Susceptibility ofHelicoverpa zea(Lepidoptera: Noctuidae) Neonates to Diamide Insecticides in the Midsouthern and Southeastern United States

Abstract

Corn earworm, Helicoverpa zea (Boddie), is a significant pest of agroecosystems in the midsouthern and southeastern regions of the United States. These insects have developed resistance to, or inconsistent control has occurred with, most insecticide classes. With their unique mode of action, insecticides in the diamide class have become a key component in management of agriculturally important lepidopteran pests. In this study, field populations of H. zea were collected in the southern United States and compared to susceptible laboratory colonies to generate baseline concentration–mortality data. LC50 and LC90 values were generated for flubendiamide and chlorantraniliprole using neonates. To achieve equivalent levels of mortality, a higher concentration of flubendiamide was required compared to chlorantraniliprole. Flubendiamide LC50 values for H. zea ranged from 16.45 to 30.74 ng/ml, with a mean of 23.53 ng/ml. Chlorantraniliprole LC50 values for H. zea ranged from 2.94 to 4.22 ng/ml, with a mean of 3.66 ng/ml. Significant differences were observed for some field populations relative to the laboratory colony. For flubendiamide, five populations had greater LC50 values and two populations had lower LC50 values compared to the laboratory colony. For chlorantraniliprole, three populations had greater LC50 values and three populations had lower LC50 values compared to the laboratory colony. The response of these populations most likely represents natural variability among populations and does not indicate a significant shift in susceptibility of this species.

Contrasting susceptibility of lepidopteran pests to diamide and pyrethroid insecticides in a region of overwintering and migratory intersection

“…This result agrees with those obtained for populations from seven states across the Midsouthern and Southeastern U. S 60 . Our study extended coverage to populations in Florida, which were not included in that baseline assessment.…”

“…No change in the susceptibility to the diamide was observed in cotton bollworm populations. This result agrees with those obtained for populations from seven states across the Midsouthern and Southeastern U. S. 60 Our study extended coverage to populations in Florida, which were not included in that baseline assessment. In a scenario of increased cotton bollworm population levels in the Florida Panhandle associated with reduced efficacy of some Bt technologies, 11 chlorantraniliprole can be one valuable tool in a resistance mitigation program.…”

Managing pyrethroid‐ and Bt‐resistant bollworm in southern U.S. cotton

“…In soybean, bollworm can currently be controlled using foliar insecticides. For example, a recent survey of bollworm populations across the southern U.S. found that they were very susceptible to diamide‐class insecticides (Adams et al, 2016a) and that these could be effective, if used properly, in soybean (Adams et al, 2016b). While pyrethroid‐resistant bollworm populations have been present since the 1990s, use of this class for bollworm in both cotton and soybeans was still widespread until the 2010s.…”

Effects of chlorantraniliprole residual on Helicoverpa zea in Bt and non‐Bt cotton

“…As mentioned previously, chlorantraniliprole has been recommended nearly exclusively across the US Cotton Belt to manage H. zea since Bt resistance became widespread; 8 moreover, H. zea is susceptible to chlorantraniliprole in this region. 10,11 Soybean is another important host of H. zea and chlorantraniliprole is a commonly used insecticide for management of this insect, even though other effective insecticide classes are available. Cotton is thought to contribute little to the overall population size of H. zea relative to maize and soybean 23 .…”

“…The insecticide chlorantraniliprole is a ryanodine receptor modulator (MoA Group 28), and is widely recommended to control H. zea in cotton because of its persistence and residual activity as a systemic insecticide 9 . Furthermore, this insecticide has been recommended, nearly exclusively, across the US Cotton Belt to manage H. zea since Bt resistance became widespread; it is highly effective to manage H. zea neonates if it is applied before the eggs hatch 8 and, to date, populations have remained susceptible 10,11 . However, while the residual effects of chlorantraniliprole on H. zea have been studied in soybean, 9 they have not been studied in cotton.…”