Treatments to control Phoma and Alternaria infections of brassica seeds

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Abstract
The screening of chemicals using agar plate tests for activity against cultures of Phoma lingam, Alternaria brassicicola and A. brassicae is described. Most fungicides which were inhibitory to growth at 20 μg/ml or less showed eradicant activity when used as seed treatments. Selected on this basis, thiabendazole, applied as a slurry at 2–5 g a.i./kg seed, showed excellent eradicant activity against seed‐borne Phoma but not Alternaria when tested under laboratory, glasshouse and field conditions. Triarimol, tridemorph and azepine‐A2151, nuarimol, fenarimol and imaza‐lil although effective in agar plate tests against Alternaria and Phoma were phytotoxic when applied to seeds at rates sufficient to eliminate these fungi, Iprodione and fenpropimorph inhi bited the growth of the fungi at concentrations of 0.625 to 4 μg/ml and subsequent treatment of infected seeds at 1.25–2.5 g a.i. fungicide/kg seed with these fungicides proved effective against all three pathogens. Neither chemical adversely affected germination or emergence.