Series/Report Number: COARC2014

Abstract: Verticillium wilt, caused by the fungus Verticillium dahliae, is the most important disease of commercial mint production in the Pacific Northwest. Green manure crops with biofumigant properties, specifically those which produce compounds such as allyl isothiocyanate (AITC), can suppress Verticillium wilt. The objective of this research was to determine the efficacy of different rates of the synthetic AITC to reduce V. dahliae inoculum and wilt symptoms in peppermint in the greenhouse. A greenhouse bioassay and a growth chamber soil tube assay were conducted to determine the efficacy of AITC treatment to reduce wilt symptoms and reduce inoculum in field soils. Although significant effects of AITC treatment on wilt symptoms were not observed, AITC treatments resulted in lower area under disease progress curve values in Black Mitcham peppermint compared to inoculated, non-treated controls. Verticillium dahliae was not recovered from any soils treated with AITC at 10, 20, 30, and 40 gal/acre, suggesting that AITC can reduce V. dahliae populations in field soils under laboratory conditions.