BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 41 
were EPN, at 0.5 pound per acre, and endrin at 0.4 pound per acre. 
CS-708 and heptachlor at 1 pound per acre, although matching each 
other in their effectiveness, were inferior to EPN and endrin. Isodrin 
at 0.4 pound per acre was better than the untreated check but was 
inferior to the other insecticides compared in this experiment. 
Parasites aid in control of European corn borer 
An additional 30,000 parasites of the European corn borer, com- 
prising six introduced species, were released in Maryland and Minne- 
sota, in a cooperative undertaking with these States. 
During a 7-year period in most of Connecticut and Massachusetts 
and all of Khode Island, an average of 24 percent of the overwintering 
borers have been parasitized. Macrocentrus gifuensis, an imported 
wasplike parasite, was chiefly responsible. Over a 5-year period in 
other eastern States the introduced fly Lydella stabulans grisescens 
was the most important parasite of the borer. Parasitization by this 
fly in fall collections averaged 23 percent throughout New Jerse}^, 22 
in Delaware, 27 in northern Maryland, 26 on the Eastern Shore of 
Maryland, and 15 in the Tidewater area of Virginia. Parasitization by 
Lydella in 1951 amounted to 28 percent in southwestern Ohio, 12 
percent in west central Ohio, and ranged from 25 to 43 percent in 
live districts in Illinois. In Iowa in 1951 no introduced species were 
recovered in two western districts, but a maximum of 45-percent 
Lydella parasitization occurred in one eastern district in that State. 
A protozoan disease, Perezia pyraustae, was studied in cooperation 
with the Iowa Agricultural Experiment Station. This disease was 
found to be widespread in the Corn Belt. It proved to be highly 
pathogenic to the corn borer in laboratory studies. 
Insect-Proof Selfing Bag Benefits Sorghum Breeders 
For the benefit of sorghum breeders, work was continued in 1952 
to improve methods of insect-proofing bags that are placed over 
sorghum heads to prevent cross pollination. A 25-percent aldrin 
emulsifiable concentrate applied in a streak approximately y 2 inch 
wide by 4 inches long on the inside of the selfing bags, at the rate of 
72 mg. of actual aldrin per bag, effectively controls corn leaf aphids 
and corn earworms on sorghum heads inside the bags. The Oklahoma 
Agricultural Experiment Station and a commercial paper company 
have cooperated in producing at the factory at least 100,000 of thes 
treated selfing bags. These were for use by sorghum breeders and 
certified seed producers during 1953. Previously, all such bags have 
been treated manually. 
Entomologists Test Cereal Grains for Resistance to Greenbugs 
Apparent high resistance to greenbug attack was found in Dickinson 
No. 485 C. I. 3207, a variety of durum wheat. This variety is being- 
tested more thoroughly in cooperation with the Bureau of Plant 
Industry, Soils, and Agricultural Engineering, and the Oklahoma 
and Texas Agricultural Experiment Stations. Two hundred durum 
wheats and 200 wheats of Chinese origin were tested under greenhouse 
conditions at Stillwater, Okla., and Denton, Tex. Two other varieties 
of durum, Kubanka, C. I. 2094 and C. I. 1354, appear to be very 
