Date of Award
5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Entomology, Soils and Plant Sciences
Committee Chair/Advisor
Francis Reay-Jones
Committee Member
Jeremy Greene
Committee Member
Matt Turnbull
Committee Member
Dominic Reisig
Abstract
In the southeastern United States, the brown stink bug, Euschistus servus (Say), and the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), are common economic pests of corn, Zea mays L. (Poaceae: Poales). Although commonly found, the corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is generally not an economic pest and is managed with transgenic corn hybrids expressing toxins produced by the Bacillus thuringiensis (Bt). Resistance to Bt toxins is a major thread to the sustainability of Bt crops. Understanding the ecology of stink bugs and corn earworms in field corn can help to effectively implement integrated pest management (IPM) and insecticide resistance management (IRM). We performed field studies to assess the spatial patterns of stink bugs, corn earworm, and their respective injuries in corn fields, understand the spatial interactions of these pests with plant phenology, monitor sublethal impacts of Bt toxins on corn earworm, and determine how corn stakeholders perceive the relative importance of these pests and implement management. We identified patterns of spatial aggregation of stink bugs and corn earworm. For stink bugs, spatial associations between bugs and ear injury were identified more commonly when stink bugs were sampled during the late vegetative stages of development. Both pests were also spatially associated with plant phenology that varied throughout a corn field. Corn earworm larval populations, in particular, were tightly linked with areas of the field that were more advanced through corn growth stages when sampled. We were the first to identify a competitive interaction between stink bugs and corn earworm in these sampling studies and in a follow up controlled trial. Stink bug ear injury and feeding resulted in a significant decline in corn earworm oviposition, larval density, and total larval feeding across four trials in two study years. In a study assessing the sublethal impacts of Bt toxins on corn earworm, we identified a continued decline in the impact of Bt corn expressing Cry1A.105 + Cry2Ab2 and Cry1Ab + Cry1F on pupal weight over nine years (2014-2023) due to resistance development. Finally, in a survey of corn stakeholders, we identified the most important insect pest considerations for growers, their reasonings for implementing various IPM and IRM strategies, and knowledge and use of IPM. Grower selections for hybrids and seed treatments were heavily dependent on perceived yield potential and industry recommendations rather than specific insect management concerns. Only 59% of growers surveyed indicated that they planned to plant non-Bt refuge, which is a major issue for IRM success. The results of these studies will aid in effective sampling and management of several major pest of field corn.
Recommended Citation
Bryant, Tim, "Ecology and Integrated Pest Management of Major Insect Pests of Field Corn" (2024). All Dissertations. 3591.
https://tigerprints.clemson.edu/all_dissertations/3591
Author ORCID Identifier
0000-0003-4071-3104