Andrei N. FROLOV
All-Russian Institute for Plant Protection, Pushkin - St. Petersburg, 189620 Russia,

Ecological factors critical for the European corn borer (ECB), Ostrinia nubilalis (Hbn.), (Lepidoptera: Pyralidae) were studied intensively (Shchegolev, 1934; Kozhanchikov, 1935; Bugdanov, 1941; Patch, 1943; Guthrie et al., 1960; Barlow, 1971; Khomyakova, 1972; Showers et al., 1974; Lewis, 1975; Hudon, LeRoux, 1986; Ross, Ostlie, 1990; Manojlovic, 1994 et al.), but their actual joint influence on the population dynamics was not sufficiently understood yet. Wide growing of genetically engineered maize in near future demands to check ECB population dynamics just now before significant alterations occurring. During 1994-1998 we arranged life tables of two local populations inhabiting eastern part of the Krasnodar Territory (two-generation zone) and southern part of the Belgorod Province (one-generation zone). Using graphic K-factor analysis (Varley, Gradwell, 1960) and regression component analysis (Harcourt, 1966) it was established that population dynamics of the ECB was mainly determined by the effects of single factors distinctive for the populations tested. At the Krasnodar Territory the key factor performs during the 1st-2nd instar larval feeding of the 1st generation, in the Belgorod Province - during the period of moth activity. Both the density-dependent and density-independent components of the key factor action are involved into operation; density-independent effects seem to be ascertained by the influence of weather and host plant resistance. Definite link was observed between total K and density of eggs laid both for the Krasnodar and Belgorod populations. One can consequently conclude that key factor action would result in regulation of the ECB population dynamics. It is supposed that the behavioral responses of 1st-2nd instar larvae on aggregation may play an important role for density dependent population decline. The density-dependence of the process of egg realization by females most likely based also on behavioral reactions of adults leaving overpopulated places.

Acknowledgments: The author is grateful to Dr M.Chumakov and Dr K.Dyatlova for their helpful assistance. The study was partly supported by RFBR grants # 94-04-11328 and 97-04-48015.