U.S. DEPARTMENT OF AGRICULTURE.

DIVISION OF POMOLOGY.
BULLETIN NO. 4.

4 in T

ON THE

| RELATIVE MERIT OF VARIOUS STOCKS FOR THB ORANGE, |

WITH NOTES ON

MAL DI GOMA AND THE MUTUAL INFLUENCE OF STOCK AND SCION,

PUBLISHED BY AUTHORITY OF THE SECRETARY
OF AGRICULTURE.

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1891.

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U.S. DEPARTMENT OF AGRICULTURE.

4 DIVISION OF POMOLOGY.

Brae N BO. 4.

REPORT
RELATIVE MERIT OF VARIOUS STOCKS FOR THE ORANGE,

MAL DI GOMA AND THE MUTUAL INFLUENCE OF STOCK AND SCION,

PUBLISHED BY AUTHORITY OF THE SECRETARY
OF AGRICULTURE.

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
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TABLE OF CONTENTS.

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NOR aioe oe reece eaten Some eats Se at oe sea ecionee sauces cus ose Sees

Mal Di Goma (foot rot, gum disease, sore shin, etc.)..---.--..---.-----------.
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CARO OleUN OG CISOASOmre re merece cece Soleo re eee des, use eoetiee canoe coaeace
Treatment suggested ....-.- Joocde SadeRO Chases CHU opEEcEb aes dscses duaasece

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LETTER OF SUBMITTAL.

FEBRUARY 27, 1891.

Str: I have the honor to submit herewith the following report upon
the subject of stocks for orange trees. It has been prepared from re-
ports received in answer to a circular sent to the orange growers of the
United States, and the conclusions reached are based upon the testi-
mony of a large number of those who are actively engaged in the ecul-
tivation of this fruit.

Respectfully,
H. E. VAN DEMAN,
Chief of Division of Pomology.
Hon. J. M. Rusk, Secretary.

5

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INTRODUCTION.

For a number of years the question of the proper stock upon which
to bud the orange has been actively discussed, but no decisive conclu-
sions have heretofore been reached to aid an inexperienced planter in
the selection of the stock upon which to found his grove. Recognizing
the necessity of some guide to the subject, the Department of Agricul-
ture, through the Division of Pomology, issued early in the current
fiscal year a circular to the orange growers of Florida and Louisiana,
asking for an opinion, based upon their individual experience, in regard
to the merit of the several stocks in use, and particularly in regard to
the sweet (Citrus aurantium) and sour (C. bigaradia) orange stocks.
Numerous replies have been received, and upon them the conclusions
and recommendations of the present paper are based. The author’s
personal views have been eliminated as carefully as possible. Circu-
lars were not sent to California, as the introduction of the sour orange
stock there is too recent to warrant a final judgment upon its value,
but correspondence has been had with some. of the growers in that
State who have had experience in the matter.

Conclusions deduced from the reports of experienced cultivators will
doubtless be considered of practical importance to those desiring to
plant orange orchards, and may thus serve to lessen the cost of produc-
tion of fruit, so that both grower and consumer may be benefited. The
work of collating the information given in the circulars returned has
been committed to and performed under my direction by Mr. William
R. King, an assistant in this office. He has also added notes upon Mal
di Goma and The Mutual Influence of Stock and Scion.

H. E. VAN DEMAN.

Ss
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THE RELATIVE MERIT OF VARIOUS STOCKS UPON WHICH
TO BUD ORANGES.

In general terms, the question of stock resolves itself into two parts:
(1) The stock suitable for strong soil, and (2) that suitable for light,
sandy soil. In regard to the first there is little room for doubt or de-
bate; in every orange-growing section where the test has been made
the verdict is decidedly in favor of the sour orange stock on strong,
well-watered land, particularly that classed in Florida as “ hummock.”*
This is quite natural, since these lands are the adopted home of the
wild sour orange. The superior natural vigor of the wild tree under
these conditions, its freedom from disease, especially the dreaded Mal
di Goma (foot rot or gum disease), and the early age at which it
bears paying crops when budded, all contribute to make it popular.
The reports of our correspondents have been tabulated and the sum-
mary will be discussed in detail under the different topics.

SWEET STOCK.

