Disease Note.

First Report of Rhizoctonia solani AG-4 on Canola in Georgia. R. E. Baird, Plant Pathology Department, University of Georgia, RDC, P.O. Box 1209, Tifton 31793. Plant Dis. 80:104. Accepted for publication 6 November 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0104C.

Canola (Brassica napus L.) seedlings have previously been reported to be killed by Rhizoctonia solani Kuhn in Georgia (1). This fungus has been found throughout the state causing patchy stands in fields with cool and wet soils. However, the anastomosis group(s) of this pathogen responsible for seedling blight was not determined. Rhizoctonia solani AG 2-1 and AG-4 have been reported to cause seedling blight on canola in western Canada (2). In January 1995, canola seedlings in a field located near Arlington, GA, were dying. Brown, discolored lesions were present on the lower base of the stems and portions of the roots. Ten cultures of R. solani AG-4 were isolated from 10 lesions. Identification was confirmed using anastomosis pairing with tester isolates. Three AG-4 isolates (Can 1,2,3) were tested in the greenhouse (17 to 28°C) for pathogenicity by mixing 50 ml of 2-weck-old cornmeal sand inoculum (3 g of corn-meal, 100 g of sand, and 20 ml of distilled water) into six pots per isolate containing 2.0 liters of sterile soil per pot (20 x 100 cm). Six pots containing noninfested soil were evaluated for comparison. Six nonfungi-cide-trcaled canola seeds (cv. Bingo) were sown into each pot. For all three isolates, plant stands averaged three plants per pot, compared with five or six plants in the noninfested pots. When the roots were evaluated for disease severity, brown, discolored lesions were observed at the base of the stem and roots in the infested pots for all three isolates. The three cultures of the pathogens were reisolated from lesion tissue. The experiment was repeated with similiar results. This is the first report of AG-4 on canola in Georgia.