SOME. EFFECTS OF THE USE OF
HIGHLY REFINED OILS AS SUMMER
SPRAYS ON THE PEAR

Thesis for the Degree of M. 3.

LELAND E. SCOTT
1929

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SOME EFFECTS OF THE USE OF HIGHLY REFINED OILS
AS SUMMER SPRAYS ON THE PEAR.

Thesis

Presented to the faculty of the Michigan State
College of Agriculture and Applied Sci-
ence as partial fulfillment of
the requirements for the
degree of
Master of Science

by
Leland E. Scott

 

1929

 

TH E615

 

 

Introduction

v vi

 

flhe use of highly refined oil as an insecticide for
summer or foliage spraying has become very popular in
certain sections during the last few years. In California
a combination oil spray and fumigation program is proving
most effective for the control of scale insects on citrus.
In the north.west and in certain Mississippi valley states.
oil is being used with the usual arsenical spray for codling
moth control on apples. Michigan pear growers are using oil
as a summer control measure for the pear psylla.

Although these soocalled "summer” oils have been
treated to remove the unsaturated compounds that are found
to be toxic to plants, their use has caused injury in many
cases. The inJury may be direct, involving a ''burning" or
destruction of the plant tissues; or indirect, effecting the
normal physiological processes of the plant. The direct
injury can usually be avoided by the use of a more highly
refined oil. still retaining the insecticidal value of the
'oil by decreasing the volatility. The indirect inJury is due
to the presence of the oil on the surface and perhaps in the
leaf tissues. The effect of this oil film upon the function-
ing of the leaf is difficult to explain and may prove to be

a limiting factor in the use of summer oil sprays.

103?; 5:5

Review of hiterature

 

One of the most significant developments in the
field of oil sprays was the discovery of the relation
between the unsaturated hydrocarbon content of an oil
and its toxicity to plant tissue by Gray and DeOng (l)
in 1915. This work showed the possibilities of the use
of heavy petroleum oils as foliage sprays.

DeOng et a1 (2) found that various physiological
disturbances are induced in citrus trees by the use of
highly refined or "neutral" oils. These disturbances
were evidenced by the dropping of mature leaves and
fruit and by a delay in the artificial coloring of green
lemons.

Woglum (3) found that oil applications in late
autumn delayed the ripening of oranges and lemons and
reduced blossoming the following spring.

Driggers (4) noticed a yellowing of the foliage and
a drop of young fruit on peach trees sprayed with a one
per cent "white" oil in May and June.

Parrott and Harman (5), however, observed no inJury
to peach trees sprayed with two or three applications of

oil during the growing season.

Bourroughs (6) found that the amount of starch
in oil sprayed apple leaves was much less than in
unsprayed leaves, although this did not hold true in
all cases.

Regan (7) obtained a discoloration of the calyx
end of apples, especially on the varieties, Grimes and
Yellow Newtown, by the use of "summer oils." This injury
was associated with drought conditions.

Cross (8) noted a marked reduction in the rate of
water loss from plants sprayed with Volck, even though
there was no apparent injury to the foliage.

Although none of these experiments refer to the

pear, it is conceivable that the pear might react similarly

to oil applications.

Obiect of‘Emperiment

 

Late dormant applications of oil have been found
to control the pear psylla fairly well in most locations
and in most seasons but many Michigan pear growers have
to use supplementary control measures to insure freedom
from the pest. In the past, nicotine sulphate has been
used but has never proved entirely satisfactory for
several reasons. First, it has no "hold-over" effect and
reinfestation occurs very soon after spraying. Second,the
material is relatively expensive. Third, and this is not
of least importance, many growers object to using nicotine
because of its effects on them personally.

Therefore, instead of nicotine sulphate, summer oil
sprays have been.used recently with very good results as
far as psylla control is concerned. Several brands of
summer oils are available to the grower. Ehese studies
were made to determine the degree of safety with which

these can be used on the pear.

materials and Methods

 

The oils used in the experiments are in the form
of commercially prepared emulsions that are specifically
recommended by their manufacturer for foliage spraying.
12125, manufactured by the California Spray Chemical
Company, is a "white oil" emulsion having an.unsu1fonat-
able residue of 99 to 100 per cent. Orthol-K; manufactured
by the same company, is a less highly refined oil with an
unsulfcnatable residue of about 90 per cent. The stock
emulsions of Orthol-K and Volck contain 83 per cent oil
by volume. Each is made in three grades, (1) heavy, with
a viscosity ranging from 100 to 110, (3) medium, viscosity
90 to 100, and (3) light, viscosity 80 to 90. (Ssybolt
viscosity at 100°C.). When the terms Volck and Orthcl-K
are used alone the heavy grade oil is meant. Leda, a
product of the Standard Oil-Company, is a white oil emul-
sion containing about 65 per cent oil with a viscosity of
83 . Medina Summer mnuiaiog. manufactured by the New York
Insecticide Company, is a white oil emulsion.

