LIBRARY
rATE PLANT BOARD
January 1%7
E-7H
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
REPORT ON COOPERATIVE EXPERIMENTS CONDUCTED BY
THE BUREAU 07 ENTOMOLOGY AND PLANT QUARANTINE AND
THE CALIFORNIA STATE DEPARTMENT OP AGRICULTURE
RELATIVE TO THE FUMIGATION OF FRUIT AND NURSERY- STOCK HOSTS
OF THE ORIENTAL FRUIT MOTH l/ Zj
By A. C. Johnson, C. H. Bowen, and G. L. Phillips,
Division of Control Investigations
The secretary of the Western Plant Board, in letters dated
December 11, 1942, and January 12, 1943, transmitted a request from
the Board to the Bureau of Entomology and Plant Quarantine for stud-
ies to be undertaken on the development of treatments for host fruits
originating in areas quarantined by Western States because of the
oriental fruit moth (Granholitha molesta (Busck)). The answer from
the Bureau, dated January 23, 1943, pointed out that such studies
were already under way on a limited scale in the Division of Control
Investigations, but only on fumigation schedules for summer-maturing
fruits intended for immediate consumption. It was stated that funds
were not available to undertake studies of fall-maturing fruits in-
tended for storage.
In February 1943, the late D. B. Mackie, of the California State
Department of Agriculture, proposed that a cooperative project be
undertaken on this problem, and it was finally arranged that the
State of California would allot to the Bureau a sum not to exceed
$8,000, to be available during the fiscal biennium of 1944 and 1945,
to aid in carrying out studies along the line proposed in the orig-
inal request by the Western Plant Board. Later,at the request of
the California State Department of Agriculture, studies were also
made with hibernating larvae in an effort to reduce the dosage sched-
ules and the temperature requirements in effect for the treatment of
nursery- 8 tock hosts.
l/Thls report was submitted to the member States of the Western
Plant Board, November 15, 1945, and is now reproduced in substantially
the original form for the information of others interested in this
subject.
2/These investigations were under the immediate supervision of
Randall Latta.
JAN 2 7 1947
- 2 -
The cooperative agreement with California terminated June 30, 1945*
This report is a presentation of the studies made during the period
covered "by the agreement.
OBJECTIVES
The objectives of the study were threefold:
(1) To develop fumigation dosage schedules for the treatment of
fresh -fruit hosts of the oriental fruit moth.
(2) To study further the dosage schedules needed for the destruc-
tion of hibernating larvae on nursery-stock hosts, in an effort to de-
velop fumigation schedules at temperature levels "below 60°P. and to re-
duce the schedules now authorised at 60c and 70°.
(3) To study the tolerance of host fruits to fumigation schedules
that are effective against this insect.
METHODS
All the tests were conducted at St. Louis and Louisiana, Mo., by
the Division of Control Investigations of the Bureau. The University
of California Citrus Experiment Station supplied all oriental fruit
moth eggs and hibernating larvae of California origin. Hibernating
larvae from New Jersey were supplied by the Division of Fruit Insect
Investigations of the Bureau. Stark Eros. Nursery, Louisiana, Mo.,
assisted in taking nursery-stock storage shed temperatures and humidity
records, which are shown in figure 1.
The experimental fumigations were performed in portable chambers,
which were in excellent condition. Commercial cold-storage facilities
were utilized for the storage of s-opies. Except where otherwise noted,
all fruit 8 were purchased from local sources, and were especially se-
lected for condition.
All dosages are expressed in pounds of methyl bromide per 1,000
cubic feet of space. For conciseness the dosage schedules are abbre-
viated as indicated in the following example: A schedule of 3 pounds
per 1,000 cubic feet for an exposure of 2 hours at 70°E. is shortened
to 3 lb./2 hr. at 70°.
As certain portions of the experimental test9 were finished, cor-
roborative tests were made in California to check the results under
their conditions. These tests were reported by Arm it age and Steinweden
in March 1945. 3/
3/Armitage, H. H., ejri& Steinweden, J. 2. Development of methods of
fumigation for control of the oriental fruit moth. Dec. 1944 - Mpr. 1945.
Unpublished report of Anaheim Stetion, California State Department of
Agri culture.
The results are presented under the following headings: ( l) Fumi-
gation of fresh-fruit hosts of the oriental fruit moth, (2) mortality
of larvae exposed to cold storage, ( 3) fumigation of hibernating larvae,
and (4) tolerance of fruits to methyl "bromide fumigation.
FUMIGATION OF FRESH- FRUIT HOSTS
OF THE ORIENTAL FRUIT MOTH
All studies relative to the fumigation of fresh- fruit hosts were
limited to the summer broods of the oriental fruit moth. The results of
tests with each stage of this insect are given. Overwintering larvae were
considered only in their relation to dormant nursery stock and are the
subject of another section.
Larvae
Tests in an effort to develop fumigation schedules for larvae of
the oriental fruit moth embedded in fresh fruit were first made in the
summer of 1943. At first green apples were infested by enclosing them in
cages with infested peach twigs; later naturally infested fruit was ob-
tained.
Dosages of methyl bromide ranging from 1 to 2 pounds per 1,000 cubic
feet were used at temperatures of 60° and 70°F. The results of these
tests pre given in table 1. Complete mortality occurred at all dosages
except 1 lb./? hrs. at 60°, where 1 larva and 2 pupae survived.
In 1944 plans were made to infest fruit artificially so that greater
quantities would be available. Through the courtesy of the University
of California Citrus Experiment Station, eggs, deposited on sheets of wex
paper, were supplied at frequent intervals ( 2 to 3 days) by air mail.
Bushel lots of apples were infested by placing a small piece of wax paper
containing about 6 eggs in contact with each apple. Nineteen bushels in-
fested in this manner proved to have an average infestation of slightly
more than one larva per apple. Apples were ready for use in fumigation
tests in about 6 days if immature larvae, or about 12 to' 15 days if
mature larvae, were desired. Fifty-nine tests were made with dosages
ranging from 0.5 to 2,5 lb. at temperatures from 40° to 80CF. A total
of 4,247 apples were used, containing 4,455 larvae.
It was considered desirable to develop fumigation schedules suitable
for the treatment of fruit that had been refrigerated, or placed in cold
storage, as well as for freshly picked fruit. A minimum of 40 eF* was
used, since it was considered that most fruit coming from cold storage
would be at approximately that temperature by the time it had been made
ready for fumigation. The results of these tests are given in table 2.
The minimum dosage schedules causing complete mortality of larvae
were 0.75 lb./2 nr. at 80°, 70°, and 60°F. and 1 lb./2 hr. at 50° and 40c.
The location of surviving larvae within the apples varied. No particular
area, such as the center, was noted where survival would most likely occur
- 4 -
Table 1. — Results of 1943 tests on methyl bromide fumigation of fresh
fruits infested with oriental fruit moth larvae. Fumigation for 2
hours unless otherwise noted
Treatment
:
Total :
Condition
of larvae
Temperature*
•
•
— •
Do sage '
*
i
Date s
fruit :
•
•
•
Total
•
•
Mortality
Of
Mm
^ ounus
Number
jDtumoor
i" ere en v
Apples
70
2
5/13
6
32
100
1.5
5/13
6
27
100
5/19 .
16
94
100
5/19 1/
16
75
100
60
2
6/23
19
67
100
JL«0
6/23
20
1UU
1
7/20
29
9
2/ 89
Peaches 5/
70
1*5
7/26
37
12
100
7/28
75
16
100
1
7/26
33
22
100
8/4
32
5
100
60
1.5
8/12
100
12
100
Pears
2J
70
1
8/4
32
5
100
i/Fumigation 1.5 hours.
,2/Two live pupae also found, under skin of apples.
2/Naturally infested fruit.
Table 2. — Resulte of 1944 teats with 2-hour methyl bromide fumiga-
tion of fresh fruit infested with oriental fruit moth larvae
Treatment
Tenperature: Dosage
80
Pounds
0.5
.75
1.0
Total
tests
Number
2
3
5
Apples
Number
34
280
490
Condition of larvae
Total : Mortality
Number
35
176
519
Percent
91
100
100
70 .5 2
.75 2
1.0 4
1.25 5
60 .5 1
.75 2
1.0 1
1.5 5
2.0 1
50 .5 1
.75 1
1.0 2
1.25 1
1.75 5
2.0 2
2.5 1
40 .5 1
.75 1
1.0 1
1.25 2
1.5 1
2.0 6
2.5 1
92 70 91
183 161 100
441 370 100
500 686 100
53 19 89
63 38 100
112 57 100
626 644 100
150 189 100
40 21 52
39 19 63
66 50 100
43 48 100
300 427 100
39 51 100
22 22 100
41 31 74
42 39 92
44 35 100
64 29 100
46 20 100
413 650 100
24 49 100
- 6 -
Ho difference in reaction was observed between the different larval
stages.
