BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 51 
throughout the remainder of the season. Systox controlled the 
aphids so well that only a single application was necessary. Two 
applications were required of either parathion or malathion. Systox 
is not, however, recommended for use on potatoes, because further 
studies are necessary to determine whether or not there may be any 
hazard from residues of this material or its breakdown products due 
to translocation to the tubers. 
Wireworm Control Effective for Several Years 
Soil treatments with DDT at 10 pounds per acre of the active ingre- 
dient will control wireworms and remain effective for as long as 6 
years, investigations in California have shown. Fumigation with 
ethlyene dibromide will also control wireworms immediately, but 
gives no lasting effect. In experiments heptachlor, dieldrin, aldrin, 
endrin, and chlordane showed promise of being as effective as DDT 
for wireworm control. Most of these materials were more effective 
when applied 60 days before planting than when applied 20 days 
before planting. Lima beans grown in soil treated with four annual 
applications of 20 pounds of chlordane, 20 pounds of toxaphene, 4 
pounds of aldrin, or 3 gallons of ethylene dibromide per acre were not 
affected as to yield or flavor. The flavor appraisals were made by an 
experience taste panel of the Bureau of Agricultural and Industrial 
Chemistry at Albany, Calif. 
Field experiments in Washington have shown that DDT as a con- 
tact insecticide in the soil will control wireworms for as long as 8 
years. At least 30,000 acres of the worst wireworm-infested lands, 
devoted to the growing of truck crops in the Pacific Northwest, have 
now been treated at the rate of 10 pounds of DDT per acre. 
Research during 1952 to develop methods for controlling wireworms 
in potatoes in South Carolina showed that aldrin, dieldrin, and 
heptachlor gave adequate wireworm control when applied to the soil 
at 1 and 2 pounds per acre shortly before potatoes were planted. 
Slightly less effective results were obtained with 2 and 4 pounds 
of chlordane. No differences between several methods of applying 
aldrin and chlordane were found. Chemical analyses and bioassay 
studies made by Bureau chemists and representatives of the insecticide 
industry showed no significant quantities of insecticide residues in 
tubers grown in soils receiving the maximum dosages of the four 
materals. 
Improved Feeder Devised for Duster 
An improved feed and metering device for a ground duster was 
constructed and installed in Oregon in cooperation with engineers 
of the Bureau of Plant Industry, Soils, and Agricultural Engineering. 
These improvements reduced difficulties previously experienced in 
obtaining the desired uniform rate of dust discharge under varying 
conditions of temperature and humidity. 
Spray Equipment Evaluated for Pea Aphid Control 
Observations of equipment performance were made in connection 
with a series of ground spray applications of miscellaneous insecticides 
