Verticillium wilt, caused by Verticillium albo-atrum, is a major pathogen of cotton and several other California crops. The pathogen is a soilborne fungus, attacking its host through the root system. It survives long host-free periods in naturally infested soil as micro-sclerotia, which are formed in infested host tissue. Incorporation of this host tissue into the soil and its subsequent decomposition are responsible for the inoculum levels of this fungus in the soil.

This research was supported in part by California Planting Cotton Seed Distributors; California Processing Advisory Board; and Cotton, Incorporated.