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A Technical Guide for Wine Producers
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Vine framework renewal of trellised eutypa infected vineyards
The main reason for this is that parts of the cordon arms die back, resulting in fewer bearers and thus also a decrease in the allocated number of bearer buds per vine.
A characteristic symptom of eutypa is shoots with short nodia that are noticeable on parts of the cordon arm/s early in the season. The leaves on these shoots are usually small and misshapen and yellowish green/pale yellow in colour. Brown spots occur on the yellow leaves and necrosis of the leaf edges is often obvious. Bunches on these shoots are either very small or altogether absent and may die after flowering. The disease may spread, causing parts of the vine, or even the entire vine, to die. Cutting through affected shoot or cordon sections will reveal an obvious division between hard, dead wood and healthy wood.
Eutypa fungi penetrate the vine mainly through larger pruning wounds. Bad suckering practices, or the absence thereof, mean that many more pruning wounds per vine are caused in winter. The infestation points (pruning wounds) are thus far more accessible to the fungi than a properly suckered vine. It should be remembered that pruning wounds never heal, while suckering wounds heal completely in summer.
The purpose of this article is not so much to avoid eutypa in the vineyard, but to try and extend the productive lifetime of vineyards that have already been infected by eutypa.
The method to be followed is simple and involves the vine to be sawn off in winter. The next season, the vines are redeveloped on the cordon wire, using the green shoot method. Although this means that one year’s production will be sacrificed, the productive lifetime of the vineyard can be extended by quite a few years. Usually an entire vineyard block is not sawn off in one year, but by doing so in gradual stages, interim production losses for a block can be restricted to the minimum.
Over the past few seasons a Sauvignon blanc vineyard on the farm Good Success of Mr Dudley Marklew has been redeveloped using the sawing off method.
To illustrate the case in point, production of an infected section of the vineyard is compared to the redeveloped section of the same vineyard.
The block of Sauvignon blanc was grafted on Richter 99 and established in 1983. The total size is 2,5 hectares. Production is indicated as from 1996.
As a result of the poor yields in 1998 and 1999, caused mainly by ever increasing eutypa infections, it was decided to redevelop the vineyard.
In the winter of 1999 1.14 ha of the vines were sawn off. This section therefore produced no crop in 2000. The remaining 1.36 ha constituted total production. In the winter of 1999 the 1.36 ha were pruned in such a way that it would compensate in 2000 for the production loss of the sawn off 1.14 ha.
In the winter of 2000 0.68 ha of the vines were sawn off. This section yielded nothing in 2001. The total production consisted of the 1.14 ha (sawn off in 1999) together with the remaining 0.68 ha of the original vineyard not yet sawn off. The remaining 0.68 ha of the original vineyard will be sawn off in the winter of 2001.
Despite the reduction in producing hectares, total production of the vineyard increased in the course of the redevelopment period.
Consequently there was no loss in production. It is important, however, to undertake the sawing off and redevelopment of a vineyard in phases to limit production losses to a minimum. A general rule of thirds applies where, ideally considered, no more than one third of a specific vineyard should be sawn off in one year.
Producers should take note of a few points, however, before considering this course of action. These are the following:
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It is a common occurrence for Eutypa infections to reach alarming propotions, especially in vigorously growing, older Sauvignon blanc and Cabernet Sauvignon vineyards. The result is a progressive decrease in the production of eutypa infected vineyards. 
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