D3356: Fumigation effects of methyl benzoate, ethyl benzoate, and vinyl benzoate on stored grain insects

Phosphine, widely used as a fumigant in grain storage, currently faces resistance issues, necessitating the search for alternative fumigants. Methyl benzoate (MBe), a volatile organic compound, has shown effectiveness against various insects and is considered a food-safe natural product according to recent studies. This study selected two types of stored product pest insects, Rhyzopertha dominica and Sitophilus oryzae, to evaluate the fumigation toxicity of three benzoate compounds [methyl benzoate (MBe), ethyl benzoate (EB), and vinyl benzoate (VB)] against PH₃-susceptible and PH₃-resistant strains. The PH3-susceptible and PH₃-resistant strains were exposed to different concentrations (0 ~ 20 µL/1.5 L) of the benzoate compounds for 24 hours. Additionally, experiments were conducted with and without the presence of grain. There were no significant differences in insecticidal efficacy due to resistance. Among the three benzoate compounds, MBe showed the highest insecticidal effect, followed by VB and EB against stored product insects. Notably, the mortality rate differed by 10 to 17 times depending on the presence or absence of grain. Overall, MBe is effective in controlling PH₃-resistant strains of R. dominica and S. oryzae and can be used for PH₃-resistance management. Thus, MBe might be a suitable option for food security programs as an environmentally benign alternative fumigant.