The mortality obtained in artificially infested apples was compared
with that in naturally infested fruit collected near St. Louis, These
data are given in table 3. The naturally infested fruit required slightly
higher dosages than the artificially infested fruit. Single survivors
appeared with a dosage of 1 lb. at 50° and 60°E. and it would apparently
require a dosage of 1.25 lb. for complete kill at these temperatures.
With a dosage of 0.75 lb., survival occurred at 70°, indicating that a
dosage of 1 lb. would be necessary at this temperature level.
Fumigations at the 40°F. temperature level would probably be on
fruit either refrigerated or from cold storage. In order to determine
whether a period of cold storage would change the susceptibility of
larvae to fumigation, a series of tests was made wherein infested apples
were removed from cold storage at weekly intervals and fumigated with a
dosage of 2 lb./2 hr. at 40°. The apples were placed in storage Septem-
ber 25, 1944, and contained both mature and immature larvae.
The results are given in table 4. No survivals occurred. However,
all larvae in the check samples were deed from cold storage alone at the
end of the eighth and ninth weeks.
Eggs
The results of fumigation tests with oriental fruit moth egge, at
Beltsville, Md., in 1939, reported in 1942, 4/ showed some hatching with
schedules of 1.5 and 2 lb./4 hr. at 60C]T. Later it appeared that these
schedules might be excessive because of certain errors connected with the
use of too small a fumigation chamber.
Therefore, further tests were conducted in 1944 with eggs supplied
by air mail from the University of California Citrus Experiment Station.
Pieces of wax paper upon which eggs had been deposited were fumigated
without other load in a 20-cubic foot temperature-controlled chamber.
Since experience had shown that the displacement by a load is usually
greater than the absorption by it, results in an empty chamber are valid.
Tepts were made between 50° and 70°P. with exposures of 2, 3, and 4 hours
in an attempt to develop fumigation schedules for eggs comparable to
those used for larvae in fresh fruits. A check sample was kept from
each shipment of eggs. The results are given in table 5.
4/Johnson, A. C., Livingstone, E. M. , and Bulger, J. W. Methyl
bromide fumigation to control oriental fruit moth on dormant nursery
stock. Jour. Econ. Ent. 35i 674-677. 1942.
- 7 -
Table 3. — Comparison of mortality obtained by fumigation of artificially
and naturally infested fruit. (Numbers of larvae involved are given
in parentheses)
* Mortality at treating temperatures of —
Do sagft *
: 40°?. : 50 °P. { 60°?. : 70 °F. 5 80°Po
; : _j i :
Pound g Percent Percent Percent Percent Percent
Artificially infested apples, treated July 17 to Oct. 31, 1944
1.5 100 ( 20)
1.25 100 (29) 100 (48) —
1.0 100 ( 35) 100 ( 50) 100 ( 58) 100 ( 370) 100 ( 522)
.75 97 ( 36) 100 ( 40) 100 ( 16l) 100 (176)
.5 90 (19) 87 ( 69) 94 (17)
Naturally infested pears, treated Nov. 1 to 7, 1944
1.75 100 (8) —
1.5 100 (7)
1.25 100 ( 8) 100 ( 7) '
1,0 100 (5) 100 (8)
.75 90 (10) 100 (8) 100 (6)
,5 — 100 (10) 100 (7)
Naturally Infested apples, treated Nov. 14 to 19. 1944
1.75 100 (8)
1.5 100 (16) -
1.25 100 (8) 100 (12)
1.0 88 (8) 90 (10)
.75 85 (7) 100 (8) 100 (12)
,5 91 (11) 100 (10)
- 8 -
Table 4.-- .Results of weekly fumigations of infested apples from cold
storage, with a dosage schedule of 2 lb./2 hr. at 40°F.
Storage
Check samples
Fumigated samples
>eriod •
s
<
Apples ' ,
, , i
Total
larvae
! Mortality
• *
• •
Apples '
•
Total
larvae
! Mortality
• *
t
Weeks
Number,
Number
Percent
Number
Number
Percent
0
12
9
0
1
12
10
100
2
12
8
100
3
12
6
100
4
12
9
100
5
12
13
100
6
12
10
90
12
8
100
7
12
7
86
12
6
100
8
24
16
100
12
7
100
9
51
21
100
- 9 -
Table 5. — Hatching of eggs fumigated with methyl "bromide at temper-
atures between 50° and 70°F. Tests conducted March to June, 1944.
Treatment
fn_ _ i i
xocai •
tests !
Results
of hatching
i emp e rs w u.r© # x>o sag©
•
• «
If' «*- .»-. A A •>« «. A
# Jaxposure f
•
Total
eggs
Eggs
S hatching
6F. Pounds
Hours
Number
Nua ier
Percent
50 1
2
4
1,009
82.3
3
2
413
63a]
4
2
403
4,9
1.5
2
4
808
32.3
3
2
379
0
4
2
336
0
2
2
3
795
0.7
3
1
168
0
4
1
190
0
2.5
2
2
401
0
1
169
\j
4
1
166
0
3
2
1
228
0
55 1
2
3
755
36.3
3
1
191
1.5
4
1
211
0
1.5
2
2
414
24.4
3
1
168
0.5
4
1
197
Xw r
ft
2
2
3
R92
ft Q
3
1
209
0
4
1
232
0
2.5
2
2
443
o
3
1
163
0
3
2
1
203
0
60 1
2
4
1,160
7.8
3
2
407
2.4
4
1
2?5
0
1.5
2
3
1,057
0.6
3
1
170
0
4-
1
188
0
- 10 -
Table 5.— Continued
Treatment
Total
i Results
of hatching
•
in , •
Tempera ture,
•
Dosage
• •
Expo sure
tests
: Total
» eggs
"66'
: hatching
op.
Pound?
Hours
Number
Number
Percent
60
2
2
3
690
0
2.5 '
2
3
670
0
65
1
2
3
4
3
1
1
824
191
142
16.0
0
0
1.5
2
3
4
3
1
1
663
139
130
0
0
0
2
2
2
431
0
2.5
2
1
215
0
70
1
2
2
443
0.4
1.5
2
2
457
0
2
2
1
200
0
Check e
44
5,271
93,6
- 11 -
It is evident from the results shown that the ejcposure period
can "be shortened to 2 hours to conform with schedules for the fumi-
gation of larvae. The minimum schedules for the 2-hour exoosure at
vhich no eggs hatched were as follows:
c7. Pounds
50
55
60
65
70
Pupae
Specific tests were net made with pupae. However, it has been
observed that, wherever pupae were included with larvae, they gen-
erally showed grerter mortality than did the larvae. For example, a
test with a dosage of 1 lb./2 hr. at 60CF. showed 14 dead larvae out
o^ a. total of 18, and complete mortality among 25 pupae.
Adults
No further tests were made against adults eince it had been pre-
viously shown that they were very susceptible to methyl bromide fumi-
gation (0.25 lb./4 hr. at 70°F.) .
"Discussion
Dosage schedules for fresh fruits should "be sufficient to destroy
not only larvae, but eggs and pupae as well, tfh.il e pupae are seldom
found on the fruit, they could be present in containers. Adults prob-
ably would not be present, but they are the easiest to kill of all
stages of this insect.
A. review of the results obtained with artificially infested fruit
( table 2) shows that complete mortality was obtained with the following
schedules:
0.75 lb./2 hr. at 80c, 70°, and 50 °F.
1 lb./2 hr. at 50c end 40°
Tests with naturally infested fruit (tables 1 and 3) show that
slightly higher schedules are needed, as follows:
2.5
2.5
2
1.5
1.5
1 lb./2 hr. at 70 °F.
1.25 lb./2 hr. at 50° and 60°
- 12 -
Tests with eggs ( table 5) indicated them to be more resistant
than summer-brood larvae, and the following schedules were the mini-
mum causing complete mortality:
2.5 lb./2 hr. at 50CF.
2 lb./2 hr. at 60°
1.5 lb./2 hr. at 70°
It would appear then, on the basis of the available data herein 5/,
that a satisfactory series of fumigation schedules for fresh fruit in-
fested with oriental fruit moth, or suspected of being so, would be:
Z lb./2 hr. at 40°?.
2.5 lb./2 hr. at 50°
2 lb./2 hr. at 60°
1.5 lb./2 hr. at 70°
1 lb./2 hr. at 80°
Owing to the discovery of the oriental fruit moth in California
in 1942, and the subsequent program of regulation and control of this
insect in 1943 during which tons of fruit and thousands of containers
were fumigated, it was necessary to select dosage schedules for that,
purpose before much of this experimental work was performed. The
dosage schedules set up by California, in 1943 of 1.5 lb./2 hr. at 70°P.,
2 lb./2 hr. at 65°, and 2.5 lb./2 hr. at 60° are substantially con-
firmed by the results of the present studies.
