Acceptance and suitability of ultraviolet-irradiated Helicoverpa armigera (Hühner) (Lep., Noctuidae) eggs for Trichogramma chilonis Ishii (Hym., Trichogrammatidae)

Helicoverpa armigera (Hbn.) eggs were irradiated with a 30 W ultraviolet (UV)-lamp from a distance of 30 cm. Egg mortality increased with duration of exposure to the UV-light source; exposure for 48 min was sufficient to kill 98% of the eggs. Survival of the egg parasitoid Trichogramma chilonis Ishii was lower on eggs irradiated for 60 and 90 min than on untreated control eggs. Clutch size and sex ratio of the parasitoid progeny were similar in irradiated and control eggs. The lower suitability of irradiated host eggs was not recognized by female wasps as they accepted irradiated and control eggs equally in a choice test. The higher parasitoid mortality in irradiated eggs may be a result of morphological changes in the host egg chorion. Supporting this hypothesis, it was observed that the duration of drilling by the parasitoid was significantly shorter on irradiated eggs than on control egg