BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 25 
Improved Power-Equipped Crop Dusters Tested 
In experiments for the improvement of methods of applying insecti- 
cides to vegetables with ground equipment in Oregon and Washington, 
excellent progress was made in studies of power-equipped ground 
dusters. Information was obtained on the relation of insect kill to 
dust-impact velocity, comparative performance of different types of 
dusters, and dust distribution as affected by an improved boom and 
semicylindrical aluminum hood designed during the research work. 
These experiments were conducted principally on peas, with the pea 
aphid as the test insect, but some preliminary experiments were con- 
ducted with this equipment against various insects on cauliflower, 
clover, and alfalfa. This work was carried on in cooperation with the 
Bureau of Plant Industry, Soils, and Agricultural Engineering, the 
Agricultural Experiment Stations of Idaho, Washington, and Oregon, 
the Northwest Canners Association, pea growers, and pea processors. 
Insectieidal Dosages for Wireworm Control Compared 
In both Washington and California additional information was ob- 
tained on the minimum effective dosages of chlordane, toxaphene, 
aldrin, dieldrin, lindane, and heptachlor for wireworm control and on 
the effect of these insecticides on truck crops grown in treated soil. 
Information on whether or not crops grown in soil treated with these 
materials may constitute a hazard to the consumer must be obtained 
before any of them can be safely recommended for use in the control 
of wireworms. Most of these materials were as effective as DDT 
against irrigated-land wireworms, but did not have any marked ad- 
vantages over DDT. Methoxychlor, however, proved to be ineffective 
against wireworms. Heptachlor was particularly effective against 
the DDT-resistant wireworm Melanotics longulus in California. This 
wireworm has been a relatively minor pest in the lima bean area of 
California but with the sugar-beet wireworm brought under control 
with DDT, M. longulus is more noticeable and is causing more concern. 
As part of the research on the control of wireworms in California, 
evidence was obtained that excessive dosages of either aldrin, chlor- 
dane, or toxaphene in the soil may cause off-flavors in potatoes. Be- 
ginning in 1949. plots of Yalo fine sand}' loam soil were treated an- 
nually with 4 pounds of aldrin per acre, 20 pounds of chlordane. and 
20 pounds of toxaphene disked into the top 8 inches of soil. Bliss 
Triumph potatoes grown in these plots in 1951 were submitted to the 
Western Regional Research Laboratory of the Bureau of Agricultural 
and Industrial Chemistry where they were tested for off- flavors by a 
panel of experienced tasters. The flavors of the potatoes grown in 
the treated plots were significantly less desirable than those of pota- 
toes grown in untreated check plots. This off-flavor would not neces- 
sarily be detected by the average consumer or even the unusually sensi- 
tive consumer. Furthermore the dosages of insecticides were higher 
than would ordinarily be applied to the soil for wireworm control. 
Further Studies of Effects of Soil-Applied Insecticides on Tobacco 
Experiments were begun in 1947 at Florence, S. C. to determine the 
effects on tobacco and crops usually rotated with it. of accumulations 
