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Abstract
The diamondback moth (DBM), Plutella xylostella, is a key pest of Cole crops in the Southeastern USA. Insecticide resistance, in particular diamide resistance, is a major concern for DBM populations in Georgia and Florida based on recent maximum dose bioassays conducted during the course of this research. Colonies were established from resistant field populations from Tift County (LTF), Colquitt County (NP), and Crisp County (CSP) in Georgia, as well as Manatee County (MAN) in Florida. The LTF, NP, and MAN colonies were highly resistant to chlorantraniliprole (2,813 to 4,298-fold), while the CSP colony only showed intermediate resistance (109-fold). Intermediate resistance to both cyantraniliprole (50 to 108-fold) and spinetoram (29 to 217-fold) was also determined for the colonies. The G4946E, a target site mutation of the DBM ryanodine receptor, was confirmed for these colonies. Allele frequency estimates of the G4946E were determined to be 90%, 61%, 53%, and 32%.