Cob rots are a major cause of crop loss in areas such as western Kenya that experience-prolonged rainfall during the period of crop maturation. Cob rot fungi cause spoilage of the grain and some of them produce mycotoxins which can pose a health risk to humans and animals consuming foods prepared from contaminated grain. Surveys conducted in western Kenya in 1998 showed that cob rot incidence exceeded 20%. In the following year when rainfall was greater around the harvest period, cob rot fungi affected 68% of cobs. In 1998 stalk borer larvae (mainly Busseola fusca) damaged 12% of cobs and there was a strong correlation (R=0.87) between cob rot incidence and borer damage. In 1999 almost half of the cobs sampled showed evidence of borer damage. The results indicate that the high cob rot incidence in this part of western Kenya is due to stalk borer damage, which predisposes the cobs to fungal infection, and that management of the borer would greatly decrease cob rot incidence.