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Disease Control and Pest Management

Verticillium Wilt of the Pistachio Nut Tree: Occurrence in California and Control by Soil Fumigation. L. J. Ashworth, Jr., Plant Pathologist, Department of Plant Pathology, University of California, Berkeley, CA 94720; G. Zimmerman, Agricultural Consultant, 600 Lansing Drive, Bakersfield, CA 93309. Phytopathology 66:1449-1451. Accepted for publication 22 April 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1449.

Virgin soils of the San Joaquin Valley of California are infested lightly with Verticillium albo-atrum but are suitable without fumigation for production of pistachio trees. However, 1-3 years of cotton production preceding planting of pistachio trees can result in sufficient fungal inoculum buildup to cause significant losses of trees. Fumigation for control of V. albo-atrum with mixtures of chloropicrin-methyl bromide (2:1, w/w) reduced inoculum densities and numbers of trees killed after 2 years to levels comparable to those of virgin soils. In addition, root distribution patterns influenced by the drip-type irrigation system used may contribute to favorable results by forcing root development below the generally infested soil during part of each year.

Additional keywords: Verticillium dahliae, inoculum density and disease, V. albo-atrum in virgin soils.