Verticillium wilt - rotation crops

Abstract

Verticillium wilt continues to be a major disease problem for cotton production in Australia. Disease incidence is related to the soil population of Verticillium dahliae, so management strategies that can lower this population are required. Non-host rotation crops can be beneficial in aiding this reduction compared to continually planting susceptible hosts. A field trial located near North Star in northern NSW investigated the incidence of disease in cotton following a crop of sorghum, corn, cotton or fallow by monitoring flagged plants for external disease symptoms over time. A hot summer resulted in a lack of visible symptoms of Verticillium until a period of cooler, overcast wet weather and reduced temperatures occurred in mid-March. Expression of disease symptoms then became obvious very quickly. When assessed prior to harvest disease incidence was greatest where cotton was planted after cotton, compared to after fallow and lowest disease occurred where cotton followed either one crop of sorghum or corn. Both 2A and 1A strains of the pathogen were confirmed from the field. Additionally, soil plating and DNA quantification will provide further information on the effect different cropping rotations are having on soil populations of V. dahliae.