# Influence of Rice Seeding Rate on Efficacies of Neonicotinoid and Anthranilic Diamide Seed Treatments against Rice Water Weevil

## TL;DR

This study examines how rice seeding rates affect the effectiveness of insecticides against rice water weevils, finding that lower seeding rates may reduce insecticide efficacy.

## Contribution

The study provides new insights into the interaction between rice seeding rates and insecticide efficacy against rice water weevil.

## Key findings

- Chlorantraniliprole showed better larval suppression than neonicotinoids.
- Low seeding rates resulted in up to 47% higher weevil infestations.
- Neonicotinoids were less effective at suppressing larvae at low seeding rates.

## Abstract

Rice in the U.S. is frequently seeded at low rates and treated before sowing with neonicotinoid or anthranilic diamide insecticides to target the rice water weevil. A previous study of the influence of seeding rate on rice water weevil densities showed an inverse relationship between seeding rates and immature weevil densities. This study investigated interactive effects of seeding rate and seed treatment on weevil densities and rice yields; in particular, experiments were designed to determine whether seed treatments were less effective at low seeding rates. Four experiments were conducted over three years by varying seeding rates of rice treated at constant per seed rates of insecticide. Larval suppression by chlorantraniliprole was superior to thiamethoxam or clothianidin, and infestations at low seeding rates were up to 47% higher than at high seeding rates. Little evidence was found for the hypothesis that seed treatments are less effective at low seeding rates; in only one of four experiments was the reduction in weevil densities by thiamethoxam greater at high than at low seeding rates. However, suppression of larvae by neonicotinoid seed treatments in plots seeded at low rates was generally poor, and caution must be exercised when using the neonicotioids at low seeding rates.