Information concerning the exact nature of the emul-
sifying agent employed is not available, but in each 011
it is known to be of the inert, non-soap type. The emulsions
are "quick-breaking," that is, they contain a very low perb
cemtage of the emulsifier. This permits the freeing of the
oil immediately after the emulsion strikes a leaf surface.

Unless stated otherwise, all of the oils were applied at
a two per cent concentration of the stock emulsion.

Bordeaux and lead arsenate were combined with the oil
spray in the early season applications. The bordeaux
formula unless otherwise stated was 3-8-100, the first
figure of the formula indicates pounds of copper sulphate,
the second figure pounds of hydrated lime and the third
figure gallons of water. Lead arsenate, when used was added
at the rate of two pounds to 100 gallons of spray. Nicotine
sulphate (40 per cent actual nicotine) was used at the rate
of one pint to 100 gallons of spray, increasing the lime
content of the bordeaux formula to 25 pounds.

The following procedure was followed in diluting and
mixing the various materials in the spray tank. The stock
emulsion was diluted in a pail to several times its original
volume with the stream from the spray gun. The diluted
emulsion was poured into the spray tank and the stream from
the gun played in it, the continual pumping and agitation
giving a uniform emulsion. Solutions of the hydrated lime,
copper sulphate and lead arsenate were made separately and
added as the tank filled. Nicotine was added last.

All of the spraying was done from the ground with a
gun. To insure the covering of every leaf the applications
were made very thoroughly.

Because of the danger of psylla infestation the check
plots could not be left unsprayed. The nicotine and lime

 

'used on them caused no inJury. All of the orchards under
experiment remained very free from psylla injury throughout
the summer, due partly to weather conditions and partly to

the efficiency of the oil as a control measure.

Dpfini‘tion of Terms

 

In the brief statements of results that accompany
the summaries of the spray treatments, the effects of the
oil are described in certain terms. "InJury" refers to
any brown spotting or other discoloration of the leaf that
seems to have involved the killing of the tissues. This
appeared in a number of different forms depending upon the
oil used, the presence of bordeaux and the weather condid
tions. "Penetration? refers to the apparent entrance of
oil into the leaf or fruit tissues. The penetrated portions
of the leaf appear darker by reflected light and more trans-
lucent by strong transmitted light than the rest of the leaf.
{Injury may, and probably did, involve penetrationL.
"Russeting" refers to any roughening of the surface of the
fruit.

 

The Orchards

 

All of the work was done in pear orchards near
South Haven, Michigan, a few miles from the shore of
Lake Michigan. Since the spraying program, including
the oils used and the number of applications, varied
with the different orchards, the work done in each will
be treated as a separate experiment, giving a descrip-
tion of the orchard, an outline of the spray applications

and a brief statement of results.

1. the Hunt Orchard:

 

The experimental block in this orchard contained
336 twelvesyear-old Bartlett trees. The trees have been
making only moderate growth and have never borne heavily,
probably because of nitrogen deficiency. The trees
blossomed heavily in 1928 but the set of fruit was so
poor that the resulting crop was very small.

The spraying program is given in Table 1. The plots
were three rows wide and contained about 25 trees each.

The temperature during the petal-fall and tdeweeks
applications ranged from 55° to 60°F. and on July so the

temperature was about 7001.

Table l.-0utline of spray treatments in the Hunt orchard

 

 

 

i -il-- iv Applications__ _r_
Petal-fall Two-weeks Midsummer
Plot Mo.‘(May 22-23) {June 7) (July 50[__
1 Volck and Volck and
bordeaux bordeaux - ------
2 Bordeaux Volck and
bordeaux -------
3 Bordeaux Volck and
bordeaux Volck
4 Nicotine and Nicotine and
bordeaux bordeaux -------
5 Orthcl-K and Orthol-K and
bordeaux bordeaux -------
6 Bordeaux Orthol-K and
‘ bordeaux .......
7 Bordeaux Orthol-K and
bordeaux Orthol-K;__

 

v v w v vfi vw—v

Volck caused no injury but did result in some penetra-

tion and formed a heavy oil accumulation on the leaf that

collected dust. The Orthol-K and bordeaux caused considerable

brown spotting, especially when used in the petal-fall spray.

This was accompanied by a rolling and curling of the leaves.

The later applications of Orthol-K did not cause as much injury.

There was a slight rolling of the leaves in the Volck sprayed

plots. The foliage on the oil sprayed plots was mottled and of

a distinctly yellower appearance than that of the check plot.

This was more noticeable on the Orthol-K sprayed trees which

seemed to be checked in growth throughout the summer.

10

II. The Egg Orchard

 

This orchard comprises 686 trees, eve of which are
mature trees suitable for experimental purposes, the rest
are nonpbearing replants. About three-fourths of the 478
are Bartlett, the remaining fourth consisting of Clapp's
Favorite, Howell and Seckel with a few Kieffer, Bose and
Flemish Beauty. The trees have been kept in good condition
and have been bearing fair crops. All varieties blossomed
and bore heavily in 1928.

The spraying pregram is given in Table 2. Bordeaux
and lead arsenate were used with the oil in the first
application that constituted the regular two-weeks spray.
The oils were used alone in the second application.

