HOP PESTS AND THEIR CONTROL
HOP PESTS AND T:PiEIR CONTROL
19)42
by
H. E. :orrison
Table of Contents
Page
Summary
1
Introduction
2
Economic Status of Fops
4
Status of Fop Project
5
19/42 Objectives
9
Seasonal History of the Hop Aphis
Seasonal History of the Hop Red Spider
Small Plot Testing of Effect of Timing for
Fop Red Spider Control
Testing of Mechanically Diluted Proprietary
DH Dusts on Commercial Scale
Discussion of Results
Tabulation of Data
Biological Method of Evaluation of Efficacy
of Dust Applications
Commercial Application of Ammonium Dinitroo-cresylate Dust T
Discussion of Results
Tabulation of Data
Plant Hormone Sprays on Fops
Timing of application
Concentration of Material
:letting of Hops
Application of Material
Harvesting of Crop
Discussion of Results
Tabulation of Data
Continued Studies of Red Spider Control on
Strawberries
Discussion of Results
Tabulation of Data
Phytocidal Studies of DN Dusts
Completion of Chemical Studies of DN Dusted
Hops
Sw-r-estions For Future Tiork
10
10
11
12
15
13
25
27
29
30
29
31
31
31
32
32
33
35
54
36
38
40
112
43
RU 25 14.04) rEsts+ Their 63A-1-m1
Spiat;
HOP RED SPIDER (Tetranychus) Sp.
HOP PESTS AND THEIR CONTROL
1942 Report to the Department of Entomology
Oregon State College
Summary
The general progress of the hop pest project is reviewed with a
discussion of the economic status of hops and the hop pest project.
A
plan is submitted whereby some of the losses caused by hop pests might
be eliminated.
Seasonal history studies and control work were restricted because
of the war emergency.
Testing of the effect of timing of dust applications
were abandoned because of the severe inroads of downy mildew and the
resulting poor stand of hops in the experimental yards.
Commercial application of mechanically diluted proprietary DN
Dusts resulted in reduced controls and reduced efficiency of application.
Commercial application of the ammonium dinitro cresylate dust gave inferior
results than the proprietary DN dusts.
This is believed to be due to
mechanical mixtures of the former dust in contrast to the atomized dusts
of the latter.
Preliminary testing of Fruitone (a plant hormone) for stimulation
of hops and prevention of cone shattering resulted in inconclusive results.
Difficulty in wetting of hops and possible chemical action between wetting
agents employed with the fruitone may have resulted unfavorably.
DN dusts were applied to strawberries for the second successive
year without foliage injury and with satisfactory control of red spiders.
Work was continued in the testing of DN dusts on various crops.
Nine new
species were dusted with DN Dust D-4 and only slight foliage injury was
noted on two of these varieties.
2
A method of evaluation of efficiency of rating mechanical applications of dusts on hops by biological measurement has been devised.
The chemical analysis of hops dusted with DN Dust and DN Dust D-4
which was started in 1940 was completed.
No difference between dusted
and undusted hops was noted.
Hop Pests and Their Control - 1942
Introduction
The results of the 1941 season demonstrated the improvement of the
Trials were conducted with three proprietary dusts
experimental duster.
(DN Dust, DN Dust D-4 and DN Dust D-8) at rates ranging in amounts from
10 to 60 pounds to the acre.
It was noted that 40 pounds to the acre was
satisfactory for commercial control and this resulted in a savings of
10 pounds to the acre over the 1940 tests.
The monetary value of this
savings was estimated as $1.00 per acre.
Seasonal development of the hop aphis and hop red spiders was
studied and data were set aside for special reports.
Severe injury to
hops resulted in various localities in the Willamette Valley as a result
of the hop red spider.
The peak of infestation occurred very late in the
season and in general most hop growers were able to harvest the crop
before spider damage became acute.
The hop aphis invaded the yards early and serious damage resulted
early in the season.
Several very hot days during the latter part of
July killed the majority of the aphis.
The population never recovered
from this natural control until very late in the season and after hops
had been harvested.
Several materials were dusted on hop plants at this
time in an effort to test sooty mold control in the field.
were not promising.
These studies
3
Small plot testing of new and untried toxicants were carried on in
the experimental hopyard.
It was found that the mechanical mixture of
proprietary nicotine sulfate dusts and DN dusts resulted in lowering of
the toxicity of the DN dusts to red spiders.
Mechanical dilutions of
DN dusts with proprietary rotenone dusts did not show this incompatibility
but hop aphis were not controlled.
Population build up studied were carried on at various intervals
until fifty (SO) days after dusting.
It was learned that the proprietary
dinitro cresol dusts gave a very high initial control but that populations
build up very rapidly after dusting.
than the undusted plots.
The rate of increase was more rapid
The several DN dusts and the DN-rotenone dust
mixtures showed a marked contrast and populations were held in check for
a period of fifty days after dusting.
The guanadine and ammonium salt of
dinitro-o-cresol were inferior to the proprietary DN dusts but superior
to the proprietary dinitro-o-cresol dusts.
Some trouble was noted in
attempting to atomize these toxicants into the carrier and it was thought
that better results might be obtained with better mixing.
Attempts were made to check growers' applications of DN dusts.
It
was found in general that little attempts were made to control the hop
red spider and that growers had not equipped themselves with efficient
machinery.
Proprietary DN dusts were applied to 10 acres of strawberries for
red spider control.
Preliminary studies showed that with satisfactory
power equipment, the red spiders could be contacted on the undersurfaces
of the leaves.
Strawberries are very susceptible to DN dusts and it was
learned that the critical temperature for strawberry dusting was 70 degrees F.
Satisfactory controls were effected with DN Dust D-4 and DN
dust D-7 at 100 pounds to the acre.
DN Dust D-8 proved too heavy for
the fan in the small experimental unit and dusts became clogged in the
air stream.
DN Dust D-4 was applied to a small planting of pansies with
no foliage injury and excellent control of red spiders.
Attempts were made to control the California prionid in hop poles
and hop crowns with the use of dichlorethyl ether, chloropicrin and methylisobutyl ketone.
These attempts were unsuccessful.
The Economic Status of Hops
Hops are the most important of Oregon's specialty crops.
The five-
year average (1936-1940) of cash farm income derived from hop production
has been computed as $3,625,000.00.
Foreign hops which normally entered
into competition with domestic hops were greatly curtailed during 1941
as a result of World War II.
This resulted in greatly increased prices
and a raise in cash farm income to *4,040,000.00.
The severe inroads of
downy mildew on hops in the spring of 1942 greatly decreased production
in Oregon.
This factor combined with the total elimination of foreign
hops from the market (United States entry into the war) has resulted in
hops reaching an unprecedented high.
and $1.50 (seedless) at this writing.
Hops are quoted at $1.30 (seeded)
Many growers had already con-
tracted their hops for 1942 at $.30 and $.35 and it is not possible to
predict the cash farm income at the present time.
ever, that the figure may exceed $5,000,000.00.
taken for $.70 and higher hops for 1943.
It is possible, how-
Many contracts have been
If a normal crop is assured for
1943, the cash farm income may exceed $10,000,000.00.
The role of hops as an essential crop to the war effort has not
been definitely established.
Considerable beer is reported to have been
5
consumed by the allied armies who are stationed in tropical climates
where water is often scarce and impure.
The prospect of an exceedingly high farm income makes hop production
very important to Oregon agriculture.
There is some possibility that hop
vines may serve for manufacture of fiber and this would contribute directly
to the war effort.
The large capital investment required in hop production
makes it unlikely that hop growing will be greatly curtailed during the
near future.
camouflage.
There is also some interest in the growing of hops for
The vines grow rapidly and may serve this purpose readily.
Status of the Hop Project
The importance of hop pest control depends upon the importance
placed on the hop industry for the duration of the war.
carried on in hop pest control since 1937.
hop red spider has been developed.
Work has been
Economic control
for the
This phase of pest control has neces-
sitated the development of efficient dusting machinery.
This was accom-
plished through the cooperative efforts of the Departments of Agricultural
Engineering and Entomology and with the United States Department of
Agriculture, Division of Drug and Related Crops.
Demonstration dustings were carried on in seven different localities
during 1940.
any growers were present at these demonstrations as well as
demonstrations at the hop field days of 1940 and 1941.
The problem of motivation of hop growers is difficult.
Since 1940
there are a total of six efficient dusters in Oregon which are capable of
effecting satisfactory applications.
3,300 acres of hops in Oregon.
for this acreage.
This averages one duster for every
There are at least 96 more units needed
One grower who cooperated with the Department of
Entomology during the 1940 investigations and who had equipped himself
6
with a very efficient unit, has been reported to have dismantled his
equipment and again was dusting according to old methods.
He has not
been successful in effecting economic control during 1942 and has reported that the recommended dusts were unsatisfactory.
Hop growers from Washington State and from British Columbia have
taken to the Oregon recommendations more readily than have Oregon hop
growers.
This is evidenced by the following statistics.
Number of
efficient
dusters
Acreage
of hops
State
British Columbia
Washington
Oregon
1,500
7,600
20,000
Acres
dusted
1941
State
British Columbia
Washington
Oregon
2
8
6
Remarks
1 duster to 700 acres
1 duster to 950 acres
1 duster to 3,300 acres
Acres 7767E7ITIEusts
dusted
Percent of
Percent of
Acres
total acres
dusted
total acres
dusted 19)41
dusted 1942
1942
100
400
100
6.9
5.9
0.5
120
1800
2250
8.3
23.7
11.3
Note--No figures available from California.
Correspondence with Dr. Sid Braucher of the Dow Chemical has shown
that the following large growers from British Columbia and Washington have
adopted the red spider control program.
