Insecticidal effect of deltamethrin, pyrethin, and spinosad on metal and concrete surfaces on six species of stored product insects

Authors: Scheff, Deanna; Mueller, Codi; Markley, Alexus; Morrison Iii, William

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2025
Publication Date: 12/2/2025
Citation: Scheff, D.S., Mueller, C.E., Markley, A.L., Morrison Iii, W.R. 2025. Insecticidal effect of deltamethrin, pyrethin, and spinosad on metal and concrete surfaces on six species of stored product insects. Journal of Stored Products Research. Volume 116, March 2026, 102902. https://doi.org/10.1016/j.jspr.2025.102902.
DOI: https://doi.org/10.1016/j.jspr.2025.102902

Interpretive Summary: Food and feed manufacturing facilities and storage environments present distinctive challenges for insecticide-based management of stored product insects because insecticide efficacies can vary when applied to different surfaces, such as concrete or metal. These challenges are exacerbated in organic facilities that can only use certain types of certified organic products to control insect populations. Our research group compared the efficacies of a conventional, natural, and organic insecticide formulations applied to concrete and metal surfaces as contact insecticides on adult mortality of six different insect species, the red flour beetle, confused flour beetle, lesser grain borer, maize weevil, rusty grain beetle, and sawtoothed grain beetle. The conventional and natural insecticide were the most effective on a porous concrete surface compared to the organic insecticide for most species. However, the organic insecticide was the most effective on metal surfaces. Among all our species tested, the red and confused flour beetles were the most resistant species to all three insecticides. Overall results of this study demonstrate that natural and organic formulations can successfully be applied as broad-spectrum insecticides, but it is important to understand the impacts of surfaces on the performance of each insecticide formulation in order to a apply a successful targeted application.

Technical Abstract: Contact insecticides are one of the most utilized control and prevention methods for managing stored product insects because they are highly effective in a variety of environments and storage areas and can be applied as a pre-bin treatment, to cracks/crevices, floors, and walls of processing and storage facilities. However, the efficacy of organic or natural insecticides across multiples surfaces is limited. The objective of this study was to evaluate a deltamethrin, pyrethrin (low and high rates), and spinosad insecticide formulations applied to metal and concrete surfaces to control adults of six species of stored product insects. Metal and concrete arenas were treated with an insecticide, and ten adults of one species, Tribolium castaneum (Herbst), Rhyzopertha dominica (F.), Cryptolestes ferrugineus (Stephens), Tribolium confusum Jacquelin du Val, Sitophilus zeamais Motschulsky, or Oryzaephilus surinamensis (L.), were added to treated arenas and evaluated for survival at 1, 3, or 7 days after exposure. Insect survival was significantly lower on metal (nonabsorbent) surfaces compared to concrete (absorbent). Among all species, insect survival was <5% on metal surfaces treated at the high label rate of pyrethrin. Tribolium castaneum and T. confusum were the two most tolerant species. Tribolium spp. survival ranged from 40 – 100% on metal and concrete arenas treated with deltamethrin and spinosad. Results of this study provide information on the broad-spectrum efficacy of three formulations of contact insecticides on different surfaces, enabling pest management professional information to apply a targeted application treatment for specific species and facility designs to control stored product insects.