Reproductive biology of summer/fall populations of rice water weevil, Lissorhoptrus oryzophilus Kuschel, in southeastern Texas

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Erirhinidae), is one of the most important pests of rice, Oryzae sativa L., in the US, and has emerged as a pest of rice in eastern Asia where it reproduces parthenogenetically. Females were collected from early July to late September 2006 from flooded main crop rice, ratoon crop rice, and a light trap placed in grassy vegetation and fallow fields near Beaumont, TX. Their mating status and ovarian developmental stages were monitored, and their reproductive capacity on rice plants was determined in the laboratory. Sexually reproductive individuals occurred consistently from early July to mid-September, which accounted for more than 50% of the females in most collections. Less than 7% of females seemed to be reproducing parthenogenetically. In the laboratory, 45.1% of females were mated within 9 days after emergence. For females emerging in late July and late August, only 17.4 and 6.1%, respectively, developed to ovipositing and post-ovipositing stages after feeding on rice plants for 4 weeks. These results indicated that in Southeast Texas >80% of summer females entered diapause after emergence, but reproductive females often are abundant later in rice fields. Contributions of summer females to the occurrence and abundance of this insect in subsequent seasons are discussed.