Comparison between the control efficacy of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) and two Trichogramma cacoeciae Marchal strains against grapevine moth (Lobesia botrana Den. & Schiff.), depending on their release density

In the first generation of the grape moth Lobesia botrana, Trichogramma evanescens spread to a greater extent than Trichogramma cacoeciae and parasitized most of the grape moth eggs. Reduction of damage to grapes was improved by doubling the number of T. evanescens release points in the first and second generations. In the second generation of the grape moth, T. cacoeciae was more efficient than T. evanescens. The highest proportion of individuals belonging to the reared and natural T. cacoeciae strains were found in the plot in which they were initially released. The total number of individuals emerging from parasitized eggs was the same for each strain, which would suggest that neither predominated. Whichever the T. cacoeciae strain considered, a density of 800 release points ha(-1) did not induce greater parasitization than a density of 400 release points ha(-1).