MORTALITY OP LARVAE EXPOSED TO COLD STORAGE
Following the discovery that the viability of larvae in apples
held in cold storage was seriously affected, as shown in the check sam-
ples -in table 4, tests were conducted to obtain further evidence on
this point. Two bushels of infested apples placed in cold storage on
September 18, 1944, were sampled at weekly intervals for 10 weeks, and
the condition of the larvae was noted. One bushel contained mostly
immature larvae, and the second mostly mature larvae.
The results of the weekly examinations are shown in table 6.
There was no evidence of development of the immature larvae after en-
tering cold storage, and all were dead in samples removed at the 5th
to the 10th weeks. The mature larvae were hardier, and one survived
in the sample examined the 10th week, although all others were dead
in the sample taken the 9th veek. There was no evidence of migration
from the apples during the storage period.
5/Armitage and Steinweden (see footnote., page 2) in California
had no survivors in artificially infested fruit fumigated at the
following schedules, in series repeated four times on Dec. 5, 1944,
Jan. 2, Jan. 28, and Fab. 24, 1945: 1 lb. at 80°F., 1.25 lb. at 70°,
1.5 lb. at 30c, 1.75 lb. at 50°, and 2 lb. at 40°,
- 13 -
Table 6.— Mortality of larvae in infested apples held for various
periods in cold storage at 34° to 36°P.
Storage
: Apples !
x nuns, wur o
larvae
larvae
period
: examined :
Total 5
•
•
Mortality'*
Total !
1
1
Mortality
Weeks
Number
Number
Percent
Number
Percent
0
12
21
0
8
0
1
12
14
0
13
0
2
12
11
36
5
20
3
12
11
64
13
15
4
12
19
95
8
38
5
12
8
100
6
83
6
12
12
100
9
89
7
12
11
100
11
91
8
12
7
100
15
93
9
24
13
100
21
100
10
1/ 17
100
2] 30
93
l/36 apple 8 examined.
2/54 apples examined.
LIBRARY
STATE PLANT BOARD
- 14 -
Since some survival occurred after storage for 2 l/2 months,
furthsr tests were made for periods of 3 and 4 months. At 3 months
two temperature levels were compared, 33° to 34°F. and 35° to 35°.
The 4-month test material was stored at 35° to 36°,
The mortality in the 3 lots was almost, but not quite, complete.
In the "bushel stored for 3 months at 35° to 36CF.,4 live larvae were
recovered from a total of 129. In attempts to rear out these larvae
at room temperature, one died the 4th day, one the 5th, and the third
the 7th day. The fourth larva survived to maturity. Prestorage
examination of a sample of 12 apples showed 19 live larvae and none
dead. The bushel contained 195 apples of which 35 were soft and
rotten at the end of the experiment.
In the second bushel stored for 3 months, at 33° to 34°F. , ' 1
live larvs was found in a total of 214. This larva was weak and died
6 days later. Prestorage examination of a sample of 12 apples showed
8 live and no dead larvae. The bushel contained 219 apples of which
19 had rotted.
In the bushel stored for 4 months at 35° to 36°F., 1 moribund
larva was found in a total of 176. It died 12 days later. The
bushel contained 165 apples, 9 of which had rotted.
It is evident from these tests that there is little danger of
oriental fruit moth larvae being disseminated by fruit which has been
subjected to any considerable amount of cold storage at temperatures
below 36CF. On the other hand, a cold-storage treatment would not
appear to be entirely acceptable as a means of certifying fruit under
oriental fruit moth quarantines.
The occurrence of live hibernating larvae in used baskets often
utilized as containers for fruit to be certified under oriental fruit
moth quarantines is an additional complication. Even though the bas-
kets would be subjected to fumigation at schedules used for summer
broods of this insect, a hazard would still exist, since the dosage
schedules for infested fruit are considerably less than those for
hibernating larvae.
FUMIGATION OF HIBERNATING LARVAE
Experimental Work 1938-40
The dosage schedules now required by member States of the Western
Plant Board, with respect to nursery-tree hosts of the oriental fruit
moth, are based on experimental work carried on by the Bureau of Ento-
mology and Plant Quarantine from 1938-40 (See footnote p. 6) . The
first tests were conducted at Moorestown, N. u, , in 1938, with hiber-
nating larvae provided by H. W. Allen and associates of the Bureau.
The larval material was held at a storage temperature of approximately
40°F. until treated. After treatment many lots were divided, the
- 15 -
larvae in one lot being removed from their cocoons following treat-
ment and held for observation. The remaining larvae were stored in
an outdoor shelter and observed in periods ranging from 2 months to
2 weeks. It was found that the mortality of the larvae held for
later examination was greater than of those removed from their co-
coons soon after treatment.
Tests were made at Beltsville in the winter of 1938-39, with
larvae from the same source, but kept in outdoor storage. Mortality
occurred at lower dosages than when stored at a constant of 40CF.,
and no apparent difference existed in lots removed from cocoons
immediately after treatment, and those held for a considerable period.
The original recommendation in 1938 for treatment was for a
dosage of 3.5 lb./4 hr. at 70°F. In 1939 this was modified to 2 lb./
4 hr. at 70°, or 3 lb./4 hr. at 60°. These latter schedules have
been in effect since that time.
Recent Experimental Work
In 1943, further studies were initiated for two purposes: ( l)
To attempt to reduce the dosage schedules then in effect, and (2) to
attempt to develop fumigation schedules for lower temperature levels.
Approximately 15,000 hibernating larvae were provided for these
tests by the University of California Citrus Experiment Station.
Upon their arrival on December 5, 1943, these were placed in storage
at 32°F., and the temperature was increased later in the season to
48° to 50° in order to reproduce to some extent conditions comparable
to those in nursery storage sheds.
Six series of tests were made with these larvae between February
and May, each series including fumigation at temperatures between the
current minimum level and 70°F. The larvae were conditioned to the
temperature at which they were fumigated for the periods indicated in
table 7. Past experience in other studies had indicated that with
each temperature drop of 10°, the dosage of methyl bromide needs to
be increased. Since the tests in 1938 had shown the need for an in-
crease of 1 pound per 1,000 cubic feet in dropping from 70° to 60°,
the dosage increase was used in the first series of tests made
February 18 to March 2 - i.e., 2 lb. at 70°, 3 lb. at 60°, 4 lb.
at 50°, 5 lb. at 40°, and 6 lb. at 30°, Before the second series
was started, it became evident that this rate of increase was insuf-
ficient, so the dosages were changed to 4 lb. at 50c, 6 lb. at 40°,
and 8 lb. at 30°. The results of these tests are given in table 7.
Table 8 contains a summary of the essential data for tests of
2, 3, and 4 hours' duration. It is evident from table 7 that under
the conditions of these tests, with 4-hour exposures, that dosages
of 8 lb. at 30°, 6 lb. at 40c, and 4 lb. at 50°F. were not sufficient
- 16 -
Table 7. — Adults emerging after treatment of hibernating larvae at
intervals during the storage season. Larvae of 1943 California
origin. Samples of series A contained approximately 20 larvae
each, of series B about 25, and of series C-P about 50 larvae.
Treatment
Storage^ Condi-
' temper-* tioning
ature ' period
* •
t
1 Adults emerged from lots exposed for —
Temper-: ~
Dosage
ature : &
2 : 2.5 : 3 : 3.5 : 4
, _hours • hours : hours : hours : hours
CP. Pounds eF. Hours Number Number Number Number Number
Series A, treated Feb. 18-Mar. 2, 1944
30
6
32
2
7
3
2
13
12
35
5.5
32
3
7
20
4
6
18
40
5
32
12
8
10
11
8
2
45
4.5
32
17
8
10
2
0
0
50
4
32
18
5
2
2
o
o
55
3.5
32
24
1
2
0
1
0
60
3
32
27
3
0
1
0
0
65
2.5
32
48
0
0
0
0
0
70
2
32
48
2
1
1
0
0
Series B,
treated Mnr.
7-24, 1944
30
8
32
2
9
—
6
—
0
35
7
32
3
1
1
2
40
6
32
15
2
0
0
45
5
32
18
4
0
0
50
4
32
18
1
0
0
55
3.5
32
24
4
0
0
60
3
32
24
1
0
0
65
2.5
32
48
1
0
0
70
2
32
48
3
0
0
Series C,
treated Apr.
