Control of Verticillium dahliae by Metam-Sodium in Loessial Soil and Effect on Potato Tuber Yields. Y. Ben- Yephet, Division of Plant Pathology, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel. E. Siti, Extension Service, Israel Ministry of Agriculture, Beer Sheva, Israel, and Z. Frank, Division of Plant Pathology, Agricultural Research Organization, Volcani Center. Plant Dis. 67:1223-1225. Accepted for publication 9 May 1983. 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-67-1223.

Penetration of metam-sodium applied with irrigation water into loessial soil in the field was studied by measuring viability of Verticillium dahliae microsclerotia placed 2, 10, 20, 30, and 40 cm deep in the soil. Equal quantities of metam-sodium were applied as concentrated solution, dilute solution, or concentrated solution followed by dilute solution. The dilute application was inferior to both the concentrated and the combined ones. More chemical was required to kill microsclerotia by the combined than by the concentrated application. With the concentrated application, penetration of the chemical was maximal when the dose was dissolved in the first 5–10% of the irrigation water. Metam-sodium applied to commercial fields with each of the methods at a dose of 800 or 1,000 L/ha reduced disease incidence and significantly increased potato yields compared with controls irrigated with water only or with plots treated with 300 L/ha of metam-sodium. The highest increase in yield was obtained with concentrated application of 800 L/ha of metam-sodium; in two fields of the cultivar Desiree, yields were 7.5 and 10 t/ha over those of controls.