Parasitism of Developing Eggs by Trichogramma pretiosum (Hymenoptera: Trichogrammatidae): Host Age Preference and Suitability

Age of insect eggs can have considerable effects on their acceptability and suitability for parasitoids. In this context, we evaluated the extent to which age of Helicoverpa zea (Boddie) eggs affects their acceptability and suitability for the parasitoid Trichogramma pretiosum Riley, and whether acceptance of hosts was influenced by female experience. Three ages of host were tested: 14-, 38-, and 62 h old. Suitability declined in older hosts. Developmental time was longer and survival lower in 62-h-old eggs than in younger ones, and parasitoid size was inversely related to host age. Experienced and inexperienced females differed little in their responses to various host ages. Both preferred 14-h-old hosts over the other two ages on the first contact and acceptance, but no preference was exhibited after the first egg. The initial preference for young hosts appeared to be related to host feeding rather than host suitability: female T. pretiosum generally fed more on the first egg accepted for stinging than on subsequent ones. Overall parasitoid-induced mortality of hosts was unaffected by host age.