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Bulletin 27

April, 1895

NEW HAMPSHIRE C0LLP:GE

AGRICULTURAL EXPERIMENT STATION

SPRAYINa EXPERIMENTS IN 1894

BY H. H. LAHSON

NEW HAMPSHIKE COLLEGE

OF

AGRICULTURE AND THE MECHANIC ARTS

DURHAM, N. H.

NEW HAMPSHIRE COLLEGE

OF

AGRICULTUHE AXD THE MECHANIC ARTS

AGRICULTURAL EXPERLAIENT STATION

Durham, N. H.

BOARD OF CONTROL

Hon. Geo. A. Wason, Chairman^ New Boston.
Pres. Chas. S. Murkland, e.c-officio, Durham.
Charles W. Stone, A. M., Secretary^ East Concord.
Hon. John G. Tallant, Pembroke.
Henry AV. Keves, A. M., Haverhill.

THE STATION COUNCIL

President Chas. S. Murkland, Acting Director.
Henry E. Alvord, C. E., Agricxdtxirist.
Chas. H. Pettee, A. M., C. E., Meteorologist.
Fred W. Morse, B. S., Chemist.
Herbert H. Lamson, M. D., Bacteriologist.
Clarence M. Weed, D. Sc, Entomologist.

ASSISTANTS

Edward P. Stone, B. S., Assistant Chemist.
Fred D. Fuller, B. S., Assistant Chemist.
RuEL S. Alden, B. S., Farm Superintendent.
Richard Fitzgerald, Clerk.

The BuUctins of this Stsition are sent to any resulcnt of New Hampshire
upon application.

SPRAYING EXPERIMENTS IN 1894

BY H. H. LAMSON

The experiments recorded in tliis bulletin are a continuation
of similar ones carried on in 1892 and '93, directed chiefly to
the treatment of the fungous diseases of the apple, pear, and
potato.

Numerous varieties of apples aud pears are affected with the
disease known as the scab, which is caused by the growth of a
minute parasitic or fungous plant. Frequently very serious
injury is done, both to the foliage and fruit, aud some varieties
are almost a complete failure on account of it. The scab
grows on the surface of the leaves and fruit. On the leaves
it grows in dark green or smoky spots and patches, frequently
causing them to become much wrinkled ; on the fruit the scab
produces characteristic dark green or black spots, rounded in
outline with sharply defined margins. When attacked early,
the fruit is liable to be one-sided, and in many cases it is badly
cracked.

PEARS

About two-thirds of a Flemish Beauty pear tree was sprayed
and the other third left unsprayed. The spraying was done
on April 30, May 22, June 1.5 and 30. 1 to 12 Bordeaux mix-
ture (1 pound blue vitriol to 12 gallons of water; see under
heading Bordeaux mixture) was used. The pears, when gath-
ered, showed the following result :

Unsprayed.

Sprayed.

1st quality, 23 per cent.

70 per cent.

2d " 67

30

3d " 10

An increase of 47 per cent, apparently due to spraying.

The third qualit}' iu this and the following tables of results
of pear experiments means fruit cracked as well as scabby.

A Louise Bonne pear tree was sprayed with 1 to 12 Bordeaux
mixture ou April 30, May 22, and June 15 and 30. Another
tree of the same variety was left unsprayed for comparison.
The pears, when gathered, showed the following result :

Unsprayed.

Sprayed.

1st quality, 4 per cent.

•20 per cent

2il " 93

80

3d " 3

An increase of 16 per cent of first quality fruit. Very many
of the pears were classed as second quality on account of their
small size. The following table shows the percentages of
scabby pears on the two trees :

Unsprayed. Sprayed.

Pear.s free from scab, 58 per cent. 98 per cent.

" more or less scabbed, 42 " 2 "

Giving an increase of 40 per cent of pears free from scab on
the sprayed tree.

Five Lawrence pear trees were made the subjects of another
experiment. Three were sprayed with 1 to 12 Bordeaux mix-
ture and two were left unsprayed. The spraying was done
on May 2, June 0 and 26, and July 26. The pears, when gath-
ered, showed the following result :

Unsprayed.

Sprayed.

1st quality, 50 per cent.

67 per cent,

2d " 50

33

Giving an increase of 17 per cent of first quality pears on
the sprayed trees.

