VIEW ARTICLE

Disease Control and Pest Management

Comparison of Fungicide Application Methods for Systemic Control of Sugar Beet Powdery Mildew. C. A. Frate, Research assistant, Department of Plant Pathology, and extension agronomist, University of California, Davis 95616; L. D. Leach(2), and F. J. Hills(3). (2)Professor emeritus, respectively, Department of Plant Pathology, and extension agronomist, University of California, Davis 95616. Phytopathology 69:1190-1194. Accepted for publication 14 May 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1190.

Several methods of applying four systemic fungicides to control sugar beet powdery mildew were tested in the greenhouse and field over a 5-yr period. When applied as seed treatments, benomyl, ethirimol, and triadimefon had no effect on yield or disease levels under field conditions. However, when used as a preplant soil treatment, triadimefon at 1.12 kg/ha reduced disease levels and resulted in yields comparable to sulfur-sprayed controls. When applied as foliar sprays (0.28 kg/ha) twice during the growing season, nuarimol and triadimefon provided disease control comparable to that of two sulfur applications, each at 44.8 kg/ha. All foliar sprays protected leaves for approximately 4–6 wk and required repeated applications for effective control. When applied directly to the crowns of 8-wk-old sugar beets, low-concentration (5%) granules of nuarimol (0.56 and 1.12 kg/ha) or triadimefon (0.56, 1.12, and 2.24 kg/ha) resulted in low levels of disease throughout the season and in yields as high as or, in some trials, significantly higher than the sulfur sprays tested.