# Effect of Transgenic Cotton with Bt Event Mpp51Aa2 on Cotton Fleahopper (Pseudatomoscelis seriatus) During Early Cotton Growth and Resulting Plant Injury

## TL;DR

This study evaluates how transgenic cotton with the ThryvOn trait affects cotton fleahopper populations and plant injury during early growth.

## Contribution

The study provides empirical evidence on the limited efficacy of ThryvOn trait cotton against cotton fleahopper compared to insecticide treatments.

## Key findings

- Flupyradifurone insecticide significantly reduced cotton fleahopper populations and protected yield.
- ThryvOn trait cotton showed modest (~10–30%) reductions in fleahopper abundance but inconsistent yield protection.
- Cotton maturity was unaffected by ThryvOn trait or insecticide treatments.

## Abstract

The cotton fleahopper is an important early-season hemipteran pest of cotton. Transgenic cultivars expressing the ThryvOn trait affect some plant bug species. Field experiments conducted in Corpus Christi, Texas, USA, evaluated the responses of cotton cultivars with and without the ThryvOn trait to cotton fleahopper infestations and early-season insecticide application (flupyradifurone). Cotton fleahopper populations reached the economic threshold midway through the first four weeks of squaring, when cotton plants are most sensitive to feeding injury, in 2024 and later in the same period in 2025. Flupyradifurone application reduced adult and nymph cotton fleahopper populations, reduced square loss, and protected yield across cultivars. Cultivars expressing the ThryvOn trait exhibited modest and variable reductions in adult cotton fleahopper abundance (~10–30%) and did not provide consistent yield protection. Cotton maturity was not affected. These results indicate that ThryvOn cultivars may provide limited supplemental benefits but cannot replace insecticide-based cotton fleahopper management.

The cotton fleahopper (Pseudatomoscelis seriatus (Reuter)) is an early-season hemipteran plant bug pest of cotton. In transgenic cotton cultivars, Bt event Mpp51Aa2 (Cry51Aa2) affects some other plant bug species (Hemiptera: Miridae) (we henceforth use the common terminology, stating that these cultivars have the ThryvOn trait). Field experiments were conducted in Corpus Christi, Texas, USA, to evaluate the responses of four cotton cultivars with and without the ThryvOn trait to cotton fleahopper infestations, comparing them with early-season foliar insecticide applications of flupyradifurone. Naturally occurring cotton fleahopper populations rose to the economic threshold midway through the first four weeks of squaring, when cotton plants are most sensitive to feeding injury, in 2024 and later in the same period in 2025. Flupyradifurone application significantly reduced adult and nymph abundance, resulting in reduced square abscission (2025) and yield protection that was consistent across cultivars in 2024 but more variable in 2025. Cultivars expressing the ThryvOn trait exhibited modest and variable reductions in adult cotton fleahopper abundance (~10–30%), occasionally benefiting from reduced square abscission but not protected yield. The open boll ratio, used to assess maturity delay, was not affected by cultivar or cotton fleahopper pressure. These results indicate that ThryvOn cultivars may provide limited supplemental benefits but do not replace or enhance the effectiveness of flupyradifurone for cotton fleahopper management.