These pears were affected with two different species of fungus,
the scab, and what, for want of a better name, we have called
the ^^ moth patch." The latter gives the fruit a dirty, smoked
appearance, occurring sometimes in roundish blotches, but
frequently almost entirely covering the fruit. This disease
also affects some varieties of apples, e. g., the Greening and

the Northern Spy. It is readily distinguished from the scab,
which usually occurs in darker, thicker, and more sharply de-
fined spots. The following table shows the percentages of
scab and moth patch on the sprayed and unsprayed trees :

Unsprayed. Spraj'ed.

Scab, 36.1 pel' cent. 3.5 per cent.

Moth patch, 98.9 " 1.3

Giving a decrease of 33 per cent of scab and 97 per cent of
moth patch on the sprayed trees.

APPLES

About forty Baldwin apple trees in the orchards of the col-
lege farm were sprayed with Bordeaux mixture. The apples
from these trees and from unsprayed ones for comparison were
gathered and stored in the barn which was burned Nov. 3, '94.
The apples were all destroyed. The apples from five trees only
had been sorted. Of these trees, two were sprayed and three
unsprayed. The two trees were sprayed four times with 1 to
12 Bordeaux mixture, viz., on April 28, May 23, June 13 and
30. On May 23 and June 13, six ounces of Paris green per
fifty gallons was added to the Bordeaux mixture for the codling
moth. The following table shows the result :

Unsprayed.

Sprayed.

1st quality, 58 per cent.
2d " 23
3d " 19

79 per cent.
14

7

Giving an increase of first quality in favor of sprayed trees
of 21 per cent.

The percentages of scabby and wormy fruit were :

Unsprayed. Sprayed.

More or less scabby, .33 per cent. 3 per cent.
Wormy, 17 " 6

In the orchard of Mr. DeMeritt twenty-four Baldwin apple trees
were sprayed with 1 to 12 Bordeaux mixture. The first spray-
ing was done May 2, just as the leaf buds were beginning to

open, June 9, just after the blossoms had fallen, the trees were
spraj'ed again. At this spraying six ounces of Paris green per
fifty gallons was added to the Bordeaux mixture for the codling
moth. This sprayiug did considerable injury to the foliage, so
that only half of the trees were sprayed a third time on June
2C, Bordeaux mixture alone being used at this time.

"When the apples were gathered, the fruit from eight of the
sprayed trees was saved for examinatiou, and also the fruit
from eight unsprayed for comparison. Four of the sprayed
trees received three applications aud four only two, but owing
to lack of time and conveniences, the apples were not kept
separate, so that the apples from the eight trees as a whole
may be said to have received two and one-half sprayings. The
following table shows the result:

Unsprayed.

Sprayed.

1st quality,

20 per cent.

30) per cent.

2(1

58

42

3fl

22 "

22

Giving an increase of IG per cent of first qualit}^ fruit in
favor of the sprayed trees.

The percentages of scabby and wormy fruit were :

Unsprayed.

Sprayed.

Scabby, 79 per cent.

lit per cent

AVormv, 20

8

The windfalls which were under the trees were picked up
before the fruit on the trees was gathered, and were sorted and
counted. The following shows the percentage of windfalls to
the total number of apples on and under trees :

Unsprayed. Sprayed.

Windfalls. 35 per cent. 23 per cent.

The windfalls showed :

Unsprayed. Sprayed.

Scabby, 50 per cent. '.) per cent.

Wormy, 59 " 32

Aside from the scab, much of the unsprayed fruit was affected

by another fungous disease, which made its appearance in
the form of dark brown spots varying in size from mere dots to
spots one-sixteenth inch or more in diameter. The spots
were usually slightly depressed or sunken below the gen-
eral surface. The presence of this disease made it necessary
to class many apples of good size and shape as seconds. The
sprayed apples were almost entirely free from this trouble. Our
observation indicates that the diseased spots tend to grow
larger on the stored fruit and to serve as the starting points of
decay.

In case of nearly all of the sprayed trees more or less injury
was done to the foliage by the second spraying, when Paris
green was added to the Bordeaux mixture. The usual amount
of Paris green recommended is four ounces to a barrel, or fifty
gallons. In this case six ounces were used. It was thought,
however, that the lime in the Bordeaux mixture would prevent
any bad results, and we are at a loss to account fully for the
injury done. It may perhaps be partl}^ accounted for by the
fact that where the worst damage occurred the spraying was done
on a bright, hot day — a condition which is known to favor the
injurious tendencies of Paris green.

