Selectivity of the Acaricides Clofentezine and Hexythiazox to the Predator Metaseiulus occidentalis (Acari: Phytoseiidae)

Abstract
Two new ovicidal acaricides were tested in the laboratory to determine their relative toxicity to the predator Metaseiulus occidentalis (Nesbitt) and the Pacific spider mite, Tetranychus pacificus McGregor. Clofentezine and hexythiazox caused little mortality of adult females, larvae, or eggs of M. occidentalis. It seems unlikely that, at the proposed field rates, these ovicides will be toxic to this predator. Clofentezine is equally toxic to eggs (0–24 h old) of the spider mites T. pacificus and T. urticae Koch. However, both clofentezine and hexythiazox are less toxic to eggs of T. pacificus 49–72 h old than to younger eggs. Fecundity of M. occidentalis and T. pacificus females was significantly increased within 48 h on disks sprayed with hexythiazox at rates 0.5-fold the field rate and above.

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