Impact of Rice Water Weevil (Lissorhoptrus oryzophilus, Kuschel) in Water Conservation Rice Production Systems

Water conservation has become an important aspect of Mid-South agriculture over the last decade due to declining aquifer levels. Of the agronomic crops grown in the Mid-South, rice is the greatest user of water because it is grown under a flooded culture. Consequently, the biology of numerous Arthropod pests of rice are dependent on flooded conditions. The rice water weevil, Lissorhoptrus oryzophilus (Kuschel), is an important and economically damaging insect pest of rice globally. It will only oviposit during flooded culture, so water conservation practices may influence its biology and pest status. One conservation method currently being studied is furrow irrigated rice. During 2017, an experiment was conducted to evaluate the temporal and spatial distribution of rice water weevil in commercial row watered fields. A total of five fields were sampled across the region. Each field was divided into three zones based on soil saturation levels. In most cases, rice water weevil densities were greatest in the areas of the fields where the flood never dissipated (Zone 3). Rice water weevil larvae densities were very low in areas of fields that never became flooded (Zone 1). Areas that held a brief flood but remained muddy (Zone 2) had intermediate levels of rice water weevil larvae. These preliminary data suggest that water conservation practices in rice will impact the pest status of rice water weevil. In the case of row watered rice, most of the weevils were concentrated in the flooded portion of fields which may create some unique management opportunities for growers.