Feeding behavior and fruiting form damage by bollworm (Lepidoptera: Noctuidae) in bt cotton

Authors: GODBOLD, RUSSELL - Mississippi State University; CROW, WHITNEY - Mississippi State University; CATCHOT, ANGUS - Mississippi State University; GORE, JEFF - Mississippi State University; COOK, DON - Mississippi State University; DODDS, DARRIN - Mississippi State University; MUSSER, FRED - Mississippi State University; Little, Nathan

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2021
Publication Date: 11/17/2021
Citation: Godbold, R.E., Crow, W.D., Catchot, A.L., Gore, J., Cook, D.R., Dodds, D.M., Musser, F.M., Little, N. 2021. Feeding behavior and fruiting form damage by bollworm (Lepidoptera: Noctuidae) in Bt cotton. Journal of Economic Entomology. 115:160-167. https://doi.org/10.1093/jee/toab220.
DOI: https://doi.org/10.1093/jee/toab220

Interpretive Summary: The bollworm is a major insect pest of cotton. Transgenic cotton expresses proteins that are toxic to bollworms when they feed on this tissue. Bollworms have become tolerant of some proteins expressed by transgenic cottons and have been observed to avoid feeding on certain plant tissues that are known to express high levels of these toxins. This study evaluated bollworm behavior and survival on different transgenic cottons as well as damage to various fruiting structures in these cultivars, which express various Bt toxin combinations. Findings from this study indicate that dual-gene transgenic cottons may no longer be economically-adequate for bollworm control without the need for supplemental foliar insecticide applications when insect pressure is moderate or high. Newer triple-gene Bt cottons provides superior control due an additional vagatatively-produced toxin and will likely decrease the amount of supplemental control measures needed to control bollworm.

Technical Abstract: Bt technologies have played a major role in the control of bollworm, Helicoverpa zea (Boddie), in cotton. Variation in expression levels among varieties and plant parts, along with selection pressure on bollworm populations, has led to the development of resistance to some Bt proteins. Trials were conducted to evaluate how cotton varieties expressing different Bt proteins affect bollworm larval behavior and their damage in flowering cotton. Differences in recovery were observed among cotton varieties at 3 d with 3-gene Bt cotton having the lowest recovery and non-Bt cotton having the greatest recovery. Loss of bloom tags and abscission of small bolls at the site of infestation affected bollworm larval recovery among varieties. Day after infestation was the main factor that affected bollworm movement across all varieties. Number of total damaged fruiting forms by an individual bollworm larva was different among all varieties. Overall, flower bud (square) and fruit (boll) damage by an individual larva was lower on 3-gene cotton than 2-gene cotton and non-Bt cotton. An individual larva damaged fewer squares on 2-gene cotton than non-Bt cotton, but boll damage from bollworm was similar among 2-gene cotton and non-Bt cotton. The level of square and boll damage in 2-gene cotton has increased compared to previous research further supporting the occurrence of bollworm resistance to Cry proteins. The 3-gene cotton containing the Vip3A gene experienced low levels of damage and survival. These results will be important for improving management recommendations of bollworm in Bt cotton technologies.