Analysis of preventive treatments for control of rice water weevil in Texas.

摘要

urrent treatment recommendations for controlling the rice water weevil (RWW) in Texas are based primarily on Arkansas data. Questions on the transferability of that information for Texas conditions, and the controversy over management control alternatives of the RWW arising out of EPA's recent decision to gradually phase out Furadan, provided the impetus for this study.;Main crop damage functions relating RWW larval populations to rice yield loss were estimated using the Nelson-Olson simultaneous equations' estimator. The linear, quadratic, and square root specifications of the variables RWW larvae and Furadan 3G were used. Using several evaluation criteria, the "best" models were selected. Damage relationships for the ratoon crop were estimated. Stochastic economic decision models to address the preventive method of treatment based on maximizing expected net returns above specified costs were developed for both crops. An economic paradigm for future research that comprehensively examines alternative scouting and treatment methods with the objective of developing economically based management strategies for the RWW is then presented.;Main crop results indicate that significant inverse relationships exist between Furadan 3G and larvae, and larvae and yield. The tall stature rice variety had significantly lower yields than the semidwarf variety. The later rice is planted during the growing season the fewer the number of larvae, but the lower the yields. Broadcast-seeded rice had significantly higher yields than drill-seeded rice. The lower the seeding rate, the higher the larvae and the lower the yields. It was found that, on average, highest expected net returns were associated with optimal Furadan 3G levels of zero. Larvae present in the main crop were also found to significantly reduce ratoon yields. Including consideration of ratoon crop effects tended to, in some cases, result in preventive applications.;Because only the preventive method of control for the RWW was discussed, the issue of season-long RWW control is considered incomplete. An economic paradigm evaluating different scouting and treatment methods using a split-split plot design to facilitate collection of relevant data is suggested for a future study. The tentative budget proposed for the four-year study is estimated at about