5-20, 1944
35
8
34
None
8
18
9
18
10
40
6.5
50
3
24
19
4
5
5
45
5
48
3
9
15
5
1
3
50
4
50
None
5
1
0
0
0
55
3.5
48
16
7
0
0
0
0
60
3
48
16
1
0
0
0
0
65
2.5
48
36
5
0
0
0
0
70
2
43
48
10
1
0
0
0
- 17 -
Table 7. — Continued
Treatment
Temper-:
Storage
temper-
ature
Condi-
tioning
ueriod
Adults emerged from lots exposed for—
2
hours
2.5
hour 8
3
hours
3.5
hours
4
hours
Wait t\ A a
■rounds
Houxe
Number Number
xmm.Qex
n umu
Series D,
treated
Apr. 5-20,
1944
35
7.5
34
None
13
17
25
19
n
40
6.5
48
3
12
11
16
5
19
45
5
48
3
9
12
6
5
1
A
*x
50
None
1
4
1
0
O
55
3.5
48
16
3
0
0
1
0
o
48
72
4
0
1
0
0
65
2.5
48
60
10
1
1
0
0
70
2
48
72
2
2
0
0
0
Series E,
treated
Apr. 29-May 3, 1944
45
5
48
18
12
7
2
50
4
48
3
14
5
9
60
3
48
20
5
1
0
70
2
48
36
7
0
0
Series F,
treated
May 4-11,
1944
45
5
50
15
15
1
7
50
4
50
None
5
3
4
55
3.5
48
15
12
4
1
60
3
48
36
8
3
0
65
2.5
50
36
1
0
0
70
2
1/
48
0
0
0
l/Taken out of storage at 48°P. and subjected to room temperature
varying from 55° to 70° for one week, then held at 70° for 48 hours.
- 18 -
Table 8. — Mortality of hibernating larvae of 1943 California origin
following treatment at interval? during the storega season; data
of table 7 summarized for each treatment temperature and exposure
Treatment
: Total
: tests
: Average i
: larvae :
: per J
• f a a f I
• xesv «
Mortality of larvae
exnosed for —
Temper- :
ature :
j-'o sage
2 :
hours :
3
hours :
4
hours
Pounds
Number
Number
Percent
Percent
Percent
30
6
3
17
65
82
43
8
o
do
65
74
100
35
5.5
3
20
63
76
22
ry
f
n
«3
do
y/
7.5
3
49
75
46
78
Q
O
i
o
HA
O 1
S3
O A
84
fo
A A
40
c
O
di.
DO
A Q
4o
OA
yo
6
3
25
93
100
100
C. K
D, 0
6
66
79
75
45
4.5
1
o
65
91
100
5
15
45
77
63
94
50
4
18
39
85
95
95
55
3.5
15
42
87
93
99
60
3
18
46
92
98
100
65
2.5
15
42
92
99
100
70
2
18
40
90
99
100
- 19 -
to produce complete mortality in all series. The schedules of 3 lb.
at 60°, and 2 lb. at 70° did, however, produce complete mortality.
It is also noted that as the treatment was done later in the season,
the larvae tended to become more resistant to methyl bromide fumiga-
tion. This i* contrary to results obtained in previous tests.
The program was amplified further in 1944-45. The previous
conflicte in results could have been due to the source of larvae or
to the conditions of storage. Therefore, larvae vere obtained from
both California and New Jersey and stored under ( l) cold-storage
temperature conditions, (2) simulated nursery-stock storage conditions,
and (3) outdoor winter conditions. For cold-storage conditions the
larvae were placed in commercial apple storage. For simulated nursery-
stock storage the larvae were placed in a thermostatically controlled
mechanical refrigerator which was periodically adjusted so as to
follow the weekly averages of hygrothermograph records taken concur-
rently in a nursery- storage shed in Louisiana, Mo. The weekly mean
tempera ture in this selected storage shed, and the current outdoor
temperature means are given in figure 1. The relative humidity in
this shed remained at 100 percent until almost the end of the season.
For outdoor conditions the larvae were placed in a battery jar in a
sheltered location outdoors at St. Loui6.
Tests with larvae of New Jersey origin. — Approximately 10,000
hibernating larvae were received from Moorestown, N. J.t on November 5,
1944. These were divided into four equal portions and stored as
follows: Portion 1 - cold storage at 32c to 38°F. , portions 2 and 3 -
simulated nursery-stock 6hed storage, and portion 4 - outdoors.
Larvae from cold storage (portion l) were fumigated at approxi-
mately monthly intervals frota January 25 to April 25. Since some
tests in each series were at temperature levels different from that orf
storage, the larvae were conditioned for a period prior to fumigation.
The original series of dosage schedules, ranging from 2 lb. at 70° to
6 lb. at 32°F. was again used.
In each test the larvae were removed from their cocoons follow-
ing fumigation, and kept in petri dishes for observation. Final re-
sults were based on the emergence of adults from these larvae.
The results are given in table 9. They showed no tendency for
the larvae to become more 'resistant to fumigation as the sea.son pro-
gressed. This was a reversal of the results given in table 7. In
series A, survival occurred at 32°F. vith all exposures and at 40°
and 70° with 2-hour exposures. In series B, one month later, a single
survival occurred at 40° with a 2-hour exposure. In the remaining
two series, no survivals occurred in any test.
- 20 -
Table 9.— Adult a emerging after treatment of hibernating larvae
at Intervals during the storage season. Larvae of 1944 New Jer-
sey origin, kept in apple- storage rooms at a temperature of
32° to 34°F. from Nov. 5, 1944, to Feb. 26, 1945, and at 36° to
38° from Feb. 27 to end of tests. Samples contained from 19 to
75 larvae each.
Treatment
Condi- '
' tioning
period
Adults emerged from lots
exposed for —
•
Temperature) Dosage
•
2:35 4
hour 8 : hours : hours
°P. Pounds Hour 8 Number Number Number
Series A, treated Jan. 25-27, 1945
32 6 0 12 25 9
40 5 .75 1 0 0
50 4 1.5 0 0 0
60 3 2.25 0 0 0
70 2 3 2 0 0
Check (untreated) • 10 adults from 36 larvae
Series B, treated Feb. 27-Mar. 3, 1945
32 6 0 0 0 0
40 5 .75 1 0 0
50 4 1.5 0 0 0
60 3 2.25 0 0 0
70 2 3 0 0 0
Check (untreated) . . . . 9 adults from 37 larvae
Series C, treated Mar. 26-30, 1945
40 5 0 0 0 0
50 4 .75 0 0 0
60 3 1.5 0 0 0
70 2 2.25 0 0 0
Check (untreated) 1 adult from 61 larvae
Series D, treated Apr. 25-28, 1945
40 5 0 0 0 0
50 4 .75 0 0 0
60 3 1.5 0 0 0
70 2 2.25 0 0 0
Check (untreated) 12 adults from 29 larvae
- 21 -
A similar series of tests was mads with larvae held under
simulated nursery- stock storage shed conditions.
It was desired to compare the mortality of larvae taken from
storage following fumigation, with that of larvae replaced under
nursery-cto'ck storage conditions for the remainder of the season.
To do this, a double amount of lerval material (portions 2 and 3)
was included in each test. The larvae from one portion were removed
from their cocoons following fumigation, and held in petri dishes
at room temperature for observation. The remaining larvee were re-
turned undisturbed to simulated nursery storage and held until they
were about to pupate (as indicated by examinations of check samples),
before they were removed from their cocoons. This additional stor-
age period amounted to 98 days in series A, 63 days in series B, 43
days in series C, 14 days in series D, and 6 days in series E,
The emergence from both portions is given in table 10. The
number of adults was less from larvae returned to storage than from
those placed tuider observation immediately following fumigation.
- 22 -
Table 10.— -Adults emerging after treatment of hibernating larvae at
intervals during the storage season. Larvae of 1944 New Jersey
origin, kept in simulated nursery- stock storage. Samples contained
approximately 30 larvae each in series A, E, and C, and 40 larvae
and pupae mixed in series D and S .
