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Mycologia, ASCOMYCOTINA, DIAPORTHALES, VALSACEAE .

Crops attacked: grapevine .

Dead-arm disease,

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

[R]Description
Dark elongated spots, with cracks and purplish margins, mainly near the basis of the stems (which may swell) and of the internodes, affecting or even causing the death of the buds; internal necrosis of the tissues that spreads to the branches; small roundish spots, dark with yellow margins, on the leaves.

[R]Biology
The fungus overwinters, under the form of mycelium in the dormant buds, in the bark and woody tissues of the vine shoots and branches affected and also as asexual fructifications (stromatic pycnidia) that are formed in the silver whitish areas of the shoots.
The infection occurs after the bursting of the buds at the base of the stem, or in nearer internodes, after the germination of the pycnidiospores, penetrating afterwards in the internal tissues of the xylem; the pycnidia, big and scattered, are formed in the stems and originate cirrhus of agglutinated spores.

[R]Epidemiology
The pycnidiospores are carried by the rain that dissolves the cirrhus (or these are transported by birds or insects); the combined action of the wind and of rain drops is the main way of dissemination.
The infection takes place after the bursting of the buds with favourable temperatures (8-10 °C.) and rain for at least 12 hours, as a consequence from the germination of spores that fall on the young shoots (at phenologic stages D and E) or from the growth of mycelium that remains protected by the scales of the dormant buds.

[R]Treatement
Chemical preventive control using adequate products, at the phenologic stages D and E or only D, according to the fungicide used.

[R]Possible misleading
Macrophoma flaccida , that forms in the stems beige stains with black spots (pycnidia), numerous and small, whereas in P. viticola stains are silver withish and the spots are also black, but bigger and scattered.

[R] Images

1. Phomopsis viticola , Excoriosis, Dead-arm disease (BISSON J., INRA)
   Grapevine excoriosis, Grapevine dead-arm disease View of a excoriosis cirrhi (dissecting microscope).
   
2. Phomopsis viticola , Excoriosis, Dead-arm disease (SOUSA DIAS M., MA)
   Grapevine excoriosis, Grapevine dead-arm disease Small necrotic spots with yellow borders on grapevine leaves caused by excoriosis.
   
3. Phomopsis viticola , Excoriosis, Dead-arm disease (FERREIRA J., MA)
   Grapevine excoriosis, Grapevine dead-arm disease Young grapevine shoot with brown cracks resulting from excoriosis. They are also present on .
   petioles and rachis.
   
4. Phomopsis viticola , Excoriosis, Dead-arm disease (BUGARET Y., INRA)
   Grapevine excoriosis, Grapevine dead-arm disease Grapevine shoot showing lesions from excoriosis.
   
5. Phomopsis viticola , Excoriosis, Dead-arm disease (ACTA)
   Grapevine excoriosis, Grapevine dead-arm disease Light brown longitudinal lesions from excoriosis on a grapevine branch.
   
6. Phomopsis viticola , Excoriosis, Dead-arm disease (BASF)
   Grapevine excoriosis, Grapevine dead-arm disease Lesions due to excoriosis on a grapevine branch resulting in dessication of part of the .
   grape cluster.
   
7. Phomopsis viticola , Excoriosis, Dead-arm disease (BUGARET Y., INRA)
   Grapevine excoriosis, Grapevine dead-arm disease Necrotic regions at the base of a grapevine branch due to excoriosis.
   

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