Alternaria Leaf Spot of Brassicas
Alternaria brassicicola and brassicae
Alternaria Spot of Brassicas
Description:Dark grey-brown to black circular spots with a yellow halo and a sooty mass of spores in the sunken centre. With age the centres of the spots may become papery and disappear leaving a hole in the leaf.
On stems and pods the lesions tend to have a grey centre and black margin. Infected pods may have shrivelled seed and shatter prematurely.
Species Affected:Brassica crops including Canola and weeds.
Biology:Favoured by moist conditions.
On Canola moist humid weather in spring favours epidemics.
Stressed plants are often more susceptible to infection.
Survives in soil, on crop residues and often carried by Brassica weeds.
Spread by infected seed, wind and water splash.
Canola seed from infected pods may produce seedlings with Seedling Blight.
Life Cycle:Origin and History:
Management and Control:
Destroy or bury crop residues soon after harvest.
Buy clean seed.
Apply fungicides at the first sign of disease or when conditions favour infection.
Related and Similar Species:References:
(Donald et al., 2002)
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