Density-yield relationships for rice water weevil on rice for different varieties and under different water management regimes

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the United States. Two years of field experiments were conducted to quantify relationships between densities of immature rice water weevils and yields for two rice varieties under early and delayed flooding regimes. Larval densities during earlier stages of rice growth were more strongly correlated with yield losses than were larval densities later in the growing season. Slopes of regression models were more negative for early-flood than for delayed-flood plots, and more negative for 'Bengal' than for 'Cocodrie'. The results of these experiments confirm that short delays in flooding reduce yield losses from the rice water weevil and that 'Bengal' is less tolerant of weevil feeding than 'Cocodrie'. Estimates of yield loss caused by each weevil provide a key parameter for the calculation of economic injury levels under different management regimes. Data from this study suggest that it is possible to integrate the use of insecticides, cultural practices and host plant resistance in a management system for the rice water weevil. (C) 2003 Elsevier Ltd. All rights reserved.