BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 7 
DRIED-FRUIT INSECTS 
In 1938 the Fresno, Calif., laboratory carried out several schedules 
for the combined fumigation treatment and shade-cloth protection of 
dried peaches on the ranch, repeating largely the experiments carried 
on in 1937. Completely unprotected peaches became 99 percent in- 
fested when stored in boxes on the ranch. Similar lots which were 
fumigated but unprotected by shade cloth also later became about 
99 percent infested, indicating that fumigation alone cannot be de- 
pended on for protection. The combination of fumigation and shade 
cloth, however, eliminated practically all infestation. The use of 
shade cloth appears to be particularly effective immediately following 
fumigation, as soon as the fruit is boxed from the stacked trays. When 
cloth is used over the boxes much less is required than when drying 
fruit in stacked trays is to be protected. 
By the use of a mechanical rotary net further information was 
obtained on the flight habits and seasonal abundance of various insects 
infesting raisins. Although the saw-toothed grain beetle is one of the 
predominant species of insects in stored raisins, only 180 specimens of 
it were captured in the air throughout the entire season. It is evident 
that this insect does not fly to any extent but moves from point to 
point by crawling. This suggests the possibility of the use of barriers 
to prevent the insect from gaining access to the stacks of raisins. 
SUBTROPICAL FRUIT INSECTS 
Further progress has been made by the Whittier, Calif., laboratory 
toward the development of a standard laboratory procedure for 
studies of fumigation for the California red scale that will permit 
more precise comparisons. The so-called resistant and nonresistant 
strains of this scale which for several years have been maintained 
under identical conditions in isolated chambers at the laboratory 
have continued to maintain their difference in susceptibility. 
Two strains of the California red scale, one resistant and the other 
nonresistant to fumigation with hydrocyanic acid gas, appeared to be 
about equally susceptible to the action of methyl bromide. The stages 
of the red scale that are most resistant to hydrocyanic acid gas appear 
to be the least resistant to methyl bromide. As far as can be deter- 
mined, the phenomenon of protective stupefaction does not exist with 
methyl bromide. Promising results have been obtained in prelimi- 
nary experiments in fumigations with mixtures of hydrocyanic acid 
gas and methyl bromide. 
Field tests of oils with added toxicants, carried on in California in 
1938 for the control of the California red scale, confirmed the results 
of preliminary tests in 1937 and indicated that the addition of nico- 
tine or of cube extract to mineral-oil emulsions caused a marked in- 
crease in their effectiveness. This increase in effectiveness from the 
addition of toxicants seems most evident among the scales on wood, 
where the oil alone is less effective. Among numerous materials 
tested as mutual solvents between cube resins and oil, a trichloro- 
ethylene dibutyl phthalate mixture was the most satisfactory. 
Special attention has been given by the Orlando, Fla., laboratory 
to the relation of particle size in wet table sulfur and sulfur dusts to 
