Dispersal Pattern of Trichogramma chilonis Ishii in Sugarcane Field

The ability of the laboratory-reared egg parasitoid, Trichogramma chilonis Ishii to disperse and locate sentinel egg cards in sugarcane field was evaluated. The dispersal behaviour was monitored at different crop ages of 45 days, 3 months, 5 months, 7 months and 9 months through egg-parasitism in sentinel cards with Corcyra cephalonica (Stainton) eggs in 24 h time. The sentinel cards were placed at distances of 1, 3, 5, 7, 10, 12, 15, 20, 25 and 30 m in eight cardinal directions from the release point of the parasitoid. The effects of distance from the release point, wind direction and crop age on the host location were evaluated. Distance had a clear proportional impact on the dispersal probability but this association was complicated by the fact that distance effects changed with crop age. The dispersal of the parasitoid was found to be the highest in 45 days old crop and the lowest in 7 months old crop. The parasitoid was found to move up to 10m effectively up to 5 months of crop age which declined thereafter. Although dispersal was found up to 30m, more uniform parasitism was observed in 10m circle surrounding the release point. The direction of wind was not associated with the rate of dispersal. The influence of distance, direction and age of the crop on adult emergence was not found to vary distinctly. The inference of differential ability of the parasitoid to move in the sugarcane field in securing uniform dispersal and in fixing adequate number of release points for inundative releases are discussed.