Golding Farms (John I. Haas), Yakima, Washington
Yakima Chief Ranches (Lloyd Hughes), Yakima, Wash.
Victor BelairelMoxie City, Washington
W. C. Rivard, Maxie City, Washington
Charvet Brothers, Grandview, Washington
Horst Company, Agassiz British Columbia
H. M. Ord, Chilliwack, British Columbia
Additional information was obtained from L. G. Smith, Extension Entomologist
of Washington State.
He writes.
.
"Growers reported excellent results,
1941 Hop Field iiay
EXPERILENTAL HOP DUSTR
7
namely Lloyd Hughes Inc. and John I. Haas.
Most of the dust was applied
with effective power equipment at the rate of 60 lbs. per acre.
Richey &
Gilbert... the sole dealers in Yakima County, sold approximately )43 tons."
The failure of Oregon hop growers to respond is believed to be due
largely to lack in extension work.
Comparatively few Oregon hop growers
are known to consult with county agents and extension officials.
Essen
tial information apparently has not been made available to them.
Two
factors are largely responsible for lack of hop pest control.
1.
Inefficient equipment.
They are:
This could have been remedied prior
to 1943 with comparatively little cost.
Most growers are
equipped with machinery which could be adapted to meet approved
specifications.
New duster fans, flexible metal tubing are
scarce or not available.
The approved dust will not effect
control with the old type machinery.
Further research of the
Departments of Agricultural Engineering and Entomology may
solve this problem if such a program is thought advisable.
2.
Improper timing of dust applications.
Most hop growers are
faniliar with red spider injury but few of them have ever
seen the pest.
This is due largely to protective coloration
and smallness of the red spider.
Most growers are not aware
of the abundance of the pest until foliage has assumed either
a mottled green or rusty brown color.
This usually signifies
that hop plants are very heavily infested and that red spiders
will soon migrate into hop cones.
Control measures applied at
this time are often too late to prevent crop injury.
Some thought has been given this problem and several methods suggest
themselves for their solution.
Hop growers of the Pacific Coast States
8
are now well organized for the marketing of hops.
This has been accom-
plished by adequate leadership and. by cooperation with the United estates
Department of Agriculture, Marketing Administration, Fruit and Vegetable
One-fourth cent ($0.0025) is assessed to growers for each pound
branch.
of dry hops handled.
Funds raised in this manner are used to defray all
expenses.
It is believed that this organization could also serve to coordinate
and finance a cooperative pest control program.
The 20,000 acres of Oregon
hops should be divided into various districts and from six to eight men
employed for scouting of yards and direction of pest control operations.
The present scarcity of agricultural labor suggests the training of youths
(ages of 15 to 17 years) by the Departments of Agricultural Engineering,
Farms Crops and Entomology in cooperation with the United States Department
of Agriculture, Division of Drug and Related Plants for carrying on of
this work.
It is possible that a program of this kind may work more readily if
handled through and in cooperation with the newly organized Voluntary
Community Leadership Organization which is fully described in Extension
Bulletin S99.
Some of the responsibilities assumed by these individuals after
having been trained may be listed as follows:
1.
Regular scouting of hop acreage in their respective district
for the presence of hop aphis, hop red spider, downy mildew
and other pests throughout the season.
2.
Direction of pest control operations in infested areas if and
when needed.
9
3.
Direction of servicing of dusters, sprayers, and other equipment during the winter months in order that this equipment
should be in readiness for pest control operations during the
critical growing season.
It.
Pooling of resources and forming cooperative buying agency
for purchase of insecticides, fungicides, and other items
necessary for hop production and pest control.
Oregon hop growers spend an average of 000,000.00 annually for
pest control.
Inefficient control and non-control often cost these growers an
additional $750,000.00.
The expenditure of $20,000.00 annually by hop
growers for cooperative pest control and pest prevention could be raised
by assessing growers one mill ($0.001) for each pound of dried hops.
It is felt that an investment of this amount would eliminate non-control
costs and also aid in reduction of material cost of pest control.
The
program would also assist in increased production of hops, lower the
per acre cost of production, and increase the quality of the merchandise.
19112 Objectives
The outbreak of World War II made it necessary to greatly curtail
hop pest investigations.
unavailable.
1.
Travel was greatly restricted and labor was
The following objectives were accordingly planned.
Restricted seasonal history studies of the hop aphis and the
hop red spider.
2.
Small plot tests to study the effect of timing on red spider
control.
3.
Testing of mechanically diluted proprietary DN dusts on a
commercial scale.
1914 Eor FIELD DAY
10
4.
Commercial application of ammonium dinitro cresylate dust.
5.
Instituting of preliminary trials of the effects of the hormone
spray (Fruitone) on hops.
6.
Continued work on red spider control on strawberries.
7.
Phytocidal studies of DN dusts.
8.
Completion of chemical studies of DN dusted hops.
Procedure
Seasonal history studies - The hop aphis
Restricted labor and travel facilities made it necessary to limit
or restrict qualitative and quantitative collection of data.
All observa-
tions were made in the College Experimental Hopyard, East Farm, Corvallis,
It will be recalled from the 1941 report that a large number of
Oregon.
hop aphis eggs were deposited on plum trees adjacent to the Experimental
hopyard,
These eggs were watched throughout the fall and winter months.
A severe "silver thaw" occurred early in January 1942 and all trees in
the vicinity of Corvallis were encrusted with a heavy coating of ice.
A
number of checks were made after this occurrence and no hop aphis eggs
could be found.
Continued checks during the spring months showed that
hop aphis were no longer present on these trees.
It is possible that
this natural factor contributed to the extremely light infestation of
aphis in hopyards during 1942.
Temperatures exceeded 100 degrees F.
during the early part of July and this resulted in added natural control.
Aphis populations did not reach a peak until the latter part of November
and hops were harvested before economic damage was effected.
Seasonal history of the hop red spider
The spring of 1942 was very wet and cool.
Red spiders were found
on hop foliage during the latter part of May but development was probably
11
retarded by climatic conditions.
Warm dry winds were prevalent during
the latter part of June and vegetation about the hopyard became desiccated.
Red spiders immediately began to increase rapidly after this dry period.
In all probability the increase could be credited to migration from
desiccated plants to hops.
Red spiders reached their peak of abundance
during the latter part of August and the beginning of September.
Con-
siderable damage to hop cones was noted in several trips through the Willamette Valley during harvest time.
Few growers attempted control measures
and little attempts were made to purchase or obtain efficient dusting
equipment.
There were an estimated six dusters which were capable of doing
a satisfactory job in the 20,000 acres of hops.
At least 96 more dusters
are estimated as necessary for serving this acreage.
Red spider control
as recommended by the Oregon Entomology Department was adopted on a large
scale by Washington hop growers.
Approximately L3 tons of DN dusts were
sold for red spider control in the Yakima Valley during 1942.
Small plot tests to study the effect of timing on hop red spider control
The phenomenol action of the proprietary DN dusts in preventing
red spider development for as long as 50 days after dusting led to the
possibility of applying these dusts to hops early in the season before
plants had reached maturity and probably preventing red spiders from
establishing themselves.
If this were possible, considerable savings
may be effected by applying less dust per acre.
With this in mind, a
series of 16 plots of eight replicates each were laid out in the Entomology section of the experimental hopyard.
DN Dust D-4 to these plots according
It was planned to apply
to the following schedule.
12
Plot No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Date of application
No application
June 1
June 8
June 15
June 22
June 29
July 6
July 13
July 20
July 27
August 3
August 10
August 17
August 24
August 31
June 1, 8, 15, 22, 29,
July 6, 13, 20, 27
August 3, 10, 17, 24,
and 31
It was planned to make intensive studies on the rate of population
buildup upon all of these plots at weekly intervals throughout the season.
Information of this kind it was thought would be of great value in making
control recommendations.
It was unfortunate that circumstances prevented the carrying out
of this program.
The experimental yard was severely damaged by downy
mildew which either killed or severely stunted the majority of the hop
plants.
It was not until the middle of July that any plants assumed signs
of normal growth.
This was too late to undertake the above experiment.
The thought is left at this time as one piece of unfinished business
which should be attempted at some future time.
Testing of mechanically diluted proprietary DN dusts on a commercial scale
Preliminary experiments were undertaken with DN dusts in 1937.
The proprietary DN dust and mechanical dilutions of the proprietary dust
to concentrations of 0.75, 0.50, 0.25, 0.125, 0.0625, and 0.03125%.
Walnut shell flour was used as the diluent in all instances.
It will be
13
recalled that these dusts were applied with a small power duster in the
same manner as spray applications.
Attention was given to coverage of
undersurfaces of hop leaves and no effort was made to control amounts per
acre (See 1939 report to Department of Entomology).
It was thought advisable to attempt to duplicate this experiment
when dusts were applied with a commercial hop duster.
It was thought that
if mechanical dilutions were proven to giver, adequate control, considerable savings could be made to the grower.
For example:
DN Dust D-4 at 40 lbs. per acre costs
$4.00
DN Dust D-4 mechanically diluted to I% in frianite and
applied at 60 lbs. per acre
83.00
DN Dust D-4 mechanically diluted to *% and applied at
80 lbs. per acre
$2.80
Two proprietary dusts (DN Dust D-4 and DN Dust D-3) were mechanically
diluted in frianite at the ratio of 50-50 and 25-75.
are tabulated as follows.
scored August 22, 1942.
These treatments
Dusts were applied August 18 and results were
Fifty leaves were scored according to number of
living and dead red spiders in accordance with techniques reported in
previous reports.
i)t
Treatment
Treatment No.
1.
2.
3.
5.
6.
Amt. toxicant
per acre
DN Dust D-14
DCHA salt of DNOCHP
DNOCHP
Frianite
1%
1 %
98i%
40 lbs.
