Plant cues influence searching behaviour and parasitism in the egg parasitoid Trichogramma nr. brassicae

1. The effect of experience of plant cues at emergence on searching behaviour and parasitism was investigated in two strains of Trichogmmma nr. brassicae (Hymenoptera: Trichogrammatidae). 2. Wasps reared on Sitotroga cereallela were allowed to emerge on a tomato plant or in a vial, with or without food. For one of the strains, females emerging on tomato searched significantly longer on a tomato seedling than females emerging in a vial. 3. The experience effect lasted between 1 and 2 days. It involves associating plant stimuli with the remains of the host, because females emerging from their host on a tomato plant had an increased searching response to tomato, but females transferred to the plant immediately after emergence did not. 4. The effect of emergence environment on parasitism of the host Helicoverpa punctigera on tomato and lettuce seedlings was tested. Wasps were allowed to emerge on seedlings of tomato or lettuce, or in an empty vial. For one strain, females experienced with tomato at emergence parasitized significantly more hosts on tomato than did females emerging on lettuce or in a vial. Parasitism on lettuce was not influenced by the treatments.