Effect of Root Diseases and Nematodes on Yield of Corn in an Irrigated Multiple-Cropping System with Pest Management. Donald R. Sumner, Department of Plant Pathology, Coastal Plain Experiment Station, Tifton, GA 31793. C. C. Dowler, Agronomist (USDA, ARS), A. W. Johnson, Nematologist (USDA, ARS), R. B. Chalfant, Department of Entomology, N. C. Glaze, Plant Physiologist (USDA, ARS), and S. C. Phatak, Department of Horticulture, Coastal Plain Experiment Station, Tifton, GA 31793; and J. E. Epperson, Department of Agricultural Economics, Georgia Station, University of Georgia, Experiment 30212. Plant Dis. 69:382-387. Accepted for publication 14 November 1984. 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, 1985. DOI: 10.1094/PD-69-382.

Corn was planted each of 6 yr in an annual multiple-cropping system of turnip-corn-cowpea with four types of soil pest management. Treatments were 1) broadcast soil fumigation with 98% methyl bromide + 2% chloropicrin (MBR-CP) each fall or winter; 2) broadcast soil fumigation with 20% methyl isothiocyanate + 80% chlorinated C₃ hydrocarbons (DD-MENCS) each fall + maximum pest control with nonvolatile nematicides, herbicides, and insecticides; 3) nonvolatile nematicides, herbicides, and insecticides used for an intermediate level of pest control; and 4) one herbicide and cultivation used as needed on each crop for a minimum level of weed control. Root diseases of corn were caused primarily by Pythium aphanidermatum, P. arrhenomanes, Rhizoctonia solani AG-4, a sterile white basidiomycete, and Phoma terrestris. Soil fumigation reduced root disease severity significantly in 5 of 6 yr and increased grain yield an average of 7.5% (0.94 t / ha). Populations of Meloidogyne spp., Paratrichodorus minor, and Pythium spp. and root disease severity ratings were correlated negatively with yield.

Keyword(s): intensive cropping, Macroposthonia ornata, Zea mays.