Under ordinary conditions the sweet seedling has long been consid-
ered the longest lived and most thrifty of the orange family, but as the
foundation of a commercial grove it is now seldom thought of by pro-
gressive growers. The same reasons that have been advanced in the
argument for seedling orange groves were used years ago by the advo-
cates of seedling apple and peach orchards, and are about equally for-
cible. The more recent plantings are based on a more progressive prin-
ciple. Every one can remember when all oranges from Florida or Cal-
ifornia were simply “ Florida oranges” or “ California oranges ;” now
we hear Washington Navel, Majorca, Jaffa, Maltese Blood, and other
varieties spoken of almost as freely by orange dealers as we hear Ben
Davis, Yellow Newtown, Baldwin, and York Imperial referred to by
apple consumers. The sweet seedling is long lived and in the course of

*¥or definition of the various types of Florida land see explanatory notes on
page 21.
9

10

time will make a very large tree; it is thrifty and will do fairly well on
dry, thin soil where the sour orange will not succeed. A budded tree,
however, is in full bearing before the seedling has more than com-
menced to bear; it may not make so large a tree, but it is more prolific
and a greater number may be planted on an acre, facilitating the gath-
ering of the fruit, and allowing better care. As a stock upon which to
bud some standard variety, the sweet seedling will always find more or
less favor. Upon the high pine lands of Florida about 30 per cent. of
the growers are found to favor sweet stock (including seedlings), against
49 per cent. who favor sour orange stock, this difference of opinion being
traceable to different soii conditions or to the presence or otherwise of
Mal di Goma. In general terms the sweet stock is most in favor upon
the poorer class of high pine land, or with growers who are not able to
give the trees proper attention and sufficient fertilizer. With them the
sweet stock proves more hardy than the sour, enduring drought better
and making a better growth under similar conditions. There is but one
drawback to the general use of sweet stock on that class of land in north
and central Florida, but that is very nearly fatal at present. The dis-
ease variously known as Mal di Goma, foot rot, sore shin, and gum dis-
ease invariably appears in every orange-growing district where sweet
stock is used. Trees on high dry land are less liable to its attacks than
those on stronger or damper lands, but no district depending on sweet
stock can hope to be free from the disease for any considerable length
of time. In the orange-growing districts of Europe it has-compelled
the almost total abandonment of the sweet stock, and in California,
under the name ‘‘gum disease,” it is beginning to cause alarm. Ina
number of localities in Florida this disease has not yet appeared to any
extent, and from these the greater number of the replies favoring sweet
stock come; but, on the other hand, there are many reports from growers
who planted sweet stock trees, believing that their locality would be ex-
empt, only to see them die soon after they reached a good bearing age.
The subject of Mal di Goma will be discussed under asubseqent heading.

The question of sweet or sour stock is not so much one of relative
vigor as of the grower’s willingness to run the risk of Mal di Goma, and
opinions vary according to soil conditions. Replies to inquiries on the
subject indicate that sweet stock is favored by only about 17 per cent.
of those who grow the fruit on flat woods or poorly drained high pine
land, and by only about 3 per cent. of those whose trees are on ham-
mock or other rich, damp land. This shows that sweet stock is not
favored by the majority of growers.

SOUR STOCK.

The origin of the various species and subspecies of citrus is very
difficult to determine, but Gallesio proves beyond doubt that the sour
orange (Citrus bigaradia) was cultivated in Europe about the middle of
the fifteenth century, long before the sweet orange was known there.

11

At that time, and indeed for nearly two centuries, it was popularly sup-
posed that the sweet orange could be propagated only by grafting, and
for this purpose the bigarade stock was almost universally used. It was
quite natural, therefore, that the Spaniards at the time of their first
settlemént of Florida should have introduced the sour orange into that
country. Perhaps no plant has ever been naturalized so rapidly and
successfully as the orange tree. Indeed, did not the original narratives
of the Spanish discoverers of these regions and the testimony of contem-
porary historians prove that this treasure was received from Europe, it
would surely be regarded as indigenous to American soil.

In Florida the sour orange is found wild only in the hummocks.
There it seems to delight in the rich, moist soil, and it is on this kind
of land that its value as a stock is most apparent. While it does well
on the better class of high pine land, especially when well cared for, it
is never so vigorous as on stronger land. Its great point of value isits
freedom from disease, and it is upon this one claim that its popularity
is generally founded. Upon high pine land in Florida about 40 per
cent. of the growers are found to favor sour orange stock against 50
per cent. who favor sweet, and 30 per cent. who are divided in their
choice between rough lemon, pomelo, bitter sweet, lime, or who have
no choice. On the flat woods near 70 per cent. favor sour orange stock
against 17 per cent. who favor sweet, while on the hummocks fully 90
per cent. of the replies have been favorable to sour orange stock against
3 per cent. for sweet stock, including seedlings. Of the famous Indian
River groves fully 99 per cent. are founded on sour stock.

In some localities in Florida, notably in Orange and Volusia Counties,
it is claimed that drought is less injurious to sour than to sweet stock,
and there may be some foundation for this opinion, owing to the rela-
tively slower growth of the sour stock on sandy land, but the claim is
not general. Its claim for superior resistance to frost is much more
widespread, and despite some contradictory evidence, which may per-
haps be due to local causes, we must accept it until more accurate com-
parative experiments are made. The California returns are decidedly
corroborative of this claim.

