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Mycologia, ASCOMYCOTINA, DOTHIDEALES, PLEOSPORACEAE .
Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images
[R]Description
Small white greyish spots (2 - 3 mm diameter) occur on the cotyledons and larger ones (5 - 15 mm) on the leaves, stems and pods.
Dark marks (pycnidia) form on these spots and produce a pink-red mucilagenous mass.
Collar rot : in seedlings brown rot is noticed on the collar which appears strangled.
In older plants the base of the leg is "cankered" under the leaf wounds.
The collar can be cut through and cause death of the plant anytime from early winter to late flowering.
Necrosis develops progressively and often results in lodging.
[R]Biology
The fungus persists in the soil for three to four years.
Ascospores produced in the perithecia on debris form the primary inoculum.
Inoculum is dispersed by the wind (at long distance) and by rain splash (to neighbouring plants).
After ascospore germination mycelium develops in the vessels of the host plant.
The first symptoms (small marks) show after 15 days incubation.
High humidity favours sporulation on the lesions.
Conidial dispersal by splash can cause secondary contamination.
The necrotic process leads to the production of a large number of toxins.
[R]Epidemiology
Perithecia form in September in conditions of 15 °C. average temperature, rain, dew, exposure of mycelium to light.
Ascospores are released when the asci split open in the rain.
Dispersal of ascospores can go on 4 to 6 hours after rain stops.
[R]Treatement
Chopping and burying the contaminated straw and debris (light favours perithecia formation).
Use tolerant cultivars.
HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.
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