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ARS Home » Southeast Area » Stoneville, Mississippi » Southern Insect Management Research » Research » Publications at this Location » Publication #428989
Research Project: Enhancing the Endurance of Bt Toxins in Cotton

Location: Southern Insect Management Research

Title: Impact of crystalline and vegetative protein expression in dual- and multi-gene transgenic cottons on bollworm larval survival

Author
item Little, Nathan
item Paulk, Ryan
item Elkins, Blake
item Mullen, Regina
item Allen, Kerry

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2026
Publication Date: 1/14/2026
Citation: Little, N., Paulk, R.T., Elkins, B.H., Mullen, R.M., Allen, K.C. 2026. Impact of crystalline and vegetative protein expression in dual- and multi-gene transgenic cottons on bollworm larval survival. Crop Protection. 202:1-8. https://doi.org/10.1016/j.cropro.2026.107543.
DOI: https://doi.org/10.1016/j.cropro.2026.107543

Interpretive Summary: The bollworm is a major pest of U.S. cotton. Genetically modified (Bt) cotton helps control this pest by producing insect-killing proteins. This study looked at how three Bt proteins (Cry1Ac, Cry2Ab, and Vip3A) are produced in two types of Bt cottons during the growing season, and how they affect bollworm survival. We found that Cry1Ac and Cry2Ab levels dropped over time, while Vip3A stayed steady. Bollworms died most often when feeding on squares, followed by blooms and bolls. One cotton type (Bollgard II) had more Cry1Ac early in the season, which may help with early pest control. The other type (Bollgard III) had more Vip3A in blooms, which could help control bollworms later in the season. Our results suggest farmers should check newer multi-gene cottons (Bollgard III) for bollworms later in the season, especially in blooms and bolls, and monitor for signs of resistance to keep Bt cotton effective.This research supports the Secretary of Agriculture’s priority of increasing profitability of farmers and ranchers.

Technical Abstract: The bollworm (Helicoverpa zea), a persistent pest of U.S. cotton, poses ongoing challenges to producers. Transgenic cotton expressing Bacillus thuringiensis (Bt) insecticidal proteins has revolutionized bollworm control while reducing reliance on broad-spectrum insecticides. However, variability in toxin expression across plant structures and developmental stages may reduce efficacy and contribute to resistance development. This study evaluates relative Cry1Ac, Cry2Ab, and Vip3A protein expression in two Bt cotton cultivars throughout the growing season and correlates these data with bollworm larval mortality on fruiting structures. Our results show a general decline in Cry1Ac and Cry2Ab levels throughout the growing season, while Vip3A expression remained relatively stable. Bollworm larval mortality was highest in squares, followed by blooms and bolls. The Bollgard II cotton variety exhibited higher early-season Cry1Ac levels than Bollgard III, potentially influencing early season pest suppression. Vip3A expression was the highest in blooms of Bollgard III cotton, followed by squares and bolls. These findings underscore the importance of mid- to late-season scouting for surviving larvae on blooms and boll damage in Bollgard III cotton. A better understanding of the spatiotemporal expression of Vip3A coupled with preemptive resistance screening will be vital for preserving Bt cotton’s longevity and maintaining its role in sustainable production systems.