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Reduced Number of Microsclerotia Formed by Verticillium dahliae in Cotton Tissue Exposed to Systemic Benzimidazole Fungicides and Desiccation. D. C. Erwin, Professor, Department of Plant Pathology, University of California, Riverside, CA 92521; S. D. Tsai(2), and R. A. Khan(3). (2)(3)Postdoctoral Research Associate, and Staff Research Associate, respectively, Department of Plant Pathology, University of California, Riverside, CA 92521. Phytopathology 68:1488-1494. Accepted for publication 8 May 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1488.

Application of benomyl, carbendazole, thiophanate M, or folcidin to cotton plant tissue, infected with Verticillium dahliae, suppressed microsclerotia production markedly in leaf tissue and to a lesser extent in petiole or stem tissue. Addition of a paraffinic oil increased the effectiveness of the fungicides in some experiments. Drying infected leaves of cotton reduced the number of propagules of V. dahliae from 6.81 × 104/g in nondried (81.8% moisture) plant tissue to 1.66 × 104/g in dried tissue (9.5% moisture). Application of 2,500 μg/ml benomyl or folcidin to infected leaves, stems, and petioles for different periods of drying prior to incubation in moist soil, reduced the number of microsclerotia markedly in leaves treated for 0.01 and 1 hr. Microsclerotia were suppressed in petioles and stems only after treatment for 3 to 5 hr. The degree of reduction of microsclerotia in the plant tissue was greatest when benomyl was applied to infected leaves, petioles, and stems followed by different periods of drying before incubation in moist soil. Application of benomyl and methyl 2-benzimidazolecarbamate·HCl with oil on infected plants in the field suppressed 70% of the microsclerotia production in leaves.

Additional keywords: inoculum density, adjuvant.