Attraction of Sitophilus zeamais (Coleoptera: Curculionidae) to Four Host Plants

Abstract

The maize weevil Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) is an important pest of stored grains, predominantly maize (Zea mays L.), wheat (Triticum L. spp.), rice (Oryza L. spp.), and sorghum (Sorghum bicolor [L.] Moench) (all Poaceae). Weevil infestations occur in the field and weevils are carried to the storage facility after harvest. Infestation also occurs in the grain storage facility. There is no effective field or storage trapping system for control. They are commonly parasitized by Pteromalidae Dalman (Hymenoptera: Chalcidoidea) spp. parasitoids in the Tropics; however, there is no biocontrol use of these Hymenoptera. Therefore, pesticide application and the development of resistant grain are the current control strategies; although, studies have indicated that odors associated with the grain upon which the weevils feed, mate, and oviposit are attractive to the weevil. Host plant produced volatiles and their associations with the maize weevil have not been investigated fully. To better understand the weevil's attraction to crop plants, a study was initiated to investigate the weevil's preference for immature host plants. Weevils that had been reared on 4 types of grain for several generations were presented immature plants of all 4 types of grains in choice tests to determine if they prefer grains of the host plant on which they had been reared. This research demonstrated that immature rice plants have the greatest attraction, and that previous feeding did not influence the weevil's host plant attraction. The isolation of key rice plant semiochemicals will be the focus in the development of an attractant for S. zeamais and may also prove effective for the control of Sitophilus oryzae (L.) (Coleoptera: Curculionidae).