0.60 lbs.
DN Dust D-8
DCHA salt of DNOCHP
DNOCHP
Oil (Heavy)
Frianite
1%
40 lbs.
0.60 lbs.
1 %
2 %
961%
60 lbs.
0.45 lbs.
60 lbs.
0.45 lbs.
80 lbs.
0.30 lbs.
80 lbs.
0.30 lbs.
DN Dust D-4 (Mechanically
diluted with frianite 50-50)
DCHA salt of T)NOCHP
DNOCHP
Frianite
4.
Amt. per acre
DN Dust D-8 (Mechanically
diluted with frianite 50-50)
DCHA salt of DNOCHP
DNOCHP
Oil (Heavy)
Frianite
DN Dust D-4 (Mechanically
diluted with frianite 25-75)
DCHA salt of DNOCHP
DNOCHP
Frianite
DN Dust D-8 (Mechanically
diluted with frianite 25-75)
DCHA salt of DNOCHP
DNOCHP
Oil (Heavy)
Frianite
1%
%
99-41
leg
c,/
-n-,
1 %
98%
1/
995,8%
1/8%
14
n
2/Q
991/8%
The results of these tests departed widely from the hypothetical
assumption.
DN Dust
DN Dust
DN Dust
DN Dust
DN Dust
DN Dust
Check -
The following effectiveness is tabulated as follows.
D-4
D-8
D-4--Frianite (50-50)
D-8--Frianite (50-50)
D-4 -- Frianite (25-75)
D-8 -- Frianite (25-75)
No treatment
% Kill
Standard
deviation
98.1
98.7
90.8
88.1
79.8
82.8
6.5
2.655
3.359
12.118
12.657
15.330
14.544
6.643
S.E.M.
0.377
0.475
1.714
1.789
2.168
2.057
0.939
15
Discussion of results
The results of these tests were very interesting.
It was evident
that:
1.
Mechanical dilution of the proprietary dusts resulted in greater
lowering in effectiveness.
The amount of toxicant applied
according to treatment is listed in the following table.
The
amounts of toxicant required for satisfactory kills based on
laboratory studies and computed on an acreage basis according
to the report to the department of Entomology in 1940 (page 57).
Treat
No.
1
2
3
4
5
6
Treatment
DN Dust D-4
DN Dust D-8
DN
DN
DN
DN
Dust
Dust
Dust
Dust
D-4
D-8
D-4
D-8
--Frianite
- -Frianite
- -Frianite
- -Frianite
(50-50)
(50-50)
(25-75)
(25-75)
Lbs.
toxicants
per acre
Computed toxicant
needed for
control
0.60
0.60
0.45
0.45
0.30
0.30
0.05
0.05
0.05
0.05
0.05
0.05
It will be noted that at the lowest amount of toxicant applied
the dosage was six times higher than that of the computed amounts
necessary for satisfactory control.
2.
One factor which was noted in the scoring of the effectiveness
of the treatments is not indicated by the data.
In nearly all
leaves examined, coverage of foliage was considered adequate.
In many instances, sporadic kills were noted on the dusted
foliage.
A portion of a leaf was often observed to have one
hundred percent kill on 1/2 to 3/4 of its surface and 0 percent
kill on the remainder.
This suggested that mixing of the diluted
dusts might offer the explanation.
Samples of the dusts were
16
accordingly submitted to Dr. R. H. Robinson for analysis.
His findings are reported as follows:
Dust
% Dicyclo salt of DN
1.01
DN - D-4
50-50 mix of #1
25-75 mix of #1
DN - D-8
50-50 mix of #4
25-75 mix of #t
Ammon. dinitro cresol
1.
2.
3.
I.
5.
6.
7.
.53
.27
1.02
.49
.27
.97
These analyses show clearly that the mixing of the diluted dusts
were very satisfactory.
Several hypothesis may be accordingly advanced to
explain the sporadic kills.
1.
The proprietary dusts are mixed by atomizing the toxicant unto
the carrier.
Each dust particle is therefore supposedly coated with the
toxic material.
Mechanical diluting of this dust to 1 and i percent of
the original must in effect reduce the number of toxic particles by 50
and 75%.
Increase of rates of application from 40 to 60 and 80 lbs. per
acre respectively would serve to cut the number of toxic particles to
.75 and 50 percent of the original.
The reduction in toxicity separates itself according to these
dilutions but does not explain the sporadic type of kill.
This type of
kill was not noted in the plots treated with the proprietary dusts.
A
difference in specific gravity between the toxic and non-toxic particles
suggests that these may settle out in the airstream leaving only part of
the foliage covered with toxic particles.
Laboratory studies should be
undertaken in order to test this hypothesis.
Walnut shell flour was used as the diluent in the 1939 investigations in which
satisfactory kills were obtained by mechanically diluting
17
DN dust.
It will be recalled that satisfactory kills were obtained in
commercial applications of DN dust D-3 (i% toxicant in walnut shell flour)
at 50 lbs./acre.
Decidedly inferior results with DN Dust D-7 (i% dicyclo-
hexylamine salt of DN dust in frianite) at rates of 100 lbs./acre.
All
studies on hops to date show that there is no difference in toxicity between the proprietary DN dust and DN dust D-4 when frianite is used as a
carrier.
This suggests that the difference in toxicity between the
proprietary dusts and the mechanically diluted dusts may be due to the
physical and/or chemical properties of the carriers employed.
studies should he undertaken to explor this possibility.
tests are submitted as follows:
Laboratory
Data from these
18
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Date of dust application - Aug. 18, 1942
Material - DN Dust D-4
Rate of application - 40 pounds per acre
Equipment used - Experimental hop duster
Corvallis, Oregon
Data collected:
Aug. 22, 1942
Plant
Leaf
Plant
Leaf
No.
No.
No.
No.
6
3
1
Mean
Number of red spiders
Dead Alive Total % dead
0
I---- 45
100.0
45
2
85
0
85
100.0
3
54
3
94.7
57
49
0
100.0
4
49
63
63
0
100.0
5
299
286
99.0
3
1
2
2
216
21
237
2
422-
3
144
139
18
0
440
144
7B
1
79
913.11
5
131
0
0
8
114
143
174
14
641
96.2
100.0
100.0
95.4
97.8
8
2g.5
12
0
16
242
1
2
217
230
115
145
118
2
115
161
120
825
38
863
3
223
735
213
0
0
0
223
735
213
4
5
421
112
3
424
.0
112
1707
3
4
5
Mean
1
2
Mean
1
92.1
96.6
94.6
100.0
97.3
126
114
143
166
627
Mean
1767----3
Liean
100.0
2
3
4
5
67
38
148
92
136
481
1
4
5
5
3
1468
Mean
4
0
5
5
0
13
3
4
5
3
67
35
143
87
136
2
Number of red spiders
Dead Alive Total % Dead
130
0
1)0
100.6
129
132
3
97.7
127
127
0
100.0
119
119
100.0
108
108
0
100.0
616
613
99.5
3
96.4
95.0
100.0
90.1
98.3
95.6
100.0
100.0
100.0
99.3
100.0
99.ff
7
4
5
Wan
1
2
8
3
4
5
Mean
f
2
9
3
4
5
Mean
1
2
10
3
4
5
2
141
277
8
1198
49
285
1247
417
0
0
209
167
144
191
3
5
2
112ti
10
-235
0
14
172
185
341
8
292
0
0
1223
22
277
388
0
0
405
119
23
78
0
0
1267
Mean
23
Vt. Mean
9351
178
Ari . Mean
Standard deviation
Standard error of mean
Efficiency rating
417
209
170
149
193
1138
235
186
193
341
292
1247
277
388
428
119
78
129 0
9529
91.1
95.9
100.0
98.6
97.2
96.1
106).0
100.0
98.2
96.6
98.9
99.1
100.0
92.5
95.9
100.0
100.0
98.2
1b0.0
100.0
94.6
100.0
100.0
96.2
98.1
9 .09
2.655
0.377
81%
19
Population Counts
1942 Hop Red Spider Investigations
East Farm
Corvallis, Oregon
Data collected: Aug. 22, 1942
Oregon State College
Date of dust application - Aug. 18, 1942
Material - DN Dust D-4 (Mechanically diluted
with Frianite 50-50)
Rate of application - 60 lbs./acre
Equipment used - Experimental hop duster
Plant Leaf
No.
1
No.
23
2
583
84
230
53
67
78
998
2
80
136
1134
450
260
268
170
273
17
2
L67
260
268
170
275
114
19
114/10
408
217
194
320
105
63
42
19
0
0
124
471
259
4
5
Mean
1
2
2
3
4
5
Mean
1
2
3
3
4
5
Mean
1.244
1
2
3
4
5
150
Mean
1
2
5
3
4
5
Mean
377
165
107
212
389
437
291
327
503
145
1703
9
5
32
588
137
297
1
3
Plant Leaf
Number of red spiders
Dead Alive Total- % dead
0
0
0
213
320
105
1368
71.9
99.1
61.3
77.4
97.5
96.4
100.0
100.0
100.0
1
6
3
14
288
98.4
100.0
100.0
75.4
83
7/1
75.9
92.9
3
5
0
0
4
5
92
63
30
716
55
4
5
Mean
20
272
-----1----7-47-77-73:17-37.72
9
3
4
5
81.5 Mean
Note: Sporadic kills observed on
foliage. Portions of leaf had
from 100 to 0% kills. Dust
coverage good in nearly every
instance.
313
116
137
122
308
116
137
3
2
90.3
97.o
100.0
100.0
100.0
96.8
187
1416
14].
