Factors affecting the post-release dispersal of Trichogramma cacoeciae Marchalin the vineyard

Abstract: Several releases of 20,000 and 40,000 individuals of Trichogramma cacoeciae weremade at a central point in a vineyard in order to follow the dispersal of trichogrammes and thedistribution of parasitism on Ephestia kuehniella egg-cards. The dispersal of trichogrammesessentially occurred along the release row and over the nearest rows, since the vine rows formed aplant screen that channelled their dispersion. The daily captures of trichogrammes increased withthe number of trichogrammes released and decreased over time. It increased with minimaltemperature and solar radiation, but did not depend on other meteorological factors. The number ofparasitised egg-cards decreased with the distance from the release point and increased with theamount of wind received at the control points. The doubling of the number of trichogrammesreleased influenced parasitism by increasing both the discovery rate and the exploitation rate ofegg-cards.