Lichens or 3/o.s.s. — Many fruit trees are covered with differ-
ent varieties of lichens or "moss," as they are often called. It
is a question not yet decided how much direct injury they do to
the trees, but they are unsightly and oft"er protection to insects
and their eggs. The Bordeaux mixture is very effective in
destroying them.

Russety Fruit. — Among our spraj^ed apples we found some
with a rough or russety skin, and thought at first that it was
due to spraying, but we found that many uusprayed ones were
just as bad. In fact many apples last season showed this
russetiug. The late frosts last spring, just as the trees were
in bloom, were perhaps to blame for this. It must be noted,
however, that the Bordeaux mixture does sometimes produce a
similar effect. We also heard of numerous instances last fall
of Flemish Beauty pear trees which had not been sprayed, but
which produced a fair crop of pears ; something unusual for this

8

part of the country. The pears were also unusually russety.
It seems possible that the russety surface due perhaps to frost
presented an unfavorable condition for the development of the
scab fungus, aud thus in a measure protected the fruit from its
injuries.

POTATOES

In the case of potatoes the experiments were directed chiefly
towards the prevention of the Early Blight and the Scab.

The following description of the early blight is reprinted
from the New Hampshire College Experiment Station Bulletin
No. 22.

EARLY BLIGHT

The early blight ( Macrosporimn solani ) has come to be rec-
ognized as a serious disease of the potato only within the last
two or three years. It was first noticed at this station in the
summer of 1892. As its name indicates, it makes its appear-
ance earlier than the ordinary blight — by the middle of July or
earlier. It first appears, as sharply defined, rather irregular,
dark brown or blackish spots on the leaves. The surface of
the spots is usually marked with minute wrinkles, which take
roughl}' the form of numerous circles with a common centre;
this has been called the '•'target marking," from its resemblance
to the concentric rings of a target. The spots increase gradu-
ally in number and size till the whole leaf is destro3'ed.

The fungus producing this disease differs considerably in the
details of its structure from the late blight, but like it, consists
of mycelial threads which grow in the tissues of the leaf and
send out spore-bearing stalks on the surface. The early blight
may be distinguished from the late blight by its characteristic
spots, l)y the absence of the mould-like growth on the under
side of the leaf in the case of the latter, by its earlier appear-
ance and slower growth, and by the fact that it does not aflfect
the tubers.

The experiments against the early blight wore made in the
Station potato field. On Jul}' 7, plots aggregating one and one-
sixth acres were sprayed with Bordeaux mixture. Alternate
plots aggregating four-fifths of an acre were left unsprayed

9

for comparison. The spraying was repeated July 26, August
8, 21, and September 4.

The early blight did not make its appearance in the field until
about the time of the third spraying, August 8, and did not
begin to seriously affect the unsprayed vines until two weeks
later. By the middle of September, however, the unspraj'ed
vines were dead, while the sprayed vines, in varying proportions
in dift'erent parts of the field, were alive the first of October
when the potatoes w^ere dug.

Owing to the uneven character of the field and the effects of
the drouth, the yield of the sprayed plots as a whole could not
be compared with that of the unsprayed plots. Smaller plots
of each, as similar in character as possible, were chosen and
and the yields compared. Five pairs of plots were selected,
each consisting of a sprayed and an unsprayed plot of equal
size lying side by side. The sprayed plots showed an increase
in yield over the unsprayed as follows :

Pair No. 1 an increase of '2H.1 bushels per acre.

2

f (

.•51.9

3

((

54.7

4

(<

28.4

5

a

21.3

The average increase per acre apparently due to spraying was
33 bushels.

