Host age selection behaviour of Trichogramma aurosum Sugonjaev & Sorokina (Hymenoptera: Trichogrammatidae).

Abstract

Host age selection in several German strains of Trichogramma aurosum Sugonjaev & Sorokina was examined in laboratory choice tests under direct observation for 90 min., in order to select candidatestrains for attempts at controlling the codling moth, Cydiapomonella L. (Lepidoptera: Tortricidae). Experiments were conducted at room temperature by exposing combinations of two host ages (zero vs. 4 and 1 vs. 5-day old) to a single female wasp. Host age did not appear to affect the wasps parasitization behaviour, although they spent longer time drilling on old eggs (4 and 5 days old) compared with fresh ones (0 and 1 day old). This not necessarily means that they preferred fresh eggs over old ones, since both type of hosts were parasitized in the choice test. Possibly an in-creased mechanical resistance of the chorion of older eggs was responsible for the prolonged drill-ing time. Mean drumming time was independent of host age. Mean duration of drilling and drum-ming was in general longest in the first and last egg attacked by all T. aurosum strains tested and for all host ages. Drilling time consumed more than 80% of the mean handling time of all strains tested for all host ages, followed by resting and walking.