Host Density-Dependence of Discovery and Exploitation Rates of Egg Patches of Lobesia botrana (Lepidoptera: Tortricidae) and Ephestia kuehniella (Lepidoptera: Pyralidae) by the Parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae)

Simple laboratory tests were developed to evaluate the potential efficiency of Trichogramma cacoeciae Marchal for biological control against Lobesia botrana Denis & Schiffermuller, a major pest in vineyards. From different host egg densities in the patches, discovery and exploitation rates were studied for eggs of L. botrana and for eggs of the reference the factitious host, Ephestia kuehniella Zeller. The effect of the wasp age, the contact time between parasitoid and host eggs, and the presence of kairomones (scales) on these rates also was tested. Mortality was induced by the presence of the parasitoid in L. botrana eggs. The two rates were differently modified according to host species, host density, presence of kairomones, and by wasp age. Discovery rates were density-dependent according to host density and the other factors taken into account, except for younger Trichogramma with L. botrana eggs. Exploitation rate was always inversely density-dependent according to host density. Behavioral and physiological aspects of these relationships and interest for biological control of these tests were discussed.