Bioactivity of brassica seed meals and its compounds as ecofriendly larvicides against mosquitoes

Authors: Weiler, Lina; Behle, Robert; Berhow, Mark; McCormick, Susan; Vaughn, Steven; Muturi, Ephantus; Hay, William

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2023
Publication Date: 3/9/2023
Citation: Flor-Weiler, L., Behle, R.W., Berhow, M.A., McCormick, S.P., Vaughn, S.F., Muturi, E.J., Hay, W.T. 2023. Bioactivity of brassica seed meals and its compounds as ecofriendly larvicides against mosquitoes. Scientific Reports. 13. Article 3936. https://doi.org/10.1038/s41598-023-30563-6.
DOI: https://doi.org/10.1038/s41598-023-30563-6

Interpretive Summary: The geographic spread of Aedes aegypti coupled with their vectoring of human and animal diseases and rapidly increasing resistance to synthetic insecticides has created a need for ecofriendly tools to control mosquitoes. Mustard seed meals are byproducts of processing for botanical oils and spices. When mixed in soil, these seed meals can act as biofumigants to suppress weed growth, control soil borne plant pathogens and kill insect pests. We added four defatted mustard seed meals and two of their major chemical constituents to water and found these treatments to be toxic to mosquito larvae. Creating mosquito control products from mustard seed meals will add value to these seed crops while providing cheap and practical ecofriendly control of human and livestock disease vectors.

Technical Abstract: Strategic, sustainable, and ecofriendly alternatives to chemical pesticides are needed to effectively control mosquitoes and reduce the incidence of their vectored diseases. We evaluated several Brassicaceae (mustard family) seed meals as sources of plant derived isothiocyanates produced from the enzymatic hydrolysis of biologically inactive glucosinolates for the control of Aedes aegypti (L., 1762). Five defatted seed meals (Brassica juncea (L) Czern., 1859, Lepidium sativum L., 1753, Sinapis alba L., 1753, Thlaspi arvense L., 1753, and Thlaspi arvense—heat inactivated and three major chemical products of enzymatic degradation (allyl isothiocyanate, benzyl isothiocyanate and 4-hydroxybenzyl isothiocyanate) were assayed to determine toxicity (LC50) to Ae. aegypti larvae. All seed meals except the heat inactivated T. arvense were toxic to mosquito larvae. L. sativum seed meal was the most toxic treatment to larvae (LC50'='0.04 g/120 mL dH2O) at the 24-h exposure. At the 72-h evaluation, the LC50 values for B. juncea, S. alba and T. arvense seed meals were 0.05, 0.08 and 0.1 g/120 mL dH2O, respectively. Synthetic benzyl isothiocyanate was more toxic to larvae 24-h post treatment (LC50'='5.29 ppm) compared with allyl isothiocyanate (LC50'='19.35 ppm) and 4-hydroxybenzyl isothiocyanate (LC50'='55.41 ppm). These results were consistent with the higher performance of the benzyl isothiocyanate producing L. sativum seed meal. Isothiocyanates produced from seed meals were more effective than the pure chemical compounds, based on calculated LC50 rates. Using seed meal may provide an effective method of delivery for mosquito control. This is the first report evaluating the efficacy of five Brassicaceae seed meals and their major chemical constituent against mosquito larvae and demonstrates how natural compounds from Brassicaceae seed meals can serve as a promising ecofriendly larvicides to control mosquitoes.