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

Summary

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 candidate
strains for attempts at controlling the codling moth, Cydia pomonella 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 increased
mechanical resistance of the chorion of older eggs was responsible for the prolonged drilling
time. Mean drumming time was independent of host age. Mean duration of drilling and drumming
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.