: : Adults emerged from i
Treatment : Condi- : lots removed to
: tionine : room temperature :
Adult 8 emerged from
lot 8 replaced in
nursery storage
Temper-: « : period : 2 : 3 : 4
ature : ■Uosage: .hours • hours j hours «
2 » 3:4
hours • hours » hours
°F. Pounds Hours Number Number Number Number Number Number
Series A, treated Jan. 22-24, 1945
32
6
0.75
11
19
17
10
5
9
40
5
0
1
11
4
3
0
2
50
4
.75
2
0
0
0
0
0
60
3
1.5
0
0
0
0
0
0
70
2
2.25
1
0
0
1
0
0
Check
(untreated)
• • e
9 adults
from 28
larvae
9 adults
from 30
larvae
Series B, treated Feb. 22-Mar. 1, 1945
40
5
0
2
8
0
0
0
0
50
4
.75
0
0
0
0
0
0
60
3
1.5
0
0
0
0
0
0
70
2
2.25
0
0
0
0
0
0
Check
( untreated)
. . 7
adults
from 28
larvae
5 adults
from 30
larvae
Series C, treated Mar. 19-20, 1945
50 4 . 75 4 1 0 4 0 0
6030 00000 0
70 2 .75 0 0 0 0 0 0
Check (untreated) . . 6 adults from 23 larvae 10 adults from 30 larvae
Series D, treated Apr. 17-20, 1945
50 4 . 75 1 0 0 5 0 0
60 3 0 0 0 0 0 0 0
70 2 .75 0 0 0 0 0 0
Gheck (untreated) . • 20 adults from 41 larvae 13 adults from 27 larvae
and pupae and pupae
Series E, treated Apr. 30-May 3, 1945
50 4 . 75 1 0 0 0 0 0
60 30 00000 0
70 2 .75 0 0 0 0 0 0
Check (untreated) 3 adults from 3 pupae
- 23 -
The mortality following fumigation of lervae kept in cold stor-
age can be compared with that of larvae kept in simulated nursery-
stock storage by referring to table 9 and the results of immediate
examinations given in table 10. There were fewer instances of sur-
vivals from larvae held -in cold storage than from those stored under
simulated nursery-rtock conditions. In table 9, series A, there were
no survivals from 3-and 4-hour exposures at 40CF. , or after 2 hours at
50°, none in series B after 3 hours at 40°, none in series C after
2 and 3 hours at 50°, and none in series D after 2 hours at 50c. Sur-
vivals occurred at all of these points with larvae held in simulated
nursery- stock storage.
Additional tests were made April 9 to 11 with larvae stored out-
doors (portion 4) . These larvae had been exposed to normal winter
temperatures for approximately 5 months. Tests were made at 50°,
60c, and 70°F. , with exposures of 2, 3, and 4 hours at each temperature
level. No adults emerged from any of the tests. The check samples
yielded 135 adults from 222 larvae and pupae.
Tests with larvae of California origin.— Larvae were" received from
California in three shipments on November 15, 1944, December 29, 1944,
and January 26, 1945. Since this made the prefumigation storage dif-
ferent, seasonal series of tests were made with each lot. The November
shipment was paired with the New Jersey material so that the series of
tests would be directly comparable. This shipment was divided into
three portions, and stored with the New Jersey larvae as follows*
Portion 1 - cold storage -at 32° to 38CF., and portions 2 and 3 - sim-
ulated nursery-stock shed storage.
Larvae from cold storage (portion l) were fumigated at approxi-
mately monthly intervals in* the same tests with New Jersey larvae.
The results of these tests ere given in table 11. There was no evi-
dence that there was any appreciable change in the resistance of the
larvae with the advance of the season. With the 40_-oercent schedule
for 3 hours a single survivor occurred in series B, C, and D. With
the exception of survival at 70 CF. for 2 hours in series A, no sur-
vival occurred in any series at any schedule »t 50° or above.
Series of tests were also mode with the November shipment of
larvae held under simulated nursery- stock storage. These were again
paired with New Jersey larvae from the same storage in series of tests
at intervals through the storage season. A double amount of larvae
was used (portions 2 and 3), one portion being removed from the co-
coons following fumigation, and the other being replaced in simulated
nursery-stock storage until nearly ready for pupation. The emergence
from both portions is given in table 12. The mortality was greatest
when the treated larvae were replaced in nursery- stock storage, both
from the standpoint of the number of tests showing no emergence, and
in the fever numbers of adults emerging.
- 24 -
Table 11. — Adult b emerging after treatment of hibernating larvae
at intervale during the storage season. Larvae of 1944 Califor-
nia origin, shipped Nov. 15, and kept in apple- storage rooms at
a temperature of 32° to 34°F. until Feb. 26, and at 36° to 38°
from Feb. 27 to end of the tests. Samples contained from 24 to
70 larvae each.
Treatment
Temperature] Dosage
Condi-
tioning
period
Adults emerged from lots
exposed for —
2
hours
3
hours
4
hours
32
40
50
60
70
Pounds Hours Number Number
Series A, treated Jan. 25-27, 1945
6
5
4
3
0
.75
1.5
2.25
7
10
5
0
0
4
16
0
0
0
0
Number
12
0
0
0
0
Check (untreated) 11 adults from 25 larvae
Series B, treated Feb. 27 -Mar. 3, 1945
32 6 0 1 1 0
40 5 . 75 0 1 0
50 4 1.5 0 0 0
60 3 2.25 0 0 0
70 2 3 0 0 0
Check (untreated) . 22 adults from 25 larvae
Series C, treated Mar. 26-30, 1945
40 5 0 0 1 0
50 4 .75 0 0 0
60 3 1.5 0 0 0
70 2 2.25 0 0 0
Check (untreated) 10 adults from 53 larvae
Series D, treated Apr. 25-26, 1945
40 5 0 4 1 0
50 4 . 75 0 0 0
60 3 1.5 0 0 0
70 2 2.25 0 0 0
Check (untreated) 15 adults from 27 larvae
- 25 -
Table 12. — Adults emerging after treatment of hibernating larvae at
intervals during the storage season. Larvae of 1944 California
origin, shipped Nov. 15, and kept in simulated nursery-stock storage.
Samples contained from 17 to 29 larvae each in series 5, unu C, and
from 13 to 54 larvae and pupae mixed in series D and E.
•
•
Adults emerged from
: Adults
emerged from
Treatment :
Condi-:
lot 8 removed to
: lot 8 replaced in
: tioning:
room temperature
: nurnery storage
Temper-! :
period:
2:3:4
: 2 :
3
: 4
ature : Dosage.
hours . hours . hours
. hours •
hour 8
. hour 8
Pounds
Hours Number Number Number
Number Number
Number
Series A, treated Jan. 22-24,
1945
32
6
0.75
11 25 17
11
4
10
40
5
0
19 19 15
6
5
1
50
4
.75
14 2
1
0
0
60
3
1,5
5 0 0
0
0
0
70
2
2.25
7 0 0
0
0
0
Check
(untreated)
... 12 adults from 27 larvae 8 adults from 24 larvae
Series B, treated Feb. 22-K?r. 1, 1945
40
o
0
5 7 0
0
0
0
50
4
.75
0 0 0
0
0
0
oU
1.5
0 0 0
0
0
0
70
2
2.25
0 0 0
0
0
0
Check
(untreated)
• . 9 adult 8 from 24 larvae
10 adults
from 24 larvae
Series
C, treated Mar. 19-20,
1945
00
4
.75
7 5 1
1
0
0
60
3
0
0 0 0
0
0
0
70
2
.75
0 10
0
0
0
Check
(untreated)
. . 11
adults from 25 larvae
10 adult s
from
24 larvae
Series
D, treated Apr. 17-20,
1945
50
4
.75
5 2 0
1
0
0
60
3
0
10 0
0
0
0
70
2
.75
0 0 0
0
0
0
Check
( untreated)
• Q 22
adults from 41 larvae
28 adults
. from
42 larvae
and pupae
and pupae
Series
B, treated Apr. 30-May 3, 1945
50
4
.75
0 10
5
0
0
60
3
0
0 0 0
0
0
0
70
2
.75
0 0 0
0
0
0
Check
(untreated)
from 11 larvae and pupae
- 26 -
Additional tests with larvae kept tinder simulated nursery-
stock storage were made with the December and January shipments.
The results of these are given in tables 13 and 14. In these tests
the additional storage amounted to 48 days for series A, 26 days
for series B, 15 days for series C, and 6 days for series D. These
series of tests showed less survival than the November shipment.
The cause for this difference is not known. Less emergence occurred
from larvae replaced in storage, as was the case in the tests with
the November shipment.
- 27 -
Table 13. — Adults emerging after treatment of hibernating larvae at
intervals during the dormant season. Larvae of 1944 California
origin, shipped Dec. 29, and kept in simulated nursery-stock
storpge. Samoles contained from 15 to 68 larvae each.
Treatment : Condi-:
: tloning:.
Temper-: ^ : period:
a*we { _i L
Adults emerged from
lots removed to
room temperature
2
hours
3
hours
4
hours
Adults emerged from
lots replaced in
nursery storage
2
hour 8
3
hours
4
hours
Pounds Hours Number Number Number Number Number Number
Series A, treated Mar. 14-16, 1945
0
0
50 4
0.75 12
7
0
3
0
60 3
0 2
2
0
1
0
70 2
.75 8
0
0
2
0
Check (untreated)
. . 18 adults
from 64
larvae
9 adults
from 60
Series B, treated Apr. 4-7, 1945
504 .75 00 0 0 0 0
60 30 000000
70 2 ,75 0 0 0 0 0 0
Check (untreated) . . 6 adults from 53 larvae 12 adults from 60 larvae
Series C, treated Apr. 17-20, 1945
504 . 75 000000
60 3 0 0 0 0 0 0 0
70 2 .75 0 0 0 0 0 0
Check (untreated) . . 10 adults from 20 larvae 0 adults from 9 larvae
Series D, treated May 1-3, 1945
50
4
.75
0
0
0
0
0
0
60
3
0
0
0
0
0
0
0
70
2
.75
0
0
0
0
0
0
Check (untreated) 6 adults from 16 larvae
- 28 -
Table 14.-- -Adults emerging after treatment of hibernating larvae at
intervale during the storage season. Larvae of 1944 California
origin, shipped Jan, 26, 1945, and kept in simulated nursery-stock
storage. Samples contained from 41 to 72 larvee each.
