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Title: Natural and synthetic isothiocyanates for pest control in soil

Author
item ASHWORTH, DANIEL - University Of California
item Yates, Scott
item Wang, Dong
item LUO, LIFANG - University Of California

Submitted to: ACS Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 8/8/2014
Publication Date: 10/23/2014
Citation: Ashworth, D., Yates, S.R., Wang, D., Luo, L. 2014. Natural and synthetic isothiocyanates for pest control in soil. In: Coats, et al., editors. Biopesticides: State of the Art and Future Opportunities. Washington, D.C.: ACS Symposium Series. p. 159-177.

Interpretive Summary: Synthetic and natural isothiocyanates are volatile chemicals that have biocidal properties and can be used to control a wide range of soil organisms including nematodes, bacteria and fungi prior to plant production. Chemical companies have produced synthetic methyl isothiocyanate for many years as one of the active ingredients in pre-plant soil fumigants. Due to similarities in chemistry between synthetic and naturally produced isothiocyanate, there is increasing interest in the use of natural products as a biofumigation agent for pre-plant pest control in soils. Naturally produced isothiocyanate comes from certain plant materials like Brassica species. These plants can be used for biofumigation as rotation crops, or intercrops, by incorporating fresh, chopped plant material as green manure, or by incorporating processed plant products such as seed meal or dried plant material. Gas phase diffusion of synthetic and natural isothiocyanates via the soil pore space affords a degree of pest control within the root zone of agricultural soils prior to the planting of a crop. This paper provides a brief review of the use of natural isothiocyanate as a biofumigant and highlights some of the problems and limitations of this approach to pest control. The use of synthetic isothiocyanages is also described and details some of the environmental problems that result from its use for pest control. This research would be of interest to scientists, regulators, cooperative extension personnel and grower groups.

Technical Abstract: Synthetic fumigants are widely used in agriculture to provide highly efficacious pre-plant pest control for high cash crops. However, stringent regulations aimed at controlling soil to air emissions govern fumigant use. This has led to increased interest in biofumigation using Brassica species which release volatile isothiocyanate (ITC) chemicals into the soil. These ITCs have a similar chemistry to the synthetic fumigant methyl isothiocyanate (MITC) and are therefore of interest in pest control. However, there are significant disadvantages to natural ITCs when compared to MITC; most notably, a relatively low release efficiency into the soil, and rapid degradation/sorption within the soil. The inconsistent pest control efficacy of biofumigation indicates a lack of robustness and suggests that non-organic growers may be reluctant to switch from traditional fumigants. MITC, despite being subject to regulations, offers efficacious pest control and its emissions to the atmosphere can be significantly reduced using plastic tarps or water sealing. Compared to other soil fumigants, MITC exhibits relatively low soil diffusion. Although this lower diffusion is advantageous in terms of limiting atmospheric emissions, it needs to be considered in relation to pest control, for example in the positioning of drip lines, emitters, or shank spacing, during application.