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Sclerotium bataticola Taub.
Rhizoctonia bataticola Taub.

Mycologia, DEUTEROMYCOTINA, SPHAEROPSIDALES, PHOMACEAE .

Crops attacked: sunflower .

[R]Common Names :

Charcoal rot

Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images

[R]Identification
Macroscopic aspects seen with the naked eye, especially after removing the epiderm from the lower third of the stem .
Microsclerotia can be observed with a binocular lens.
Study done with a light microscope.

[R]Description
Silvery grey coloring all around the stem on about a third of its lower end ; medullar tissues are cut in disc shapes ("pile of dishes" symptom) showing a high density of black spheric microsclerotia.

[R]Biology
The fungus persits in the soil as microsclerotia and mycelium.
The mycelium penetrates the roots of the young plant and colonizes the lower part of the stem.
Microsclerotia formation takes place at the end of the vegetative cycle of the plant.

[R]Epidemiology
The colonization of the tap root and lower stem tissues actually takes place only if the host is in a state of physiological weakness (draught, shallow soil) and if the conditions are favorable to fungus growth, such as high temperature.

[R]Treatement
Care should be taken to provide proper watering and nutrients (balanced fertilization, irrigation).

[R]Possible misleading
Verticilium spp. but in this case the symptoms are localized at the base of the stem and are present throughout the thickness of the stem.
With the draught symptoms (medulla cut in a "pile of dishes" pattern) when unaccompanied by microsclerotia formation.

[R] Images

  1. Macrophomina phaseoli , Charcoal rot (INRA)
    Charcoal rot on sunflower Silvery grey spots (microsclerotia) due to Macrophomina phaseoli spreading around the base of a sunflower stem.

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HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.

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