Field evaluation of biological and conventional insecticides for managing multiple insect pests in cotton

Authors: Little, Nathan; Elkins, Blake; Portilla, Maribel; Allen, Clint; Read, Quentin; Paulk, Ryan

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2023
Publication Date: 1/3/2024
Citation: Little, N., Elkins, B.H., Portilla, M., Allen, K.C., Read, Q.D., Paulk, R.T. 2024. Field evaluation of biological and conventional insecticides for managing multiple insect pests in cotton. Journal of Entomological Science. https://doi.org/10.18474/JES23-37.
DOI: https://doi.org/10.18474/JES23-37

Interpretive Summary: The tarnished plant bug and bollworm are the two major pests of cotton in the southern US. The vast majority of broad-spectrum pesticide applications are made to control these two insect pests. This study evaluated the potential of two biological insecticides, one for each pest, to control these two major insects in conventional and genetically modified cottons that produce toxins for control of bollworm. Although these insecticides reduced insect numbers, the biological insecticides used in this study did not increase cotton yield above that seen for the untreated control. Cotton plots treated with conventional synthetic insecticides for control of the tarnished plant bug had higher numbers of bollworms than those untreated or treated with biological insecticides. Holistic management of the two major insect pests of cotton with current biological insecticides alone is not yet feasible. However, future research will focus on timing of applications, integration with synthetic insecticides, and incorporation into traditional management strategies.

Technical Abstract: Cotton is an economically important crop in the southern United States plagued by a complex of insect pests. Two key pests of cotton in the Mississippi Delta region, in terms of impact on yield and economics, are the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), and bollworm, Helicoverpa zea (Boddie). A well-established suite of highly effective conventional synthetic insecticides is available for these pests. It is unclear how the management of the tarnished plant bug and bollworm in combination impacts the economics of cotton production. It is further unclear how biological insecticides such as Bt and entomopathogens fit into cotton IPM programs to manage these key insect pests. To address these shortcomings, we conducted a field experiment in the Mississippi Delta over two years to study the effects of synthetic and biological insecticides for control of the tarnished plant bug and bollworm on yield and economics of cotton. The results indicated the control of tarnished plant bug with conventional insecticides had the most significant impact on yield and net return above treatment costs. The conventional tarnished plant bug treatment also increased bollworm density and damage, though not enough to significantly impact yield or net return above treatment costs. The biological insecticides utilized for this study were ineffective at significantly altering yield or net return. This research demonstrates why conventional insecticides are featured heavily in current cotton pest management strategies. However, for insect management in cotton of the mid-southern U.S. to be sustainable in the long term, alternatives must be found to complement conventional synthetic insecticides.