Trichogramma platneri (Hym.: Trichogrammatidae) : Host choices between viable and nonviable codling moth, Cydia pomonella, and three-lined leafroller, Pandemis limitata (Lep: Tortricidae) eggs

In laboratory host-preference studies, Trichogramma platneri Nagarkatti (Hym.: Trichogrammatidae) females, reared on viable codling moth, Cydia pomonella (L.) (Lep.: Tortricidae) eggs, parasitized significantly more viable than nonviable codling moth eggs produced by cobalt 60 irradiated adults. This ovipositional preference was maintained when competition increased per host egg. Similarly, one, three and five T. platneri females consistently oviposited more eggs into viable versus nonviable host eggs. A single female T. platneri parasitized a similar number of viable C. pomonella and three-lined leafroller, Pandemis limitata (Robinson) (Lep.: Tortricidae) eggs. However, as the number of females per host eggs increased, a significantly larger number of codling moth versus leafroller eggs were parasitized. One, three and five Trichogramma females parasitized significantly more P. limitata versus non-viable C. pomonella eggs. Nonviable C. pomonella eggs deflated to less than 25% of their original volume in four and ten days when held under dry and humid conditions respectively. The blackened prepupal stage of the parasitoid generally occurred in the nonviable C. pomonella eggs four days post-parasitization whereas the parasitized viable eggs blackened zero to one day earlier. Incubation under dry or humid conditions did not appear to influence the number of parasitized eggs that were able to blacken and show evidence of parasitism.