The cost per acre of each spraying was $3.52; for the five
sprayings, S17.60. The potatoes were sold for 60 cents per
bushel. At this price the 33 bushels were worth $19.80. De-
ducting the cost of spraying, $17.60, there was left a profit of
$2.20. This, as it stands, would not be a ver}^ brilliant result,
but there are several circumstances which should be taken into
consideration along with it. It seems probable that three
sprayings, beginning the first of August, would have answered
as well as the five, beginning the seventh of July. Sprajnng was
begun at this early date to make sure of getting ahead of the
blight, which, however, did not appear till about the middle of
August. Had three sprayings only been made, the cost would
have been $10.56 and the profit $9.24 per acre. It is probable
that owing to the drouth and the late appearance of the blight,

10

the difference in yield between the sprayed and unsprayed pota-
toes was not as great as it would be ordinarily. Again, it is
possible that with the desire to make the treatment thorough,
more materials were used and more time taken than was actually
uecessar}'. At each spraying 150 gallons of Bordeaux mixture
per acre were used. The mixture was made according to the
following formula :

Blue Vitriol 5 lbs.

Lime (Fresh)... 5 lbs.
Water .^0 gallons.

The blue vitriol cost, in 25 pound lots in Boston, G cents per
pound, and about 6.^^ cents laid down. The lime was purchased
in small quantities, and cost 1 cent per pound.

At these prices 150 gallons of Bordeaux mixture cost $1.12|^,
or about | of a cent per gallon. In spraying an acre, two men
were employed eight hours at 15 cents per hour; the time
expense was S2.40. The actual time of spraying was six hours ;
two hours were occupied in obtaining water, making the mix-
ture, etc.

It is probable that the expense for labor can be considerably
reduced. The total expense will vary with the luxuriance of
the vines, the number of applications required, the local cost
of materials, the form of apparatus used, and the convenience
of water. It is our belief, however, that spraying against the
early blight will be found to be a profitable operation.

Late Blight of the Potato. — The late blight, or the rust or
rot, as it is often called, makes its appearance usually about
the first of August. It is characterized by the rapid withering
and dying of the leaves, and by the appearance on the under
side of the affected leaves of a fine white mold-like growth,
which consists of the spores and spore stalks of the fungus
producing the disease. The tubers are usually more or less
affected. If the weather is warm and wet, the course of the
disease is very rapid.

The early and the late blight are often present together.

I'OTATO SCAI'..

Within a few years it has been found that this serious disease

11

is not caused, as has been supposed, by any condition of soil
or fertilizers, but by minute parasitic plants belonging to the
class known as bacteria. These little plants grow in the super-
ficial portions of the tuber, where they act as an irritant, caus-
ing a growth of the tissues, which results in the production of
the characteristic scab spots. A scabby crop of potatoes
results either from the use of scabby seed, or from planting on
ground which has previously produced a scabby crop. The
germs of the disease live on the harvested potatoes, and also
for an indefiuite time in infected soil. When it was found that
the scab was caused by bacteria, it readily occurred to experi-
menters that corrosive sublimate, a substance extensively used
for the destruction of other bacterial germs, might prove useful
in treating it. This has been tried, and the corrosive sublimate
found to be capable of destroying the germs on scabby seed, so
that when the latter was planted on soil itself free from the
germs, a smooth crop was produced.

An experiment in this Hue was tried here last summer. Po-
tatoes of the Ueleware variety, very badly scabbed, were used.
Previous to planting, half of the potatoes were treated with
corrosive sublimate in the following way : Two and one-fourth
(2^) ounces of corrosive sublimate were dissolved in two or
three gallons of hot water. This was poured into a half barrel
and sufficient cold water added to make fifteen gallons in all.
The potatoes contained in a coarse "feed" sack were placed in
this solution and allowed to remain for an hour and a half.
The sack of potatoes w^as then taken out and after draining the
potatoes were emptied out and allowed to dry. They were
then cut and planted. Treated and untreated seed were planted
side by side in alternate plots of two rows each, on land which
had not been plowed for many years and was therefore presuma-
bly free from scab germs. When the plots were dug the tubers
of marketable size were sorted into three grades, viz. : the first,
practically free from scab ; second, more or less scabbed ; third,
badly scabbed. The following table shows the results:

Treated.

Untreated.

1st grade, 60 per cent.

31 per cent

"Jd " 31

3(5

3d " 9

33

12

This shows that although the scab on the treated plots was not
wholly prevented, it was greatly reduced. The seed which was
xevy badly scabbed was not washed previous to treating it, and
possibly the solution of corrosive sublimate did not penetrate to
all parts of the scabby patches.