Treatment :
, Condi-
! tioning
period
! Adult 8 emerged from i
: lots removed to i
: room temperature
Adult 8 emerged from
i lots replaced in
nurserv storage
Temper-: Dog i
ature : I
: 2 : 3 : 4
> hours • hours ; hours -
: 2 1 3 1 4
I hours • hour 8 j hours
°7. Pounds Ho\trs Number Number Number Number Number Number.
Series A, treated Mar. 14-16, 1945
50 4 0.75 11 2 1 2 0 0
60 30 200000
70 2 .75 1 0 0 0 0 0
Check (untreated) - - 23 adults from 66 larvae 10 adults from 60 larvae
Series B, treated Apr. 4-7, 1945
50 4 . 75 0 0 0 0 0 0
60 30 000000
70 2 .75 0 0 0 0 0 0
Check (untreated) . . 10 adults from 62 larvae 10 adults from 60 larvae
Series C, treated Apr. 17-20, 1945
50 4 .75 000000
60 30 000000
70 2 .75 0 0 0 0 0 0
Check (untreated) . . 18 adults from 56 larvae 8 adults from 37 larvae
Series D, treated May 1-3, 1945
50
4
.75
0
0
0
0
0
0
60
3
0
0
0
0
0
0
0
70
2
.75
0
0
0
0
0
0
Check (untreated) • • 4 adults from 26 larvae
- 29 -
Discussion
To analyze the data better, the tests from tables 9 through 14
have been summarised in table 15. In these tables, the results from
larvae immediately removed from cocoons, and of those replaced in
storage, as given in tables 10, 12, 13, and 14, have been combined.
The combined data in tables 8 and 15 show that the first objective,
that of reducing the present dosages at 60° and 70°F., cannot be ful-
filled. It is true that under certain circumstances reduced schedules
were effective, but taken from the overall standpoint, a reduction
would not be advisable. The experimental tests were planned to dupli-
cate conditions often associated with nursery-stock fumigation, i.e.,
treatment at any date between January and May, replacement in nursery
storage after fumigation, the shipment of stock immediately following
fumigation, possible differences in resistance of larvae in different
localities, and different storage conditions. Therefore a satisfac-
tory fumigation schedule should be one that produces complete mortality
under all of these conditions in experimental tests.
The same conclusion was reached by Armitage and Steinweden in
corroborating tests in California ( see footnote, p. 2) . In series of
tests with hibernating larvae fumigated for 3 and 4 hours with 2 lb.
at 70°, and 3 lb. at 60°F., in December 1944, January, February, and,
March, 1945, there were survivors with 3-hour exposures under both
60° and 70° schedules in February with larvae that had been in hiberna-
tion 7 1/2 weeks, and in a March test with 3 lb. for 3 hr. at 60° with
larvae that had been in hibernation for 9 weeks.
It is also shown that on the basis of available data, the second
objective, that of developing additional dosage schedules for lower
temperature levels, cannot be fulfilled. The two projected series of
dosage schedules, i.e., 4 lb. at 50°F.; 6 lb. at 40°; and 8 lb. at
30° (table 8); and 4 lb. at 50°; 5 lb. at 40°; and 6 lb. at 32°
(table 15) were both insufficient to produce complete mortality of
larvae under all the nursery-stock fumigation conditions tested. This
does not mean that such schedules cannot be developed, but rather that
the selected dosages were not high enough. Until further studies are
made, therefore, schedules for fumigation at 50°, 40c, and 32° cannot
be recommended.
Further analysis of the data demonstrates these additional points.
(l) Tests with larvae from the two sources showed that those from
California consistently yielded slightly higher survival than those
from Hew Jersey. This could be interpreted to mean that larvae from
different localities or areas will not react exactly the same. On the
other hand, it could mean that the differences in handling and rearing
methods were responsible.
( 2) Hibernating larvae held in cold storage at 32° to 38°F. showed
less survival than those kept under simulated nursery-stock storage
conditions.
- 30 -
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- 31 -
(3) Larvae returned to simulated nursery- stock storage follow-
ing fumigation showed a lower survival than those subjected to higher
temperatures following fumigation. These two conditions of post fumi-
gation handling are the same as those associated with the handling of
nursery stock, where some stock is fumigated and replaced in stock
piles or order bins, while other stock may he shipped soon after treat-
ment .
(4) Tests with larvae stored outdoors over winter were limited,
but the results compared favorably with tests made at approximately the
same date using larvae stored under controlled conditions, and indi-
cates that outdoor storage did not materially increase the resistance
of the larvae to fumigation.
(5) The previous evidence (table 7) that larvae became more
resistant as the season progressed was not substantiated in the 1944-45
tests (tables 10 through 14). Rather, the resistance appeared to be
about the same throughout the season.
(6) Of incidental interest was the fact that live adults were
found in check samples while still in simulated nursery- stock storage
beginning May 4. No adults emerged, however, from check samples as
long as they remained in cold storage.
TOLERANCE OP FRUITS TO METHYL BROMIDE FUMIGATION
Summer- Maturing Fruits Intended for Immediate Consumption
Tests were made as opportunity permitted to study the tolerance
of summer- maturing fruits. Fruits maturing in early or midsummer,
which moved directly to consumer markets were included in this classi-
fication. These may have been subjected to refrigeration, but were
not intended to be stored for winter marketing.
Samples of fruits were fumigated with dosages of 1 and 2 lb. at
70°F. , and 1.5 and 3 lb. at 60°. Two schedules at each temperature
level were selected, since the final results of tests with eggs and
larvae were not known at the time the tests were made. Likewise, the
higher schedules helped to determine if a sufficient margin of toler-
ance existed. The condition of fumigated fruit was compared with that
of untreated checks at intervals following treatment.
Auricotsi— The variety Royal (California origin)was used in tests
of July 12, 1944. This fruit was firm and well ripened. It was ob-
tained in the St. Louis fruit market, had been shipped under refrigera-
tion, and was in fruit storage at 60°F. when purchased. After fumiga-
tion it was held at room temperature (85°) for observation. There was
no evidence of injury, and all treated samples reacted similarly to the
check.
- 32
Apples. — At St. Louie, the applee infested for mortallt7 studies
were closely observed for symptoms of Injury from the fumigation.
These included the varieties Wealthy, Black Twig, Lowland Raspberry,
Duchess, and Golden Delicious in all stages of maturity. Ho evidence
of injury was observed with dosage schedules ranging from 0.5 lb. at
80° to 2.5 lb. at 40°?.
The State Entomologists Office of Colorado kept records of ship-
ments into that State in 1942, when their oriental fruit moth regula-
tions were amended to allow apples to be received under fumigation
certificates. These records were supplied to the Bureau by courtesy
of F. H. Gates, State entomologist. A sample was removed at destina-
tion from each carload and kept under observation for effect of the
treatment on quality. Ho injury or decrease in quality was observed
in 21 carloads of early apples. These included some fumigated with
4-hour exposures as follows:
Number of cars Origin Variety of apple Dosage schedule
13 Delaware Delicious 2 lb./4 hr. at 70°?.
Gano
3
3
2
Kansas
-do-
-do-
2 lb./4 hr. at 70°
3 lb./4 hr. at 60*
2 lb./2 hr. at 70°
In other experimental studies by the Division of Control Investi-
gations, it has been shown that the variety Williams Early Red is sus-
ceptible to injury under certain circumstances. The same studies
showed no injury to Wealthy or Starr apples. It appears from these
observations that most varieties of summer apples can be fumigated
without risk of injury.
Cherries. — Local Montmorency cherries were purchased in June 1945,
and fumigated with dosages of 1.5 and 3 lb. at 60 °F. , and 1 and 2 lb*
at 70° for 2-hour exposures. The cherries were well ripened and in
excellent condition, all with stems on. There was no evidence of in-
jury1 in fact, the treated samples maintained a higher percentage of
marketable cherries over a 2 weeks' period than did the checks, owing to
a greater amount of "nesting * in the check samples.
