Efficacy of Sulfur for Controlling Rhizoctonia Root Rot in Sugar Beet. E. G. Ruppel, Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Crops Research Laboratory, Colorado State University, Fort Collins 80523. R. J. Hecker, Research Geneticist, Agricultural Research Service, U.S. Department of Agriculture, Crops Research Laboratory, Colorado State University, Fort Collins 80523. Plant Dis. 67:156-158. Accepted for publication 26 June 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-156.

Soil application of wettable sulfur and two flowable sulfurs was tested in the greenhouse for the control of seedling damping-off of sugar beet caused by Rhizoctonia solani. Wettable sulfur did not control the disease. The flowables increased seedling survival over that of the control, but only in unautoclaved soil, which indicated that the effect of sulfur may have been on some other biotic system with indirect effects on the pathogen. Another biotic system was not identified; however, a biocontrol mechanism involving antagonism by Trichoderma spp. seemed unlikely. In a 1980 field test of the two flowables, preplant broadcast incorporated applications of both significantly reduced root rot intensity over untreated controls. In 1981, no control was obtained with one flowable at three rates and two methods of application. If the action of sulfur is on some other biotic system as greenhouse tests indicated, conditions were not conducive for such a system to be operative in the 1981 field test.

Keyword(s): Beta vulgaris.