In the nursery the sour seedlings are apt to become infested with
leaf-scab to a considerable extent, which often causes serious loss. No
critical study of the disease has yet been made, but it is clearly fungous
in its origin, and until such study can be made it might be well to ex-
periment with the ammoniacal fungicides which have proved so effica-
tious in pear leaf blight and apple scab. Once budded, all danger is
over, the sweet top being quite proof against the disease. Lemon
leaves and fruit are, however, subject to it.

Upon the subject of sour orange stock Mr. M. E. Gillett, of South

Lake Weir, Florida, writes the Pomologist as follows:
. -
-
This subject is one of vital importance to orange growers. All European countries

years ago discarded the sweet root as a stock to bud or graft, and use the sour almost
exclusively. I have been in the nursery business for some years, and have grown

12

many thousands of trees, have also charge of large grove interests here. One grove
on heavy hummock land is about gone with gum disease. Out of 1,200 to 1,500 trees
we have lost at least one-half, but have replanted all with others on sour roots, many
of which are 5 years old and bearing, and show no sign of any foot rot. Another
grove near here has lost every sweet stock (almost 600). All were replanted with
sour stock 6 years ago, and are doing well. Ona high pine grove, 80 feet above Lake
Weir, we have lost several large sweet seedlings from same cause, though we have a
remedy* which checks it on high land. On the low, heavy land, attacked trees
always die. We have been shipping about 150,000 trees per year for the past 3 years
to California, and from our experience we have contended all along that the sour
stock was in many particulars the better stock. I learn that they have foot rot in
California quite bad in some places, but in the face of it all there are a number of
California nurserymen who have trees on sweet stock who will argue against the
sour orange root. My experience with the two has been large, and the sweet seed is
easier to get and cheaper, but for many reasons we always get the sour. We believe
they are longer lived, hardier, more thrifty, and will stand more exposure than the
sweet. In the Speer grove at Sanford the old seedlings are dying apparently from
old age, while sour stock planted at the same time are beautiful old trees. I never
knew a case of gum disease on a sour tree in the wild groves or on those that were
transplanted, though sometimes when a tree is bruised it will gum, especially in hot
weather, but it soon heals.

ROUGH LEMON STOCK.

Within the past few years a new stock, combining most of the good
points of the sweet and sour stocks, has come into prominence, espe-
cially on the flat woods and scrub lands of the southern citrus belt of
Florida. This is the “French” or “Florida Rough” lemon, which has
been grown from time immemorial in Florida and the West Indies, and
seems to correspond almost exactly in tree, flower, and fruit with Hy-
brid XX V (citroned orange, citrus auwrantium indicum, citratum fructu
magno, cortice auro, crasso, amaricante, medulla acid et arma) of Gal-
lesio; it is also closely related to the Pomo d@’Adamo citron, and par-
takes of the nature of the citron, lemon, and orange. The tree has
escaped from cultivation and become naturalized in some parts of
south Florida, where the hummocks contain numbers of bearing trees
growing luxuriantly in the midst of thick underbrush and forest trees.
It is very valuable for home use, though not for shipping; the fruit
hangs on the tree in fair condition until the new crop is large enough
to use, and is very healthful and refreshing in the raw state.

As a stock for the orange and lemon it is becoming favorably known
all through south and central Florida, although in the northern part of
the State the pomelo may prove a trifle hardier. Either stock should
be budded as near the collar as possible as a safeguard against frost.
Upon its value Reasoner (Pom. Bul. No. 1, p. 76) remarks:

The rough lemon is most desirable on poor land or on low and wet land, as it suc-

ceeds better than any other stock in such lucations, being a free, rampant grower,
not particular as to location.

* To be found Sk, Se of ‘‘Mal di Goma.”

13

This statement, in fact, summarizes the whole subject. The rough
lemon does not take the natural place of the sour orange stock for
hummock or other strong soils, but it is practically as free from Mal
di Goma, and is considerably more thrifty than sweet stock upon high
pine land, at the same time doing well on wet flat woods, underlaid
with hardpan. Its practical value upon sandy soil is indicated by the
fact that 45 per cent. of the growers in south Florida favor it for high
pine, 50 per cent. for flat woods, and 8 per cent. for hummock. On
hummock the sour orange stock holds its own, 84 per cent. of the re-
plies favoring it for that class of land.

POMELO STOCK.

In habit of growth and thriftiness the pomelo much resembles the
rough lemon and practical trial has proved it a good substitute for
sweet stock on high pine land in the northern citrus belt of Florida.
It is more vigorous in growth than the sweet seedling on this class of
Jand, and while it does not gain favor on flat woods or hummock, yet it
is reputed to be considerably more hardy than the rough lemon, and
may possess all the advantages of that stock on dry, sandy land. Among
the reports furnished this office not over3 per cent. of the writers have
a large number of trees on this stock, but a much larger proportion
pronounce in its favor.

