Use of Common Weeds of Rice as Hosts for the Rice Water Weevil (Coleoptera: Curculionidae)

Abstract

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most important insect pest in rice, Oryza sativa L., in the United States. Prior research indicates that rice water weevils feed primarily on monocotyledonous plants. Many monocot weeds occur in rice elds, but little is known about rice water weevil-weed interactions in rice. Host utilization of the rice water weevil was evaluated on rice, cultivar Cocodrie, and seven weeds commonly found in rice elds in preference and life cycle compatibility tests in the greenhouse. Barnyardgrass, Echinochloa crus-galli Beauv., yellow nutsedge, Cyperus esculentus L., broadleaf signalgrass, Brachiaria platyphylla Nash., and fall panicum, Panicum dichotomiflorum Michx., were more preferred for oviposition than rice. More neonate larvae eclosed on barnyardgrass and yellow nutsedge than eclosed on rice. Densities of late instars feeding on roots of yellow nutsedge and broadleaf signalgrass were signicantly lower than densities on rice. Barnyardgrass was also more preferred for adult feeding than rice and all other weeds. Rice water weevils were able to complete their life cycle on all plants examined except hemp sesbania, Sesbania exaltata (Ran.) Cory, the only dicotyledonous plant species tested in the greenhouse. Several new hosts can be added to an existing list of host plants for the rice water weevil. Field surveys conrmed larvae infested roots of all weed species sampled in the greenhouse, as well as several other weed species. Many of the plants infested with larvae were dicotyledonous plants, suggesting that the host range of rice water weevil is much broader than previously reported.