The damage caused by corn (Zea mays) stalk rot, the incidence of infected stems and the species of fungus associated to them were determined in a sampling carried out in 29 commercial or seed producing corn fields, located in the regions of Planalto Médio (RS) and in Campos Gerais do Paraná (PR) during the summer growing seasons of 1997/98 and 1998/99. Damage in the 1997/98 season ranged from 213 to 3,089 with an average of 678 kg.ha-1 in the 1998/99 season it ranged from 358 to 3,086 with a mean of 1,151 kg.ha-1. The incidence of infected stalks in the first season ranged from 11.2 to 71.4 with an average of 40.9 and in the second season from 21.9 to 79.3 with an average of 45.9%. A negative correlation was not found between damage and incidence of diseased stalks probably due to a great diversity of field management regarding factors such as corn genotype, husbandry, drilling system, soil fertility, fertilization and environmental conditions. The fungus specie with the highest incidence in the first season was Colletotrichum graminicola and, in the second, Fusarium graminearum.Additional fungal species found were Diplodia maydis, D. macrospora, F. moniliforme and F. subglutinans.