OTHER STOCKS.

Several other species of Citrus have been used as stocks for the
orange, among which may be named the lemon, lime, China lemon, bit-
ter sweet, citron, and trifoliata. The sweet lime, especially, is much
esteemed as a stock in India, and the Florida lime stock promises to
extend the southern limit of profitable orange culture. None of them,
however, are of great practical importance for grove culture in the
United States. The lemon 1s too susceptible to gum disease, the lime
and citron lack resistance to cold, the China lemon, commonly propa-
gated from cuttings, soon loses thrift and dies, the bitter sweet is not
so thrifty as the sour orange, and the trifoliata is a hardy dwarf stock
for indoor use, or for dwarfing the Satsuma. Upon this stock the Sat-
suma is hardy as a garden tree beyond the usual limits of orange cul-
ture, but its value has been greatly exaggerated, especially in Texas,
where it has been advertised as able to stand a zero temperature. A
Satsuma, Kumquat, Mandarin, or Tangierine on trifoliata stock makes

.a@ compact and highly ornamental house plant which bears good crops
in 3 or 4 years from the time of budding.

14
ORANGE STOCKS IN FLORIDA.

Per cent. of growers favoring each kind of stock on high pine, flat-
woods, and hummock land, by districts:

Northern citrus dis-| Central citrus dis- | Southern citrus dis-
trict. trict. trict.
Kind of stock. : 3 ee a ee
Mish) wat |Hum-) 2182) at |Hum|Aish) Pat | Hum.
Bnd. woods. |mock. eh wood. |mock. Bnd. woods. |mock.
Sega lp Leerde, Wea Rh eaytd Pct.) P. €t. |\Pct.| 2b Chan eaners
Sweetoranvesia:2 mses eeeeeeeeee ace 32 13 3 35 30 1 23 9 6
SEU RE oe oc stS osc o sabe soc n ae 52 77 97 34 64 90 29 40 84
Roughilemonwcsrsoo-seaeeee= eae ee Dil ae tool aeetsets Ve ee eee 4 45 50 8
Pomelo 225... scc<cscceccscs See HAE ete DH eee lees Bl seaenee if | A eee neo S-
Bitter sweeb. nis .ccsa nec scen. Saeco Ll .Sodos cel asbeeel sep ewal Redes cool zeae ee ae eee eee | aes
Worchoice of stocks -- 22-225 coscnnessee 11 TO is oes 17 6 4 2 1 2

* Sweet orange stock includes sweet seedlings.

SUMMARY AND RECOMMENDATIONS.

FLORIDA.

Northern citrus belt.—Upon high pine land, particularly of the second
or third class, use pomelo or rough lemon stock, taking care to bud very
low—as near as possible to the collar. The pomelo is cecidedly the
most hardy, comparing favorably with the sweet orange in this re-
spect. Ifthe grower is prepared to cultivate highly and perhaps irri-
gate, sour orange stock will be as satisfactory as any. Sweet stock
should be used only after carefully weighing the risk from Mal di Goma;
it will make large trees in less time than the sour, but not so quickly as
rough lemon or pomelo, and will not bear so early or be so prolific. In
planting sweet stock an excellent plan is to set it high, so that the
crown roots may be more or less exposed to the light and air, thereby
lessening the danger of disease.

For flat woods, especially when decidedly wet and underlaid with
hardpan, the sour root is decidedly better than the sweet, and although:
both rough lemon and pomelo are more thrifty, their comparative ten-
derness renders them undesirable except where the benefit derived
from thrifty growth is marked.

Upon hummock land sour stock is beyond all question to be pre-
ferred. Indeed, on such land no other should be planted.

Central citrus belt.—In this section the rough lemon root can be used
with much more safety, but should be budded low, both as a safeguard
against frost and in order to shade the trunk from the sun. Sour stock
is not in so much favor as in the more northern counties, especially upon
high pine land and flat woods. Upon hummock in this section the sour
orange root is far superior to any other for a stock.

Southern citrus belt—Upon high pine land, scrub, and flat woods use
the rough lemon stock. in the South the superiority of this stock is

15

beyond question, and it does fully as well upon flat woods as upon drier
land. Even in the hummocks it is superior to sweet orange, although
the sour orange is much more satisfactory in the end, on that class of
land, anywhere in the orange-growing regions.

LOUISIANA.

