Susceptibility of weed species to Sclerotinia minor and Sclerotium rolfsii: Epidemiologic implications on peanut disease management

Abstract

Scope and Method of Study: The purpose of this study was to determine the susceptibility of a selected group of weeds common to Oklahoma and Texas peanut production areas to isolates of S. minor and S. rolfsii, to determine the effect of S. minor and S. rolfsii-diseased weeds on viable sclerotial density (of the blight pathogens) in soil, to determine disease incidence of peanut following infection of weed species at various weed densities, to evaluate the mode of penetration by S. minor of the weed species as compared with peanut, and to study the early reaction response of weed species and peanut to S. minor by monitoring Relative Water Content of leaves throughout disease progression.

Findings and Conclusions: Each weed species evaluated showed some degree of susceptibility to both pathogens. Five weed species were chosen to be evaluated in more depth and each was found to cause an increase in soilborne inoculum equal to or greater than the two peanut varieties alone. The same species were also found to be capable of causing an increase in disease incidence of the blight pathogens that was not significantly different from the increase in disease incidence caused by the two peanut cultivars. Evaluation of the mode of penetration by S. minor on the weed species indicated that the five weed species evaluated had similar responses to peanut when inoculated with S. minor as well as decreases in Leaf relative water content during infection by the pathogen. These data suggest that the weed species evaluated are capable of affecting the epidemiology of the blight pathogens when present in fields where disease is present and peanut production is conducted.