However, late sprays are often beneficial as they can decrease the severity of ascochyta on pods and reduce seed discolouration. Late sprays are unlikely to significantly reduce the incidence and severity of disease on the leaves and stems. Early sprays must be applied at the first sign of disease to be effective.
Strategic use of foliar fungicidesįungicide strategies are more effective if applied prior to infection.Ī successful fungicide program relies on crop monitoring, correct disease identification and timeliness of spraying with the correct product. Plan to sow within the optimum sowing window for your district. Sowing rateįollow the recommended sowing rates for your district, remember that rates may vary between varieties. Reduce disease risk by not sowing adjacent to vetch, chickpea or lentil stubble. Seed that has less than five per cent seed coat discolouration will usually have normal levels of germination Paddock selectionĪ break of at least 3 years should be observed between faba bean crops.Īim to separate this year's faba bean crop from last year's faba bean stubble by a distance of 500m. Old, frosted or damaged seed may have reduced germination and reduced vigour.įaba bean seed that has greater than 25 per cent seed coat discolouration can reduce the emergence of seed by 30 per cent. Seed should be sourced from the 'cleanest' crops. Seed selectionĪim to use the 'cleanest' seed possible with 5 per cent to nil levels of ascochyta present. Select the variety with the highest level of resistance to the important disease risk in your district. ManagementĪn integrated approach is the key to successful management of ascochyta blight in faba bean. Discolouration of seed can seriously reduce its market value. Yield losses of 10 to 30 per cent can occur in seasons favourable for the disease. Its severity varies considerably from crop to crop and between seasons. The disease is widespread in southern Australia. The disease is usually most severe early in wet years. Infection may occur at any stage of plant growth, providing there has been either rain or heavy dew. During wet weather the disease can spread from infected to healthy plants by rain splash and wind-borne spores. Wet conditions are required for infection. The disease usually becomes established when spores of the fungus, produced on old bean stubble, are carried into the new crop. The fungus can survive on crop debris, self-sown volunteer plants, and infected seed.
Disease cycleĪscochyta leaf and pod spot is caused by the fungus Ascochyta fabae. Late infection with ascochyta can sometimes cause seed staining when disease levels in the crops have appeared too low to warrant fungicides sprays. Well developed lesions can penetrate the pod and infect developing seeds causing them to be shrunken and discoloured.īadly infected seeds have yellowish-brown stains on the outer seed coat, which considerably reduces its market value (Figure 4). On pods, lesions are sunken and have pale centre and dark margins they can be covered by numerous pycnidia (Figure 3). Stems may split and break at the point of infection causing plants to lodge. On the stem, lesions are more elongated, sunken and darker than leaf lesions and are usually covered with scattered pycnidia (Figure 2). These appear only under moist conditions and are often concentrically arranged (Figure 1). Within the lesions, numerous pinhead- sized black fruiting bodies (pycnidia) of the fungus develop. Leaf tissue next to the lesions may become black and necrotic. They become irregular in shape, often zonate, and may coalesce to cover most of the leaf surface. As the disease develops, lesions enlarge and turn light and then change to dark grey in colour. On leaves, small, circular, dark-brown spots appear first. Symptoms occur on leaves, stems and pods of infected plants, and can be confused with the early stages of chocolate spot. This disease can be managed through an integrated approach including: Temperate pulse viruses: subterranean clover stunt virusĪscochyta leaf and pod spot is an important disease of faba beans in Victoria and South Australia. Temperate pulse viruses: pea seed-borne mosaic virus Temperate pulse viruses: bean yellow mosaic virus Temperate pulse viruses: bean leafroll virus Temperate pulse viruses: cucumber mosaic virus
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