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Armilaria mellea (Vahl) Kummer x grapevine


Crops attacked: grapevine .

[R]Common Names :

Root rot

Whenever the inoculum is present the disease can occur, mainly in humid and compact soils with vegetal debris.

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

The root rot is visible, under the bark of the collar and roots (eventually rhizomorphs can appear externally); basidiocarps (mushrooms) can sometimes be seen near the base of the plant; the fungus can be isolated and grown in artificial nutritive media.

Lost of vigour of the plants which show reduced growth, weak wine shoots and yellowish leaves in summer; progressive drying of the branches, canker formation near the collar and rot and death of roots with musty smell; eventually all the plant may collapse.
The infection and death occurs in zones or areas which gradually progress in the vineyards. Under the bark of the affected roots fan like plates of yellowish-white mycelium appear; outside the bark, however, rhizomorphs can be found.
After the first autumn rains, honey coloured mushrooms may appear on the basal part of the plants.

The fungus maintains in the infected timber and roots and saprophitically in the dead timber for several years; it grows mainly on permanently humid soils with plant debris, particularly when they have dimensions over 3 cm.
The infection results from the contact of the healthy plant roots with the diseased ones, with the inoculum present in the soil or with the rhizomorphs or fragments of them.
The fungus penetrates through the roots, kills the cambium and destroys the xylem; the infection may start from the basidiospores that germinate in the root wounds and dead tissues; the mycelium develops always under the bark, whereas the rhizomorphs may appear also surrounding the external part of the root.
The sexual fructification, basidiocarps, are honey-coloured mushrooms.

The conditions favourable to the attack are the presence of roots from ligneous plants formerly existent in the soil, the incorporation of farmyard manure not totally decomposed, the use of green plant material as manure, mainly with branches having more than 3 cm in diameter and permanent excess of soil humidity.

Remove plant debris and roots from previous crops;.
Use well decomposed farmyard manure, avoiding the use of plant debris with large diameter.
The chemical control is difficult and alleatory.

[R]Possible misleading
Rosellinia necatrix , but A. mellea appears in fan like plates of yellowish-white mycelium under the .
bark, whereas R. necatrix forms a greyish, cobweb like external mycelium.

[R] Images

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