Evaluation of Seed Treatments for Reducing Alternaria porri and Stemphylium vesicarium on Onion Seed. Theresa A. S. Aveling, Margaretha Mes Institute for Seed Research, University of Pretoria, Pretoria 0002. H. G. Snyman, and S. P. Naude. Margaretha Mes Institute for Seed Research, University of Pretoria, Pretoria 0002; and Vegetable and Ornamental Plant Institute, Private Bag X293, Pretoria 0001, Republic of South Africa. Plant Dis. 77:1009-1011. Accepted for publication 26 May 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1009.

During surveys in the Cape province of South Africa, Alternaria porri and Stemphylium vesicarium were found to be destructive seedborne pathogens of onion (Allium cepa L.). Six fungicides were evaluated for their efficacy in reducing pathogens both on seed and in culture. These fungicides included anilazine, benomyl, a carbendazim/flusilazole mixture, procymidone, tebuconazole, and thiram. An untreated control, hot water soak (50 C for 20 min), and a sodium hypochlorite treatment were also included for comparison. Treated seeds were rated for germination by the blotter method and by emergence and seedling growth in seedling trays in the glasshouse. None of the treatments eradicated A. porri and S. vesicarium from onion seeds. The hot water soak proved to be the best treatment for reducing these pathogens, although the percentages of germination and emergence of onion seeds were reduced compared to the control.