First Report of Helicoverpa armigera (Lepidoptera: Noctuidae) Resistance to Flubendiamide in Brazil: Genetic Basis and Mechanisms of the Resistance

The cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is a significant pest in the world and it was identified in Brazil in 2013, causing severe economic losses. Recent studies showed a significant decrease in the susceptibility of H. armigera to diamide insecticides in Brazil. Understanding the genetic basis and mechanisms of the resistance are essential to develop proactive resistance management strategies. A laboratory strain of H. armigera resistant to the phthalic acid diamide flubendiamide (Flub-R) was selected from a field-collected population to characterize the resistance. The resistance ratio of the Flub-R strain was >50,000-fold. The inheritance pattern of the resistance was characterized as an autosomal dominant trait. Flub-R showed no cross-resistance to the anthranilic diamides chlorantraniliprole, cyantraniliprole or cyclaniliprole. Susceptible strain larvae that fed on flubendiamide-treated soybean leaves at field-recommended rates were killed while heterozygotes and Flub-R larvae showed a high survival and no reduction in the leaf consumption, confirming the functional dominance of the resistance. No indication of metabolic resistance was detected. The partial sequencing of ryanodine receptor (RyR) genes covering the transmembrane II to VI did not show any amino acid mutations, indicating the presence of a non-common resistance mechanism to diamide insecticides in the Flub-R strain.