The temperature ranged from 56° to 70°F. during the
first application and from 70° to 86°F. during the second.

No injury was caused by any of the materials used in
the first application, except the medina Summer Emulsion
and bordeaux combination. The foliage sprayed with this
showed brown spots within a few days. This injury increased
for about ten days. Later in the summer the more vigorous
trees did not show any injury but the weaker ones remained
noticeably checked in growth. All of the fruit was russetted
so badly that it was thrown out of degrade. The L~43 and
Yolck sprayed trees showed slight oil penetraction on the

leaves, otherwise they appeared normal. The nicotine used

with the oil caused no difference.

11

Table z.- Outline of Spray Treatments in the dye Orchard

 

 

————fv~‘v v

First Application

Second Application

 

 

P1 t (June 9-14} wfi (Aug. lagld)
o
no. Materials .i lEffects Materials Effects‘fi
l Volok heavy, Slight oil Volck heavy Mederate oil
bordeaux and penetration penetration
lead arsenate
2 velck heavy,
nicotine*and Slight oil
bordeaux penetration no spray
8 Volck light, No Trace of oil
bordeaux penetration Volck light penetration
4 Nicotine
sulphate and no noticeable Velck Slight oil
bordeaux effect medium penetration
5 L948,
Nicotine
sulphate‘and Slight oil
bordeaux penetration No spray
6 1948 and Slight oil Very heavy
bordeaux penetration L-dz penetration
7 Nicotine and no noticeable Orthol-K. No noticeable
bordeaux effect light effect
8 Medina and 95 per cent
bordeaux of leaves
injured, 100 Orthol-K
per cent of medium no noticeable

fruit scarred

effect

* Nicotine content of spray reduced to one-half pint for
100 gallons.

There was no injury from the second application but

heavy penetration occurred, especially on the L943 sprayed

trees. On these trees the oil penetrated both the leaf and

fruit. There was a moderate foliage penetration on Volck

sprayed trees and a slight.indication of fruit penetration.

12

 

III. The Dennett Orchard

The Dennett orchard is situated in low sandy soil.
Lack of care and the nature of the soil have prevented the
trees from attaining normal size although they are in
good condition. In 1928 the Barteltt trees in the orchard
bore a good crop. '

The spraying was done with a hand-operated Hardie
barrel pump hauled through the orchard on a Ford truck.
From 6 to 12 gallons of spray were mixed for each applica-
otion. One or two materials were applied to a tree leaving
one side of the tree unsprayed to serve as a check. Only
the largest of the Bartlett trees were sprayed. The
pressure at the pump varied from 150 to 200 pounds. Each
time there was to be a change in the material used the
barrel was flushed out and clean water pumped through the
pump and hose.

Table 3 gives a list of the applications and the
effects caused. The bordeaux in the spray undoubtedly
caused the severe injury obtained by the applications
number 41 and 47 inclusive. Since there was no bordeaux
check to application number 40 it is impossible to
determine the causative agent but the injury seemed to be
of the oil-bordeaux type rather than a strictly bordeaux
burning.

 

 

15

 

 

Table 3.- Summary of Oil Sprays used in the Dennett Orchard
he. material'used Date Induryfi Penetration
1 Volck heavy 1% July 6 Rene . none
2 Velck heavy 2% " 6 ' Light
3 Velck heavy 3% "' 6 " Heavy
4 Volck heavy 2%
and bordeaux . " 6 Trace none
5 Volck heavy 2%, v 21 None Light
6 Velok heavy 2p
and Kayso " 21 " Light
7 Velok heavy 2%
and soap " 21 Slight '
8 Velok heavy 2% Aug.20 lene medium
9 Velck medium :2 July 9 " Bone
10 Velck medium 2% " 9 " Idght
11 Velck medium ' 9 ” medium
12 Volck light 1 V 9 " Rene
13 Volck light 2% " 9 n n
14 Volck light 3% V 9 " Light
15 Orthol-K heavy 196 n 6 " None
16 Orthol-K heavy 2% n 5 Moderate Light
17 Orthol-K’ heavy 3% " 6 Severe
18 Orthol-K heavy 2%
and bordeaux ' 6 Severe
19 Orthol-K‘heavy.2% dug.25 none Heavy
20 Orthol-K 2%
and soap ' 25 Slight Heavy
31 Orthol-K medium 1% July 6 none None
22 Orthol-K medium 2% V 5 " Medium
23 Orthol-K medium 3% .. 6 n v
24 Orthol-K medium 2% lug.25 " '
25 Orthol-K medium 2%
and soap " 25 " medium
26 Orthol-K light 1% July 9 " Bone
27 Orthol-K light 2% ' 5 " Ldght
28 Orthol-K light 3% V 5 Trace Medium
39 Medina 1% n 6 Slight
30 Hedina 2% " 6 Very severe
31 Medina 556 n 5 ~ ~
32 L-43 1% n 6 None None
33 1945 2% * 6 Slight Very slight
34 L43 3". v 6 " Light
25 L-43 1% Aug.29 Rene "
36 L-43 2’: " 20 " Very heavy
57 L943 3‘ " 20 V " '
38 L943 2% " 25 " " "

