Effect of Host Unavailability Durations on Parasitism Behavior of Trissolcus grandis (Hymenoptera: Scelionidae) Egg Parasitoid of Sunn Pest

Sunn pest Eurygaster integriceps Puton is the most important pest of wheat and barley in Iran. Using biological control agents, within which egg parasitoids are the most promising agents, is an effective tactic of management of this pest. For optimal use of biological control agents, one needs to beware of efficacy of them in different ecological conditions. Regarding priority of the parasitoids in their emergence in wheat fields compared to their host in spring, they are in a high risk of encountering with durations of host absence early season; hence in this study we evaluated the effect of different intervals of host unavailability upon the egg parasitoids in terms of parasitism rate. The parasitic wasp, Trissolcus grandis (Thomson) (Hym., Scelionidae), which is dominant species in Iran wheat fields was chosen for experiments. The wasp specimens were collected from Garamalek and Kujuvar villages, located in west of Tabriz. The experiments were conducted under laboratory conditions (25±1ºC, 50±10% RH and 16L: 8D h photoperiod) with five treatments including a control (complete access of wasps to the hosts), access every other days, every third days, once a week and complete access following a six day prevention period in 15 replications. The results revealed that parasitism rate decreases by increasing unavailability intervals of host. Results showed that a partial compensation was occured in all treatments except young females of T. garndis in the second treatment that the wasp could completely overcome host deficiency of the previous days during first few days of her lifespan.