Efficacy of Metam-Sodium Applied Through Overhead Sprinkler Irrigation for Control of Soilborne Fungi and Root Diseases of Vegetables. Donald R. Sumner, Department of Plant Pathology, University of Georgia Coastal Plain Experiment Station, Tifton 31793-0748. Sharad C. Phatak, Department of Horticulture, University of Georgia Coastal Plain Experiment Station, Tifton 31793-0748. Plant Dis. 72:160-166. Accepted for publication 4 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0160.

Metam-sodium was more effective against Rhizoctonia solani AG-4 and Pythium spp. when applied through overhead sprinkler irrigation than when injected with chisels in a fall experiment and had equal efficacy in spring experiments. There was a linear increase in efficacy when metam-sodium was applied in 1.3 cm of water, and low dosages of 187 to 280 L/ha increased plant stand by an average of 149 and 212%, respectively, in fall crops of turnip, kale, mustard, collard, and spinach. In contrast, metam-sodium was less effective in controlling root diseases and increasing plant stands in spring crops of snap bean, okra, cucumber, tomato, and pepper, and 468 L/ha or more was required for effective disease control. Application of metam-sodium in 2.5 cm of water was more effective in controlling root diseases in deep-rooted vegetables such as okra than in 1.3 cm of water, and applications in 0.6 cm of water were ineffective. Increasing rates of metam-sodium caused a significant linear reduction in populations of R. solani AG-4 and AG-2 type 2, Pythium spp., Fusarium spp., and saprophytic fungi, and applications through irrigation water had greater or equal efficacy to injection with chisels.