Upon the rich alluviums of the Lower Mississippi and its delta, where
all the large orange groves of Louisiana are situated, the sour orange
stock is preferred by about 90 per cent. of the planters. In a few in-
stances sweet seedlings have been used on the higher, gravelly lands
with fair results, but the sweet stock as such is almost unknown, while
danger from frost precludes the use of pomelo or rough lemon stock.
Mal di Goma is a common disease among the sweet seedlings, under
the name ‘sore shin.”

The greater part of this orange region is liable to inundation for a
month or more in the spring, as the river is above the level of the land
and frequent crevasses occur. Nothing but the sour orange root can
safely be used in locations subject to overflow.

CALIFORNIA. —

The orange has held a leading place among the fruits of California
ever since American occupation, but the question of stock has not been
considered to be of particular importance. Within the past few years,
however, the introduction and remarkable success of the wild sour
orange stock ((. bigaradia) of Florida has opened up a discussion which
will result in lasting benefit to the State. Certain nurserymen who
have large interests in sweet stock at stake bitterly oppose the intro-
duction of the sour orange, and endeavor to bias public opinion by mak-
ing the term sour stock include all roots except that of the sweet orange,
thus seeking to make the condemnation which all California growers
award to the lemon, China lemon, lime, etc., as stocks cover also the
sour orange stock. The injustice of this is manifest and can but work
injury to those employing such means.

The deep, rich alluvium, formed from granite and limestone and
underlaid with a retentive subsoil and sufficient surface irrigation, form
a combination of conditions to which the sour orange is peculiarly well
suited.

From data sent this office by California orange growers who have tried
the sweet and sour orange stocks side by side on a large scale it is safe
to conclude : ,

1. That the sour stock trees make a more thrifty growth;

2. That they are more free from disease and are entirely resistant to
Mal di Goma (foot rot or gum disease) ;

3. That they are less liable to be injured by cold while young ;

4, That the quality of the fruit is not impaired.

16

It seems high time for the California nurserymen to import sour
orange seed and grow their own sour stock, which would then be much
more satisfactory than the sour seedlings now brought from Florida
by the carload.

The great value of the Florida rough lemon as astock in Florida has
led to some inquiry as toits probable value in California. No extended
experience has been had with it in the latter State, and no positive
opinion can be given, but its remarkable thriftiness and precocity of
bearing make it worthy of full trial. It is considerably more sensitive
to frost than the sweet orange, and should invariably be budded low.
If it proves desirable in other respects it may be safely used wherever
the lemon succeeds commercially. It is entirely free from Mal di Goma
in Florida.

As an indication of the present status of the sweet and sour orange
stocks in California, extracts from the reports of several representative
growers are appended :

My ranch is on the northern border of the valley of San Bernardino, near its east-
ern extremity. It isin the valley proper, and at the base of the foothills by which
it is bounded on the north and east, and has an altitude of 1,250 feet. The location
is such that the cold air comes down from the San Bernardino mountains at night,
displacing the warm accumulations of the day, which rise to the foothills, assuring
them safety from frost during the night. Thisisat the expense of the lowlands, which
sufier from the extreme changes of temperature. The soil is a rich, sandy loam, well
irrigated. Manifestly, the abrupt changes in temperature to which I have alluded,
while perhaps not sufficient to kill the tree, are not for its good, and if there is any
difference in the sweet and sour stocks in ability to withstand these changes, it will
be found in the superior vigor and vitality of the one over the other.

Early in 1886, I procured from relatives at St. Mary’s, Ga, 40,000 reliable sour
orange seed, which I planted and subsequently budded to Washington Navel. In
May, 1890, I transplanted about 1,100 in orchard form, In 1888, on my ranch, four-
year old buds on sweet stock were frozen tothe collar. Within the past few days the
1,100 trees spoken of have been subjected to the lowest temperature I have ever
known on my farm, and in no instance have they suffered. Fresh growth is nipped
in cases only. The registers were for January 10, 6:30 a. m., 24° above zero; for 11th,
23°; and for 13th, 2L°. Within 10 feet of one row of these trees, ice formed one-
half inch thick.

I have never seen anything in sweet stock comparable with the wealth of roots on
my sour stock. The tops have grown even more luxuriantly. By reason of this and
my experience of the low temperature of the past few days, I am pleased to have
this opportunity to testify as to the performance of the sour stock and to venture the
opinion, based upon the experience in 1888, that the sweet stock trees would not have
survived.

Permit me to refer to the prejudice which exists here, fostered by our local nursery-
men, against sour orange stock, and to‘ recommend the procuring and planting of the
seed in all cases. * * * Whole orchards have been lost by planting Florida grown
trees which were poorly packed, and frequently kept out of the ground for months.—
H. J. QUINAN, Messina.

