VIEW ARTICLE

The Effect of Peanut Leafspot Fungicides on the Nontarget Pathogen, Sclerotium rolfsii. P. A. Backman, Assistant Professor, Department of Botany and Microbiology, Auburn University, Agricultural Experiment Station, Auburn, AL 36830; R. Rodriguez-Kabana(2), and J. C. Williams(3). (2)Associate Professor, Department of Botany and Microbiology, Auburn University, Agricultural Experiment Station, Auburn, AL 36830; (3)Associate Professor, Department of Research Data Analysis, Auburn University, Agricultural Experiment Station, Auburn, AL 36830. Phytopathology 65:773-776. Accepted for publication 19 February 1975. DOI: 10.1094/Phyto-65-773.

White mold damage (caused by Sclerotium rolfsii) was visually assessed in Florunner peanut plots sprayed with fungicides for control of Cercospora spp. during two growing seasons. Although the fungicides gave similar leafspot control, unsprayed plots had consistently lower levels of white mold; those sprayed with benomyl consistently had the highest, and other fungicides were intermediate. Regression analysis revealed that both S. rolfsii and Cercospora were causing yield loss, but that losses due to each were not related. In vitro tests indicated that the treatment responses could be attributed to a direct effect of the fungicides on S. rolfsii, or indirectly by affecting Trichoderma viride, a natural antagonist to S. rolfsii. Highest field levels of S. rolfsii were found for those fungicides with no toxicity to S. rolfsii, but which were toxic to T. viride. Leaf loss caused by high levels of Cercospora, or by mechanical removal of leaves, resulted in lowest levels of S. rolfsii.