New biofumigation-based approaches to sustainable control of soil-borne pathogens

Control of soilborne pathogens such as Verticillium wilt has become a major problem in UK horticulture since withdrawal of the broad-spectrum chemical fumigant methyl bromide. A previous project involving the RTO's investigated biofumigant green crops as replacements for methyl bromide. Cultivation and incorporation of biofumigant crops proved difficult, but a brassica seed meal soil amendment and lavender byproducts were highly effective against Verticillium wilt in strawberry. Various isothiocyanates in the former and monoterpenoid compounds in the latter were identified as the active chemicals. This project will exploit this knowledge to develop novel biofumigant products for control of soilborne diseases, particularly Verticillium wilt in strawberry, but with potential application to a much wider range of crops including raspberry, potato and cotton. Firstly, microencapsulation technology will be adapted to develop a slow-release formulation of the biocidal terpenoid compounds in lavender and delivery systems appropriate for use by growers. Secondly, the possibility of producing a novel, pelletised formulation of lavender waste will be investigated as an alternative for organic growers. These and the brassica seed meal product will be evaluated in the laboratory and in several field sites for their efficacy against Verticillium wilt in strawberry, alone and in combination. Their effects on other soil-borne pathogens and non-target organisms will also be determined. The project will provide optimised strategies for using these new products in practice under different levels of pathogen inoculum and various soil moisture conditions.