It would not be advisable, of course, to plant scabby seed even
with this treatment, if clean seed could readily be obtained ; but
it is difficult to obtain seed in regard to which one can be cer-
tain that it is not more or less contaminated, for small patches
of scab are easily overlooked. Tubers absolutely free from
scab themselves, if selected from a biu in which there are a few
scabby ones, would be liable to carry germs iu the dirt adhering
to them. In using such seed it would doubtless be beneficial to
wash thoroughly in water aloue, but better iu the corrosive
sublimate solution. The relation of fertilizers and conditions of
soil to the development of scab has not yet been definitely made
out, aside from the fact that they are not the direct cause of it.
It seems likely that certain conditions of soil, existing naturally
or produced by the use of certain fertilizers, are especially favora-
ble to the growth of the scab plant w^hen its germs happen to
be present on the seed or in the soil.

The cost of treating the seed for an acre ought not to exceed
$1.50 for both labor and materials. In the above experiment
thei'e was a gain of thirty bushels of marketable potatoes per
acre on the treated plots.

As corrosive sublimate is a powerful poison, it should not be
used carelessly.

BORDEAUX MIXTURE

The Bordeaux mixture is coming to be recognized as the
most efficient among the many fungicides which have been tried
during the past few years.

The ingredients of it are copper sulphate, which is commonly
known as l)lue vitriol, or blue stone, lime and water. A large
number of formulas, differing in the proportion of these ingre-
dients, have been published.

3

The original formula, as published in this country, was Blue
Vitriol, 6 pounds ; Lime, 4 pounds ; and Water, 22 gallons.

This has been found to be much stronger than necessary for
effective work, and various degrees of dilution have been rec-
ommended. The formulas for the dilute Bordeaux mixture
have been almost as numerous as the individual experimenters,
While many of them have been practically identical in strength,
the different wording and arrangement of proportions have been
confusing, so that the movement on foot among experimenters
for a simplification of formulas seems wise.

We think the method of expressing the strength of the
mixture suggested in N. Y. Agricultural Experiment Station
Bulletin No. 84, page 3, a good one. It is the first publication
of the method which Ave have seen, but we have personally used
it in our notes and computations for the last two years. This
is, in substance, to make some weight of the blue vitriol the
unit of the formulas, and to express the strength by the pro-
portion of water used with it, it being understood that a sufficient
quantity of lime is to be used. The pound naturally suggests
itself as the unit of weight for the blue vitriol, and the gallon
for the unit of water.

According to this mode of expression the original formula
quoted above, viz., 6 pounds of blue vitriol to 22 gallons of
water would be 1 to 3|; 1 to 8 Bordeaux Jiiixture would be 1
pound of blue vitriol to 8 gallons of water; 1 to 12 Bordeaux
mixture would be 1 pound of blue vitriol to 12 gallons of
water. By using this method it is very easy to compute the
amount of materials necessary for any given quantity of the
mixture.

The important ingredient of the Bordeaux mixture is the
copper sulphate, or blue vitriol. This alone, dissolved in water,
would be an efficient fungicide ; but it would so seriously injure
the foliage of plants, that the remedy would be worse than the
disease. The object of the lime in the Bordeaux mixture is to
prevent this injury. This it does, when used in a sufficient
quantity, by producing a chemical change in the solution of blue
vitriol which renders it harmless. The lime is also of use in
Causing the mixture to adhere more strongly to the sprayed
foliage, so that it is not quickly washed oft' by rains.

14

As indicated by the origiual formula given above, two-thirds
of a pound of lime has been found to be sufficient to neutralize
a pound of blue vitriol. For convenience we have used and
recommended equal weights of blue vitriol and lime. We do
not know of any l)ad results from using this amount of lime.

Instead of weighina: the lime a test has been in use during
the past year or two which indicates when sufficient lime has
been used. This test consists in adding a few drops of a solu-
tion of yellow prussiate of potash, or potassium ferrocyanide, as
it is known chemically, to the Bordeaux mixture, when a brown-
ish color will appear if too little lime has been used. More lime
must then be added until the brown color fails to appear on
adding a fresh quantity of the ferrocyanide solution. This test,
when rightly used, is probably reliable. Instances are however
•reported of the Bordeaux mixture causing injury to foliage and
fruit where this test has been used, probably from the fact that
not quite enough lime had been used. It is therefore recom-
mended that after the addition of the ferrocyanide solution ceases
to produce the brown color, a still further quantity of lime
should be added for safety, for a small excess is far better than
a slight deficiency. Perhaps, under the circumstances, it would
be safer to continue to weigh the lime, using two-thirds as much
as of blue vitriol.