Hectarlnes. — The variety John Rivers (California origin) was pur-
chased in the St. Louis fruit market on July 12, 1944. It had been
shipped under refrigeration and was in fruit storage at 60 °F. when pur-
chased. The fruit was firm and in excellent condition. After fumiga-
tion the samples were placed in room storage (85°7.) and compared daily
with untreated checks. There was no evidence of injury, and all treated
samples reacted similarly to the checks.
- 33 -
Pears.— Bartlett pears (California origin) were purchased on the
St. Louis fruit market on August 9, 1944. These pears were firm but
well ripened. After fumigation internal injury showed in all pears,
being more severe with the heavier schedules. Typical injury is shown
in figure 2.
It was suspected that the maturity of the pears might have been a
contributing cause. Therefore additional Bartlett pears of California
origin were obtained, which were selected as being less mature than
the first purchase. These pears were in fruit storage at 60°?. when
obtained. The entire lot was warmed to 70°. Two samples were fumiga-
ted with 1 and 2 lb. for 2 hr. as soon as they reached 70°, Two more
samples were allowed to ripen at 70° for an additional 2 days, and a
third pair of samples were ripened for 4 days before treatment. The
results are given in table 16. They show that as the pears became more
mature, the amount of internal Injury increased markedly.
Table 16. — Injury in Bartlett pears fumigated upon removal from
storage, and after 2 and 4 days' ripening at 70°F. Fumigated
at 70° with 2-hour exposures
Ripening period after : Dosage ! Pears showing internal
removal from storage * injury on 6th day i/
* I
Day Pounds Percent
0
1
7
2
0
2
1
60
2
87
4
1
100
2
100
i/ Check samples shoved all pears sound on the 4th day, and
7 percent unmarketable on the 6th and 7th days.
- 34 -
Further tests were made with unref rigerated pears of local origin.
These were of the varieties Kieffer and Garber, which at this season
were very green and hard. Samples of these were fumigated with the
same schedules used with the Bartlett pears. No evidence of injury
occurred even after several weeks of observation.
The evidence from these tests suggest that fully mature pears
may be susceptible to injury from methyl bromide.
Plums. — The variety Duarte (California origin) was purchased in
the St. Louis fruit market on August 9, 1944. These plums had been
shipped under refrigeration and were in storage at 60°?. when purchased.
They were firm and in excellent condition. After fumigation the sam-
ples were placed in room storage at 85° and compared daily with un-
treated checks. There was no evidence of injury, and all treated sam-
ples reacted similarly to the checks.
Peaches. ^-Five lots of ripe peaches, variety unknown, of local
origin were fumigated in St. Louis in July and August 1943. No injury
was observed.
Fall-maturing Fruits Intended for Cold Storage
In the development of fumigation schedules for the host fruits
of oriental fruit moth, it was necessary to consider the treatment of
late- maturing fruits that normally are placed in storage for various
periods before marketing, as well as the treatment of summer- maturing
fruits intended for immediate consumption. Apples are the principal
class of host fruit going into storage; therefore attention was con-
fined to them.
As shown in previous sections of this report, fumigation schedules
were developed for the treatment of fruit at temperatures as low as
40°?* The problem of the reaction of apples to such treatments remained
to be studied.
In experimental work done by Phillips et al. §] in Canada, the
apples were injured unless they were stored for 6 weeks after picking
before treatment. Further tests by Phillips and Monro 7j indicated a
varietal difference in tolerance. While most of these tests had been
made under conditions of vacuum fumigation, they indicated that the
problem of fumigating apples immediately prior to storing, or after a
period of storage, required thorough study.
£/tehillips, W. H. , Monro, H. A. U., and Allen, C. E. Some obser-
vations on the fumigation of apples with methyl bromide. Sci. Agr. 19:
7-20, 1938.
7/Phillips, W. R. , and Monro, H. A. U. Methyl bromide injury to
apples. Jour. Scon. Ent. 32: 344-345, 1939.
- 35 -
Teste were planned In 1943-44, to give evidence of the reaction
of apples fumigated before being placed in storage, as well as after
various periods of storage. As many varieties as could be obtained
were to be included to study varietal tolerance. The apples were to
be fumigated with a dosage schedule appropriate for the temperature
level existing at the time of treatment, as follows:
1.5 lb./2 hr. at 70°FD
2 lb./2 hr. at 60°
2.5 lb./2 hr. at 50°
3 lb./2 hr. at 40°
To provide information on the points listed above, four series
of tests were made at Louisiana, Mo.
Series A.-- Apples were fumigated at packing-shed temperatures as
soon as picked. One half was placed in cold storage at 32° to 38°!\,
and the other half at marketing temperatures of 40° to 55°,
Series B.— Apples were held 2 weeks at packing -shed temperatures,
then fumigated. One half was placed in cold storage, and the other
half a» marketing temperatures.
Series C— Apples were held 1 month in cold storage, then fumi-
gated at 40°F. One half was replaced in cold storage, and the other
half was held at marketing temperatures.
Series D. — Apples were held 3 months in cold storage, then fumi-
gated at 40°?. One half was replaced in cold storage, and the other
half was held at marketing temperatures.
It was not possible to obtain a sufficient quantity of all vari-
eties to carry them through the four series. Three varieties, Commerce,
Black Ben Davis, and Giant Geneton, were used in Series A and B only,
while small lots of Northern Spy, R. I. Greening, and Rambo were used
in series A only. The following varieties were used in all four series:
Black Twig King David Starking
Golden Delicious Red Delicious Staymen Wine sap
Grimes Golden Red Winesap Willow Twig
Jonathan Rome Beauty York
In the varieties used in all four series, six bushel lots were
used, with one exception, divided as follows: one and one-half bushels
in each series, subdivided into one-half bushel for cold storage, one-
half bushel for marketing temperatures, one-fourth bushel for cold
storage check, and one-fourth bushel for marketing temperature check.
Pertinent data relative to these treatments are given in table 17.
- 36 -
Table 17. — Date relative to the treatment of apples in series A, 3, 0,
and D, all exposures for 2 hours
Variety
! Date
I picked ]
Quantity^
used \
Date j
fumigated.
Apple •
tempera-**
ture ;
Dosage
Bushels
1943
J? m
w9i loo Ay
treated at picking
Bl«rlf Ben D«vi«
io h
1
10/8
60
Blnrlc Twl v
in l\ p
1.5
10/13
64-65
&
in /7
1
10/8
ou
A
f~l •? ■ p f f» a t ^ r
vxiauv « oil c u ii
in /7
y
1
10/8
An
flrt 1 on Dal 1 r>\ ah a
9 /P5
1.5
9/26
4&.4A
P 5
urimc8 VXOJ.Q.OU
Q /l A
1.5
9/19
UO~UC
*>
Q /l 7
1.5
9/18
o
c,
Kin^r David
9/l4
1*25
9/18
c
1
9/26
9 A
Ho I0 Greening
9/25
0.25
9/26
46-48
2.5
Rambo
9/25
1
9/26
46-48
2.5
Red Delicious
10/2
1.5
10/3
62-63
2
Red Wine sap
10/16
1.5
10/18
52-53
2.5
Rome Beauty
9/25
1.5
9/26
46-48
2.5
Starking
9/23
1.5
9/24
58
2
Staymen Wine sap
10/2
1.5
10/3
62
2
Willow Twig
10/6
1.5
10/8
60
2
York
10/6
1.5
10/8
60
2
Series B, treated 2 weeks after picking
Black Ben Davis
Black Twig
Commerce
G-ipnt Geneton
Golden Delicious
Grimes Golden
Jonathan
King David
Red Delicious
Red Wine sap
Rome Beauty
Starking
Staymen Wine sap
Willow Twig
York
10/7
10/12
10/7
10/7
9/25
9/18
9/17
9/14
10/2
10/16
9/25
9/23
10/2
10/6
10/6
1
10/23
56-58
2
1.5
10/26
53
2.5
1
10/23
56-58
2
1
10/23
56-58
2
1.5
10/9
59
2
1.5
10/3
63
2
1.5
10)3
9/30
63
2
1.25
63-64
2
1.5
10/17
50
2.5
1.5
11/1
56
2
1.5
10/9
59
2
1.5
10/9
59
2
1.5
10/17
50
2.5
1.5
10/23
56-58
2
1.5
10/23
56-58
2
Table 17.— Continued
Variety
\ Date
] Quantity \
Date
| picked
used [
fumigated)
1943.
Bushel s.
I94£
Apple t
tempera-s Dosage
ture ;
Series C, treated after 1 month of cold storage
Black Twig
Golden Delicious
Grimes Golden
Jonathan
King David
Bed Delicious
Bed Wine sap
Borne Beauty
Starklng
Staymen Wine sap
Willow Twig
York
10/12
9/25
9/18
9/17
9/14
10/2
10/16
9/25
9/23
10/2
10/6
10/6
Series D, treated after 3 months of cold storage
Black Twig
Golden Delicious
Grimes Golden
Jonathan
King David
Bed Delicious
Bed Wine sap
Borne Beauty
Starking
Staymen Wine sap
Willow Twig
York
10/12
1.5
9/25
1.5
9/18
1.5
9/17
1.5
9/14 .