14

Tahle 3.7 Continued

 

Bo. Material used Date Injury: Penetration
39 Leda 2% and soap Aug.25 Rene Very heavy
40 L943 2% and
bordeaux 3-8-100 July 9 Severe
41 1943 2% and
bordeaux 2-4~100 Aug. 2 '
42 L-es 2% and
Bordeaux 6-12-100 " 2 Very severe
43 Leda 2% and
bordeaux 4-8-100 " 4 " "
4d Bordeaux 4-8-100 " 4 " "

45 Velck medium 2%
and bordeaux

4-8-100 " 4 II n
46 Volck light 2% and
bordeaux 4-8-100 " a n n

47 Orthol-K medium
and bordeaux

4-8-100 " 4 " "
48 L943 2% and

bordeaux 4-8-100 Sept.28 Slight
49 Bordeaux 4-8-100 " 28 Bene

 

15

IV. The Station Orchard

Three trees of each of the four varieties, Bartlett,
Howell. Flemish Beauty, and Kieffer in the Experiment
Station orchard. were sprayed with Volck and Orthol-Kf
‘used alone and in combination with bordeaux and with a
drybmix spray known as Kolcform. The spraying was done
may 26. very soon after the petals had fallen and at a
period when the leaves were young and growing rapidly.

The temperature was about 50°F.

flhe effects of the sprays on the different varieties
are given in Table 4. Howell seemed to be the most suscept-
ible to inJury and Kieffer the least. Flemish Beauty showed
less iniury than Bartlett. no defoliation.was caused by
the oils used alone or with bordeaux. Ihc partially burned

leaves remained on the trees.

V. ghe Green Orchard

 

Mature trees of five varieties, Bartlett, Clapp's
Favorite, Flemish Beauty, Bose, and D'Aniou.were sprayed
in the Green orchard. The trees bore a moderate crop in
1928. Table 5 gives a summary of the applications and
effects. The weather at the time of spraying was bright
and hot, the temperature ranging from 80° to 89°F.

16

Table 4.-Effects of Oils used in Station Orchard

 

 

Material used Variety? ' Effect
VOlck Bartlett Slight penetration
Velck Howell Heavy penetration
Volck Flemish Beauty Very light penetration
Volck Kieffer V ' V V
Orthol-K‘ Bartlett Moderate injury
Orthol-KL Howell Severe injury
Orthol-KI Flemish Beauty V V
Orthol-Kf Kleffer Slight injury
VOlck and Bordeaux Bartlett Trace of injury

V V V Howell Slight injury

' V " Flemish Beauty Trace of injury

V V V Kieffer V V
Orthol-K’and Bordeaux Bartlett moderate injury

" “ " Howell Severe injury

V V " Flemish Beauty moderate injury

V V " Kieffer Slight injury
Volck and Koloform Bartlett Ono-half defoliated

V V V Howell Totally V

V V V ' Flemish Beauty Three-fourths V

V V V Kieffer One-fourth V
Orthol-K and Koloform Bartlett Totally V

I I! W How, 11 I! I!

V V V Flemish Beauty V V

V V V Kieffer V V

 

vv—v 'fi V—v— ‘w— YWV a... w w— v—v' v v w ——

Table 5.-Outline offiSpraijreatmentsrinqthe Green_Orohard

V vvfiv—v—fiv—fi V‘v ‘

 

 

 

Mi --iliaterielainsfln Bat! - ififiiaata- i n
D'Lnjou Lees £ug.7 moderate penetration
Flemish Beauty Velck,bordeaux, V 7 Slight penetration,

lead arsenate bordeaux burning on
young leaves.

Bose Lde and

lead arsenate V 7 Heavy penetration
Clapp's Favorite Volck V 8 Light penetration
Bartlett L~43 ' V 8 Heavy penetration

 

vvv‘w fiv‘ vvvvvvaVvavvvv 'v' v V W‘— V

17

Bffects of Oil on Foliage

Injury

Oils used 51922" None of the Volck applications

 

caused any injury to the leaves when the oil alone was
used in the spray. The Orthol-K Heavy burned the foliage
in some instances and had little effect in others. In

the Dennett orchard the Orthol-K Heavy at a two per cent
concentration injured the leaves when used July 5 and

did not when used August 25. L three per cent concentra-
tion caused severe burning July 5 while a one per cent
caused none. The Orthol-K Heavy applied in the Hunt
orchard July 30 caused no injury but when used on several
varieties of the Station orchard trees severe damage
resulted. The light and medium grades of OrthcléKTdid not
injure foliage except in one case when a three per cent
application of Orthol-K Light in the Dennett orchard
burned slightly.

The Lpes. when used in the Dennett orchard July 6
at two and three per cent concentrations. caused a slight
injury. This was not obtained again by any application of
Leda. neither later in the summer in the Dennett orchard
nor in the Nye or Green orchards.

