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Mycologia, FUNGI IMPERFECTI, SPHAEROPSIDALES, PHOMACEAE .
Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images
[R]Description
The fungus usually causes collar rot and a purplish-brown girdling lesion between the lower nodes of the stem in young plants.
During the vegetative stage, pale brown spots occur on the leaves and stems which extend in the presence of free water on leaves. There are not many, though, and they cause limited loss.
On the pods and the seeds, the spots are reddish-brown, have well defined margins and appear sunken on the skin of the pod. The infected seeds show dark lesions.
Loss mainly affects the seedlings which die (damping-off).
[R]Biology
The fungus survives in the soil for about three years as chlamydospores and in the seed which is the main carrier of the pathogen.
The diseased seed causes early infection ; the fungus invades the roots and the stems of the young plants.
Pycnidia appear on the foliar lesions allowing for the secondary infection to take place through the pycnidiospores.
Chlamydospores form in the infected tissues of the plant.
[R]Epidemiology
The fungus is transmitted by the seed to the young plant which becomes a primary focus.
The disease is rain and wind-spread (splash carries the pycnidiospores).
Cool temperatures favour the development of the infection.
[R]Treatement
Use certified, treated seeds.
Over three years rotations recommended.
Sow in cleaned warmed-up soil.
[R]Possible misleading
The Mycosphaerella pinodes and Ascocyta pisi , but in the latter there are few foliar symptoms, few pycnidia and symptoms located at the base of the stem.
HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.
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