Perfectly fresh lime should be used. Air-slaked lime will not
answer. It is therefore better to use only the lumps. Care
should be exercised in slaking the lime. Water should be ad-
ded only just fast enough to keep the lime wet. It should be
kept thoroughly stirred after it begins to slake, as when any
considerable quantity is used the bottom poi'tions are apt to be-
come dry and " burnt." After the lime is slaked, sufficient water
should be added to make it of the consistency of fresh cream.
It is then ready to be added to the solution of blue vitriol. The
blue vitriol may be dissolved quickly in hot water, or the re-
quired amount may be placed in a basket or loosely woven
sack and suspended in a tub or other wooden vessel of cold
water. As fast as it is dissolved the solution, which is heavier
than the water alone, will sink to the bottom of the vessel and
a fresh portion of water will come in contact with the crystals

15

until they are completely dissolved. About two quarts of
cold water are required to dissolve a pound of blue vitriol. This
is a good way of dissolving the blue vitriol when it is not wanted
for immediate use, and is preferable to putting the crystals
loose in the bottom of the vessel, for in that case they will dis-
solve very slowly unless kept constantly stirred.

Our actual practice has been to make a stock solution, by
dissolving the blue vitriol in a sufficient quantity of hot water
and then adding enough cold water to make half as many gal-
lons as there were pounds of blue vitriol. Two quarts of this
stock solution therefore represents one pound of blue vitriol.
This is a very convenient way, especially where small quanti-
ties only of Bordeaux mixture are used at a time. A stock
solution of lime also may be made. These stock solutions
should be carefully protected from evaporation.

The slaked lime should be strained before adding to the solu-
tion of blue vitriol ; or better still, perhaps, the completed Bor-
deaux mixture should be strained before pouring into the pump
tank, in order to remove the coarser particles, which would be
liable to clog the spraying nozzle. The straining may be done
through coarse sacking, or a wire strainer with a mesh about
one-sixteenth of an inch wide.

The Bordeaux mixture should be kept thoroughly stirred up
during the time of spraying. It is at its best for only a few
hours after its preparation ; it soon develops a greater tendency
to settle and loses a part of its valuable property of sticking to
the foliage. We would recommend as a formula for Bordeaux
mixture for general use :

Blue Vitriol, 1 pound.
Lime, fresb, =3 "
Water, 10 gallons.

This makes a 1 to 10 mixture. To make a combined insecti-
cide and fungicide, Paris green or London purple may be added
to the Bordeaux mixture, in the proportion of four ounces
(^ pound) to fifty gallons. This combination is useful in the
spraj'ing of apple trees just after the blossoms fall, as it serves
to destroy both the scab and the codling moth. A second
spraying with it ten days or two weeks later is also advisable.

16

The combination may also be used for potato blight and bugs.

Paris green may be used with water in the proportion of four
ounces to fifty gallons. A pound of fresh lime, or an equiva-
lent quantity of slaked (not air-slaked) lime added to it, will
lessen the danger of injury to foliage from its use. This answers
for canker worm.

One of the most important points to be observed in the use
of mixtures containing Paris green, is to keep them thoroncjhly
stirred up.

RECOMMENDATIONS

Pear and Apple Scab. — Spray with Bordeaux mixture once
before the. blossoms open; again just after they have fallen,
and then a third time after ten days or two weeks. Rainy
weather may make a shorter interval and an additional spraying
advisable. ^

At the second and third sprayings Paris green or London
purple,, in the proportion of four ounces to fifty gallons, may
be added to the Bordeaux mixture for the codling moth.

Potato Blight. — For the early blight spraying with Bordeaux
mixture should be begun by the middle of July, or sooner if the
characteristic brown spots of the disease make their appear-
ance. The spraying should be repeated twice, with an interval
of ten days or a fortnight. If the weather is rainy, the inter-
val between sprayings should be shortened and a fourth appli-
cation may be advisable. This treatment will serve for both the
early and the late blight. If it were known that only the late
blight was to be dealt with, the spraying might usually be de-
layed till the last of July.

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