[Comparaison de l'efficacité d'une technique de lutte chimique et d'une technique de lutte biologique pour la protection de la culture de la tomate contre l'acarien tisserand Tetranychus urticae (Acari: Tetranychidae)]

Two methods to control the two-spotted spider mite (Tetranychus urticae) on glasshouse tomatoes were compared. In the first method, an initial introduction of the pest was followed by the introduction of 2 predators, Amblyseius andersoni and Phytoseiulus persimilis. These predators differ in their demographic properties and polyphagy and should exert a complementary action on the pest population. The aim of this "pest in first" technique was to ensure a successful colonization of the crop by the predators throughout the season. In order to avoid any interference, biological control was applied against the other pest problems. The second method consisted of a chemical pest control. Each week, both crops were observed and the evolution of leaf damage was recorded by means of a visual index (figs 1, 2). Moreover, yield, fruit size and gross income were recorded in both cases (tables II, III, IV). Leaf damage was greater in the biological control greenhouse, and this led to further introduction of predators. But at the end of the season, no significant differences in yield and fruit size were observed between treatments. Nevertheless, gross income was greater in the biological control greenhouse. This experiment shows that biological control may be a feasible alternative in tomato glasshouse crops