The Iodine Summer Emulsion was used alone only in

the Dennett orchard. It caused such serious injury there

18

that further use was impracticable. All of the leaves
were burned and some defoliation occurred. The injury
increased with the concentration. the one per cent con-

centration causing little damage.

 

Oilwandwhordeaux.- The combination of bordeaux
with the oil generally tended to increase the likeli-
hood of injury. This injury was different from that
caused by oil or bordeaux alone.

The Volck and bordeaux used in the Hunt orchard
caused a little burning on the under sides of the
leaves but the injury was nearly as bad on the check
plot where bordeaux alone was used. In the Bye orchard
this injury was not noticeable. On the Station trees
it was more severe.

When Orthol-K was used with bordeaux the injury
resulting was more serious than that from either used
alone. The petal-fall application in the Hunt orchard
burned and curled the leaves to such an extent that the
growth of the trees was noticeably checked. The later
applications in this orchard caused similar injury but
to a lesser degree. In the Dennett orchard Orthol-K
and bordeaux again caused severe burning.

The Leda and bordeaux used in the Bye orchard

showed no sign of injury but when the same combination

was used in the Dennett orchard a month later severe

19

injury of the oil-bordeaux type resulted. On August 4
when L943 and bordeaux was used again in the Dennett
orchard and the injury compared with that of a bordeaux
application, it was found that the bordeaux alone caused
nearly as severe injury as when the oil was used. This
was repeated with L~43 and with the other oils and the
same results obtained. This spraying was done on very
hot days following a dry and hot period of weather. It
was thought possible that the bordeaux so increased
transpiration that the leaves suffered from drought.
During September there were several rains and cooler
weather and the bordeaux was tried again September 28.
This time the bordeaux alone gave no injury while the
L-43 and bordeaux burned the leaves slightly at the margins.

The Medina was used with bordeaux only in the Rye
orchard. The injury obtained was similar to that caused
by the medias in the Dennett orchard. Leaves on the
rapidly growing shoots were injured most but the weaker,
less vigorous trees showed the greatest general injury,
probably because they lacked the power of recuperation.
There was no defoliation, the partially burned leaves
remaining on the trees.

Oil_andfi3gyéfltx.- Growers are cautioned not to
mix lime-sulphur with the dormant oil sprays. An effort
was made to determine whether or not this caution applied

to the use of dry-mix lime and sulphur with summer oil

20

emulsions. On the Station orchard trees Koloform was
used with Volck and Orthol-K. The leaves showed injury
within two days and within a month the sprayed limbs
were totally defoliated. Little difference was notice-
able between the two oils. Volck and Koloform seemed

to be.a little slower in action. Four varieties were
sprayed and the results with each were so positive that

the combination was not tried again.

Penetration

V 'V—v

 

Great variation was observed in the degree of
penetration of the different oils and in the penetra-
tion of the same oil used at different times during
the summer.

When light, medium, and heavy grades of the same
oil were used, the heavy grade caused the most penetra-
tion. This is shown by the results of the Volck and
Orthol-K applications in the Dennett orchard.Penetration
varied directly with the concentration of the oil. Volck
and Orthol-K of the same grade seemed to penetrate about
equally although the degree of penetration of the Orthol-K
‘was hard to determine because of the injury to the leaf.
It is reasonable to suppose, however, that wherever injury
was found the oil had penetrated the leaf tissues. L-43 ,

caused a much greater penetration than Volck or Orthol-K. *

21

Medina caused so much injury that the penetration was
of minor importance. However there was evidence of
penetration before the burned areas appeared.

Oils used late in the summer penetrated more than
when used earlier in the season. This may have been due
to the higher temperatures that prevailed in the later
summer. L~48 caused very slight penetration in the Dennett
orchard July 6 but very heavy penetration when used
August 20.

The presence of bordeaux in the spray lessened the
amount of penetration. probably because of oil adsorp-
tion.by the bordeaux, thus decreasing the amount of free

oil on the leaf surface.

Permanence of Oil Film

 

It was very evident that differences existed among
the various oils in the length of time a noticeable oil
film remained on the leaf. A rough test for the presence
of such a film was to rub the sprayed leaves between the
fingers. If oil was present the leaf felt gummy or sticky
in contrast to the smooth surface of the unsprayed leaf.
As with penetration, when light, medium, and heavy grades
of the same oil were used, the heavy grade gave the
heaviest and most persistent oil film on the leaf. L-4s
collected on the leaf as drops of the free oil that could

22

be spread about with the finger as late as a week after
the application. Volck did not do this but after a longer
period, a month or six weeks, there seemed to be as much
of the Volck oil on the leaf as there was of the Lp43. On
the Hunt orchard the Volck was more persistent on the ~
foliage than the Orthol-K; This accounted for the greater
dust accumulation on the Volck sprayed plots.

leaf Fall

 

