Tuesday, October 26, 2010

Eutypa Dieback -ID Photos.

Eutypa and other trunk diseases have been identified as causing significant problems in South Australian vineyards.

Eutypa is present in many vineyards- of all ages. Pictured below is a grafted vineyard in Willunga, in the McLaren Vale region


Eutypa lata (Dieback) symptoms in spring on Shiraz.
All wine grape varieties are susceptible to Eutypa Dieback along with many other plants including Almonds, pome fruit trees and willows. All can be a source of disease.

For those growers unfamiliar with Eutypa in their vineyard it is often confused with zinc and manganese deficiency and rust mite, both of which also cause stunted shoots and pale leaves.

Note Eutypa dieback is most obvious in early spring when infected vines show stunted shoots with shortened internodes and small leaves that are usually pale in colour, cupped and tattered around the margins.  Bunches on affected shoots appear normal early in the season but after flowering they often shrivel and die. 

Eutypa is caused by the fungus Eutypa lata. The fungus produces ascospores on old infected wood and is spread by rain splash traveling on the wind.

The spores are able to travel large distances and can infect fresh, unprotected wounds, such as those left by pruning cuts. Spores are produced all year but can only infect fresh cuts during wet weather.

Above - Eutypa dieback disease cycle in grapevines(taken from 'Grape Pest Management' Flaherty et al., 1992).

Once inside the vine the fungus slowly grows spreading over a period of years along cordons and down to the trunk. The disease spreads to adjacent parts of the vine and eventually kills affected vine arms. Eutypa moves along the vines water-plumbing (the xylem).

Removal of any infected wood is recommended during spring, the symptoms are easy to see and the vines are naturally pushing sap which will limit infection spread to any fresh cuts you make - SARDI have published work on the problem here.

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