Defoliation of plants caused by severe leafspot infection. Note that defoliation progresses upward from the lower canopy. Stem lesion resulting from infection by the early leafspot fungus. The fungi that cause early and late leafspots reproduce and infect by means of microscopic spores called conidia. Both fungi are capable of producing tremendous numbers of spores on infected plant parts.
Spore production is favored by high humidity.
Primary inoculum that causes the initial leafspot infections during the growing season are spores produced on infested peanut residue in the soil. Visible spots develop 10 to 14 days after infection. New spores are produced in spots on infected leaves. These spores will subsequently infect plants and produce secondary infections. Spores are spread by wind, splashing rain, and insects.