4 
> 
INSECT PEST SURVEY BULLETIN 
Vol. IS Supplement; to Number 9 • December 28, 1938 
RELATIVE ABUNDANCE OE THE- EUROPEAN CORN BORER IN 193 ^/ 
W. A. Baker and A. M. Vance 
Bureau of Entomology and Plant Quarantine 
United States Department of Agriculture 
The relative abundance of the European corn borer ( Pyrausta nubilalis 
(Hbn.)) in 1938 in several representative sections of the territory infested 
was determined by field surveys. Data on the status of the borer in corn gen- 
erally was obtained in the fall by surveying fields selected at random over a 
wide area, whereas that on infestation in early market sweet corn was obtained 
by summer examinations of the earliest and most severely attacked fields in 
local sections of the country. Potato fields selected at random in three of the 
Eastern States were also surveyed for infestation by the first generation of the 
borer. In each case field methods tested in previous years were used. 
Eor the fourth consecutive year since 1934, when a significant decrease in 
its abundance from 1933 occurred, the European corn borer has increased in 
numbers over an area west of Lake Erie comprising 6 counties in Michigan and 12 
in Ohio. Comparative data on abundance of the borer in this area over a 12— year 
period are summarized in table 1 . It should be noted that, in addition to the 
fluctuations just mentioned, a significant decrease had occurred in 1930 fol- 
lowed by an appreciable increase 'in 1931 , * 
Data on corn borer abundance in Indiana became available through cooperation 
with the State Conservation Department of Indiana, which in 1938 conducted 
an extensive survey of most of the infested territory in that State. 
643 
