Sterol-Inhibiting Fungicides for Control of Sugar Beet Powdery Mildew, Methods and Rates of Application and Evidence of Growth Regulation. F. J. Hills, Department of Agronomy, University of California, Davis 95616. G. A. Nikolich, Department of Agronomy, and L. D. Leach, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 69:257-261. Accepted for publication 17 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-257.

Trials were conducted to evaluate various rates and methods of applying three sterol-inhibiting fungicides: triadimefon, nuarimol, and propiconazol. Crown sprays, and especially crown-applied granules, generally provided superior season-long control compared with broadcast applications. Rate of application of crown-applied materials was related negatively to disease severity, with 0.56 kg a.i./ha providing consistently effective long-term disease suppression. Results suggest that a slow-release granular formulation applied to crowns may improve the duration of disease control. Triadimefon or nuarimol granules applied at 1.12 kg a.i./ha gave significantly higher yields than did biweekly sulfur treatments even though disease levels were comparable. This indicates that these fungicides may have a growth-promoting effect.

Keyword(s): Erysiphe betae, E. polygoni.