Helping cotton growers battle insecticide resistant pests

Virginia Tech entomologist Tim Bryant is developing sustainable pest management strategies to protect cotton profitability

By Julie Shlisky

Tim Bryant, assistant professor of entomology and Extension Specialist at the Virginia Tech Tidewater Agricultural Research and Extension Center, is on a mission to help cotton growers fight back against insects that threaten their yields and profitability.

His Hatch project focuses on integrated pest management and monitoring insecticide resistance in three of the most challenging pests for Virginia cotton: tarnished plant bugs, thrips, and bollworms. Insecticide resistance happens when insecticides become less effective over time as genetic mutations allow a population of insects to survive and reproduce. Each insect Bryant focuses on occupies a different feeding niche, bringing their own unique challenges that require a targeted approach.

Since 2015, tarnished plant bugs — once only occasional nuisances — have steadily become one of the most damaging pests to Virginia cotton. Thrips remain consistent, early-season threats that have developed resistance to several commonly used insecticides. Bollworms are largely controlled using Bacillus thuringiensis (Bt) cotton, a genetically modified plant with an incorporated protectant, but widespread use of Bt has raised concerns about the evolution of pesticide resistance.

cotton bollworm
Cotton bollworm on a cotton plant. Photo by Suzanne Pruitt for Virginia Tech.

Bryant’s work aims to find chemical alternatives and test agronomic practices that could provide long-term, sustainable solutions.

“We’re examining specific practices like nutrient management, plant growth regulation and cover cropping that can affect pest populations as well as beneficial insects,” Bryant said. “Promoting beneficial insects creates a natural layer of pest population control that ultimately supports improved pest management and cotton yields.”

Cotton is valued at $84.2 million annually in southeastern Virginia’s economy, but growers can lose an estimated $12.7 million each year to insect damage and control costs. With cotton prices down and pest management costs up, Bryant sees systems-based approaches as critical to helping farmers maximize return on investment.

During his first year on the project, Bryant is studying how plant growth regulation strategies and nitrogen rates influence cotton pests and beneficial insects. Both agronomic decisions shape plant architecture and resource allocation between vegetative and reproductive growth — factors that also interact with how insect populations fluctuate over time and with changes in environment. By aligning management practices with these ecological relationships, growers may improve cotton yields without needing additional input.

Bryant is also actively monitoring bollworm populations for signs of resistance to Bt cotton. If shifts are detected, growers will be alerted promptly through the Virginia Ag Pest and Crop Advisory and through in-person extension meetings.

“This work is about building long-term solutions that fit within the reality of cotton production,” Bryant said. “We want to stay ahead of resistance, reduce costs and make pest control more sustainable for Virginia growers.”

Data from the project will serve as the foundation for future funding proposals and expanded efforts with regional and national partners to develop resilient pest management strategies that safeguard one of Virginia’s most economically important crops.