KAIROMONES AND THEIR USE FOR MANAGEMENT OF ENTOMOPHAGOUS INSECTS: II. MECHANISMS CAUSING INCREASE IN RATE OF PARASITIZATION BY Trichogramma spp.

When the effect of the kairomone, tricosane, on parasitization by Trichogramma achaeae Nagaraja and Nagarkatti of eggs of Heliothis zea (Boddie) was studied in petri dish tests, the greatest percentage parasitization ((X) over bar = 64%) was obtained if the entire falter paper was treated. Treatment of smaller areas ( about the eggs) resulted in decreased parasitism. In the greenhouse, highest parasitization ((X) over bar = 71%) by T. pretiosum ( Riley) of H. zea eggs placed on pea seedlings grown in pie pans was obtained if the whole pan was treated; lowest parositism ((X) over bar = 29%) occurred when the pans were untreated. Parasitization was intermediate ((X) over bar = 52%) in other pans treated only at selected spots. Dissections of H. zea eggs collected from kairomone-treated and untreated field plots revealed that eggs of Trichogramma spp. were more efficiently distributed (less superparasitism) among host eggs in treated plots. These kairomones increase parasitization of Trichogramma spp. by releasing and continuously reinforcing an intensified searching behavior rather than by attracting and guiding the parasite directly to the host.