VIEW ARTICLE

Ecology and Epidemiology

Influence of Crop Rotation on Survival of Verticillium albo-atrum in Soils. O. C. Huisman, Assistant Professor, Department of Plant Pathology, University of California, Berkeley 94720; L. J. Ashworth, Jr., Plant Pathologist, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 66:978-981. Accepted for publication 23 January 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-978.

Inoculum density of Verticillium albo-atrum was followed in soil of eight variously cropped commercial fields at about monthly intervals for 3.5-4.0 years. High inoculum densities (20-60 microsclerotia/g soil) persisted under continuous susceptible crop (cotton) culture in infested fields. The inoculum usually increased rapidly following 1 year of a susceptible crop, with a higher inoculum density often occurring the second year regardless of whether the subsequent crop was a nonsusceptible or a susceptible host. Once soils were infested, the rate of decrease in inoculum, even in the presence of immune crops, was very low, and seasonal decreases in inoculum in continuous susceptible crop culture were similar to seasonal decreases during immune crop culture. Immune-host culture has little influence on V. albo-atrum survival in soils and the pathogen’s rate of attrition is too low to make short-term rotations of value for wilt control.