殺蟎劑對二點葉蟎Tetranychus urticae Koch及加州捕植蟎Amblyseius californicus (McGregor)之選擇性

Abstract

The responses of two-spotted spider mite, Tetranychus urticae (Koch) and their predator, Amblyseius californicus (McGregor) to acaricides tested were different. The selective ratio between the spider mite and predatory mite was depended on the chemical structure of acaricides. Generally, synthetic pyrethroids, organophosphates and carbamates are more toxic to the predatory mite than to two-spotted spider mite, and resulted high selective ratios. Other groups of acaricides stated safer to the predatory mite, usually, the LC5, selective ratios were less than 4. Six acaricides i. e. bromopropylate, binapacryl, dinobuton, propargite, oxythioquinox and smite showed effective control to the two-spotted spider mite, and less harmful to the predatory mite, the LC,0 selective ratio were less than 1. These acaricides can be used as agents for the integrated control of mite pests. Formetanate and dinobuton are the two most effective acaricides that we used in this treatment for the two-spotted spider mite control. While after 15 and 16 generation of selections, two-spotted spider mite developed 11.8 and 2.5 folds of resistance to f or- metanate and dinobuton, respectively. Two-spotted spider mite showed ability in rapidly developing resistance to formetanate, so this acaricide should be carefully used in the field. The chemical structure of azocyclotin is similar to cyhexatin. Field two-spotted spider mite have showed 3.5 folds of resistance to the former, although azocyclotin has not been used in Taiwan before. The insensitivity may due to the cross-resistance from cyhexatin, since azocyclotin and cyhexatin are very similar in their chemical structure.