Ascochyta fabae
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Ascochyta, sometimes called target spot because of its characteristic lesions which appear as a brown spot with a series of darker concentric rings within them, is often confused with chocolate spot in its early stages. Lesions often become sunken in the later stages of development with paler centres. It is a seed and trash borne disease, seed infection being related to infection of the pods in the seed crop. Ascochyta occurrence is optimised in temperatures of 20oC and high relative humidity. Yield reductions from Ascochyta are less well documented than for chocolate spot although an experiment conducted in 1988 demonstrated yield reductions of 13 % from an infection of Ascochyta, which began once leaf area had reached a maximum, i.e. late in the season. Ascochyta is thus potentially a very damaging disease.
Seed treatments such as ‘Hy-TL’ are available to reduce seedling infection whilst Ascochyta can be controlled preventatively with various fungicides or with 'Wakil XL' seed treatment.
