Areawide susceptibility of Spodoptera frugiperda to four common chemical insectides in the southern U.S.

Authors: PATLA, B - Louisiana State University; SILVA, TIAGO - Louisiana State University Agcenter; LIN, S - Louisiana State University; HEAD, G - Bayer Cropscience; DAVIS, J - Louisiana State University; SWORD, G - Texas A&M University; MILLER, A - Texas A&M University; REAY-JONES, F.P.F. - Clemson University; Ni, Xinzhi; QURESHI, J - University Of Florida; CARRILLO, D - University Of Florida; VILLEGAS, J - Louisiana State University; COOK, D - Mississippi State University; DAVES, CHRIS - Bayer Corporation; THRASH, B - University Of Arkansas; PAULA-MORAES, S.V. - University Of Florida; HUANG, FANGNENG - University Of Florida

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2025
Publication Date: 11/19/2025
Citation: Patla, B., Silva, T., Lin, S., Head, G., Davis, J., Sword, G., Miller, A., Reay-Jones, F., Ni, X., Qureshi, J., Carrillo, D., Villegas, J., Cook, D., Daves, C., Thrash, B., Paula-Moraes, S., Huang, F. 2026. Areawide susceptibility of Spodoptera frugiperda to four common chemical insectides in the southern U.S.. Pest Management Science. 82(3):2501-2512. https://doi.org/10.1002/ps.70385.
DOI: https://doi.org/10.1002/ps.70385

Interpretive Summary: Although the fall armyworm is a native pest to the Americas, it has been an invasive pest threatening food security in Africa, Asia, and Australia in the recent years. During the past quarter century, fall armyworm damage on corn and cotton in the southern U.S. states has been primarily controlled by utilizing Bt transgenic varieties, while its damage on all other host crops, such as, forages and pastures, has encountered increased frequencies of infestations, and its damage is mainly controlled by applications of chemical insecticides. However, information on area-wide resistance of the fall armyworm to insecticides in the southern region is still limited. The current study presents an area-wide investigation of changes in fall armyworm susceptibility to four commonly used insecticides in the southern U.S. states. The findings show that the heightened fall armyworm problems in recent years are associated with development of insecticide resistance. The information generated from the current study can be utilized for insecticide selection not only to control its damage, but also to mitigate its insecticide resistance across the region.

Technical Abstract: In recent years, forages, pastures, and other host plants across the southern U.S. have encountered the increase of fall armyworm, Spodoptera frugiperda (J.E. Smith) infestations. Information on the susceptibility/resistance status of the insect to insecticides, especially to some new chemistries in the region, is limited or has not been updated for many years. In this study, bioassays were performed to determine the susceptibility of 24 field populations of S. frugiperda from corn, sorghum, and grasses/rice to four common insecticides from seven southern U.S. states. The four insecticides were '-cyhalothrin (belongs to pyrethroids), diflubenzuron (benzoylureas), methoxyfenozide (diacylhydrazines), and chlorantraniliprole (diamides). Relative to a laboratory susceptible strain, 82.6 and 60.8% of the populations demonstrated a resistance ratio (RR) of >10-fold to '-cyhalothrin (up to 2,290-fold) and diflubenzuron (up to 672.6-fold), respectively. In addition, at least 10 (or 41.7%) populations had > 10-fold (up to >67.7-fold) resistance to chlorantraniliprole. Resistance to methoxyfenozide was less common with four (or 16.7%) populations having a RR of >10 (up to 23.9). No correlations were found in susceptibility among the four insecticides. Across all four insecticides, no significant differences were found in the mean susceptibilities among populations from different host plants, or between geographical locations (mid-south versus southeast coastal, and overwintering versus migratory regions), or between corn and rice strains of the pest. The information generated from this study can be used to select insecticides for S. frugiperda management and resistance mitigation in the region.