Developmental Predisposition of Maize to Anthracnose Stalk Rot. N. P. Keller, Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. G. C. Bergstrom, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Plant Dis. 72:977-980. Accepted for publication 26 June 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0977.

The influence of maize developmental stage at time of inoculation with Colletotrichum graminicola on the development of anthracnose stalk rot (ASR) was investigated in a 3-year field study. Maize hybrids were inoculated by stalk injection with conidia of C. graminicola at various plant growth stages from midwhorl to late kernel dent. Plants of each hybrid inoculated at whorl vegetative stages developed little stalk rot by physiological maturity, as evidenced by internal stalk discoloration. Cornell 281 and Pioneer 3901 plants (susceptible to ASR) inoculated at the late whorl stage showed increased susceptibility to the pathogen, but pronounced levels of ASR did not develop until plants had reached anthesis. Severe ASR developed in plants inoculated at all subsequent growth stages through physiological maturity. In hybrid RD6501 × A632 (moderately resistant to ASR), significant ASR developed only in plants inoculated after the kernel dough stage. Rating of hybrids for ASR prior to kernel dent reduces misinterpretation due to the development of other stalk rots.