1
484
300
327
503
145
1759
1
12
64
87.8
96.9
99.5
99.6
93.6
95.5
296
246
364
271
175
1352
83.8
91.1
100.0
100.0
90.9
47
9
0
0
0
56
337
254
366
104
86.7
81
283
8
2
)144
98./ Mean
97.1
76.4
56.4
82.8
82.7
100.0
81.2
98.3
100.0
92.7
0
1325
2
8
480
127
85
293
444
1429
83
16
5
0
1
7
Number of red spiders
Dead Alive Total % dead
397
127
69
2
99.3
100.0
164
No.
88.0 Lean
377
170
140
376
470
1533
0
5
33
No.
10
Van-
196
89
247
118
694
1
47
2
178
307
271
144
947
11650
3
4
5
156
?87
95
260
127
850
68.3
93.7
95.0
92.9
81.6
5
0
0
52
178
307
90.4
100.0
100.0
91
6
13
9
8
12
25
1022
Wt. Mean
Arith. mean
Standard deviation
Standard error of mean
Efficiency rating
279
156
9'72
12672
97.1
92.3
97.4
91.9
90.76
12.118
1.714
58%
20
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Corvallis, Oregon
Date of dust application: Aug. 18, 1942
Data collected: Aug. 22, 1942
Materials DM Dust D-4 (Mechanically diluted with
Frianite 25-75)
Rate of application: 80 lbs./acre
Equipment used: Experimental hop duster
Plant Leaf
No.
No.
2
66
185
0
15
3
249
4
5
66
302
87
5
1
1
Mean
568
1
3
316
178
45
4
5
73
226
2
2
Mean
838
1
2
3
3
4
5
Mean
1
2
4
3
4
5
Mean
5
103
129
267
46
97
642
316
118
225
187
302
1148
66
200
336
71
497
1170
145
12
67
19
461
190
112
9
252
235
1090
41
73
144
202
19
68
4o
241
286
114
137
583
13
96.0
36.5
383
329
323
291
278
310
1531
76.2
99.1
64.2
91.5
93.6
86.2
205
66
91
8
92
144
45
1139
2
212
63
97
88
2
214
98
106
94
701
3
604
100.0
92.5
74.1
92.9
60.7
195
302
1
4
5
Mean
Number of red spiders
Total % dead
Dead Alive
35
9
6
97
74.2
Plant Leaf
No.
6
Number of red spiders
Total % dead
No.
Dead Alive
83
27
110
2
95
274
71
531
1054
38
52
18
20
133
326
89
3
5
Mean
68.5
1
278
93.7
40.2
79.3
96.2
76.9
2
389
3
288
4
5
479
65
1499
71.5
63.9
93.3
40.4
70.8
72.7
77.3
67.3
97.4
74.9
Note: Sporadic kills observed on
Portions of leaf had
foliage.
from 100 to 0% kills. Dust
coverage good in nearly every
instance.
7
Mean
1
2
8
3
4
5
Mean
2
9
3
4
5
Wan
1
2
10
3
4
155
36
65
12
0
22
87
1634
45
75
244
875
16
87
252
112
5
69
279
66
54
473
314
127
1271
73
229
146
232
147
827
9629
314
454
300
479
135
149
302
108
297
421
551
1209
81
23
19
7
28
29
63
5
Mean
146
Wt. mean
2436
Arith. mean
Standard deviation
Standard error of mean
Efficiency rating
75.5
71.4
84.o
79.7
96.4
57.2
88.5
85.7
96.0
100.0
74.7
91.7
230
64.8
347
87.0
131
82.4
91
82.4
331
73.7
1130 ----7777-
117
366
700
380
181
1744
92
236
174
261
210
973
12065
95.7
81.1
60.1
82.6
70.2
72.9
79.3
97.0
83.9
88.9
70.0
84.9
79.5
79.76
15.330
2.168
62%
21
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Date of dust application: Aug. 18, 1942
Material: DN Dust D-8
Rate of application: 40 lbs./acre
Equipment used: Experimental hop duster
Plant
Leaf
No.
No.
1
0
5
314
100.0
1
65
227
2
247
37
14
0
56
215
299
197
1252
3
285
197
1196
97.8
82.8
95.3
100.0
95.5
315
194
39
860
433
97
84
316
0
0
0
14
204
1134
8
22
267
317
63
149
108
904
0
0
0
0
0
0
1
b9
2
42
5
3
3
315
205
397
1028
0
0
0
ei
45
315
205
397
1036
1
3111
8
322-
2
201
7
208
3
4
5
349
166
169
1199
0
0
349
3
4
1
2
3
1
2
3
4
5r
Mean
4
5
Mean
Mean
Number of red spiders
Total % Dead
Dead Alive
222
178
Mean
5
No.
314
4
5
4
Leaf
No.
2
5
3
Piant
1
Mean
2
NuMber of red spiders
Dead Alive 'Dotal % dead
Corvallis, Oregon
Data collected: Aug. 22, 1942
0
15
433
97
84
330
212
1156
267
317
63
149
108
904
74
100.0
100.0
100.0
95.8
96.2
98.1
100.0
100.0
100.0
100.0
100.0
100.0
6
4
5
Mean
1
2
7
4
5
Mean
1
2
8
Mean
1
2
9
166
169
1214
98.8
3
4
5
Mean
97.5
96.6
100.0
100.0
100.0
3
4
5
9)22
93.3
100.0
100.0
100.0
99:2
3
87
167
141
45
197
637
4
0
3
0
0
199
347
214
308
16
29
3
4
5
0
100.0
100.0
98.7
100.0
100.0
99.5
91
167
144
45
197
644
95.6
100.0
97.9
100.0
100.0
98.9
215
376
214
318
102
1225
92.6
92.3
100.0
97
1165
60
217
443
191
287
411
21
0
4
9
11
45
443
195
296
422
91.2
100.0
97.9
96.9
97.4
1594
'97.2
14
0
0
5
10
29
246
157
245
316
432
195
1375
11264
1'73
10
7
65
247
319
194
39
864
10
5
1549
2
0
0
4
0
0
4
245
316
427
185
1346
Mean
11018
Wt. mean
Arith. mean
Standard deviation
Standard error of mean
Efficiency rating
-238
96.9
95.1
95.1
92.5
100.0
100.0
98.8
94.9
97.9
97.8
98.74
3.359
0.475
66%
22
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Date of dust application: Aug. 18, 1942
Material: DN Dust D.-8 (Mechanically diluted
with Frianite 50-50)
Rate of application: 60 lbs./acre
Equipment used: Experimental hop duster
Plant Leaf
No.
1
No.
1
95
2
32
3
39
47
39
4
5
Mean
252
1
2
2
3
4
5
Mean
3
4
5
Mean
1
4
50
33
134
67
59
3143
2
3
Number of red spiders
Total- % dead
Dead Alive
23
4
5
Mean
149
275
513
109
313
1359
-47
67
0
3
8
3
81
8
0
5
3
5
21
12
64
89
0
5
170
6
4
T4
9
145
378
967
13
608
311
205
505
2034
162
32
42
55
42
333
58.6
100.0
92.9
85.5
92.9
75.1
58
33
139
70
86.2
100.0
96.4
95.7
64
364
92.2
94.2
161
339
602
109
318
1529
92.5
81.1
85.2
7)
137
100.0
98.4
88.9
88.1
97.9
96.0
8
223
158
386
40
1007
91.8
97.9
96.0
0
6
5
608
317
210
584
2124
100.0
98.1
97.6
86.5
95.5
Corvallis, Oregon
Data collected: Aug. 22, 1942
Plant Leaf
No.
No.
1
2
6
3
4
5
Mean
1
2
7
3
4
5
Mean
2
3
4
Mean
1
2
9
3
4
5
Mean
3
4
5
Mean
Note:
79
90
Sporadic kills observed on
foliage. Portions of leaf had
from 100 to 0% kills. Dust
coverage good in nearly
every instance.
10
407
145
89
371
216
27
82
167
5
0
281
169
72
63
0
5
309
67
195
122
48
316
17
42
0
0
768
62
219
427
95
158
213
1112
41
2
189
473
3
87
1
5
413
263
305
89
221
1291
1228
1
8
Number of red spiders
Dead Alive Total % dead
3
8
19
73
81
222
41
0
72
19
165
204
81
Mean
1115
213
10472
Wt. mean
1489
Arith. mean
Standard deviation
Standard error of mean
Efficiency rating ..
4
5
440
345
472
94
221
1572
94.9
76.2
64.6
94.7
100.0
82.1
576
217
152
371
221
1537
/0.7
66.8
58.6
100.0
97.7
79.9
104
237
122
83.7
82.3
100.0
48
319
830
100.0
99.1
92.5
260
435
114
231
294
84.2
98.2
83.3
68.4
72.4
83.3
-1334
ZO
82.2
473
159
184
285
100.0
54.7
1)31
11961
89.7
71.5
83.9
87.6
88.12
12.657
1.789
61%
23
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Corvallis, Oregon
Date of dust application: Aug. 18, 1942
Data collected: Aug. 22, 1942
Material: DN Dust D-8 (Mechanically diluted
vith Frianite 25-75)
Rate of application: 80 pounds per acre
Equipment used: Experimental hop duster
Plant
Leaf
No.
No.
1
2
1
3
4
5
Mean
1
2
2
3
4
5
Mean
1
3
2
3
4
5
5
100.0
1
99.3
2
113
330
215
452
318
1428
84.1
71.8
92.1
82.1
84.6
81.9
180
92.2
90.2
79.5
59.1
67.6
76.1
7
33
6
78
164
468
83
44
239
28o
218
1184
98
3
116
148
1514
72
115
195
95
237
198
371
269
18
305
3
97
205
169
942
93
17
81
49
258
14
33
35
142
81
295
303
219
57
2
3
145
78
64
0
191
936
29
233
4
5
Mean
473
684
101
188
263
1709
166
1
No.
