Table 1. Accumulated degree-days (developmental threshold of
50°F) from initial capture of moths in the spring to first occurrence
of life stage or activity of first-generation European corn borers.
(
From European Corn Borer: Ecology and
Management
, NCR Publication No. 327, Iowa State University, Ames, IA.)

aAverage number of days of development to reach the first occurrence of
the stage or event since initiation of the previous stage listed. For example,
it takes about 16 days from first moth capture to egg hatch; first instars
require about 6.6 days to develop to second instars; etc. The number of days
varies if temperatures are cooler or warmer than average.