Consequências ecológicas do ataque de plantas de tomate por Tetranychus evansi

Abstract

The spider mites Tetranychus evansi and Tetranychus urticae are pests of tomato plants. The species T. urticae induces direct and indirect defenses of tomato plants. The species T. evansi suppresses direct defenses of tomato plants and protects its feeding site with dense web. The performance of insect pests on plants infested by T. evansi mites is not known. The objective of this study was to evaluate the colonization of plants infested by T. evansi and T. urticae by other arthropods in the field. In the first chapter of this thesis I evaluated the performance of females of T. evansi in clean or infested tomato plants by T. evansi or T. urticae. I observed that the oviposition of T. evansi females was significantly lower on plants previously infested by T. urticae than on clean or infested plants by T. evansi. In another experiment, I evaluated the preference of arthropods in each treatment. Plants were divided into three treatments (clean plant, infested with 400 T. urticae or 400 T. evansi) and after 4 days they were positioned in a hexagon in the field. The largest amount of herbivores were found on clean plants, than on plants infested by T. urticae or T. evansi. The whitefly Bemisia tabaci (byotipe B) was the most abundant herbivore found on the plants. In the second chapter, I studied the preference of whitefly (B. tabaci) for clean plants or plants infested by T. evansi or T. urticae with and without web. The whiteflies were found in greater quantities in clean plants or plants infested by T. urticae. In the third chapter, I assessed the oviposition and performance of whitefly B. tabaci in clean plants or infested plants with T. evansi or T. urticae. The whiteflies laid more eggs on plants infested by T. evansi and clean plants. There was no significant difference in mortality of whiteflies nynphs between treatments. This thesis has been proved that arthropods in the field avoid plants infested by T. evansi, in the field.