0
5
2
Mean
Leaf
No.
473
679
1
4
5
Plant
26
158
390
156
236
966
1170
Mean
4
Number of red spiders
Dead Alive Total % dead
83
338
122
347
250
1237
360
302
209
78
220
1169
78.8
96.3
83.3
65.3
84.3
81.6
97.0
61.7
56.3
88.6
84.2
72.5
69.4
100.0
86.8
80.1
Note: Sporadic kills observed on
foliage. Portions of leaf had
from 100 to 0% kills. Dust
coverage good in nearly every
instance.
1
189
217
169
231
165
971
2
6
3
4
5
Idean
7
3
4
5
Mean
2
8
3
4
5
Mean
9
67
41
8
52
9
177
218
73
952
5
0
89
73
79.9
loo.o
98.1
97.8
100.0
1041
91.5
201
45
63
395
142
846
49
250
7
52
89
152
397
163
1014
80.4
86.5
41.4
99.5
185
407
3
2
21
168
3
89
4
5
.,
645
63
0
97
15
97
7
1423
182
133
230
42
18
5
36
41
2
3
96
42
5
352
853
10573
Mean
Wt. mean
174
1145
73.8
84.1
95.5
81.6
94.8
84.6
81
0
2
-1
256
258
177
283
322
185
154
1
1[e an
10
Number of red spiders
Dead Alive Total % dead
142
1937
403
185
157
223
248
407
186
660
104
1605
175
248
101
78
393
995
11530
87.1
83.4
74.6
100.0
47.8
97.7
93.3
86.7
76.6
92.7
95.0
53.8
89.6
85.7
84.4
MM. mean
8273
Standard deviation
Standard error of mean
Efficiency rating
14.544
2.057
62%
24
Population Counts
1942 Hop Red Spider Investigations
East Farm
Corvallis, Oregon
Oregon State College
Data collected: Aug. 22, 3942
Materials Check treatment - No dust application
Plant
Leaf
No.
No.
1
2
1
3
4
5
Mean
2
371
128
949
130
387
140
1045
95
8.4
8.7
26.9
4.1
8.6
9.2
19
23
125
136
144
159
3
0
3141
3141
4
5
8
577
422
1601
585
434
1663
328
219
169
375
381
1472
342
389
1569
4.1
11.6
8.6
5.3
4.3
6./
147
153
218
165
133
816
182
162
218
165
140
867
19.2
5.6
0.0
0.0
5.0
5.9
321
345
350
6.9
1.4
6.3
27.9
6.9
6.4
12
6A
1
14
2
29
16
3
4
5
21
17
97
35
2
9
3
4
0
0
5
7
Mean
51
1
3
24
5
11
4
5
19
20
2
Mean
227
161
2
1
5
208
147
1
Mean
4
19
14
35
16
12
96
Wan
3
Number of red spiders
Dead Alive Total % dead
79
345
163
49
270
1148
248
185
396
174
68
290
127
13.2
14.5
0.0
1.4
2.8
3.7
Plant
Leaf
No.
No.
6
1
0
2
1
3
4
5
Mean
1
2
7
3
4
5
Mean
8
0
15
35
145
75
183
217
655
0.0
2.1
1.3
0.0
0.5
0.7
194
122
216
53
387
972
197
122
222
53
402
996
1.5
0.0
2.7
0.0
3.7
2.4
3.6
8
2
29
3
9
12
216
301
117
143
67
125
1074
224
330
126
155
364
1199
1
7
173
180
2
211
223
3
12
31
4
5
19
17
509
75
540
94
305
1342
Wan
56
1
2
3
4
5
Wan
3
0
6
35
142
74
183
216
650
1
Mean
10
1
0
1
5
24
4
5
9
Number of red spiders
Dead Alive Total % dead
297
288
1256
10
97
5
144
0
0
33
48
673
123
63
209
636
Wt. mean
10574
Arith mean
Standard deviation
Standard error of mean
Efficiency rating
107
149
123
63
242
684
11247
8.8
7.1
7.7
18.4
10.4
3.9
5.4
5.7
20.2
5.6
6.5
9.3
3.4
0.0
0.0
13.6
7.0
6.0
3. '52
6.643
0.939
74.0
25
For a long time there has been a need for biological evaluation of
the efficiency of dust applications.
Some thought was given this problem
during 1941 when the standard deviation of the percentage kills was plotted
against the rate in which various DN dusts were applied per acre.
(See
report to the Department of Entomology 191i1s page 14.)
The standard deviation may be considered as mathematical evaluation
of the manner a given set of variables will group themselves about the
If it is assumed that a duster is working
mean value of these variables.
under optimum conditions, it should be capable of applying a uniform amount
of toxicant on each dusted leaf.
If this were trues then the standard
deviation could be employed as a biological measure of efficiency of the
duster.
The standard deviation of percentage kill varies in scope with
The greatest standard
changes in numerical value of percentage kill.
deviation of 0 and 100 percent kill. is 0 while the greatest possible
standard deviation of 50 percent kill is 50.
(See Figure 1).
Table 1
shows the scope of the greatest possible standard deviation which corresponds to a given percentage kill.
A simple formula for evaluating per-
centage efficiency of on the basis of 100% is as follows.
100-BA (100)
B-The measured standard deviation
Where
A-Greatest possible standard deviation
of the measured % kill
Example-A given dust was applied at a given rate per acre. The
measured kill of a given number of leaves was 89%. The
standard deviation of this measured kill was 13.05.
Procedure-The greatest possible standard deviation of 89% kill
is 31.288(a). The measured standard deviation was 13.05 (B)
solving in the equation we have
100-131.3.0265
100
8
or 100-(.417) (100)
or 100-41.70...58.3% efficiency
:
001
:
MOMOMMOMMIM
0
M
0
T
IMMIMMIOMMIIMMEMMI
111111111MOMMIMMIMI
MMIMENIMMOMMIMMIMOMM
111111111011111AMMIMMIMMFAIMME
is
a
8
0 17
O
IIMM
=
11
oppearommommum
_.......fighimmoummimin
MEM
0
MEMMIMMIMMOIMMIMMII
MMEMEMEMEMMEMM
UMMII
INNIMMIMMIMMIMIMMIMMEMINIIMMI
Emu
MEMOMMEMEMEMEMEMEMMEM
1111111MMINIIIMIIIIErum
muummonmskim...monm
PRivipihmitr. 110
INIMINIMILO I
iIkamispoporaimmi
WEIN I II: PI 0 ttli IP UM le 11
MI- 1111111.11111111111111111111111111111
ur
25
For a long time there has been a need for biological evaluation of
the efficiency of dust applications.
Some thought was given this problem
during 19141 when the standard deviation of the percentage kills was plotted
against the rate in which various DN dusts were applied per acre.
(See
report to the Department of Entomology 19/41, page 14.)
The standard deviation may be considered as mathematical evaluation
of the manner a given set of variables will group themselves about the
mean value of these variables.
If it is assumed that a duster is working
under optimum conditions, it should be capable of applying a uniform amount
of toxicant on each dusted leaf.
If this were true, then the standard
deviation could be employed as a biological measure of efficiency of the
duster.
The standard deviation of percentage kill varies in scope with
changes in numerical value of percentage kill.
The greatest standard
deviation of 0 and 100 percent kill. is 0 while the greatest possible
standard deviation of 50 percent kill is 50.
(See Figure 1).
Table 1
shows the scope of the greatest possible standard deviation which corresponds to a given percentage kill.
A simple formula. for evaluating per-
centage efficiency of on the basis of 100% is as follows.
100-BA (100)
there
B-The measured standard deviation
A-Greatest possible standard deviation
of the measured % kill
Example-A given dust was applied at a given rate per acre.
measured kill of a given number of leaves was 89%.
standard deviation of this measured kill was 13.05.
The
The
Procedure-The greatest possible standard deviation of 89% kill
is 31.288(a). The measured standard deviation was 13.05 (B)
solving in the equation we have
100-13.05
100
.8
or 100-(.417) (100)
or 100-1,1.70...58.3% efficiency
11111114] 0. I MUNI el 2111 Wag
Allik di
MEM
11,
11 NMI
aril I
WWII 1111411:111FAIMP11161111,111/1
1
1111111111111111111111111111111rniallailla
amommilorammommiiii
nimillipprimmamor_
musirmitam
.110111113111
51
LU
MEI MI
1111
";
1
0
.
.
E
111111EMENE mEENIP
m
E®®
posmom...0.
Ensmum
=mg=
Esimisimimmiumminisimmoomm
mmEgENENEE
EIRIMMEMEMEmimmEMEMINEEMEMENIMEMEN
26
The standard deviations of the various percentage kills obtained during
1941 with three proprietary DN dusts at different rates per acre were
accordingly converted into efficiency ratings.
(See original data in 1941
report to Department of Entomologypages 117 to 181 of appendix).
The resultant curve (Figure 2) assumes that of a straight line in
contrast to that of the curvilinear nature of the standard deviation of
the different measured kills.
There is a significant correla tion between rates of application and
efficiency rating.
This is at variance with the original assumption that
a duster should be capable of applying a uniform deposit on all dusted
foliage and the corresponding correction coefficient should approach 0.
The departure of theoretical expectations from measured observations in
this instance may in all probability be credited from imperfect methods
of field applications of dusts.
The follcwing efficiency ratings of the 1942 applications are of
interest.
Treatment
Treatment
No.
1
DN Dust D-4
2
DN Dust. D-8
3
4
5
DN Dust D-4Frianite (50-50)
DN Dust D-8Prianite (50-50)
DN Dust D-4Frianite (25-75)
6
DN Dust D- 8--- Frianite (25-75)
lbs. per acre
40
40
60
60
80
80
Efficiency
Rating
81
66
58
61
62
61
The efficiency rating of 81 credited to 1)N Dust D-4 is decidedly
higher than a similar rating of the same material apnlied at the same rate
during 1940.
