MODELING INDUCTION OF DIAPAUSE IN NORTH-AMERICAN OSTRINIA-NUBILALIS (LEPIDOPTERA, PYRALIDAE) POPULATIONS

A general model for predicting diapause induction in most North Americ an populations of European corn borer, Ostrinia nubilalis (Hubner), wa s created by statistically testing the influence of scotophase, civil twilight (the period before sunrise or after sunset when the sun is 6 degrees below the horizon), temperature, and latitude in equations cal ibrated with and validated against laboratory and field data. The best equation includes scotophase as hours of darkness per day, mean tempe rature, and latitude in decimal degrees. To predict diapause induction in the field, a larval maturation model and a function for determinin g the response of different larval instars must be calculated along wi th the basic equation. In the field, scotophase should be calculated b y subtracting daylength and civil twilight from 24 h. The overall mode l explained about half the variability in the independent data for Eur opean corn borer populations in North America between 30 and 50 degree s N latitude.