Thursday, July 9, 2009

Eutypa Dieback - Winter Identification Photos

There a three things to remember when dealing with Eutypa during pruning season.



Canker symptom.
1. Eutypa is often called Dead Arm because it slowly kills vines.

Symptoms start out low in young vineyards and increase over time as the vineyard ages.

Eutypa is caused by the fungus Eutypa lata. The fungus produces spores on old infected wood, called cankers, and these spores spread by rain splash and wind.

All winegrape varieties are susceptible to Eutypa Dieback but Grenache & Shiraz show the most severe symptoms. Many other plants including Almonds, pome fruit trees and willows are a source of disease.

A broken 'Dead Arm' caused by the fungus Eutypa lata. Note the cankers above the break.

2. When it rains Eutypa Dieback produces spores.

Note the the wedge shaped area of dead wood.
The spores are able to travel large distances and can infect unprotected wounds, such as those left by pruning cuts. Once inside the vine the fungus slowly grows spreading over a period of years along cordons and down to the trunk. Each spring the fungus releases chemical toxins that cause the stunted shoots and cupped leaves with tattered margins (shown in our Spring pictures).


3. Don't make large cuts during rain.

Cankered wood becomes distorted and twisted after a number of years.
Eutypa infection can be prevented by avoiding pruning cuts during wet weather.

Pruning cuts made in early winter remain susceptible to the disease for some weeks, while those made in early spring heal much quicker. If possible delay pruning until August for blocks with known Euytpa or at risk.

Should I spray chemicals to seal the cuts?

We think you shouldn't, in SARDI's independent testing, pruning wound dressings are just as effective and a lot safer for you to use. DJ's agronomists recommend 'Green Seal' wound dressing.

We don't recommend treating your pruning cuts with chemical protectants because some of the chemicals tested and used for pruning wound protection have question marks over their side effects eg. Carbendazim - Tradenames including Spin-flo ans Carbend. These have been removed for use from the 2009/2010 Guide to Agrochemicals (the Dogbook) onwards. 

For more information visit SARDI's research.

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