ENTOMOLOGY AND PLANT QUARANTINE 
51 
treated plptiits that had been run thronsrh the commercial process of vinin? and 
canning. The result of the analysis of this product indicated that when lima 
beans are treated as described above and run through the ordinary washing 
process, the canned product is free from harmful fluorine residues. Since lima 
beans are shelled before being consumed, it appears that cryolite may be applied 
safely for the control of the corn earworm on this crop. 
TOMATO INSECTS 
Although the tomato pinwr)rm has continued to cause serious losses in southern 
California, good progress has been made on biological and control studies. Re- 
sults of field-plot tests have indicated that a cuprous cyanide dust mixture with 
talc as the diluent (1 to o), cuprous cyanide used as a spray at the rate of 3 
pounds to 100 gallons of Avater, and natural cryolite diluted with talc and dia- 
tomaceous earth reduce infestation^ of this pest from 67 to SO percent, based 
upon the percentage of noninfested fruit produced on the treated as compared 
to the untreated plots. Negative or poor results were obtained with sprays 
containing an organic thiocyanate. cryolite, calcium arsenate, nicotine sulphate 
and a light oil-pyrethrum extract combination, and phenothiazine, as well as 
with dust mixtures containing pyrethrum. calcium arsenate, and phenothiazine. 
Observations on the habits of the insect .show that the tomato pinworm adult 
favors the lower surface of the tomato leaf for egg laying. The.se studies indi- 
cated that 57.4 percent of the eggs were deposited on the lower surface of the 
leaf. 40.8 percent on the upper surface, and the remainder on the petioles. Field 
records .'^how that approximately 91 percent of the pinworm-infested leaves were 
folded on the upper surface, which indicates the necessity of applying insecti- 
cides, if any are found satisfactory, so as to cover thoroughly the under sur- 
faces of the leaves. Examinations in fields heavily infested by the tomato 
pinworm have indicated that approximately 80 percent of the larvae pupate in 
the top half-inch layer of soil and that approximately 98 percent of them 
pupate in the first inch of soil. It is apparent that the tendency of the tomato 
pinworm larvae to pupate very close to the soil surface may render it possible 
to develop some m-easure of control of these pests through the medium of cul- 
tural practices designed to disturb or destroy the pupal cells during critical 
periods. The ability of the tomato pinworm to survive under adverse condi- 
tions was demonstrated during the winter of 1936-37 when a very high per- 
centage of survival occurred in southern California even though the longest cold 
spell on record prevailed in this area during January 1937, including a minimum 
of 22^ F. and a total of 17 nights during which the temperatures at Alhambra, 
Calif., fell below freezing. 
During the year the work on tomato fruitworm {Heliofhis ohsoleta F.) was 
expanded, and particular attention was given to the habits of the pe.st as well 
as to control tests. Dust mixtures containing calcium arsenate, cryolite, or 
cuprous cyanide have given best results in experimental plots, although none 
of these gave an entirely satisfactory measure of control. Derris, pyrethrum, 
and phenothiazine have given poor results. The importance of combating the 
tomato fruitworm in its early stages was substantiated by the results of labora- 
tory experiments in California wherein it was shown that each larva of the 
fruitworm is capable of injuring or destroying six tomato fruits, on an average, 
during its larval period. The number of tomato fruits destroyed by each larva 
under ob.servation ranged from 4 to 10. These studies also demonstrated con- 
clusively that the young larvae are migratory in their habits and travel com- 
monly fron> fruit to fruit during their period of larval activity. Cage studies 
in Utah indicated that the tomato fruitworm was unable to survive the winter 
of 1936-37 in that locality even though the individuals kept under observation 
were placed in cages under very favorable conditions during the fall of 1936 
and supplied with sufl[icient food to enable them to reach maturity before 
entering the soil. 
MISCELLANEOUS VEGETABLE INSECTS 
Additional experimental work has shown that paradichlorobenzene is effective 
against larvae, pupae, and adults of the sweetpotato weevil when used to fumi- 
gate seed sweetpotatoes in banks and barrels. Preliminary experiments have 
Indicated that the eggs of the sweetpotato weevil may be killed also during the 
process of paradichlorobenzene fumigation in l)arrels. The grade of material 
used and the temperatures during the fumigation period are important factors 
in .successful fumigation. It was .shown that fumigation with this material did 
not injure the seed or reduce plant production. Biological investigations dem- 
onstrated that the adults of the sweetpotato weevil are able to fly for a distance 
of at least 400 yards. 
