Evaluation of three pesticides against phytophagous mites and their impact on phytoseiid predators in an eggplant open-field

The present study aimed to evaluate the effects of two insecticides (deltamethrin and acetamiprid), and an acaricide (fenbutatin oxide) on diversity and abundance of mite fauna in replicate experiments carried out in an open-eggplant field in Latakia, Syria. Each pesticide was applied three times with an interval of three weeks between two consecutive applications. Two phytophagous mites were observed in all treatments: Tetranychus urticae and Polyphago-tarsonemus latus. However, the number of predatory mite species (in particular Phytoseiidae) was different according to the pesticide applied and the lowest number observed was in the fenbutatin oxide treatment. This acaricide caused high mortality of T. urticae, decreased the abundance of P. latus, and negatively affected Phytoseiidae. Acetamiprid and deltamethrin induced the resurgences of T. urticae (3.5-fold and 1.5-fold for the former and the latter respectively). The abundance of P. latus was not affected by acetamiprid but by deltamethrin. The results clarified also that these insecticides seemed harmless to Phytoseiidae [i.e. Phytoseiulus persimilis, Phytoseius finitimus and Typhlodromus (Anthoseius) recki]. Data obtained here are interesting for integrated management programs of the major eggplant phytophagous mites, although the generalization of these results requires some caution and additional experiments are needed.