

197

Table 43.

-RelcUions of peach varieties to peach leaf curl, with records of glands, time of
ripening, and adhesion of pit — Continued.

No.

Peach varieties.

o

Oi ^

"a
fi

S
S*

i'"
t

a
o

<

^ .
o

3

as

■OS

0-

0)

^ .

>.

u

>

n

a ^3

0 03 y

100

Late Rareripe .

r
r
r

1

1
1

0

f
c

f
f

1
1

1

101

Lemon Cling

5
1
2

-

3

10''

Lemon Free

108

"'i'

1
......

1

13

2

......

1

104

1

105

Lola (Miss) .

r

g

r

e

1
1
1

f
f
f

f

1

106

Lord Palmerstoi'

1
1

1

2

2

107

15

108

Lovetts White

2

109

Lovetts Wonder

1

1

110

1

c

1

111

4

2
1

2

112

McClish

1

113

McCoIlister

1

114

McCowan (cling) . . .

c
c
c

1
1
1
1

2

1

115

2
1

1
2

2

116

McKevitts (cling)

3

117

1

118

Moore

r

e
e
1
c
1
e

f

f

c

f
f
f

c

f

c

f
f

c

......

1
10
9
4
3

'"'e'
1

2

7
2

1
5

1

119

Morris White

7

1'>0

Mother Porter

l-^l

r

5
11

4
4

9

T>?

Muir

15

123

1?4

T'5

s
g
g
r
r (?)

e
1

1
e

1

1
3
4

2

......

10

1

1

1?6

Oldmixon Cling

4

T'T

14

1?8

Onderdonk

2

19q

2

^'^o

Oregon

131

g

r

e
e

f
f

1
2

......

1

I

is'>

VQeu-To, South China Saucer

2

1S3

Perkins

1
3

1

1S4

Picquets Late

r

1

f

3

5

135

Plummer

1

136

Pratt

r
g

e
1

f
f

1
1

137

138

Red Ceylon

1
1

1

139

Red Cheek

g

1

f

1
1

1

140

Red Madeline

141

g

e

f

1
1

1

142

Reeds Early Golden.

1

143

g

1

f

2

1

4

4

144

Reeves Golden Yellow..

145

r
r
g
s
g
s
r

1
e

1
e

1

0

1

f
f

c

f

c

f
f

1

1

146

2

1

147

1
2

....„

1
1

13
1

2

1

148

Royal George

1

149

Riinyons Orange .

3

150

Sallie Worrell

1

151

Sal way

11

12

25

15''

1

153

Sellers Cling

c

f
f

5
1
1
1

1
1

1

154

Sellers Free

3

155

r

e

156

157

g

1

1"

2

1

......

2

158

1

159

r
r
r
r

g
r
r

1
1
1
e
e
1
1
1

£

f
- f

f
f
f
f
f
c
£
£
c
£

2
7
3
2
5

1

8

1

160

11

161

16'>

Snows Orange

4
4

'""3'
2

4

163

7

164

Steadly

2

165

2
7

'"'i'

166

Stilsons

1

10

1

""X

6

1

167

4

168

Stump the World, Jersey Stump

g
g
g

r

1
e
1
1

16

169

1

170

171

6
1

1

6

172

5

4

173

g
g

1
c

f
f

1

174

Tillotsoa (early)

3

2

2

198

PEACH LEAF CURL: ITS NATURE AND TREATMENT.

Tablk 43. — lii'htlions of peach varieties to peach leaf curl, irlih records of (jlands, time of
ripening, and adhesion of pit — Continued.

175
176
177

178
179
180
181
l.sii
I8;i
IM
IS-J

i8t;

187
188
189
190
191

192
193
I'M
195
196
197

Peach varieties.

Thissells White

Troths (early)

Tuskena, Tiii'can Cluu;.

Ulatis

Wager

Wards Late Free

Wattrloo

Wheatland ( early)

White Eiif<Iish

White Meloeoton

Wilcox Cling

Wilev

Wil kins Cling

Willow (peach )

Winters

Wonderful

Yellow Rareripe

NKCT .BRINKS.

Boston

Karly Newington

Hardwicks Seedling .

Lord Napier

Rivers Orange

Victoria

2 >■.

A digest of 98 reports on peach varieties in respect to the form of
glands, earliness or hitoncss of ripening, and adhesion or nonadhosion
of the pits, as these characters mav or may not be rchitcd to suscepti-
bility to curl, is given in the following ta})lo.

Table 44. — Comparative suscepiiJnlity of 98 peach varieties in relation to form of (jlamk,
earliness or lateness of ripening, and adhemm or nonadhesion of pit.

Character of glands.

Hcniforni, 5u varlctli's.

Glohose, 12 varieties.

Serrale, (; varieties.

