The influence of imidacloprid seed treatment on non-ThryvOn and ThryvOn cotton.

Abstract

In the southern United States, thrips are a significant early season pest of cotton. In the United States, in 2022, 98% of cotton acres were infested with thrips, and, of those acres, 45% were treated for thrips. Thrips injury resulted in over $113 million dollars in losses plus control costs to the cotton industry in the United States that year. A new Bacillus thuringiensis trait known as ThryvOn has been commercialized to provide control against thrips. There is ongoing debate about the need for an insecticidal seed treatment to improve thrips control on ThryvOn varieties. Field studies were conducted to determine if the addition of an imidacloprid seed treatment improved efficacy against tobacco thrips and to determine if reduced rates of seed treatments (0, 25, 50, 75, and 100% of the labeled rate) provided benefits for thrips control in ThryvOn cotton. To control for infestation pressure, a complementary greenhouse study was conducted using the same treatments under controlled conditions. Imidacloprid provided only a limited benefit for improved management on ThryvOn cotton in the greenhouse study, but no benefit in the field study. Efforts in pest surveillance should be continued in ThryvOn cotton to allow for foliar applications when warranted based on established thresholds. No conclusions can be drawn about the benefits of an imidacloprid seed treatment for resistance management in ThryvOn cotton from this study, but these data suggest that any benefit would be minimal.