A simple plant trap for collecting acariphagous insect predators and their parasitoids

Although insect predators [Feltiella acarisuga (Vallot), Scolothrips takahashii Priesner, Oligota spp. and Stethorus spp.] play a role in controlling spider mites, it is difficult to collect insect predators directly under field conditions. To prove the suitability of a plant trap for collecting the predators, we investigated the efficiency of potted komatsuna (Brassica rapa L.) and kidney-bean (Phaseolus vulgaris L.) plants inhabited by Tetranychus urticae Koch, using as novel and conventional plant traps respectively, for collecting living insect predators. Large numbers of predators were found on these traps placed in a kudzu vine community [Pueraria montana var. lobata (Willd.) Sanjappa and Pradeep] despite being observed in low densities under the naked eye in the weed community. Significantly higher survival rates (99.5-100 %) were obtained when collecting them from komatsuna traps than those (26.6-61.1 %) obtained with kidney-bean traps due to predators' entrapment by the hooked trichomes on bean leaves. These results indicate that the komatsuna trap is suitable for collecting living insect predators, even when predators are rarely or not observed directly under the naked eye. We also showed that the komatsuna trap is effective for collecting a parasitoid (Aphanogmus sp.) of F. acarisuga.