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 determin e the causal pathogen(s) of red root rot (RRR) of corn. Corn hybrids D ekalb DK 522, DK 572, DK 677, and DK 582 were utilized. Phoma terrestr is, 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 i n the KRR 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 less than or equal to 0. 01) root rot, basal stalk mt, and wilt. F. acuminatum played a minor r ole in causing the disease, with little additional symptom development when combined with P. terrestris or Pythium irregulare.