1.25
10/2
1.5
10/16
1.5
9/25
1.5
9/23
1.5
10/2
1.5
10/6
1.5
10/6
1.5
1/15/44
1/1
1/1
12/31
12/31
1/2
1/15
1/1
H1
1/2
1/2
1/2
39
38
38
36- 40
36
37- 38
38- 39
38
38-41
37-38
38
38
Pounds
1.5
11/9
37
3
1.5
10/25
40
3
1.5
10/17
36-38
3
1.5
. 10/17
36-38
3
1.25
10/14
36
3
1.5
11/1
39
3
1.5
11/16
36
3
1.5
10/25
38
3
1.5
10/24
36
3
1.5
10/31
39
3
1.5
11/7
36
3
1.5
11/7
36
3
3
3
3
3
3
3
3
3
3
3
3
3
LIBRARY
STATE PLANT BOARD
- 38 -
The samples held at marketing temperatures were examined at
approximately 10-day intervals until they were no longer of marketable
quality. Those in cold storage were examined at Intervals throughout
the storage period.
No external nor internal injury was discovered on any variety in
series A, B, or D. External injury only was present on, two varieties
in series C, In Grimes Golden, 19 percent of the apples had from mild
to severe spotting of the skins (see figure 3) in the sample held at
marketing temperatures, hut only 8 percent of those held in cold stor-
age. In Jonathan apples, 14 percent of those held under marketing
temperatures were spotted, while 5 percent of those in cold storage
showed injury ( figure 4) .
Evidence of injury showed up on apples held under marketing tempera-
tures earlier than on those returned to cold storage. Spotting was pres-
ent at the first observation of the former samples on the 9th day, but
did not appear until the second examination of the cold-storage apples
on the 22nd day. In each case the Injured area increased somewhat after
its first appearance.
Since no injury appeared in apples fumigated before cold storage,
and none appeared in apples fumigated after 3 months of cold storage,
further tests were confined to the periodical treatment of apples in the
earlier part of the cold storage period. These tests were made in the
1944-45 season.
The two apple varieties which showed injury in Series C of the
1943-44 tests, Grimes Golden and Jonathan, were selected for these tests,
with a third variety, Starking, which had shown no injury. Seventeen
bushels of each variety were placed in cold storage within a day after
picking. Samples were withdrawn from storage and fumigated at intervals
up to 17 or 18 weeks. On each date two samples of each variety were
fumigated, one with 2 lb./2 hr. at 40°F. and one with 2 lb./4 hr. at 40°.
The two dosage schedules were used in order to better delimit the margin
of tolerance. Each sample was divided after fumigation, one half being
returned to cold storage, the other half being placed at room tempera-
tures of 55° to 75°. Check samples were handled and divided similarly.
The results are presented in table 18. It is evident that the
apples under the conditions of these tests were more susceptible to in-
jury during the first few weeks of storage. In each instance the sus-
ceptibility appeared to reach a peak after the start of the storage period,
then recede until no injury occurred after the 5th or 6th week. As would
be. expected, more apples showed injury with the 4-hour exposures than with
the 2-hour. Also, apples held at room temperature following fumigation
showed more injury than those returned to cold storage, in fact, Jonathan
and Starking showed no injury to apples fumigated for 2 hours and returned
to cold storage. As was the case in 1943-44 tests, injury became apparent
on the apples held at room temperature before it did on those returned to
cold storage.
- 39 -
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- 40
Practically all applet were eventually cut to determine the
presence or absence of internal injury. No instances of internal in-
jury were found in any test.
Tests made in California to parallel those in St. Louis were re-
ported by Armitage and Steinweden (see footnote p. 2). In three vari-
eties of apples — Pearmain, Borne Beauty, and Winesap— removed from cold
storage at weekly or biweekly intervals and fumigated with a dosage of
2 lb. at 40°F. for exposures of 2 and 4 hours, slight injury appeared
in one variety, Borne Beauty, after no storage and after two weeks*
storage.
Discussion
It appears from the tests reported here that most summer -maturing
fruits intended for immediate consumption can be fumigated with methyl
bromide at the dosage proposed for oriental fruit moth control, with-
out much risk of injury. Mature pears showed evidence of injury, but
the fumigation of many carloads of pears in California with comparable
dosage schedules would suggest the period of shipment to market and
storage might have been an influencing factor. Apples show a varietal
difference in reaction, and also a single variety will react differ-
ently from year to year. Caution should be used, therefore, in fumi-
gating apples, and test samples treated first.
If fall-maturing apples are to be fumigated, it would appear best
to fumigate them before putting them in cold storage, or after 2 months
in cold storage. Fumigation of apples which have been in cold storage
less than 2 months should be avoided unless trial tests are first made.
SUMMARY
Cooperative tests were made at St. Louis, Mo., in 1944-46 by the
Bureau of Entomology and Plant Quarantine, and the California State
Department of Agriculture, to study the fumigation of fresh- fruit
hosts of the oriental fruit moth, the possible revision of fumigation
schedules for nursery-stock- hosts, and the tolerance of host fruits
to methyl bromide fumigation.
Minimum fumigation dosage schedules causing complete mortality of
artificially infested apples were 0.75 lb. of methyl bromide per 1,000
cubic feet for 2 hours at 80°, 70°, and 60°F., and 1 lb. at 50° and 40°.
Minimum dosage schedules causing complete mortality of naturally
infested fruit were 1 lb. at 70°, and 1.25 lb. at 60° and 50c.
Minimum dosage schedules causing complete mortality of oriental
fruit moth eggs were 1.5 lb. at 70°, 2 lb. at 60°, and 2.5 lb. at 50°.
A satisfactory series of schedules for fresh fruit was proposed
as follows;
1 lb./2 hr. at 80CJ.
1.5 lb./2 hr, at 70°
2 lb./2 hr. at 60°
2.5 lb./2 hr. at 50°
3 1D./2 hr. at 40°
Almost complete mortality of oriental fruit moth larvae embedded
in fruit was caused by cold storage for 2 l/2 months or more. Although
the danger of dissemination of this pest by fruit subjected to cold
storage for any considerable length of time would be slight, it was
Indicated that a cold-storage treatment as a basis of certification
under oriental fruit moth quarantines would not be entirely acceptable.
The results of tests with hibernating larvae showed that when all
conditions under which nursery stock is fumigated were considered, no
reduction could be made in the present fumigation schedules for nursery
stock of 2 lb./4 hr. at 70°*., and 3 lb./4 hr. at 60°,
It was also shown that on the basis of available data, additional
scnedulee for the fumigation of nursery stock at temperature levels
below 60°F. could not be recommended. Two projected dosage curves,
i.e. 4 lb. at 50°; 6 lb. at 40°; 8 lb. at 30°; and 4 lb. at 50c; 5 lb.
at 40°; 6 lb. at 30°, did not cause complete mortality of hibernating
larvae. Farther studies with increased dosage curves will be neces-
sary to accomplish this purpose.
These studies also indicated that hibernating larvae from differ-
ent localities will show a different degree of resistance to fumiga-
tion, as California larvae showed slightly more survival than those
from Hew Jersey. Hibernating larvae stored in cold storage showed
less survival than those stored in simulated nursery-stock storage.
Larvae returned to simulated nursery-stock storage after treatment had
less survival than those removed to room temperature for observation.
Larvae stored outdoors were not appreciably more resistant to fumiga-
tion than those stored otherwise. The resistance of larvae to fumiga-
tion as the season progressed did not appear to change materially.
The summer- maturing fruits tested were found to be tolerant to
methyl bromide fumigation with the exception of mature pears. Green
pears were uninjured. Apples were found to have a varietal toler-
ance.
Ten varieties of fall-maturing apples fumigated in 1943 immedi-
ately after picking, 2 weeks after, picking, and after 1 month and
- 42 -
3 months in cold storage showed no evidence of injury. Two additional
varieties showed injury when fumigated after 1 month of cold storage.
In further tests in 1944, three varieties placed in storage the day
following picking showed injury when fumigated at weekly intervals
through the first 6 end 6 weeks. No injury occurred to apples fumi-
gated after 7 to 18 weeks of cold storage.
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Figure 2.— Internal injury in ripe Bartlett pears caused by fumigation
with methyl bromide.
Figure 3. — External injury on Grime? Golden apple? caused "by fumigation
with methyl bromide, after 1 month in cold storage.
-V
Figure 4. —External injury on Jonathan apples caused by fuoigati
with methyl bromide, «ft»r 1 month in cold storage.
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UNIVERSITY OF FLORIDA
3 1262 09239 1845