I have planted during the last 3 years about 90 acres of orange and lemon trees, of
which about 75 acres were on sour stock (Florida wild orange), budded to several
varieties, the remaining 15 acres being sweet seedlings. * * * These trees have
done well, making excellent growth and keeping in healthy, vigorous condition.
They have been subjected at various times to several degrees of frost, 26° once or

17

twice, 28° probably several times, and many nights cold enough to form ice on stand-
jug water, and without any serious wilting or apparent injury. Theswect seedlings
have made a larger growth than any of the budded trees planted at the same time
(1888) except the lemons, budded on sour orange stock, which have grown very
heartily indeed and are now bearing. * * * Inmy old orchard of Tahiti seedlings
there are perhaps sixty trees of Mediterranean Sweet on sweet stock, averaging 10
years old. They grow heartily and bear well, but show more sensitiveness to frost
than my young trees, many of the leaves wilting and turning white after a cold night.

One thing more may be worth mentioning as bearing on the question which has
been raised as to whether the sour root could impair the flavor of the fruit of budded
trees. On my Washington Navels, planted in 1888, I had in February and March,
1890, perhaps two boxes of perfect fruit, The flavor of these oranges was very
superior ; they were sweet, and of very lively flavor, and certainly showed no bad
etfect from the stock, I had made a similar observation in Riverside 2 years before,
on eating oranges grown on sour stock in the orchard of Mr. Bliss. They were the
best Navels I found in Riverside at that time, being a little riper, owing to some
earlier or heartier habit of the stock.—E. §8. TuatcuER, Nordhoff.

My investigations commenced in 1885 and have been faithfully followed up to date.
Previous to 1885 all the orange trees in California were on sweet stock, the sour
orange stock being unknown, hence a sweeping interest lies in sweet stock. My
own orchard was on sweet stock, but wherever I have lost trees I have sect sour stock.
Among my oldest trees I have been fighting ‘‘gum disease” for 5 years. In some
cases I have succeeded in overcoming it by cutting away the diseased wood and bark
and painting with strictly pure “rubber painf” to exclude the air. I have always
irrigated in furrows, allowing no water near the trunk of the tree, and have kept the
ground loose by cultivation. I cansee no reason for ‘‘ gum disease” except that it is
characteristic of the sweet stock ; have never heard of a case on sour orange stock.
To-day I feel warranted in saying that were I putting out a new orchard, I would
unquestionably use orange and lemon on sour orange stock.—D, C, TwoGoopn, River-
side.

Qf the 70 acres I have planted only 10 acres with trees on sweet stock. When I
made the change to sour stock, I made it mostly on the ground that I could get better
rooted trees at a less price on the Florida sour stock than on home-grown sweet
stock. I have now found that my trees on sour stock have made a better growth
than trees budded on sweet stock.

Three years ago next spring I planted 10 acres of Washington Navels on sour stock.
I was unable to get good sized trees for planting and was obliged to take trees from
2 feet to 30 inches high. On these trees there is about a box of oranges. In flavor,
sweetnes, and in all points that count to make a first-class orange, they are equal to
the best fruit ever grown. Have had no trouble from ‘ gum disease” up to date on
either stock.—C. E. HARwoopD, Ontario.

Mr. J. EK. Cutter, of Riverside, also gives the following interesting
statement:

Amount of land, 10-acre lot; soil, red granitic mesa ; depth to surface water, about
150 feet ; date of planting, April-May, 1887; stocks used, Bigaradia (sour orange); size
of stocks used, one-half to five-eighths inch diameter at base. [These small stocks had
just been brought from Florida.] Date of budding, October, 1889. [Some rebud-
ding in April, 1890.] Average diameter at base when budded, 2 inches; average
diameter at point of inserting bnd, 1} inches; average height of point of inserting
bud, 2 feet 8} inches ; average height of trees, December 25, 1890, 10 feet 84 inches;
average growth of buds, season of 1890, § feet three-tenths inch ; maximum growth
of single bud, 12 feet 1 inch.

This is by actual measurement, and Mr. Cutter further states that
the condition of his trees is the ‘ best of any grove I have ever seen.”
25170—No, 4——2

18

MAL DI GOMA.
Foot rot, gum disease, sore shin, eto.

A number of years ago a mysterious disease of the orange made its
appearance in Florida, and subsequently in Louisiana and California,
which has since baffled, to a considerable degree, all efforts to learn
its exact nature or to effect.a permanentcure. Investigation developed
the fact that the same disease had long been known as Mal di Goma in
southern Europe, where it caused the loss of millions of dollars’ worth
of orange and lemon groves, and that it first appeared in the Azores
about fifty years ago, and upon the Continent of Europe ten years later.

