Semester of Graduation
Master of Science (MS)
Spodoptera frugiperda, the fall armyworm (FAW), is a major agricultural pest causing billions of dollars in damage annually to staple crops. Agricultural losses stemming from this pest continues to increase as resistance to commercialized insecticide classes evolves and spreads. Considering this, novel chemistries with new modes of action as well as novel resistance management strategies need to be developed to achieve continued control of FAW populations. This project consisted of two main goals. First, we aimed to develop a neurophysiological assay to enable a more precise understanding of pyrethroid and organophosphate resistance at the level of the nerve. We collected FAW from whorls of late-season corn and compared neural sensitivity and susceptibility to lambda-cyhalothrin and chlorpyrifos. Field collected FAW were >700-fold resistant to lambda-cyhalothrin and had >1700-fold reduced neural sensitivity yet, no known kdr mutations were identified. These data suggest the absence of kdr mutations does not necessarily indicate pyrethroid susceptibility and vice versa and therefore, the inclusion of neurophysiological assays into existing resistance monitoring programs is likely to provide a more accurate assessment of resistance mechanisms. In the second goal, we aimed to test the neural potency and toxicity of natural product based chromene (Benzopyran) analogs to FAW to determine if chromene based scaffolds may represent a base for FAW directed insecticide development. Chromene testing included intrathoracic injections, feeding assays, and neurophysiological recordings. Select chromenes induced acute toxicity and induced abnormalities upon adult eclosion such as partial eclosion and twisted wings, indicating these molecules may interfere with development. Therefore, chromene based molecules represent a series of scaffolds that may be used to develop FAW directed insecticides and warrant further study.
McComic, Sarah, "Insecticide Resistance Management Approaches and Naturally Derived Toxicants for the Control of Fall Armyworm, Spodoptera frugiperda" (2020). LSU Master's Theses. 5227.