Sublethal effects of diamide insecticides on development and flight performance of Chloridea virescens (Lepidoptera: Noctuidae): Implications for Bt soybean refuge area management

Authors: BARROS, LUCAS - Universidad De Sao Paulo; YAMAMOTO, PEDRO - Universidad De Sao Paulo; Merten, Paul; Naranjo, Steven

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2020
Publication Date: 4/28/2020
Citation: Barros, L., Yamamoto, P., Merten, P., Naranjo, S.E. 2020. Sublethal effects of diamide insecticides on development and flight performance of Chloridea virescens (Lepidoptera: Noctuidae): Implications for Bt soybean refuge area management. Insects. 11(5). https://doi.org/10.3390/insects11050269.
DOI: https://doi.org/10.3390/insects11050269

Interpretive Summary: A key component in the sustained production of transgenic Bt crops is the management of resistance to the Bt proteins. High dose of the protein and deployment of a non-Bt refuge to generate susceptible moths is the preferred approach. The tobacco budworm, Chloridea virescens, is a target pest of Bt soybean in Brazil. Insecticide sprays are often needed in the non-Bt refuge for this crop to manage the target and other pests. The objective of this study was to evaluate the sublethal effects of diamides insecticides on C. virescens biology and flight performance, and understand the potential impact for soybean refuge area management. Sublethal doses of chlorantraniliprole effected larval survival more than flubendiamide. Both treatments increased larval and pre-pupal development times, while only flubendiamide increase pupal development times. Both insecticides reduced larval weight, while only flubendiamide negatively impacted pupal and adult weight. Both treatments reduced larval survival but did not affect pupal survival or resulting sex ratio of adults. C. virescens adult males from chlorantraniliprole treatment had longevity increased, and flubendiamide affected fecundity and chlorantraniliprole fertility. C. virescens life table parameters were negatively impacted by both treatments. Chlorantraniliprole exposed males showed significant reductions in flight duration and distance for unsustained flights less than 30 minutes and for the first flights < 30 minutes. In contrast, for flubendiamide the duration and distance of flights were significantly reduced. Sustained flights greater than 30 minutes were generally uneffected by insecticide exposure. Our results suggest that the sublethal effects of flubendiamide and chlorantraniliprole effect on C. virescens populations may lead to generation asynchrony and provide insufficient production of susceptible moths. Flight behavior of males, but not females, was negatively effected by sublethal doses but distance and duration of flight may still be sufficient to ensure mixing of potentially resistant and suceptible populations from refuge plots 800 m apart. Results would be of value to growers and regulators interested on sustaining the durability of this pest control technology.

Technical Abstract: High-dose and refuge are the most important strategies for delaying resistance evolution in Bt crops. Insecticide sprays in refuge areas could be necessary and may limit refuge effectiveness. Here, we evaluated the sublethal effects of two diamide insecticides (chlorantraniliprole and flubendiamide) on Chloridea virescens life history traits and flight performance. Sublethal concentrations of chlorantraniliprole and flubendiamide increased larval and pre-pupal development times and decreased larval weight; flubendiamide increased pupal development times. Chlorantraniliprole increased adult male longevity and reduced female fertility, while flubendiamide reduced fecundity. Overall life table parameters were negatively impacted by both treatments. Males exposed to either insecticide showed significant reductions in flight duration and distance for unsustained flights (<30 min). The duration and distance of the first flights were reduced when exposed to chlorantraniliprole. Sustained flights (>30 min) were generally unaffected by insecticide exposure and both sexes flew >6400 m in a single flight. The sublethal effects of flubendiamide and chlorantraniliprole on C. virescens’ population dynamics could lead to generation asynchrony and provide insufficient susceptible moths when sprayed on refuge crops. However, the distance and duration of flight may still be sufficient to ensure mixing of potentially resistant and susceptible populations from refuge plots.