Period of rii)eniiig
and adhesion of
pit.

Number of varie-
ties—

Very

stiscepti-

ble.

Little

suscepti

ble.

Total varieties —

Very
suscepti-
ble.

Little
suscepti-
ble.

Ill tlie above, tabic a most striking correlation appears between
j)eacli \aiieties with serrate leaves and susceptibility to curl. AH
the si.\ varieties foi- which full infoiination could ))c obtained are
litllc susccptil)lc, which is all the more interesting from th(> fact that
the varieties with serrate leav«^s hiixc long been known to be very

PEACH VARIETIES IN RELATION TO CURL.

199

subject to mildew. A list of seven such varieties for which the char-
acters of the leaves hav^o been obtainable is here given in contrast to
the above.

Table 45. — List of peaches subject to mildew.

Characteristics.

Glands (ir

leaves.

Ripens.

Adhesion.

Brings Ma v

Serrate .

Pearly

...do

Free.

Downing

do

Do.

do

...do

Early York

. ...do.

...do

do

...do

Do.

do

...do

Do.

Tillotson

do

...do.

Do.

Some correlations of the shape and aliscnce of leaf glands with the
time of maturity of the fruit and the adhesiveness of the pit have
been compiled from over 400 A-arieties, and these correlations are
shown in the talkie which follows.

Table 46. — Correlation of shape or absence of the leaf glands of the peach with the jwriod
of maturity of the fruit and, the adhesivenrss or nonudhesiveness of the pit.

Serrate

leaves, or

without

glands.

Early

Late

Free

Cling

Early free .
Late free . .
Early cling
Late cling .

Reniform

Globose

glands.

glands.

40

130

ito

50

124

166

G2

14

35

120

89

40

14

10

48

4

This table shows that of 208 earlj^-f ruiting varieties, -46 have reniform
glands, 130 globose glands, and 32 serrate leaves; while of 101 late
varieties, 110 have reniform glands, 50 globose glands, and 1 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 man}^ 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 16 late free
globose varieties. This table is given as a step in the direction of
future investigations along this line, which appear warranted 1)}^ the
correlations found to exist between the form of glands, the date of
maturity, the date of bloom, etc., andthe little or great susceptibility of
varieties to curl and mildew. Such facts may prove of nuich impor-
tance when taken in connection with future work in originating hardy
or otherwise desirable varieties by cross breeding.

200 PEACH LEAF CURL: ITS NATURE AND TREATMENT.

The preceding records, showing the comparative susceptibility to curl
of nearly 200 varieties of peaches, will enable the gTower who contem-
plates setting an orchard to make his choice of varieties advisedl3\
As alread}' said, however, many superior varieties are very 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 tbe most unfavorable situations, so far as this disease is concerned.
Such varieties are in fact saved to the pcjich industry of large sections
of the country by 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 be cultivated to any desired extent in regions
from whitli they have heretofore been practi(;ally excluded by curl —
advantages 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 noi-thern 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 neigh])()rs. who had a small orchard of that variety, stated that he
intended grafting the trees to some other peach, as the}^ did so badly
on account of curl. l)ut our correspondent advised the winter use of
Bordeaux mixture, cautioning the grower to spray 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 grafted to the Lovell, the variety with
which the detailed experiments of the writer were conducted in the
Sacramento Valle}^ 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
conunon interest to the oi'chardist and luirseryman. Could a luirscry
be freed from curl, many orchards planted from it would not suffer
from the disease for years, especially if isolated. Tliere rs little doubt
that curl has been largely disseminated throughout the world by
means of nurseiy trees.

It has been su]3posed that the main source of spring infection of
tr(»es was from the perennial mycelium already in the buds, and were
this hypothesis tru(^ 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 a})plica-
tion of a fungicid<i is sufficient to prevent ilo to 98 per cent oH curl
when th<^ trcatnjcnt has been thoroughly made. This appears to
indorse the view that at least 9S per cent of tlui spring infections are,
as el.scwherc ciaiincd in this bulletin, from spores upon the tree, prob-
ably largely resting upon or within the bud scales themselves.

TREATMENT OF NUKSEEY STOCK. 201

The facts given are sufficient to warrant some genei'al 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 repea,ted 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 the}^ undertook an experiment
with the use of 5 pounds of copper sulphate, 10 pounds of lime, and 15
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, 15 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^

^ This 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 frorri such shoots inserted in seedling trees of separate nursery rows. By such
method a record could be kept of the number o'f 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 tjie shoots to be used as the
source of buds.

"^ In relation to the added size and weight of sprayed over unsprayed ni^ery trees,
the reader is referred to Bull. No. 7, Division of Vegetable 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 curl: its nature and treatment.

leaving unsprayed trees for comparison. The trees of the spi-ayed block,
it is stated, were very nice and straight and made a good growth, and
there was no curl, it heing hard to lind a leaf affected, while groAvth
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 has 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 Pacihc 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
amuiallj'^.

