BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 41 
a 7-month period, whereas 563 insects penetrated one of the untreated 
bags. 
Pyrethrins and piperonyl butoxide are much less harmful than most 
insecticides to man and livestock. Although it seems unlikely that, at 
the rates and methods of application used, products packed in treated 
bags will be contaminated, further work is needed to answer this 
question and also to determine minimum effective rates of applica- 
tion. Results thus far indicate that the cost of the treatment will not 
be prohibitive. It also appears promising for use on containers made 
of other materials such as cardboard and paper. 
European Corn Borer Continues to Spread 
In 1948 the known distribution of the European corn borer, as 
determined by the annual fall survey in cooperation with interested 
State agencies, was extended by 116 counties. One borer was found 
in St. John the Baptist Parish in Louisiana, approximately 450 miles 
from the nearest known infestations in Tennessee and Missouri. Of 
the other newly infested counties 35 were in Missouri, 34 in South 
Dakota, 20 in Nebraska, 3 in Kentucky, 2 in Minnesota, 2 in North 
Dakota, 1 each in Kansas and Michigan, 7 in Tennessee, and a total 
of 10 in Maryland, West Virginia, Virginia, and Xorth Carolina. 
In the North-Central region there was little change in borer abun- 
dance in 1948 compared with 1947. Populations remained about the 
same in Indiana and Illinois. Decreases in Minnesota and Wisconsin 
were more than offset by increases in South Dakota, Nebraska, Iowa, 
Missouri, and Ohio. In the Eastern States the borer was at least as 
abundant as in 1947. The losses of grain corn caused by it were 
estimated to be about 85,485,000 bushels, or about twice as great as in 
1947, and were valued at $99,107,000. With an additional loss of 
sweet corn valued at $4,129,000, the estimated losses caused by the borer 
in 1948 amounted to $103,236,000. 
In Iowa experiments were conducted with different methods of 
applying DDT to field corn. Sprays applied with ground equipment 
were the most effective, dusts applied with ground equipment were 
next best, and sprays and dusts applied by airplane were poorest. 
One application, if properly timed, was about as effective as two. Two 
applications with ground equipment 7 days apart, at 1.2 pounds of 
DDT in 32 gallons of water per acre-application, increased the yield 
in the treated portion of a field by 15 bushels per acre over that in the 
untreated portion, where the infestation averaged 246 borers per 100 
stalks. In comparison, a 5-percent DDT dust applied with ground 
equipment at the excessive rate of 3.25 pounds of DDT per acre-appli- 
cation on the same dates and in the same field increased the yield only 
9.7 bushels per acre. 
Parasites of European Corn Borer and Sweetclover Weevil Imported 
Shipments of European corn borer parasites from Fiance during 
the year consisted of 2,867 cocoons of Campoplex oHhae E. and S.. i > 7 r> 
cocoons of Microgaster tibialis Nees, and 54,000 field-collected corn 