* CHARACTERISTICS OF THE DISEASE.*

The disease, as a rule, is first made manifest by the appearance of a
gummy effusion which appears, principally in the spring and autumn,
’ on the trunk of the tree close to the ground, or directly upon the root.
Even before there are any outward signs of diminished health, small
drops of gum appear on the bark of the trunk; these increase in size and
number and the bark appears to melt away or become honeycombed ;
finally, the gum liquefies and assumes a muddy brownish color and a
disagreeable odor. In winter or summer when the effusion of gum de-
creases or stops the greater part of the bark around the point of infec-
tion dies and becomes detached from the wood. When dry it springs
away from the wood and becomes hard and brittle. The surface of the
wood underneath the bark is also affected to some little distance in all
directions from the point of infection. The most vital part of the trunk,
the cambium layer, which lies between the bark and the wood, is par-
tially destroyed, and each year this destruction extends until it finally
girdles the tree completely, thus cutting off all communication of the vital
fluids between the root and the top, and causing the death of the tree.

When the disease attacks the roots the death of the tree follows more
rapidly—often in less than a year. The sudden changing of the leaves
to a sickly yellow color is the first visible symptom of the disease when
the roots are attacked. It must be kept in mind, however, that the
leaf-yellowing may be due to other causes.

CAUSE OF THE DISEASE.

The cause of Mal di Goma is not certainly known at present, but, con-
trary to the general supposition, indications point to a bacterial rather
than a fungous origin. Itis true that several species of fungi are found
on the diseased parts, but these are believed to be saprophytic in their
nature rather than parasitic.

Various theories as to the cause of the disease have been advanced—
improper drainage, “ wet feet,” growing over hardpan, improper fer-

* Extract from Bulletin No. 8, Division of Vegetable Pathology,

ig
tilizer, unsuitable soil, irrigating too close to the tree trunk, excess of
ammonia, setting too low, ete.—but none of them hold good except in
individual instances.
TREATMENT SUGGESTED,

The disease is a dangerous one to experiment with, and except in
unusually well drained location the tree had better be immediately dug
up and burned, root and branch. Itis even dangerous to dig about
healthy trees with the same implements used to dig about diseased trees
unless they are disinfected with carbolic acid. Positive evidence ex-
ists that the disease has been conveyed from tree to tree in this way,
by a sort of accidental inoculation. As an aid in preventing or check-
ing the ravages of the disease, growers are advised (1) to bud on resist-
ant stocks—wild sour orange, rough lemon or pomelo; (2) to plant on
dry and porous soil if sweet stock is used; (3) to irrigate sparingly and
keep the water from the trunk of the tree; (4) to cut out every trace of
diseased wood and bark when the malady appears, and burn the part
cut out.

Secretary B. M. Lelong, of the California State Board of Horticul-
ture, recommends that the wound be painted over with pure rubber
paint, after the diseased wood has been removed. Mr. M. E. Gillett, of
Florida, gives the following receipt for a treatment which he has found
reasonably effective upon high pine land:

The remedy I have used is composed of the following ingredients: One peck fresh
stone lime, 4 pounds copperas, 5 pounds sulphur, 1 gill crude carbolic acid. Put
these in a barrel and add enough water to slack the lime, cover and let it stand until
cool, then fillthe barrel with water and stir well. The mixture is then ready for
use. All the diseased bark and wood should be carefully cut away, and the wash
applied with a brush. While the preparation does not always cure, it has checked
the trouble, and trees that I have experimented upon seem to be doing well.

This, and other remedies we have seen, seem to be disinfectants
rather than fungicides, but the addition of sulphate of copper may
be an improvement, and is certainly a step in the right direction.
Washes having bisulphate of soda and carbonate of lime as a base
would probably be of some value, and are worth experimenting with.

MUTUAL INFLUENCE OF STOCK AND SCION.

While the prime object of graftin g or budding is to perpetuate the
characteristics of an individual plant, or to propagate a variety, physi-
ologists tell us that the vigor and fertility of the scion are affected more or
less by the operation. The pear grafted on quince roots is dwarfed, but
on Kieffer pear roots is made much more vigorous. On the principle
that the vigorous growth of the tree is at the expense of its fruitfulness,
and on the other hand that prolificacy interferes with vigorous growth,
working a strong growing scion upon a weak root will bring the tree into
bearing at an early age. But why the stock should hasten or retard

20

the period of ripening, or how it changes the color, flavor, or size of the
fruit, is not so easily shown. We know that a number of the superb
foreign varieties of the pear can only be grown successfully by us on
quince roots; the Angouleme and Louise Bonne are notable examples
of this, being generally conceded to be of decidedly higher quality
upon the quince, but on the other hand the Seckel needs all the vitality
of a thrifty stock to reach its greatest perfection.

