VIEW ARTICLE

Ecology and Epidemiology

Copper-Induced Fungistasis of Microsclerotia of Verticillium albo-atrum and Its Influence On Infection of Cotton in the Field. L. J. Ashworth, Jr., Departments of Plant Pathology, University of California, Berkeley 94720 and Davis 95616; O. C. Huisman(2), R. G. Grogan(3), and D. M. Harper(4). (2)(3)(4)Departments of Plant Pathology, University of California, Berkeley 94720 and Davis 95616. Phytopathology 66:970-977. Accepted for publication 21 January 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-970.

We describe a fungistasis of microsclerotia of Verticillium albo-atrum (V. dahliae) in soils of the San Joaquin Valley of California, which was absent or of low intensity between summer, 1971 and fall, 1972. It developed after unusually early and heavy rainfall during the fall of 1972 and continued throughout 1973 and 1974. Results of tests reported here indicate that the effect principally was caused by Cu⁺⁺ in the soil base exchange system and that it can be relieved by treatment of sieved soil residues with NaOCl. Fungistasis appeared to reduce inoculum efficiency; in two growing seasons prior to its onset slopes of inoculum density-infection curves were about 0.7, whereas they were about 0.4 in the two years following the onset of fungistasis.