Effects of spinosad and pinetoram on larval mortality, adult emergence, progeny production and mating in Cadra cautella (Walk.) (Lepidoptera: Pyralidae)

Authors: SAMMANI, A.M. - Rajarata University Of Sri Lanka; DISSANAYAKA, D.M.S. - Rajarata University Of Sri Lanka; WIJAYARATNE, WOLLY L. - Rajarata University Of Sri Lanka; Morrison, William - Rob

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2020
Publication Date: 9/1/2020
Publication URL: https://handle.nal.usda.gov/10113/7054615
Citation: Sammani, A.P., Dissanayaka, D.K., Wijayaratne, W.K., Morrison III, W.R. 2020. Effects of spinosad and pinetoram on larval mortality, adult emergence, progeny production and mating in Cadra cautella (Walk.) (Lepidoptera: Pyralidae). Journal of Stored Products Research. 88:101665. https://doi.org/10.1016/j.jspr.2020.101665.
DOI: https://doi.org/10.1016/j.jspr.2020.101665

Interpretive Summary: Historically, pest management in postharvest products has relied on fumigation by methyl bromide and phosphine. The former was phased out of use, and the latter is facing issues with increasing resistance worldwide. In order to preserve the efficacy of phosphine, it is important to diversify integrated pest management (IPM) programs at food facilities. One way to do so is to incorporate residual applications of other insecticides. Spinosad and spinetoram are reduced-risk and USDA organically-approved insecticides. However, up to this point, it has been uncertain whether they would be effective against the almond moth, Cadra cautella. We tested the ability of both of these compounds to kill almond moth larvae, prevent adult emergence, and reduce subsequent progeny production in rice flour at a series of concentrations. Additionally, we assessed whether they affected mating success of females under mating disruption programs. We found that there were multiple-fold reductions in larval survival, adult emergence, and progeny production when almond moth larvae were exposed to treated flour. We did not find any significant effect on mating success in the subsequent generation. Overall, these results suggest that both spinosad and spinetoram may be able to be incorporated into management programs for food facilities needing to control almond moth.

Technical Abstract: The bacterial formulations, spinosad and spinetoram, were evaluated for their efficacy in suppressing development and mating success in Cadra cautella, the almond moth. A dilution series of spinosad and spinetoram was sprayed on rice flour. Rice flour samples sprayed with water served as the control. Late instar C. cautella larvae were introduced onto spinosad-, spinetoram-, or water-treated rice flour. The first experiment tested the effects of spinosad and spinetoram on larval mortality, as well as emergence of adults and progeny at different insecticide concentrations. In the second experiment, larvae exposed to spinosad were used in a wind tunnel experiment to determine its impact on mating success in C. cautella adult progeny. Both spinosad and spinetoram increased larval mortality, whereas both compounds reduced adult emergence and progeny production. Natural mating was reduced in the presence of the synthetic sex pheromone (Z, E)- 9,12-tetradecadienyl acetate. However, exposure of C. cautella larvae to spinosad did not alter mating in adult progeny. Spinosad was more effective than spinetoram at suppressing C. cautella development. Overall, both spinosad and spinetoram reduced the survival of larvae, emergence of adults and progeny production when applied to C. cautella larvae. However, spinosad did not affect the mating success of C. cautella.