Association of Phoma terrestris, Pythium irregulare, and Fusarium acuminatum in Causing Red Root Rot of Corn

Greenhouse and field tests were conducted in 1992 and 1993 to determine the causal pathogen(s) of red root rot (RRR) of corn. Corn hybrids Dekalb DK 522, DK 572, DK 677, and DK 582 were utilized. Phoma terrestris, Pythium irregulare, and Fusarium acuminatum were used alone or in combination to infest potting mix in greenhouse tests or soil in field tests. Results indicated that P. terrestris is the primary pathogen in the RRR complex of corn in Delaware. When P. terrestris and Pythium irregulare were associated, the disease progressed faster and was more severe, resulting in significantly higher (P ≤ 0.01) root rot, basal stalk rot, and wilt. F. acuminatum played a minor role in causing the disease, with little additional symptom development when combined with P. terrestris or Pythium irregulare.