Rene of the oils used caused a leaf fall soon after
application except when they were used with Kbloform.
Even though a large portion of the leaf tissue was killed
abscission did not occur. It was thought, however, that
the oil might have some effect in.hastening or delaying
the normal leaf fall in the autumn. With this in mind the
leaves on 150 individual spurs in each plot in the Hunt
orchard were counted and the spurs tagged. The first count
was made June 9 and the final count October 27. A.count
made September 15 showed that no drop had occurred before
that time. In fact there was no noticeable drop of leaves
on any of the plots until about October 15. However by
October 27 there was a great difference in the defoliation
of the different plots. This is shown in Table 6. The

small numbers of leaves counted may render small differences

23

Table 6.-Leaf fall in the Hunt Orchard based on leaf counts
on individual spurs
' ‘ " fl ' No. of Ho. of Yer can?
leaves leaves remaining
Plot No. Spray treatment June 9 Oct. 27 Oct. 27

 

 

 

l Volok & bordeaux
petal-fall & two-weeks 791 693 87.6

2 Bordeaux - petal-fall
Volck & bordeaux
two-weeks 748 496 66.3

3 Bordeaux - petal-fall
Volck & bordeaux
two-weeks. Volck July
30 715 609 85.1

4 Nicotine & bordeaux -
petal-fall and
two-weeks 681 454 66.6
5 Orthol-K & bordeaux
petal-fall & two-
weeks 684 139 20.3
6 Orthol-K - petal-fall
Ortholék & bordeaux -
two-weeks 437 47 10.7
7 Bordeaux - petal-fall
Orthol-K & bordeaux
two-weeks
Orthol~K July 30 638» 163 25.8
in the table of no significance but the difference between
the Orthol-K plots and the other four plots is very outstand-
ing. Soil conditions may have entered into some extent but
the marked difference in leaf fall of the trees in a check
plot row and an adjacent Orthol-K sprayed row precluded the

possibility that they could be totally reaponsible.

 

24

leaf Color and Form

 

The foliage on oil sprayed trees usually appeared
yellower than that on the unsprayed trees. In some cases,
however, the difference, if any existed, was not noticeable.
0n plot 5 in the Hunt orchard where Orthol-K was used in
the petal-fall application the leaves were very mottled--
perhaps half of the leaf area showing a decided lack of
chlorophyll development. 0n the Station trees the yellowing
was obtained when the oils were used alone but not when
used with bordeaux.

The oil affected the leaf form only when applied early
in the growing season. In the:Hunt orchard, the OrtholoK
caused considerable rolling of the leaves, especially the
leaves on the growing shoots. The leaves afterward curled
as if the longitudinal growth had been checked with the
width continuing to increase giving the leaves much the
same form as those affected with peach leaf curl.

The rolling was slightly noticeable on the Volck

sprayed trees.

Effect on Fruit

 

Russetting

 

The Medina Summer Emulsion was the only oil that
caused any injury to the fruit. When it was used with

bordeaux in the Nye orchard practically every pear on

25

a sprayed tree was russetted to such an extent that it

could not be classed as A-grade. The russet blotches were
usually more or less confined to the calyx end of the fruit,
probably because the oil collected there in larger amounts
after spraying. The russetting did not appear until several
weeks after the oil application and did not deform or notice-
ably oheck the growth of the fruit. The injury was not
noticeable on the naturally russetted varieties, such as the
Seckel and Bose. 0n the Howell, Clapp's Favorite and
Bartlett it was most conspicuous.

In the Dennett orchard the Medina used alone caused
similar injury besides checking the growth to a great extent
due to the severe foliage injury. Some of the fruits were
deformed.

Although Orthol-K caused some injury to the leaves

it did not cause any russetting or other inJury to the fruit.

genetration

 

It has been said that the IP45 penetrated the leaf
much more than did the other oils. This was true with the
fruit also, especially when the oil was applied after the
fruit had attained considerable size. After the second
application of L-43 in the Nye orchard dark blotches were

noticed on the fruits of the Howell and Bartlett. These

26

became more noticeable as the fruit ripened. The same
condition was observed on the Bartlett in the Green
orchard and to a much greater extent in the Dennett
orchard where the applications were excessively heavy.

Volck used at the same time on the same varieties
did not show this penetration nearly as much as the IP45.
In the Rye orchard there was a slight indication of
penetration and in the Dennett orchard the VOlck caused!
a little blotching of the fruit.

The light and medium grades of Volck and Orthcl-K

caused no penetration of the fruit.

Keeping‘Quality

At Ordinary Temperature.- During the time the pears
were being picked for market, samples consisting of 18
fruits were taken at random from the sprayed and check
trees in the different orchards. Each lot was immediately
weighed and placed in a dark room on shelves to ripen.

The final weights were made when the pears were ripe enough
to be eaten out of hand.

The time of storage and the loss in weight in percent
of the pears from the Rye orchard are given in Table 7. The
pears from the check plot lost less in weight than those
from the oil-sprayed plots. Those sprayed with Ortholéx,
medium, L~43 and Volck showed the greatest loss. The high
loss of the pears sprayed with Orthol-K Medium was due

27

very likely to the fact that they were russetted by the

previous Medina application.

