SOME FACTORS DETERMINING THE SIZE OF INFESTATIONS OF THE EUROPEAN CORN BORER, OSTRINIA NUBILALIS (HBN.) (PYRALIDAE: LEPIDOPTERA)

Abstract

Partial regression analysis of the indicial size of first generation, or summer. infestations of Ostrinia nubilalis estimated from light-trap matches and surveys of cornfields in Kent County, Ontario, suggested that the size of infestations was largely determined by three factors: (1) the number of females in the first flight, (2) average rainfall per day during the first flight, and (3) average daily temperature during the first flight. The first factor was apparently most important, rainfall had less effect, and the influence of temperature was evidently negligible. Estimated size of first generation infestations increased by 3.7 individuals for every unit increase in the number of females trapped during the first flight, by 12.2 individuals for every 0.01 in. of rain which fell during the first flight, and by 1.3 individuals for every 1°-F increase in mean daily temperature during the first flight. The regression explained 94% of the variation in estimated size of summer infestations of the corn borer between 1947 and 1961. A hyperbolic relationship was implied between the number of females in the first flight and the number of progeny per female in first generation infestations.