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Ecology and Control of Seedling Diseases of Crucifers. Donald R. Sumner, Assistant Professor, Department of Plant Pathology, University of Georgia, Coastal Plain Station, Tifton 31794; Phytopathology 64:692-697. Accepted for publication 3 December 1973. DOI: 10.1094/Phyto-64-692.

Seedling diseases of cabbage (Brassica oleracea var. capitata), collard (B. oleracea var. acephala), turnip (B. campestris Ssp. rapifera), and mustard (B. juncea and B. perviridis) were studied in growth chambers and in experimental fields. Night-day temp cycles of 10-21 and 21-32 C with a 12-h photoperiod were used in growth chambers. The fungi most commonly associated with roots and hypocotyls of seedlings from commercial fields were Fusarium oxysporum, Rhizoctonia solani, Pythium irregulare, F. solani, Phoma spp., and F. roseum, in that order. The most virulent pathogen was Rhizoctonia solani, regardless of temp. At low temp P. irregulare, and at high temp F. oxysporum, F. solani, and Sclerotium rolfsii, caused significant reductions in stands. Sclerotium bataticola was not pathogenic. Collard, turnip, and mustard were less severely damaged than cabbage at high temp in both infested and noninfested soils. Chloroneb completely controlled Rhizoctonia solani and increased plant stands in growth chambers, but not in field tests. Benomyl, thiabendazole, and p-(dimethylamino)benzenediazo sodium sulfonate reduced stands, and the latter two were phytotoxic to cabbage and turnip. All crucifers were more vigorous, less chlorotic and spindly, and had greater root growth at 10-21 than at 21-32 C.