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Disease Note.

First Report of Rhizoctonia solani AG-7 in Indiana. R. E. Baird, Plant Pathology Department,University of Georgia, RDC, Tifton 31793.. D. E. Carling, Department of Plant Pathology, University of Alaska Fairbanks, Palmer 99645. Plant Dis. 79:321. Accepted for publication 1 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0321A.

During the last 5 yr in southwestern Indiana, root systems of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) plants were often severely damaged by an unknown pathogen(s) causing a disease referred to as "sudden wilt." One of the fungi commonly isolated from the roots was Rhizoctonia solani Kuhn anastomosis group 7 (AG-7), which was also reported to occur in Japan (1) and Arkansas on crops such as cotton (Gossypium hirsutum L.), rice (Oiyza sativa L), and soybean (Glycine max (L.) Merr.) (2). Isolate #16 of R. solani AG-7, collected near Vincen-nes, IN, from a watermelon root, was tested in the greenhouse for pathogenicity by mixing 25 ml of 2-wk-old cornmeal sand inoculum (3 g corn-meal, 100 g sand, and 15 ml of distilled water) into 20 x100 cm pots containing 2.25 L of sterile soil per pot. Pols with uninfested soil were included as a control. Six seeds per pot of either cotton, watermelon, or soybeans were sown into each pot of uninfested and infested soil. A pot was a replicate and each treatment was replicated four times At 21 days after planting, stands of cotton and watermelon in (he infested soil averaged one to two plants per pot, whereas soybean stands averaged five to six plants per pot. Stands in the uninfested pots were five to six plants per pot. Lesions were observed on cotyledons, stems, or roots of plants from pots infested with R. solani AG-7. The pathogen could routinely be reisolated from infected tissue of all three crops. When the experiment was repeated, similar results were obtained. This is the first report of R. solani AG-7 from the midwestern United States.

Reference: (1) Y. Homma et al. Ann. Phytopathol. Soc. Jpn. 49:184, 1983. (2) C. S. Rothrock et al. Plant Dis. 77:1262, 1993.