Semester of Graduation
Summer 2024
Degree
Master of Science (MS)
Department
Entomology
Document Type
Thesis
Abstract
Abstract
The fall armyworm, Spodoptera frugiperda and corn earworm/bollworm, Helicoverpa zea, are two polyphagous pests prevalent in the U.S. In recent years, there were increased infestations of the two pests in the U.S., especially in its southern region. Information on the susceptibility/resistance status of the two pests in the region to chemical insecticides, especially to some new chemistries, is very limited or has not been updated for many years. In this study, susceptibility of 17 S. frugiperda and six H. zea field collected populations from the southern U.S. during 2021-23 to common insecticides was investigated in the laboratory. Dose-responses with S. frugiperda against four insecticides showed that, relative to a laboratory reference strain, 81.3% field S. frugiperda populations had a resistance ratio ranging from 10- to 323-fold to Warrior II and the resistance in the populations from three southeast states (Florida, South Carolina, and Georgia) was greater than the ratios observed from four mid-south states (Texas, Arkansas, Louisiana, and Mississippi). In addition, 56.3% S. frugiperda populations showed 10- to 482-fold resistance to Dimilin, 58.8% populations exhibited 10- to >71.7-fold resistance to Vantacor, and 29.4% demonstrated a resistance ratio between 10- to 27.7-fold to Intrepid. Bioassays with H. zea against eight insecticides exhibited that all six field populations were still very susceptible to Orthene and Vantacor; a few populations showed low but detectable levels of resistance to Blackhawk (up to 3.4-fold), Intrepid (up to 6.4-fold), and Dimilin (up to 4.4-fold), while 10- to 13.6-fold resistance was observed in one population against Warrior II, one population to Steward, and one population against Diamond. The results from the bioassays with H. zea suggest that the insect in the southern region appeared still relatively susceptible to the eight insecticides. Information generated from this study should be useful in directing proper selections of insecticides for S. frugiperda and H. zea management and resistance mitigation in the region.
Key words: Fall armyworm, corn earworm/bollworm, chemical insecticides, susceptibility, U.S. southern region, laboratory bioassays.
Date
7-23-2024
Recommended Citation
Patla, Bhavana, "SUSCEPTIBILITY OF SPODOPTERA FRUGIPERDA AND HELICOVERPA ZEA POPULATIONS IN THE SOUTHERN REGION OF THE UNITED STATES TO COMMON CHEMICAL INSECTICIDES" (2024). LSU Master's Theses. 6026.
https://repository.lsu.edu/gradschool_theses/6026
Committee Chair
Fangneng Huang