The rating of DN Dust D-8 corresponds very well with that
obtained during 1941.
There is a marked lowering of the efficiency of the diluted DN
27
Dust D-4 over that of the proprietary dust.
the DM Dust
This does not occur with
Two factors are apparently effecting these results.
The one is differences in toxicity, the other differences due to decreased
oil content in DN Dust D-8.
The flowability of the diluted DN Dust D-8
was noticeably better than the proprietary product.
It is believed that
a reduction in oil content of the DN Dust D-8 from 2% to i or i% would
add to the effectiveness of this product and at the same time eliminate
much of the difficulty of feeding it into the air stream.
4.
The commercial application of ammonium dinitro-o-cresylate dust
Small plot testing of ammonium dinitro-o-cresylate dust in 1941
indicated that the material had some promise for hop red spider control.
The data(See 1941 report to Department of Entomology, pages 20-29) showed
78 percent kill but the material was superior to dinitro-o-cresylate dust
and the dicyclohexylamine dinitro-o-cresylate dust in holding red spider
populations in check.
Some difficulty was experienced in 19111 in atomizing the toxicant
on to the carrier.
Carbon tetrachloride, xyol and a number of volatile
It
solvents were tried but only a gelatinous mixture could be obtained.
was believed that better mixing of the dust might result in better control
of the hop red spider.
A 1% dust of ammonium dinitro-o-cresylate dust was accordingly
obtained from the American Cyanamid and Chemical Company.
This dust con-
tained talc as a diluent and was prepared by mechanically diluting the
toxicant and the carrier.
This dust was applied with the experimental
hop duster on August 18, 19112 and data were collected August 22, 1942.
28
Table 1
Showing Greatest Possible Standard Deviation for Various Percentage Kills
% Dead
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
5o
Standard Deviation
0.000
9,949
14.000
17.058
19.595
21.794
23.748
23.514
27.129
28.619
30.000
31.288
32.496
33.630
34.689
35.707
36.660
37.563
38.418
39.230
40.000
40.730
41.424
42.083
42.708
43.301
43.863
44.365
44.899
45.376
45.826
46.249
46.648
47.022
47.371
47.697
48.000
48.280
48.538
48.775
48.989
49.133
49.356
49.507
49.638
49.749
49.839
49.910
49.960
49.990
50.000
% Dead
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Standard Deviation
49.990
49.960
49.910
49.839
49.749
49.638
49.507
49.356
49.183
48.989
48.775
48.538
48.280
48.000
47.697
47.371
47.022
46.648
46.249
45.826
45.376
44.899
44.365
43.363
43.301
42.708
42.083
41.424
40.703
40.000
39.230
38.418
37.563
36.660
35.707
34.698
33.630
32.496
31.238
30.000
28.618
27.129
25.514
23.748
21.794
19.595
17.058
14.000
9.949
0.000
29
Discussion of results
Complete data from this test are found on the following page.
resultant kill measured 80%.
proprietary DN Dust
The
This was significantly inferior to the
D-4 and DN Dust D-8 at 40 lbs. per acre.
It was again interesting to note that the sporadic kills (100 to 0
percent kills in different portions of the leaf) were again noted with
this material.
DN dusts.
This same phenomenon occurred with the mechanically diluted
It is probable that similar explanations may serve to explain
this behavior.
5.
Plant hormone sprays on hops
Plant hormone sprays have been used with success by fruit growers in
order to prevent preharvest drops of Ppples, pears, cherries, and other
fruit.
It was thought that these materials in either spray or dust form
might prove of value to hop growers in prevention of hop cone shattering at
harvest.
More value might be enjoyed by growers using mechanical picking
machines if these materials proved of merit.
hormone materials on the market.
There are a number of plant
The one selected for preliminary tests
was manufactured by the American Chemical Paint Company, Ambler, Pennsylvania
and sold under the trade name of Fruitone.
Chemical composition of this
preparation is given as follows:
Napthyl acetamid
Napthyl acetic acid
Wetting agent
Talc
Fruitone is also prepared in dust form.
1.1;14%
36%
5.00%
93.20%
The formula composing the one used
during these preliminary trials is given as follows:
1 .......,.
,.1..i..l.,.
,1Pmnmm..,-.
........E.
..CIMmlwin,,.....MMI
1.
,.........
=......
IlnwaVkVIWEarlsyswlmmewm........,
...%=.1.4,an..==...m.z.,,
IMINII=k
TRERTMEI1T
I
(1.14(1,
114
INkIMILML 1..
PERRI 'OCP
N=pmel.
SPV)rv.
1,1/A
4
14% 01,1
5
841(0 0104111
6
(r11:1.'010
7.
DI.S1
(.1"
0-4
a D-8
9 Claffl..
10. DY 71N4
12
20
1.11060110C11 MI
23
144444000 0 MS00
14
LE.
TArrittfOl
14 TOPAINot
01MMN6
I
1111,14.714,40L41,1,4
'
-,4i.kerEL
1941 EYTISITS
Fop Field Day
D1SCUSSIOL Cie RF
IDR CC:7111CL
1941 T:op Field Day
-
30
Population Counts
1942 Hop Red Spider Investigations
East Farm
Oregon State College
Corvallis, Oregon
Dust applied: Aug. 18, 1942
Data collected: Aug. 22, 1942
Material: Ammonium dinitro-o-cresylate 1%,
Talc 99%
Rate of application: 50 pounds per acre
Equipment used: Experimental hop duster
Plant
Leaf
No.
No.
1
2
1
3
5
Mean
2
2
3
4
5
Mean
1
2
3
3
14
5
Mean
1
9
4
3
4
5
Mean
1
2
5
3
4
5
Mean
Number of red spiders
Dead Alive Total % Dead
220
130
187
79
24
190
25
21
33
644
190
42
188
218
70
708
195
130
218
99
149
791
269
224
317
103
211
58
913
98.2
41.0
76.7
90.0
43.1
70.5
15
67
14
11
205
109
202
229
3
73
818
92.7
38.5
93.1
95.2
95.9
86.6
4
110
3
29
37
64
27
160
7
95
212
145
188
688
1h5
233
179
213
66
836
144
15
62
90
184
15
82
0
5
37
139
198"
159
255
163
176
951
98.5
81.8
85.5
60.7
84.7
Plant Leaf
Number of red spiders
Total % Dead
No.
No.
Dead Alive
144
167
6
1
6
3
4
5
Mean
1
2
3
7
4
5
Mean
1
2
3
8
4
5
077-
can
213
422
166
1112
148
275
147
303
67
940
49
234
109
267
275
)9.T
1
181
39.7
2
509
84
135
160
315
179
90.6
73.9
100.0
218
103
975
64.1
55.7
70.0
67.6
64.2
97.7
Note: Sporadic kills observed on
Portions of leaf had
foliage.
from 100 to 0% kills. Dust
coverage good in nearly every
instance.
9
3
4
5
Mean
1
2
10
222
258
64.9
64.7
301
12
0
269
434
166
1381
70.8
97.2
100.0
16
94
19
164
369
166
310
149
1158
7
82
218
0
5
3
4
5
49
31!
239
143
123
20
390
295
1
9
121
239
227
207
278
1072
93.I
78
91
88
16
90.2
74.5
88.6
97.7
45.0
81.2
100.0
97.9
76.2
68.5
93.2
3.
643
584
214
75
0
12
17
1423
456
147
231
1689
67
388
299
287
353
1394
9470
93
16o
41
0
4
81
219
2216
429
299
291
434
1613
11686
Mean
1t. mean
Arith. mean
Standard deviation ..
Standard error of mean
Efficiency rating
80.5
84
74.5
87.2
100.0
91.8
92.6
84.3
41.9
90.4
100.0
98.6
81.3
86.11
81.0
130.0
19.1.55
2.709
52.%
31
0.072%
0.018%
0.250%
14.660%
85.000%
Napthyl acetamide
Napthyl acetic acid
Wetting agent
Talc
Frianite
The Departments of Entomology and Farm Crops cooperated and undertook preliminary tests in the experimental hopyard, East Farm, Corvallis,
Oregon.
Later tests were undertaken at the Horst Hop Ranch, Independence,
Oregon.
A number of the difficulties and problems encountered are dis-
cussed as follows:
1.
Timing of application.
been undertaken on hops.
No work of this kind had been previously
A spraying of apples 2 to 3 days before estimated
time of drop gave best results.
more rapid on hops than on pears.
differences in rate of reaction.
Reaction of the hormone was reported to he
Varieties of apples and pears showed
It was decided to spray both Fuggles and
Late Clusters at various stages of maturity (bloom, burr stage, and early
cone).
2.
Concentration of material.
One-half pound of Fruitone to 100
gallons of water was reported to give satisfactory results on apples and
pears.
and 1
The concentration used in the preliminary trials was both a lb.
lbs. per 100 gallons spray on both Fuggles and Late Clusters at
various stages of maturity.
3.
Wetting of hops.
The wetting agent in the proprietary product
was not adequate in the wetting of hop leaves or cones.
The nature of
this wetting agent was not known but attempts were made to correct this
difficulty.
Aresket, resin potash soap, Ortho K light medium oil, Penetrol,
Santex R-1001 Santex spreader-soap and tar soap flakes were among the materials tested.
It was learned that tar soap flakes (2 lbs./100 gal.) added
32
to Fruitone (i lb./100 gal.) gave satisfactory wetting.
Penetrol and nearly
all the oil type spreaders produced burning on both cones and foliage.
The
compatibility of tar soap and the active ingredients of Fruitone are matters
of speculation.
