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Ascochyta Blight Disease in Lentils
Ascochyta blight, caused by Ascochyta lentis, is a widespread disease of lentils. It causes severe yield loss and stains the seed which can cause downgrading or rejection.
Symptoms include light gray to tan colored lesions on leaves and stems. The lesions have a dark brown margin and numerous tiny black dots, which are the fruiting bodies of the Ascochyta fungus. In wet weather the lesions may coalesce, resulting in premature leaf drop and defoliation; the tips of severely diseased stems wilt, turn brown, and die. The crop looks blighted. Later in the season lesions may form on the pods, resulting in seed infection. Seed infection may occur before harvest or while the crop in the swath. Infected seed becomes partially or entirely discolored brownish-purple. Severely infected seed may be shriveled. Tiny black fruiting bodies may be present on the surface of infected seeds. Clusters of brown fruiting bodies often form on the leaves, upper stems and pods. These brown fruiting bodies are diagnostic and serve to distinguish Ascochyta from anthracnose.
Seed borne Ascochyta is an important source of the pathogen. The Ascochyta fungus also is spread in the spring by wind borne spores formed in fruiting bodies on infected crop debris. Later in the summer it is primarily spread by water-splashed spores. Wet weather in late summer can result in extensive pod and seed infection.
Control. The cultivar Laird is more resistant that Eston or Commercial cultivars and sustains less yield and quality loss. New varieties such as Indianhead, CDC Matador, CDC Redwing, CDC Glamis, CDC Vantage and CDC Milestone are resistant to ascochyta. No cultivars are resistant to anthracnose. Plant disease-free seed or seed with as low a level of Ascochyta as possible. The NDSU Extension Service Seed Health Testing Laboratory can test seed for Ascochyta. Seed treatment with currently registered fungicides does not control seed borne infection. Planting when soil temperatures are warm helps to reduce seed borne infection. Bury crop debris after harvest. Locate new plantings at some distance from the previous year's fields. Rotate with small grains.
For more information on diseases, see http://paridss.usask.ca/specialcrop/pulse_diseases/index.html
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