Table 7.- Loss in weight in per cent of pears kept in warm
storage. Samples from the Bye orchard

fifvvvvvv‘fi fifi' W

 

T fifi—

Variet and length of storage period
CIapp gavorIEe Bartlett BarEIett ‘HOwell‘"“

(lst lot) (2nd lot)

 

 

 

Plot No. Spray (12 days) (11 days) (l2fidays) (30 daysl
l Volck heavy 6.63 5.26 8.84 9.04
2 None 4.94 2.36 2.85 ~---
3 Volck light ~--- 2.26 3.72 9.59
4 Volck medium ---- 7.10 7.65 8.88
5 None 5.23 1.66 4.09 6.22
6 L-43 5.95 7.47 8.42 8.90
7 Orthol-K
light 5.55 4.27 4.61 8.73
8 Orthcl-K

 

fiw‘iVfiv—v'fifi W 7 v—v

The data on the samples from the Dennett orchard are
given in Table 8. The difference in favor of the check plots
is not as great or as consistent as in the Nye orchard samples
but there seems to be a tendency for the oil sprayed pears to
lose more weight.

There was no consistent difference in the rates of
ripening. \

All of the oil sprayed fruit was duller and lacked
the polish of the unsprayed pears. This was most noticeable
on the L~43 and Volck sprayed fruit. These pears felt sticky
or gummy in contrast to the smooth and waxy surface of those

unsprayed. The pears from the L-43 sprayed trees in the Nye

and Dennett orchards that showed 011 penetration did not

28

Table 8.- Loss in weight of Bartlett pears from the Dennett
orchard. Ripened at ordinary temperatures

 

 

 

Lot No. Spray used Date sprayed Loss in weight
per cent
1 Volck heavy 2% Aug. 19 3.43
2 L943 2% n 19 6.26
3 Check on (1) & (2) 3.70
4 LP43 3% n 19 2.49
5 Check on (4) 4.68
e L~43 2% July 6 6.45
7 Volck heavy 3% July 6 2.67
a Medina 2% July 6 7.97
9 Volck heavy 3% July 21 5.10

10 Or tho l-K

haavy 2% Allge 25 3089
11 Random check. 2.60
12 L-43 s% Aug. 4 4.29
13 L—43 2% Aug. 25 5.75

 

ripen evenly. The oil penetrated areas remained green as the
rest of the fruit ripened giving the pear a mottled appearance.
This was slightly noticeable in the Volck sprayed pears from
the Dennett orchard. The Volck sprayed pears from the Nye
orchard did not show blotching but they did appear greener
when ripe than the unsprayed pears. It seemed that the presence
of the oil prevented the development of the yellow color but
did not retard the rate of softening.

In Cold Storage.- A half-bushel of pears was picked at

 

random from each of the sprayed and check plots in the Nye
and Green orchards. These were weighed and placed in cold
storage. By Nbvember 21 none of the lots had lost any weight
although all of the Bartletts had undergone a physiological
storage break down. No difference could be observed between

the sprayed and unsprayed Bartletts. The other varieties,

29

Howell, 8080 and Flemish Beauty were taken from cold storage
and ripened at ordinary room temperature. There was no
difference in lost of weight during the ripening period or
in the rate of ripening between the sprayed and unsprayed
lots. In fact it was almost impossible to see any difference
in their appearance. The oil penetration that was evident
at picking time had disappeared and the pears did not show
green blotches upon ripening as they did in the warm storage

roome

Effect on Spur Growth

 

The rate of growth of a tree can be measured by the
increase in shoot or spur length or by the increase in
shoot or spur diameter. The latter method was used in
determining the relative rates of growth of the oil-sprayed
and check plots in the Hunt orchard.

Four trees from each of plots 1, 2, 3, and five from
each of plots 5, 6, and 7 and nine trees from plot 4, or the
check plot, were selected for the purpose of making growth
measurements. These were not chosen haphazardly but care-

. fully picked out so that the trees in the check plot and
the sprayed plots would be as nearly uniform in size and
vigor as possible. From each of the trees selected five or
more sections of branches bearing three-year-old spurs were
out. These spur bearing twigs were packed in damp moss and

taken to the laboratory for sectioning.

30

Only non-bearing spurs were used in the experiment.
Sections were cut with a sliding microtome midway between
the annual rings on the spur and midway between spurs on
the twig. These sections were stained with safranine and
haemotoxylin to distinguish the xylem and phloem more clearly,
and then mounted in balsam.

The measurements were made with a micrometer eye piece
in the ocular of a microscope. Each growth ring was measured
in four places, in the center of each quadrant, and the
average of the four measurements taken as the width of the
ring. Concentric growth rings were measured in the same
relative position on the circumference.

Widths of Annual Rings.- The measurements of the

 

annual growth rings for the different plots are given in
Table 9. Each figure represents the average annular growth
for the group of spurs taken from a plot. Twenty spurs were
measured from each of the first three plots, 25 from each
of the last three and 45 from the center, or check plot.
Columns 3 and 5 show that the growth was fairly uniform
throughout the plots in 1927. At least no one plot showed a
consistently higher or lower growth rate in 1927 than the
others. However, when the 1928 growth of the plots is com-
pared, columns 1, 2 and 4 show that in every instance but
one, the growth ring in an oil-sprayed plot was smaller than

the corresponding ring in the check plot.

