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ViewAttendees 2

10-Minute Paper

Plant-Insect Ecosystems

P-IE: IPM - Field Crops 1

No resistance to Cry1F detected in fall armyworm from the southeastern U.S. after a decade since practical resistance to Cry1F corn was documented

Wednesday, November 8, 2023
9:12 AM – 9:24 AM ET
Location: Gaylord National Resort & Convention Center, Maryland 5-6
In-Person
The fall armyworm (FAW), Spodoptera frugiperda, is a polyphagous pest that in the Americas is targeted by transgenic corn and cotton expressing Bacillus thuringiensis (Bt) proteins. A previous study during the 2011-2013 period demonstrated practical FAW resistance to corn producing the Cry1F Bt protein in the southeastern seaboard of the U.S. The main objective of this study was to investigate the current susceptibility status to four Bt proteins commonly expressed in Bt corn plants, including Cry1F, Cry1A.105, Cry2Ab2, and Vip3A, in FAW populations from the U.S. southern region. During 2021 and 2022, a total of 23 FAW populations were collected from seven U.S. southern states, including 9 populations from the southeastern coastal region. Diet-overlay bioassays showed that one of the 23 populations exhibited a < 2-fold greater LC50 for Cry1F than a reference susceptible strain, while all other 22 populations were equally (8 populations) or more susceptible (14) to the Cry1F protein. Susceptibility ratios (LC50 of field population/LC50 of the susceptible strain) of the 23 field populations ranged from < 0.15- to 4.67-fold to Cry1A.105, < 0.12- to 4.41-fold to Vip3Aa39. Three populations demonstrated a LC50 of >10-fold greater than the susceptible strain to Cry2Ab2. Overall, these findings do not provide evidence of practical resistance in FAW to any of the four tested Bt proteins. The detected Cry1F susceptibility in FAW could be the first case of documented practical resistance to a Bt protein becoming more susceptible and has important implications for IRM.