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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Stored Product Insect and Engineering Research » Research » Publications at this Location » Publication #430702
Research Project: Next-Generation Approaches for Monitoring and Management of Stored Product Insects

Location: Stored Product Insect and Engineering Research

Title: Assessing organic chemical management options for control of Sitophilus zeamais and Prostephanus truncatus at food facilities

Author
item QUELLHORST, HANNAH - Kansas State University
item ABSHIRE, JENNIFER - Kansas State University
item HETHERINGTON, MATTHEW - Kansas State University
item ATHANASSIOU, CHRISTOS - Kansas State University
item SIMPSON, KEALANI - Kansas State University
item COLLINS, RHIAN - Kansas State University
item Scheff, Deanna
item ZHU, KUN YAN - Kansas State University
item Morrison Iii, William

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2026
Publication Date: 6/17/2026
Citation: Quellhorst, H.E., Abshire, J., Hetherington, M.C., Athanassiou, C.G., Simpson, K., Collins, R., Scheff, D.S., Zhu, K., Morrison III, W.R. 2026. Assessing organic chemical management options for control of Sitophilus zeamais and Prostephanus truncatus at food facilities. Journal of Economic Entomology. https://doi.org/10.1093/jee/toag159.
DOI: https://doi.org/10.1093/jee/toag159

Interpretive Summary: Demand for organically certified insect-control practices in the post-harvest supply chain continues to grow, yet the performance of organic chemical methods for managing stored-product insects in bulk grain remains understudied. This study evaluated adult mortality and mobility of larger grain borer and maize weevil following exposure to several grain protectants approved by the Organic Materials Review Institutes that were applied to stored corn: two pyrethrin formulations (one at the label rate and one at three times the label rate), a novel 5% pyrethrin formulation, and a spinosad product. Efficacy was assessed both immediately after treatment and after a 7-month aging period in a grain bin to determine how quickly protection declines during storage. These products were compared with a conventional insecticide (deltamethrin) and a water control. Spinosad and deltamethrin caused similarly high adult mortality in both species, whereas the pyrethrin formulations produced low mortality. However, all organic and conventional treatments significantly reduced offspring production in both species and reduced maize weevil mobility, limiting its ability to colonize and feed. Overall, the findings indicate that all three organic protectants can suppress populations of maize weevil and larger grain borer, offering viable pest-management options for organic stored grain.

Technical Abstract: There has been an increasing demand for organically certified practices throughout the post-harvest supply chain. Yet, evaluating mortality and sublethal effects from organic chemical control options have received less attention. Thus, the aims of this study were to evaluate the direct mortality and changes in mobility of larger grain borer, Prostephanus truncatus (Horn) and maize weevil, Sitophilus zeamais (Motschulsky) after 1) initial treatment of maize by a suite of organically-approved grain protectants (pyrethrins at the labeled or 3-times higher rate; a separate formulation of 5% pyrethrins; or 8.66% spinosad at the labeled rate) compared to a conventional insecticide (4.75% deltamethrin) and water-treated negative control or 2) after residues have been aged by 7-months in a grain bin environment. Adults were exposed to exposed to residues on grains continuously for 24 or 168 h. There were 79-94-fold and 5.8-5.9-fold more dead S. zeamais and P. truncatus, respectively, after exposure to maize treated with spinosad and deltamethrin compared to H2O-treated controls. By contrast, there were only 2.5–7.7-fold and 2% more dead S. zeamais and P. truncatus after exposure to the pyrethrin-treated maize. Exposure to maize treated with pyrethrins, spinosad, or deltamethrin reduced progeny production by S. zeamais and P. truncatus by 27–62, 98–100, and 93–100%, respectively, compared to H2O-treated grain. We found consistent sublethal reductions in movement by both organic and conventional insecticides in this study for S. zeamais. Overall, our work helps raise the profile of the importance of assessing available organic options for management of insects after harvest.