The Effects of Fungicides on Eutypa lata Germination, Growth, and Infection of Grapevines. G. P. Munkvold, Department of Plant Pathology, University of California, Davis 95616. J. J. Marois, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 77:50-55. Accepted for publication 17 September 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0050.

The fungicides benomyl, fenarimol, flusilazole, iprodione, myclobutanil, triadimefon, and vinclozolin were evaluated for their efficacy in vitro against Eutypa lata. For inhibition of ascospore germination, flusilazole was most effective, with an EC₅₀ value of 0.06 μg a.i./ml. Fenarimol and myclobutanil were somewhat less effective, with EC₅₀ values near 1 μg/ml. Benomyl, iprodione, triadimefon, and vinclozolin did not effectively inhibit germination. Flusilazole was also the most effective fungicide for inhibition of mycelial growth. Benomyl, fenarimol, flusilazole, and myclobutanil had EC₅₀ values less than 1.0 μg/ml for mycelial growth, whereas iprodione, triadimefon, and vinclozolin had EC₅₀ values ranging from 1.49 to 6.27 μg/ml. Benomyl, fenarimol, flusilazole, myclobutanil, and triadimefon were tested in the field for their ability to prevent infection of artificially inoculated grapevine pruning wounds. In four field experiments, benomyl and flusilazole were consistently the most effective chemicals, reducing the percentage of infected wounds by over 90% in one experiment. When inoculations were performed 14 days after fungicide application, all fungicides were less effective than when inoculations were performed after 1 or 2 days, with the exception of flusilazole. Fenarimol, myclobutanil, and triadimefon were less effective when precipitation occurred immediately after fungicide application. A pneumatic sprayer-pruning shear was as effective as application of fungicides by paintbrush.

Keyword(s): deadarm, dieback.