A simple method of rearing insect natural enemies of spider mites

Abstract

Establishing effective methods of rearing natural enemies can facilitate basic and applied studies on their use in biological pest control. Insect predators of four genera (Oligota, Stethorus, Scolothrips and Feltiella) and predatory mites are important natural enemies of pest spider mites in agricultural crops. However, fewer laboratory studies have focused on insect predators due to the difficulty of their rearing. To establish a simple rearing method, we compared the rearing efficiency of four insect predator groups (Oligota spp., Stethorus spp., Scolothrips takahashii and Feltiella acarisuga) on potted komatsuna plants (Brassica rapa) infested with the two-spotted spider mite Tetranychus urticae, a new plant-prey combination for predator rearing in large containers, with that on potted bean plants infested with T. urticae. Significantly more Feltiella acarisuga and Stethorus spp. adults were obtained when offered T. urticae-infested komatsuna plants than infested lima bean or kidney bean plants (Feltiella: 70, 9 and 0 adults, respectively; Stethorus: 72, 3 and 0 adults, respectively). More adults of S. takahashii and Oligota spp. were obtained on T. urticae-infested komatsuna than on infested lima bean (Scolothrips: 181 and 27 adults, respectively; Oligota: 152 and 16 adults, respectively). Many individuals of all four predator groups such as larvae of F. acarisuga and Stethorus spp. were entrapped by the hooked trichomes on lima and kidney bean leaves, whereas no entrapped predators were observed on the komatsuna plants. These results show potted komatsuna plants infested with T. urticae to be suitable for efficient rearing of all four predator groups.