CONTROL OF ALTERNARIA DISEASES OF BRASSICA SEED CROPS CAUSED BY ALTERNARIA-BRASSICAE AND ALTERNARIA-BRASSICICOLA WITH GROUND AND AERIAL FUNGICIDE APPLICATIONS

Three fungicides (iprodione, anilazine, chlorothalonil) were evaluated for their potential to control Alternaria diseases of brassica seed c rops in field trials. In 1978 and 1979, two applications of either ipr odione at 1.2 g a.i./l, anilazine at 3.6 g a.i./l or chlorothalonil at 1.4 g a.i./l, applied with a backpack sprayer to Brussels sprouts see d plants 5 and 3 or 4 and 2 weeks before swathing, significantly reduc ed severity of Alternaria diseases caused by Alternaria brassicae and A. brassicicola. Iprodione and anilazine significantly reduced inciden ce of Alternaria spp. on surface-sterilized seeds. In 1981 and 1982, i prodione was applied by air to cabbage seed fields. A schedule of thre e aerial applications of iprodione at 1. 12 kg a.i. with 1 17 ml Biofi lm spreader-sticker in ca. 90 liters of water/hectare, made at early-, mid- and late-pod stages, at 3 week intervals, was the most effective in controlling the diseases on plants and reducing incidence of the p athogens in seeds. Percentage seed germination was negatively correlat ed to the incidence of the Alternaria spp. in surface-sterilized seeds in 1978, 1981 and 1982 but not in 1979.