First Report of \u3ci\u3ePythium ultimum, P. irregulare, Rhizoctonia solani\u3c/i\u3e AG4, and \u3ci\u3eFusarium proliferatum\u3c/i\u3e from Arrowleaf Clover (\u3ci\u3eTrifolium vesiculosum\u3c/i\u3e): A Disease Complex

Abstract

Poor stand establishment, failure to recover after grazing, and premature plant death have reduced the utilization of arrowleaf clover (Trifolium vesiculosum Savi) as a forage crop in the southeastern United States in recent years. Clover plants collected from poor stands in east Texas pastures during the 1995 to 1996 and 1996 to 1997 seasons first exhibited root disease symptoms as young seedlings in the fall. Symptoms consisted of one or more of the following: tan discoloration of lateral roots and taproot; root pruning; and small, tan, sunken lesions on the taproot and crown. Many Rhizobium nodules were brown and dead. Toward spring, symptoms increased in severity. Root lesions became larger and darker, and internal crown discoloration was observed. Disease incidence reached 100% in both growing seasons. Premature death of plants also was observed, especially in pastures where plants had been grazed