Metalaxyl and Fenamiphos Applied Through Irrigation Water to Control Black Shank/Root-Knot Complex on Tobacco. A. S. Csinos, Plant Pathologist, University of Georgia, Coastal Plain Experiment Station, Tifton 31793. A. W. Johnson, Supervisory Research Nematologist, USDA, ARS, Southern Region, Tifton, GA 31793; and A. M. Golden, Nematologist, Nematology Laboratory, Plant Protection Institute, USDA, ARS, NER, Beltsville, MD 20705. Plant Dis. 70:210-213. Accepted for publication 12 September 1985. 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, 1986. DOI: 10.1094/PD-70-210.

Tobacco (Nicotiana tabacum) was transplanted in 1983–1984 in a field site heavily infested with Phytophthora parasitica var. nicotianae (P. p. nicotianae) and Meloidogyne spp. (about 90% M. incognita race 1 and 10% M. javanica). NC 2326 (low resistance to P. p. nicotianae and no resistance to M. incognita), Coker 48 (moderate resistance to P. p. nicotianae and no resistance to M. incognita), NC 95 (low resistance to P. p. nicotianae and high resistance to M. incognita), and Speight G-28 (moderate resistance to P. p. nicotianae and high resistance to M. incognita were tested. Metalaxyl (2.24 kg a.i./ha), fenamiphos (6.7 kg a.i./ha), both chemicals applied together, and a nontreated control were the treatments. Chemicals were applied by two methods, with a tractor-powered sprayer-Rototiller and incorporated into the top 15-cm soil layer and via an experimental irrigation simulator with 2.5 mm of water. The black shank/root-knot complex was best managed where both chemicals were applied together. Resistance to M. incognita races 1 and 3 and P. p. nicotianae limited loss from P. p. nicotianae, but resistance to P. p. nicotianae did not prevent damage from Meloidogyne spp. Roots of cultivars without resistance to M. incognita contained a mixed population of nematodes (81–100% M. incognita and 0–19% M. javanica), and roots of cultivars with resistance to M. incognita contained 100% M. javanica. Cultivars resistant to M. incognita may selectively shift soil populations to other species of Meloidogyne from polyspecific communities. Application of metalaxyl + fenamiphos through irrigation water was equally effective and more economical than application with conventional tractor-powered equipment in reducing the black shank / root-knot complex.