(3) Curl is caused by a parasitic fungus known as J5IwrttS(3w-s<i!<?/wrw,a7?^,
the I'avages of which are largely dependent upon the atmosph(n"i(^ con-
ditions prevailing while the trees are leafing out. Rains and cold
weather at that time tend to increase the severity of the trouble by
favoring t\u\ growth of the parasite and interfering with the proper
functions of the host. For these reasons orchards near lai'gc bodies of
water and in low or damp situations arc more subject to curl than
those in dry regions or in elevated situations.

(4:) Most of the spring infections of peach leaves aro due to the
spores of the fungus and not to a perennial mycelium, as formerly
held, hence the efficacy of sprays.

(.5) C'url was first successfully treated in Calif ornia during the period
from 1880 to 1885, the success depending upon the application of
fungicides to the dormant trees. The disease was not successfully
ti-eated in Europe for ten years after its prevention in tlio United
States.

(ft) The copper sprays are now found to be more effective than the
sulphur or other sprays first used. Of the various sprays e\pc>ri-
mented with, Bordeaux mixture, in the proportion of 5 poujids copper
suli)hate, .5 pounds lime, and 15 gallons of water, gave the best results,
tlu! (Mjual 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 dural)ilit3- of a si)ray by
inci'casing tlie ))roi)oi'ti()n of lime, the ai)plication should he made
earlier or ('(jual |)roportions of coppci' jind lime should be maintained.

SUMMARY. 203

The total saving of foliage increases with the increase of copper sul-
phate when the amount o"f 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 l)y spraying, A net gain of GOO per cent in
foliage over that retained by adjoining unspraj^ed trees resulted in the
case 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
tmsprayed 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
upper limbs in both the iuiml)cr of fruit l)uds and lateral shoots they
produced.

(8) The average value of the fruit per tree in rows treated v/ith the
most effective Bordeaux mixture ranged as high as $0.20 aljove that per
tree in adjoining untreated rows, or the equivalent of a net gain of
^27.80 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 effective sprays.

(9) The trees should l)e sprayed each season, as the experiments
proved that treatment one season will not prevent the disease the
following 3^ear. 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 cheaplj"
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 sulplnir 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 f di* 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 arc 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,

O

DESCRIPTION OF I'LATK XXVI.

A HuitaJjlc outfit for spraying small orchards. One horse, two men, and a ))oy
spray two trees at a time. This scene represents the experimental sjiraying outtit
used hv the writer in the Rio Bonito orchard.

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

Plate XXVI.

DESCKIITIoX (»K I'l.ATK XXVII.

Spraying 4 tivi's at a time, witli ."> incn and L' hoi^t's. There is here used a 300-
gallon spray tank and long-lever (Gould), ))rass-lined i)ist()n pump, which has
sufficient capacity to supply 4 nf)zzles, 1 man i)umping. The horses are protected
hy means of gunny sack covers. Tlie Chinese hats in use furnish good ]>rotectinn
to the eves and neck, hut are too stiff for tlie most convenient work imd«-r lind)s.

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

Plate XXVII.

DESCRIPTION OF PLATE XXVIII.

Regular winter spray work in the Rio Bonito orchard. Eight trees are here
being sprayed at one time, with 10 men 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.
P>arlier 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. Veg. Phys. & Path,, U, S. Dept of Agriculture.

Plate XXVI

^^^^4

..v^,

^*^

^

■ i t .

... /■•

/»7

'«-r«^«».i<C-.

"Vfe^-,'

^-y

/^:--P

7/--\

DESCRIPTION OF PLATE XXIX.

A power s])ni\rr in use in a young orchard at Santa Barbara, (!al. This ,si)rayer
was l)nilt l)y liu" Fnion ( ias Engine CV)ni])any, San Fram;isco.

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

Plate XXIX.

DESCRIPTION OF PLATE XXX.

Views of llie right aiid left sides of the Gunnis power sprayer of San Diego, Cal.
This sprayer is one of the lightest, most eompact, and most practical power sprayers
in use for general orchard work. It supplies 2 or 4 lines of hose, as may ])e desired.
A tender is commonly used to cany the spraying materials to tlie 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 adaj)ted to extensive
orchard work. Mr. II. R. Gunnis, San Diego, Cal., is the ownerand operator of this
machint'.

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

Plate XXX.

Right and Left Views of Power Sprayer, San Diego, Cal.

s

j

SB 608 P3 P6 1909

University of British Columbia Library

DUE DATE

LlC 18 am

' %ff^jS^!!.'~**^it^->

1

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,',:0 i. 'c-;7

FOHM 3tO

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