Efficacy of predators against the two spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

摘要

Survey conducted for inventorying the natural enemies of Tetranychus urticae Koch revealed the occurrence of predatory insects viz., Stethorus pauperculus (Weise) (0.00 to 8.65 %), Oligota sp. (0.00 to 5.98 %), Scolothrips sp. (0.00 to 5.69 %) and predatory mite, Amblyseius longispinosus (Evans) (0.00 to 6.43 %) in okra growing areas of Coimbatore district. Investigations on the predatory potential of these predators against T. urticae under laboratory conditions showed that the adult female of S. pauperculus consumed significantly more number of 167.14 eggs / 63.71 nymphs / 61.42 adults of T. urticae per day per individual. The grubs of S. pauperculus were as voracious as the adults and the predation increased with the advancement of larval stages.Similarly, adult Scolothrips sp. and A. longispinosus were more efficient than the immatures in devouring the prey. However, in case of Oligota sp., the grub stage recorded the maximum consumption of prey mite by devouring 81.28 eggs / 45.71 nymphs / 15.14 adults of T. urticae per day per individual.