Effect of a Microbial-based Acaricidal Product on Spotted and Predatory Spider Mites

Tetranychus urticae is one of the most important pests of strawberry cultures in Morocco. Current control of this pest relies almost exclusively on acaricides. Unfortunately, this mite has developed resistance to most of the available acaricides. Moreover, insecticide treatments are responsible for the reduction or suppression of beneficial species such as natural predators. Thus, identification of selective pesticides that are more toxic to pest species than on natural enemies, is urgently needed. This study assessed the effectiveness of abamectin, a microbial-based miticide, and bifenthrin, a synthetic one, on two-spotted spider mites, Tetranychus urticae and predatory mites, Phytoseiulus persimilis. Laboratory tests were conducted to determine the direct and residual effects of two miticides (abamectin and bifenthrin) at several doses in geometric progression. Firstly, the direct efficacy of the two acaricides was evaluated against T. urticae and P. persimilis. Abamectin had high efficacy on T. urticae and significantly less toxicity against P. persimilis. Results indicated an effective control of T. urticae, at least 2 weeks after abamectin foliar application. Thus, abamectin could be recommended as a selective acaricide in integrated mite management programmes because of its strong efficacy on pests, its persistence and its limited toxicity on predatory mites.