32

In order to take into consideration the growth rates
of the plots in a season previous to the experiment, when
comparing the 1928 growths of the plots, the widths of the
1928 growth rings were figured on a percentage basis of the
1927 growth rings. The resulting figures are given in
Columns 6, 7 and 9. Furthermore, these relative figures
expressing the 1928 growth, can be expressed as percentages
of the check plot. This has been done in columns 11, 12 and 15.
Column 14 contains the averages of these percentages for each
plot and column 15 the percentage. decrease in growth for
each of the sprayed plots.

Since plots 5, 6, and 7 are replications of plots 1, 2,
and 3 in the order named except in the type of oil used, it
is evident that OrtholeK decreased the growth more than Volck.
The growth decrease when Volck was used varied from 17 to 30
per cent, and when Orthol-K was used from 43 to 52 per cent
depending upon the number and time of applications. 0n plots
1 and 5 where two applications were given, one at petal-fall
and the other two weeks later, the decrease is greater than
with other applications of the oils. The plots receiving a
midsummer application of oil in addition to one at the two-
weeks period showed as great a growth as those receiving only

the two-weeks application.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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7 Orthcl-K a bordeaux -
two-we ks
Orthol-K - July 30 .1776 .0870 .25

'51

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Lead arsenate 2 pounds to 100 gallons 0; spray was added when bordeaux w s used.

4-

 

54

Summary_of Results

 

The summer oil emulsions vary greatly in their
effects upon the fruit and foliage of the pear.

The Medina Summer Emulsion caused severe injury
to the fruit and foliage both when used alone and with
bordeaux.

VOlck and L-45 did not injure the tissue in any
way but did penetrate the fruit and foliage. The
penetration of the L-43 was very heavy when the oil was
used late in the summer.

Ortholcx'heavy injured the leaves to some extent
in every application. The light and medium grades caused
no inJury.

The addition of bordeaux to any of the oil sprays
increased the likelihood of injury.

The use of Keloform with Volck and Orthol-K resulted
in complete killing of foliage of the sprayed trees.

When ripened at ordinary temperatures, the oil-
sprayed pears lost weight more rapidly and did not ripen
with as yellow a color as the unsprayed fruit. This was

most evident with the L-43 sprayed pears.

b]
()1

After being held in cold storage for a period of
two months there was no observable difference between
the oil-sprayed and unsprayed pears, either in their
general appearance or in their rates of ripening.

There was a very appreciable decrease in growth
rate of oil-sprayed trees as indicated by the widths
of the annual growth rings. This was greater when
Orthol-K was used than when Volck was used.

Early season applications of oil caused some injury,
but late season applications resulted in more oil penetra-

tion.

Adknowledgments

The writer is greatly indebted to
Professor W.C. Dutton for his assistance
throughout the work, from the original
planning of the experiment to the comple-
tion of the manuscript; and to Professor
V.R.Gardner and Dr. J.W. Grist for criticiz-

ing the manuscript.

l.

2.

3.

4.

6.

7.

8.

67

Literature Cited

 

Gray, G.P. and E.R. DeOng-"California Petroleum
Insecticides" Industrial and Engineering
Chemistry, Vol. 18, 1936.

DeOng, E.R.- "A Preliminary Study of Petroleum Oil
as an Insecticide for Citrus Trees."
Hilgardia, Cal. Exp. Sta. Vol.2, No. 9
January, 1927.

Woglum, R.S.- "The‘Use of Oil Sprays on Citrus During
1926".- Jour. of Econ. Entom. Vol. 21,
August, 1928.

Driggers, B.F.- "Effect of Early Summer and Late Summer
Applications of White Oil and Nicotine
Sulphate Sprays on the Number of Eggs of the
European Red Mite Overwintering in Peach
Trees." Jour. Econ. Entom. Vol. 21,
December, 1925.

Parrott and Harman.-"The Peach Cottony Scale." Jour.
of Econ. Entom. Vol. 20, February, 1927.

Bourroughs, A.M.~"Effects of Oil Sprays on Fruit Trees."
Proc. Amer. Soc. Hort. Sci. 269-277, 1923.

Regan, W.S.- "Results of Different Insecticide Treat-
ments on the Control of Codling Moth in the
Pacific Northwest."
California Spray Chemical Company Publica-
tion 1927 0

Cross, F.B.- Unpublished thesis in Michigan State
College library, 1926. '

'08

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Lowell - Three days after spraying
with Volck two per cent and Koloform.

 

 

 

Howell - Three days after spraying
with Orthol-K two per cent and
Koloform.

 

 

,Howell - Check ~ sprayed with Koloform.

46

 

 

v Injury to leaves sprayed with bordeaux
2-4-100 and Volck two per cent August 10.
Variety - Flemish Beauty.

44

 

Howell pears sprayed with L-4S two per cent,
August 15. The oil absorption areas show dark
in the photograph.

 

Clapp's Favorite pears russetted by spraying with
Medina Summer Emulsion and bordeaux, July 6.

Ill:

 

 

 

 

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