All we know about the phenomenon of dwarfing is that the quince
stock gives out a more meager supply of sap, so affecting the growth
of the tree that it is stunted in its growth of wood and thus brought
into bearing at an earlier age and made to produce larger and more cer-
tain crops of perfect fruit, but the want of complete harmony between
stock and scion has a tendency to shorten the life of the tree. A good
example of the ordinary effect of stock upon scion may-be found in
nursery practice: a promiscuous lot of seedlings is raised and upon
these roots some particular variety is worked; all may be planted at
the same time and under exactly similar conditions, but a season’s
growth will develop a marked variation in individual vigor, which can
hardly be laid to any cause except variation in the vigor of the differ-
ent seedlings. Indeed, this difference in thriftiness, owing to varia-
tion of stock, is a matter of commercial importance, determining to a
large extent the several grades into which nursery trees of any given
variety are assorted.

Considered from a theoretical point of view no influence, as far as
the flavor of the fruit is concerned, is to be expected. The ascending
sap, which is furnished by the root or stock, is nearly a simple fluid.
The leaves digest and modify this sap, taking carbonic acid from the
air and forming the sugar compounds and sap proper. The leaves oi
a grafted tree are the leaves of the particular variety cultivated, and
have no physiological connection with the root grafted upon. Every
bud, leaf, and fruit upon a branch maintains its individuality by pre-
paring its own proper nourishment out of the general supply of the
sap. Each separate cell of the inner bark has this power of preparing
food according to its nature. In proof of this De Candolle (Physio-
logie Végétable) cites an instance where rings of bark, of closely allied
species, were grafted one above another on the same tree; no buds
were allowed to grow, but when the tree was cut for examination, char-
acteristic wood of each species was found deposited under its respect-
ive ring.

Though the stock increases in size by woody matter derived from the
sap elaborated by the leaves, its character is not perceptibly changed;
a sprout from below the point of union always being characteristic of
the original stock. Proof that the graft may communicate disease to
the stock is, however, abundant and beyond question. Yellows of the
peach has been propagated thousands of times by budding, and the
stock and bud die together from its effects. The same may also be

21

said of blight in the pear. The phenomenon of variegation, which is
now classed as a form of disease, gives an excellent example of the
power of the scion to infect the stock, variegated leaves frequently ap-
pearing upon the stock below the point of union and sometimes even
as stolons from the root. On this point Burbidge (The Propagation
and Improvement of Cultivated Plants, p. 61) gives some very interest-
ing details. In some instances the habit of root growth is influenced
toa marked degree, an upright top inducing deep rooting, and a spread-
ing top being always accompanied by good lateral roots.

A strong root produces a strong top growth, and while the top re-
mains and expands the root extends in the same ratio. When, how-
ever, we cut off the vigorous top and substitute a weaker, the root is,
to a great extent, paralyzed, even though it induces a strong temporary
growth. It can never do more than respond to the weaker growth
grafted upon it, and in the end the graft becomes just as weak as if it
had been upon its own roots. In this relation, however, recent experi-
ments incline us to the belief that far greater benefit may result to a
weak scion if a portion of the original vigorous stem and foliage be
allowed to remain, thus preserving nearly the whole vigor of the root. In
a limited way a weak variety might advantageously be grafted with
stronger ones at both ends by the practice known as double grafting.

To summarize our present knowledge of the whole subject we may
say that a strong growing variety is dwarfed by union with a weaker
stock, while a weak scion is not in the end benefited by grafting in the
ordinary manner upon a stronger stock. In either event the flavor and
quality of the fruit is only affected in proportion to the thriftiness of
the tree’s growth, the natural flavor or character of the fruit of the
stock having no influence whatever upon the fruit of the scion.

EXPLANATORY NOTE.

For the benefit of those who are not familiar with Florida, the terms ‘high pine
land,” ‘‘ flat woods,” ‘‘ scrub,” and ‘hummock ” may be explained as follows:

High pine land.—A light-gray sandy loam, more or less rolling in surface, timbered
sparsely with long-leaf pine and fairly free from undergrowth, except in localities
where saw palmetto is abundant; generally underlaid with clay at a depth vary-
ing with the height of the land, and with a yellow sand subsoil. On the lower lands
several species of scrub oak are found among the pines.

Flat woods.—Timbered like high pine, but generally has more saw palmetto; un-
derlaid with hard-pan at a depth of 6 inches to 2 feet, and in the rainy season often
flooded for weeks at a time.

Scrub.—Generally a bank of white or yellow sand, covered with a scant growth of
a species of heath known as rosemary and thickets of scrub or spruce pine (Pinus
mops), a species which grows on no other land. ‘‘ Black-jack” scrub is generally
not quite so barren as rosemary scrub.

Hummock.—A term applied indiscriminately to any land with hard-wood timber
and dense undergrowth. The soil is generally much stronger than the best pine
land, and lies on a lower level, although not always wet. Low hummock is often
very close to the water level, but can not be called swampy, although frequently
flooded in summer.

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