Stenocarpella macrospora (=Diplodia macrospora) and S. maydis (=D. maydis) Compared as Pathogens of Corn. Frances M. Latterell, Research Plant Pathologist, USDA, ARS, Plant Disease Research Laboratory, Frederick, MD 21701. Albert E. Rossi, Biologist, USDA, ARS, Plant Disease Research Laboratory, Frederick, MD 21701. Plant Dis. 67:725-729. Accepted for publication 10 December 1982. 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-67-725.

Stenocarpella macrospora, long known as a minor pathogen of corn (Zea mays) in the southern United States, traditionally has been considered a weaker pathogen in this country than the closely related and better known S. maydis. Recent studies in Latin America and Africa have indicated that S. macrospora can cause appreciable losses in yield, stored grain, and poultry fed on infected grain. Although S. maydis exhibits some competitive superiority with respect to metabolic and cultural characteristics, our tests showed that S. macrospora is actually more aggressive than S. maydis in attacking young stalks and ears. Whereas corn plants are susceptible to S. maydis only at very early stages (seedlings before the primary node develops) and at very late stages (stalks and ears several weeks after silking), S. macrospora can attack all corn tissues vigorously at all stages of growth. Our investigations indicate that the key to successful infection and disease development by S. macrospora is presence of inoculum under moderately humid conditions (mean RH = 50% day, 95% night) at typical U.S. Corn Belt temperatures. Implications of our findings are discussed with respect to the increasing production of corn in the United States under minimum tillage practices.