Fungicide seed treatments reduce seed transmission and severity of lupin anthracnose caused by Colletotrichum gloeosporioides

Abstract

Lupin production is a vital part of the farming system on coarse-textured soils throughout Western Australia. The continued viability of the lupin industry was threatened in 1996 by the outbreak of anthracnose caused by Colletotrichum gloeosporioides. The use of fungicides as seed dressings was investigated as a potential control for this disease. Twenty one fungicides were examined in vitro for their effect on growth of C. gloeosporioides: nine fungicides, including thiram and fluquinconazole, were identified with ED50 of less than 1.0 μg/mL. In a series of glasshouse experiments using artificial spray inoculation, and field experiments using rain-splashed infection from infected spreader plots, seed treatment with carbendazim or fluquinconazole provided lupin seedlings with systemic protection from anthracnose infection. Iprodione, procymidone and thiram showed no systemic activity against anthracnose. In field experiments, thiram, fluquinconazole and carbendazim were able to reduce anthracnose transmission from infected seed. Iprodione and procymidone, widely used on lupin seed in Western Australia for control of brown spot caused by Pleiochaeta setosa, did not provide systemic protection from anthracnose and were not as effective as other fungicides at reducing seed transmission. The efficacy of thiram, fluquinconazole or carbendazim was not reduced by mixing with iprodione or procymidone and these mixtures were generally more effective than iprodione or procymidone alone. As a result of these investigations, thiram has been registered as a seed treatment in Western Australia for control of anthracnose seed transmission in lupins.