The first part of this paper deals with investigations at the Phytopathological Laboratory, Wageningen, into the control of Alternaria spp. (mainly A . raphani) on radish seed by chemicals. Organic mercury compounds proved better than thiram products and were more effective wet than as dusts, ceresan and germisan wet treatments being the best (99 % control) and, as 1 % for 4 to 8 min., not phytotoxic.The fungus was able to penetrate to the interior of the seed and may thus prevent germination. The fungicidal effect of ceresan increased when seed was stored up to 32 days after treatment, but the phytotoxic effects were also greater.Of the antibiotics tested, some had no effect, and actidione, though giving control, proved too phytotoxic. Rimocidin at 200, 400 or 800 p.p.m. for 16, 8, and 4 h respectively, was more effective; at 400 p.p.m. for 30 h it eliminated deep-seated infection without injury to the seed and in this was superior to ceresan.The second part deals with the relative value of thiram and mercurials as seed protectants against unspecified soil fungi. In cold tests with maize seed (germination in unsterilized field soil at low temperature) arasan SF-X at 0.2 to 0.3 % was the most effective of the thiram products and was less phytotoxic and more persistent than ceresan-new.
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