4.
Application of material.
Spray materials were applied to several
plants in the experimental hopyard at Corvallis, Oregon by means of a small
knapsack sprayer.
a stepladder.
The tops of the plants were sprayed by the added use of
Application difficulties arose at the Horst Hop Ranch.
spray machine was not equipped with an agitator.
The
One man was detailed to
stir the spray mixture with a paddle but the efficiency of this method is
questionable.
The Horst hop duster was not sufficiently powered to reach the upper
third of the hop plants.
The college experimental duster was too high to
travel through the yard in the same direction as picking machines.
The
greater portion of the hop cones remained undusted as a result of these
difficulties.
5.
Harvesting of crop.
picking machine.
The Horst hops were picked on the stationary
This machine is equipped with powerful blowers for removing
leaves and other undesirable material.
Cleanliness of the hops varies with
the calibration of this machine and with the foreman in charge of operations.
The Fuggles were harvested when they were fully mature but the Late Clusters
were very immature when harvested.
This was attributed to the difference
in rates of maturing of the various plants because of the severe inroads of
downy mildew and the necessity of cutting back plants a number of times
throughout the season.
Some difficulty was experienced in preventing growers from picking
the treated plants in the experimental :rard in Corvallis.
As a result of
33
this eight of the fourteen plants were lost.
Discussion of Results
Samples of the treated hops were taken from the Horst Hop Ranch and
the Experimental Hopyard and examined for percentage broken cones, percentage
seeds, percentage leaves and stems, and percentage strigs by the Department
of Farm Crops.
These results are tabulated on the following page.
Fuggles are known to shatter more easily than any of the common commercial crops.
This is evidenced by the difference in percentage broken
cones between Fuggles (Mean 83%) and Late Cluster (Mean 21%).
Some of this
difference, however, must be credited to the difference in maturity of the
two varieties at time of picking.
There were few replications of either dust, spray or check hops from
There is probably no significant difference between the
the Horst Ranch.
samples.
This was largely to be expected because of wetting, mixing appli-
cation, and harvesting difficulties would have masked any differences which
might have occurred.
The samples from the experimental yard were hand-picked and separated
from the total picked lot of hops.
harvesting treatment.
vesting treatment.
treatments.
They, therefore, did not receive normal
Both treated and check hops did receive normal har-
Both treated and check hops did receive comparative
Replications are not sufficient for speculation but there may
be some difference in reduction of shattering of Fuggles.
There is some question regarding the ultimate value of reduction of
hop cone shattering.
Accomplishment of an objective of this type is filled
with difficulties, some of which were encountered in this preliminary
investigation.
It is believed that sufficient information has been obtained
314
The timing of sprays should
to warrant larger scale tests in the future.
be made at or about the time hops are in the burr stage.
this time
Spraying after
probably lessens the possibility of covering the bracts with a
coating of spray.
Considerably more work should be carried on in order
to solve some of these problems.
6.
Continued work on red spider control on strawberries.
Investigations were first undertaken on red spider control on strawberries
in 1940.
These studies were conducted on the strawberry patch of
Mr. E. A. Jones, East Farm, Corvallis, Oregon.
The plants were of the
Corvallis #12 variety (a late maturing variety), and were planted in hills
three feet by three feet.
The plants were very heavily foliated and often
exceeded 2 feet x 2 feet x 2 feet in dimensions.
It was learned during 1941 that the common knapsack dusters were
not satisfactory in depositing dusts on the undersurfaces of strawberry
foliage in a planting of this type.
The Department of Agricultural Engi-
neering cooperated in solving this problem and a satisfactory unit was
finally developed.
(See report to Department of Entomology 1941, pages
29-35).
It was also learned during 1941 that DN dusts could be applied to
strawberry foliage with safety if temperatures did not exceed 70 degrees F.
for at least three days after application.
Walnut shell flour was found
to be poorer than frianite in effecting satisfactory coverage on strawberry foliage.
It was decided to carry on additional tests in 1942 in order to
verify the 1941 results.
Red spider populations were checked throughout
the winter and early spring.
It was learned that this pest overwintered on
36
Fruitone Spray and Dust Experiments, 1942
Samples from Horst Hop Ranch
Variety
Late
Clusters
Treatment
1# Fruitone
2# soap
100 gel. water
Check - No
Treatment
State of
maturity
Variable
(prebloom,
bloom, burr
and cones
to 1 in.
long
Sample
No.
%
strigs
17.0
16.1
14.1
9.1
6.9
7.7
7.9
18.0
31.5
9.0
19.5
6.9
13.1,
11.14
7.7
10.0
8.2
15.9
9.5
12.9
8.1
9.7
9.7
77.0
90.0
83.0
83.3
13.7
12.5
13.0
13.1
0.5
0.6
1.5
0.9
11.9
9.0
9.9
10.3
81.0
88.0
83.0
1.5
6.4
1.7
3.2
8.7
7.9
814.0
14.2
13.1
12.8
13.4
81.5
81.0
10.0
9.6
2.7
2.3
12.5
9.8
2.5
13.7-
53.0
24.5
12.3
10.6
2.h
1.0
9.1
10.0
38.8
11.5
1.7
9.6
77.0
67.5
7.1
7.6
0.1
0.3
11.1
12.0
12.3
7.4
0.2
11.6
1
28.0
7.6
0.3
11.0
1
32.0
7.2
5.0
9.8
3
Ave.
2
Ave.
Cones nearly mature
and
leaves
3.6
5.7
7.5
5.6
2
3
Fruitone
Dust
% stems
%
seeds
19.0
24.0
26.5
23.2
1
1
As above
%
broken
cones
1
2
3
Ave.
9.3
Fuggles
1# Fruitone
2# soap
100 gal. water
1
Ls above
2
3
Ave.
Check - No
Treatment
1
As above
2
10.1
8.9
'.L.8
3
Ave.
0 Fruitone
100 gal, water
Burr
stage
1
2
8.13
3
Fuggles
Ave.
Check - No
Treatment
Burr
stage
1
2
3
10 Fruitone
Late
Clusters
100 gal, water
Burr
stage
Check - No
Treatment
Burr
stage
36
strawberries.
They began to increase at an alarming rate by the middle of
May and it was decided that further delay might result in crop injury.
Four proprietary dusts (DN Dust D-)4, DN Dust D-8, DN Dust D-7, and DN
Dust D-3) were applied on May 14 and 16.
The decision to time the dust
applications was made difficult by the elimination of long range weather
forecasts by the United States Weather Bureau.
Labor and travel diffi-
culties also prevented the collection of a great amount of quantitative
data.
Randomized samples of fifty leaves were taken before dusting and
from each treatment after dusting.
These data are given on the following
page but may be summarized as follows.
Treatment
Population of red spiders
Before dusting After dusting
6.9
DN Dust D-4 100 lbs./acre
93.1
DN Dust D-8 100 lbs./acre
93.1
5.3
8.2
DN Dust D-7 100 lbs./acre
93.1
DN Dust D-3 100 lbs./acre
9.5
93.1
Note--Nalnut shell flour used as carrier with DN Dust D-3.
as carrier in other dusts.
% Reduction
92.6
94.3
91.2
89.8
Frianite used
Discussion of Results
Sixty six (66) plants were examined carefully one week after dusting.
Foliage injury at this time was limited to 17 leaves.
Most of tie injury
occurred at the end of the rows where plants received excessive dust as a
result of turning of the duster.
These plants may safely be estimated
as averaging 200 leaves and the foliage injury is therefore approximately
0.13%.
This is not considered to he of economic importance.
Satisfactory controls were obtained with all of the dusts.
D-3 may be considered as inferior to DM Dust D-8.
DN Dust
This difference may
37
probably be attributed to difference in diluents of the toxicant.
Walnut
shell flour (diluent for DM Dust D-3) was reported as inferior to Frianite
in depositing dusts to strawberry foliage in 1941.
Early in the season the experimental duster was used to treat this
strawberry patch with i% Rotenone.
Talc was used as the diluent.
controls were obtained with this dust at 35-40 lbs./acre.
Excellent
Talc at this time
was noted to give excellent coverage on the undersurfaces of strawberry
foliage.
DN dusts as used did not effect satisfactory controls of the spittle
bug.
It is possible, however, that by the use of talc or diatomaceous
earth as a carrier that more effective results could be obtained.
Frianite
and walnut shell flour did not tend to be absorbed by the spittle of the
spittle bug.
Rotenone and DN dusts have been found to be compatible with
each other and it is possible that i percent Rotenone could be incorporated
into the DN Dust and that both pests could be controlled in one operation.
Talc has not been used as a carrier in DN dusts because of its
variable pH.
It is believed that treating and acidifying talc prior to
atomizing the dinitro- o- cyclohexyl phenol would result in a satisfactory
product.
Talc, because of its bulkiness and ability to adhere on strawberry
foliage, would make it possible to treat strawberries at the rate of 40
pounds per acre.
Tf costs of preparing this dust were similar, this might
result in reduction of material costs from 410.00 to $4.00 per acre.
Late in the 1941 season, two border rows of the strawberry patch
were allowed to stand after all remaining rows were topped.
that red spiders may be induced to concentrate on these rows.
It was thought
A very heavy
dusting of DN dust was applied in the middle of July and severe foliage
injury resulted.
Practically 100 percent kills of red spiders were noted.
38
These dusted plants were studied during 19112.
No permanent injury resulted
from this severe foliage injury but there was no notable reduction of the
1942 red spider population.
It may be concluded that red spiders may be controlled on strawberries with DN dusts (DN Dust I1-4, DN Dust D-8, DN Dust D-7, and DN Dust
D-3).
Extreme caution must be practiced in the use of these materials and
DN Dust D-7 will probably prove to be safer to use then the other dusts.
