A granulosis virus, possible biological agent for control ofAdoxophyes orana (Lepidoptera: Tortricidae) in apple orchards

Summary

Based on the results of ecological surveys ofAdoxophyes orana and its natural enemies in apple orchards sprayed with the granulosis virus and control plots, we constructed working models to simulate the population dynamics in three different experimental plots; those treated with chemical insecticides, those with granulosis virus, and controls. The number of individuals killed by predators, parasitoids and by miscellaneous mortality factors could be calculated on the assumption of imperfect density relations; that is, relation of the number killed by each factor with the initial number of larvae was represented by a curve with an upper asymptote. We could estimate the proportion of virus infection using curves with upper asymptotes. Rate of increase from pupa to middle instar larvae of the next generation was subject to strong density-effect.

Simulation we proposed in this paper suggests a possibility that a single spray of the virus at 1st generation can reduce not only the number ofA. orana larvae in the 2nd and 3rd generations but also the degree of fruits injured by this insect. Spray of chemical insecticide is considered to be ineffective in reducing the pest density and the degree of injury to low levels in subsequent generations, as compared with untreated plot, where the density of the 1st generation larvae is low.