Influence of Temperature and Humidity on European Corn Borer (Lepidoptera: Pyralidae) Egg Hatchability

Abstract

European corn borer, Ostrinia nubilalis (Hubner), egg hatch was studied under several temperature and humidity regimes. Percentage of hatch was severely decreased, regardless of the humidity, at 36 and 39°C. Hatch ranged from 74.0 to 0.5% at vapor pressure deficits of 7.5–32.5 mb over the temperature range of 24–33°C in 3°C increments. European corn borer egg hatch was affected similarly, from oviposition to larval eclosion, by a 12-h stress period of 14.5, 17.5, and 20.5 mb (at 30°C). Two separate aspects of the egg chorion or two processes in egg hatch are hypothesized to be disrupted by the stressful conditions as evidenced by three plateaus in percentage of eggs hatching as the length of exposure to stress increased. Percentage of hatch remained relatively stable at about 68% with exposure to 33.9-mb stress for ≤24 h. As the length of stress increased to 36–60 h, the percentage was about 22%. The percentage of hatch fell to only 2.7% at 72 and 84 h of consecutive exposure. Finally, the effect of environmental conditions on egg hatch was additive whether the eggs experienced constant stress or experienced periods of stress alternated with periods of moderate conditions. Results of this study suggest that environmental stresses (i.e., “stress units”) may accumulate and affect survival of European corn borer eggs in a manner analogous to temperature units and insect development.