Epizootiology of Nosema pyrausta in Field Populations of the European Corn Borer (Lepidoptera: Pyralidae)

Abstract

Epizootiological studies of Nosema pyrausta (Paillot) in natural populations of the European corn borer, Ostrinia nubilalis (Hübner) showed disease development in first-generation borer populations to be characterized by sharp but progressively slower rates of increase in infection during larval development. These increases in infection were concurrent with a steady, rapid decline in population density. Development of N. pyrausta in second-generation borer populations was cyclic and was characterized by a steady moderate increase in the prevalence of infection during the summer and fall, and gradual decline throughout the winter. Corn borer abundance was also cyclic and tended to have a slower rise and more rapid decline. Annual seasonal variation in the prevalence of infection and host abundance strongly suggests that even when enzootic, N. pyrausta has a direct detrimental effect upon the larval population and contributes significantly to the natural control of O. nubilalis.