Temperatures must not exceed 70 degrees F. for at least three days after
treatment.
Seasonal conditions are favorable during April and May for
the use of this material.
The use of long range weather forecasts by the
United States Weather Bureau will aid greatly in this respect after the
termination of the present war emergency.
The accompanying letter by
Mr. Jones will serve as a testament to the value of red spider control
on strawberries.
COPY
December 14, 1942
Don C. Mote
Entomology Department
Campus
Dear Mr. Motes
In reporting to you on the experiment Mr. Morrison did from your department on Red Spider for strawberries at my farm, I am very glad to say
that I think it was a success.
Taking my patch for a three year period, with the first year not
being dusted and next two years with the dust being applied, I figure the
increase in tonnage and the price I received for the berries brought me
about $85.00 per acre, You perhaps know the cost of the dust so as you
can arrive at what the net profit would be.
I wish to thank you for your support in this experiment. Also, I
wish to thank Mr. Morrison for his effort for he certainly was on the job.
He gave the experiment careful study and worked hard making mapytrips out
here after working hours in the evening.
Thanking you and your department again for the interest in the matter.
Yours respectfully,
E. A. Jones
Route 3, Corvallis, Oregon
39
Common Red Spider Population Counts
East Farm
Corvallis, Oregon
Cooperator: E. A. Jones
Data collected: 5/19/42
Date dusted: 5/14-5/16
Host plant: Strawberries (Corvallis #12)
Rate of application: All treatments at rate of 100 lbs./acre
Leaf
No.
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Red spider populations - 3 days after dusting
Original red spider
populations
DN Dust D-4 DN Dust D-8 DN Dust D-7 DN Dust D-3
29
1.
89
12
9
11
3
9
44
3
25
8
168
0
33
6
1
6
56
5
195
1
14
0
5
0
88
8
9
5
0
0
11
15a
9
0
16
16
3
97
0
0
11
41
13
0
13
7
73
7
0
0
16
so
5
0
119
5
7
3
29
27
15
0
37
11
8
96
7
5
2
1
32
13
49
0
6
19
8
82
1
63
3
5
7
0
8
2
7
58
1
195
5
0
9
8
0
2
16
218
8
0
41
5
73
6
2
0
45
9
8
22
29
5
5
0
0
0
5
73
46
91
51
47
35
44
26
27
28
29
30
31
32
33
73
16
34
35
36
37
38
39
ho
41
t.
14
9
9
7
9
6
5
1
8
7
9
9
5
31
8
3
9
21
7
2
69
19
6
0
89
155
5
0
1
12
6
0
0
346
0.0
5
0
0
14
17
5
1
9
16
66
4651
93.1
27
0
1
0
0
1
0
5
14
216
258
97
gglinina13(39.941
control
5
3
1
83
98
47
89
Mean
8
18
12
73
Total
0
0
97
46
188
95
79
189
42
43
44
45
46
47
48
49
50
0
0
0
-6.9
6.87
0.971
92.6
1
5
1
0
a
1
3
267
5.3
g:g6
94.3
11
13
0
16
0
0
19
13
15
6
12
9
408
8.2
8.43
1.12
91.2
3
6
0
0
0
5
19
37
0
0
27
19
21
8
0
5
9
2
31
16
29
1
7
0
0
0
474
9.5
10.q5
1.49;
89.8
40
Phytocidal studies of DN dusts.
7.
Several specimens of s very
minute mite were brought to the Department of Entomology during the middle
of June.
These were submitted to the United States Department of Agricul-
ture, Bureau of Entomology and Plant Quarantine, at Washington, D.C.
were identified as the broad mite Hemitarsonemus latus Banks.
They
This TRS a
new record for Oregon but they had been take: from Bouvardia by C. F.
Coucette at both Sumner and Tacoma in 1933.
This species was causing damage to cucumbers in the greenhouses of
Chase Gardens, Eugene, Oregon.
The undersurfaces of the leaves were
stripped of hair filaments causing the leaves to become very papery and
assume a glazed appearance.
Several dusts were applied on May 28 and
examination of the results was made May 31.
The following results were
obtained.
Treatment
DN Dust
DN Dust D-4
DN Dust D-8
Din:Itro-dust
Sulfur
Check
No. of
leaves counted
No. of
living mites
10
10
10
10
10
20
Mean mites
per leaf
49
57
75
5
6
185
205
1603
19
21
80
8
Severe burning resulted from the dinitro-dust application but all
other materials appeared safe on cucumbers.
and no dead mites were found.
The results were not conclusive
These mites were not web spinners and may
have fallen from the dusted leaves.
Attempts were made to pick repre-
sentative young leaves for examination after dusting because young leaves
were noted to be most heavily infested.
These mites were also found
attacking young tomato plants in the greenhouse.
)41
Attempts to establish a culture of this mite in the Entomology
culture room for additional investigations resulted in failure.
The James Gardens, Good Pasture Island, Route 4, Eugene, Oregon had
planted a variety of herbs and condiments for experimental purposes in
1942.
A number of these plants became infested with red spiders and an
Applications
attempt was made to determine their tolerance to DN Dust D-4.
were made on September 22 and the plants were again examined October 1.
Temperatures reached a maximum of 87° F. on the third day after treatment.
All other maximum temperatures were below this point.
The following is a
summary of these observations,
Plant
Degree of injury
Lavender (Lavandula vera)
Tobacco (Niaargiii-gigi7a)
Henbane (Hinscynus niger
Sweet Marjorum (Majorana hortensis)
Sage (Salivia officihklis)
Thyme (Thymus vufgaris)
BelladoriaTftrupa belladonna)
Jimson weed (Datura stramonium)
Foxglove (Digitalis purpurea)
None
None
Slight foliage injury
None
None
None
None
None
Slight foliage injury
Red spiders were more populous on Nicotina glauca than on any other
plant.
A few were found on Belladonna and Henbane and none were found on
lavender, Sweet Marjoram, sage, thyme, Jimson weed, and foxglove.
The above information may prove to be of value at some future time
if any of these plants become grown commercially in Oregon.
It is believed
that all of the above plants could be safely treated with DN Dust D-4 or
DN Dust D-7 without excessive plant injury.
Methods of application of these
dusts to the plants would require some attention,
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8.
Completion of chemical studies of DN Dusted hops.
An original
study was made during 1940 of the effects DN dust and DN Dust D-L might
have on the physical, chemical and brewing qualities of hops.
The results
of this study have been included in the report to the Department of
Entomology (pages 234-240).
It was thought advisable to continue the
study of the possible effect these dusts might have on chemical qualities
of hops after they had been allowed to stand in storage.
Chemical analyes were accordingly made by the Chemistry Department
of Oregon State College after samples had been stored at room temperatures
for a period of two years (10/7/42 to 10/17/42).
The results of the
original and final analyses are tabulated as follows.
Percentage composition
Undusted hope
DN D-L dusted hops DN dusted hops
1077/40 10/17/42 10/7/140 10/17/742 10/7/40 10/17/42
Alph*esin
7.11
Beta resin
Hard resin
Total resin
Preservation value
Moisture
11.3.5
1.17
19.64
109.00
10.7
6.52
0.32*
12.86
8.95
1.42
5.78
15.05
20.80
33.00 108.1
6.8
9.3
* Old hops always giite too low values for Alph4esin.
probably contain more 1% alpha resin.
0.20*
10.52
5.00
15.72
37.1
6.4
7.05
12.00
1.30
20.15
110.5
10.7
0.63*
11.04
5.49
17.16
43.1
6.8
None of the above
Above analyses made on moisture-free basis (Original analyses in 1940
report not made on moisture-free basis).
Discussion of results
Preservative value is computed from the formula P. V
resin !- Beta resin).
10 (Alpha
The difficulty in analyzing for Alpha resin in old
3
hops combined with its importance in determining presertrative value indicate
that there is probably no significance between any of the above samples.
DN Dust D-4 and Di
Du4st-ta-TI
therefore, be used on hops without fear
of lowering the physical, chemical or brewing qualities of hope.
report)
(See 1940
I3
SUGGESTIONS FOR FUTURE WORK
The status for continued work on hops depends largely upon the
emphasis placed upon hop growing and its importance to the war effort.
The
following phases are considered worthy of additional effort if and when
circumstances warrant their study.
1.
Continued study in improvement of dusting machinery.
More
efficient dusting would probably make it possible to further
reduce amount of toxicant per acre.
2.
Study of the various carriers and diluents for toxic materials
in an effort to reduce amount of toxicant per acre.
3.
Continued seasons] history studies of hop pests would be of value
in giving added information on the biology of these pests.
4.
There is need for the development of a simple and rapid method
of measuring populations of red spiders and hop aphis.
There
are a number of techniques which have been developed on other
plants and it is possible that one of these could he adopted
for hops.
The technique should be simple in order that growers
could use it in timing of their control operations.
There is decided need for extension work among hop growers.
This
work should include instruction on use of mechanical equipment,
timing and method of applying dusts.
6.
Research should be undertaken to determine the proper timing of
DN dusts.
It is possible that early application of dusts may
prevent serious infestations of red spiders.
evidence to support this possibility.
There is some
7.
Ammonium and guanadine salts of dinitro-c-cresol still have
promise for control of red spider.
There is need for tests of
these and other dinitro compounds, which have been atomized
with the carrier.
8.
Preliminary tests to determine the value of plant hormone sprays
on hops were not promising.
Studies should be continued, how-
ever, in order that some of the problems in applying the materials could be eliminated.
9.
The possibility of using talc or diatomaceous earth as a carrier
for DM dusts on strawberries should be undertaken.
It is possible
that these materials would reduce the amount of material neces-
sary for commercial control as well as mike them effective on
both red spider and spittle bug.