Dead Arm - Q&A
Dead Arm question.
Not the wine, the Eutypa version! What causes it, and how best to deal with it? I could of course look it up but who needs to be resourceful when you have the DJ's?!
Thanks in advance.
Eutypa is present in many vineyards- of all ages.
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.
|Eutypa dieback of grapevine caused by Eutypa lata. Courtesy G. Munkvold|
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.
Treating exposed trunk wounds with particular fungicides or physical paint based barriers will prevent Eutypa dieback infection and is a recommended practice where cuts greater than 20 mm are needed. Click here for information on wound protection - http://www.sardi.sa.gov.au/pdfserve/hort/hort_crops/grapes/eutypa_trunk_disease/eu_pruningwound_fung.pdf
Once a vine is infected with Eutypa the only method currently available to growers to eradicate the fungus, is to remove infected tissue using remedial surgery. There are two main approaches to remedial surgery.
i) Cutting off the trunk at least 10 cm below any signs of obvious infection and training up a watershoot or grafting.
|Remedial surgery - (c) SARDI|
ii) Training a healthy shoot from the base of the trunk and removing the infected trunk once the new shoot begins cropping. Click here for more tips on remedial surgery.
Once inside the vine the fungus slowly grows spreading over a period of years along cordons and down to the trunk. Eutypa moves along the vines water-plumbing (the xylem).
Eutypa dieback causes characteristic stunted shoots, most obvious in spring, small bunches and in cross-section, a wedge of discoloured dead wood. It contributes to the decline of vineyards by reducing growth and yield. Bunches are smaller from a Eutypa infected vine, compared to healthy vines. Eventually Eutypa will kill vines.
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 high risk blocks or those already showing signs of the disease - http://www.sardi.sa.gov.au/pages/hort/hort_crops/grapes/eutypa_trunk_disease/eutypapage1.htm