Simulations on the role of the egg parasite, Ooencyrtus kuvanae (Howard), in the population dynamics of the gypsy moth

Abstract

Computer simulations were run to examine the effects of Ooencrytus kuvanae (Howard) parasitism on gypsy moth populations. Two difference equation models were used, one, a simple theoretical model containing only a few important components, the other, a more comprehensive model with component functions based on field data. The simulations of the first model showed that O. Kuvanae cannot control gypsy moth populations by itself. Egg parasitism was most important during the outbreak and collapse phase of the gypsy moth population cycle, and was of little importance in the endemic phase. The endemic phase was, however, lower and lasted longer with O. kuvanae parasitism than without. Simulations with the second model generally supported these conclusions. The second set of simulations also demonstrated that due to the non-linearity of the density dependence of O. kuvanae parasitism, they gypsy moth populations could be forced into a chaotic regime (unstable, aperiodic population behavior). The variation in parasitism rate from the simulations was compared with that of field populations and found to be essentially the same, indicating that the simulation models are realistic.