Phenology of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae) in Virginia

Flight activity of adult European corn borer field populations was monitored in Bedford County (1980 - 1981), Painter (1958 - 1980), Blacksburg (1971 - 1973, 1975) and Warsaw, Virginia (1971 - 1972, 1981). Peak occurrence of flight activity was accurately estimated by measuring the accumulation of degree days above 10ºC. The appearance of cumulative percentages of adult European corn borer flight at predicted degree day accumulations is reported.

The seasonal abundance, within - field and within - plant distribution of first generation European corn borer egg masses were observed in field corn in Bedford County, Virginia. Peak egg mass abundance occurred ca. 200 degree days after the first borer moths were taken in the light traps. The spatial pattern of first generation corn borer egg masses closely approximated the Poisson distribution. The within - plant distribution of egg masses was skewed towards the lower leaves of the plant throughout the oviposition period, and nearly all egg masses were deposited on the leaf undersurfaces. Optimum sample sizes for two levels of sampling precision were developed from the sampling data.

The seasonal development of the European corn borer in the spring was studied in relation to the flowering phenology of several groups of trees and wildflowers. The potential indicator plants signalled the onset of overwintering generation adult emergence, peak overwintering generation peak flight activity - first generation egg mass abundance, and the end of overwintering generation adult European corn borer flight.