BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 93 
FUMIGATION INVESTIGATIONS 
The work on fumigation of nursery stock for the oriental fruit moth 
with methyl bromide was continued. Several of the Western States 
amended their quarantines so that treatment with this fumigant as 
found to be effective was approved as a condition for entry. One 
nursery fumigated and shipped 465 orders into these Western States 
during the year, a total of approximately 11,000 plants. It was shown 
in the investigational work during the 1938-39 season that a dosage 
of 2 pounds of methyl bromide for a period of 4 hours at 70° F. was 
effective in destroying all stages of this insect, and this modification 
of the usual treatment has been recommended, since there is less 
danger of injury to the plants with this lower dosage. 
Fumigation with methyl bromide has been adopted quite generally 
throughout the quarantine-regulated area for treatment of produce in 
carlots to destroy the adult Japanese beetle. In continuing the investi- 
gational work, it was shown that it was possible to reduce the dosage 
of methyl bromide required at the higher temperatures and still kill 
all the Japanese beetles in carloads of produce. This will reduce the 
cost of the fumigant about 20 percent. 
Investigations on the fumigation of nursery stock with methyl 
bromide for the larvae or immature stages of the Japanese beetle were 
carried on. They involved the fumigation and treatment of several 
thousand plants of 503 varieties and 187 genera to determine the effect 
of the treatment on the plants. It was found possible to obtain com- 
plete mortality of the Japanese beetle larvae in soil about the roots 
without injury to most types of nursery stock. The treatment is lim- 
ited at present to soil masses 8 inches in least diameter and to bare- 
rooted nursery stock. Approximately 300,000 plants were treated for 
the Japanese beetle by this method. 
A fumigant comprising a mixture of hydrocyanic acid and methyl 
bromide was developed. This is apparently much more toxic to the 
Japanese beetle adults than either one of the components in compara- 
ble concentrations. 
Methods for the control of the white-fringed beetle {Pcmtomorm 
imcoloma (Boh.) ) by fumigation of balled nursery stock with methyl 
bromide were developed, and about 10.000 plants were treated. This 
treatment is limited to nursery stock in soil masses not more than 3 
inches in diameter. A method of fumigating potting soil with methyl 
bromide for this insect was also worked out, and treatment of soil 
about nursery stock with a solution of methyl bromide and alcohol in 
water was tested and proved effective. 
Fumigation of sweetpotatoes with methyl bromide for the sweet- 
potato weevil was applied to about 2,000 bushels of seed sweet- 
potatoes with excellent results. Further work with sweetpotato 
plants showed that they can be freed readily from all stages of the 
sweetpotato weevil without injury by fumigation with methyl 
bromide. 
Studies on the development of treatments for plants imported into 
this country were continued, and dosages of methyl bromide neces- 
sary to destroy all stages of mealybugs, red spiders, Cattleya leaf 
miners, active cockroaches, larvae of acorn weevils, bean pod borers, 
and a number of other insects were obtained. Treatment for Maruca 
testulalis (Geyer), a bean-pod borer, was worked out on a commercial 
