VIEW ARTICLE

Ecology and Epidemiology of Rhizoctonia solani in Field Soil. G. C. Papavizas, Soilborne Diseases Laboratory, Agricultural Research Service, U. S. Department of Agriculture, Beltsville, Maryland 20705; P. B. Adams(2), R. D. Lumsden(3), J. A. Lewis(4), R. L. Dow(5), W. A. Ayers(6), and J. G. Kantzes(7). (2)(3)(4)(5)(6)(7)Department of Botany and Plant Pathology, University of Maryland, College Park, Maryland 20742. Phytopathology 65:871-877. Accepted for publication 11 March 1975. DOI: 10.1094/Phyto-65-871.

The ecology of Rhizoctonia solani was studied for more than 2 years in a field plot at the University of Maryland Vegetable Research Farm, Salisbury, Maryland. The highest inoculum density of R. solani (expressed as percentage of colonization of tablebeet seed supplied as bait) was in August and September, after the bean tissue of the first crop had been plowed under, and the lowest from February to June. Bean root rot was more pronounced in the second planting than in the first. The percentage of colonization was positively correlated with bean root rot in the field and greenhouse (r = .9858). Colonization also was positively correlated with total inorganic N and NH₄-N, but not with NO₃-N. Inoculum in the field was confined to the upper 10 cm of soil. From a total of 500 isolations made from the plot, 13 morphologically distinct isolates were obtained from soil and two from plant debris. Eleven of the 13 isolates from soil and both isolates from debris belonged to AG-4 ('Praticola'-type). Two isolates from soil belonged to AG-3. The isolates ranged from nonpathogenic to highly pathogenic on bean, cotton, lettuce, radish, and sugarbeet. Isolates R-27 and R-29 from the plot survived better in soil at 10, 15, and 20 C than at –5, 5, 25, and 30 C.