Methyl benzoate as a putative alternative, environmentally-friendly fumigant for the control of stored product insects

Authors: Morrison, William - Rob; LARSON, NICHOLAS - Towson University; Brabec, Daniel - Dan; Zhang, Aijun

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2019
Publication Date: 9/23/2019
Citation: Morrison III, W.R., Larson, N.R., Brabec, D.L., Zhang, A. 2019. Methyl benzoate as a putative alternative, environmentally-friendly fumigant for the control of stored product insects. Journal of Economic Entomology. 112(5):2458-2468. https://doi.org/10.1093/jee/toz179.
DOI: https://doi.org/10.1093/jee/toz179

Interpretive Summary: Stored product insects are a regular problem for food facilities. Historically, they have been managed using the fumigants, methyl bromide and phosphine. However, methyl bromide was phased out of use in the early 2000s, and there is growing worldwide insecticide resistance to phosphine. Concurrently, consumers are more conscious about where their food comes from, and are demanding low insecticide or green insecticide inputs throughout the supply chain. In order to preserve the efficacy of remaining tools and satisfy consumer demands, alternative, environmentally-friendly chemical control options are needed. One possible alternative, green fumigant is methyl benzoate, which has been designated a food safe compound by the FDA. In this study, we evaluated whether methyl benzoate could act as an effective tool against four stored product insect species, including red flour beetle, lesser grain borer, maize weevil, and warehouse beetle. We tested methyl benzoate with or without food as a refugia for 24 h or 72 h periods, and compared it to the efficacy of the commercial standard, phosphine. There was high mortality of red flour beetle and lesser grain borer, but maize weevil and warehouse beetle were relatively unaffected. In each case, the presence of food had a protective effect on the insects. By comparison, phosphine was much more effective at inducing mortality of each species. Future work should evaluate whether methyl benzoate could be an effective niche product for controlling phosphine-resistant strains of lesser grain borer and red flour beetle.

Technical Abstract: Insects are one of the most pervasive problems for food facilities. Historically, stored product insect pest management has been based around the use of methyl bromide and phosphine as fumigants. However, methyl bromide has been phased out of use, and there is increasing worldwide insecticide resistance to phosphine. As a result, alternative fumigant options are required to preserve the efficacy of remaining tools. One potential alternative, environmentally-friendly option is the use of methyl benzoate (MB), which is considered a food safe compound. In this study, we evaluated the direct and sublethal effects of MB exposure on the survivorship and mobility of 3-4 stored product species with diverse life histories, including Rhyzopertha dominica, Tribolium castaneum, Sitophilus zeamais, and Trogoderma variabile. Sets of insects were exposed to a control, low, or high MB concentration in flasks with or without food for 24 or 72 h in the laboratory. Further, we compared MB to phosphine exposure under similar conditions. Overall, R. dominica was the most susceptible to MB exposure, followed by T. castaneum. By contrast, S. zeamais and T. variabile were relatively unaffected by MB exposure. Exposure to MB induced multiple-fold decreases in the total distance moved and velocity of adults still considered alive or affected after assays. By comparison, phosphine effectively killed all individuals of all species. Our data suggests that while MB is not competitive with phosphine in controlling susceptible strains of these species, future work should address whether it could act as a niche product to control phosphine-resistant strains.