Researcher: Francois Halleen
New Winetech funded project 2019 – The objective of this research project is to study the effect of mechanical pruning (MP) on the incidence and severity of grapevine foliar, fruit and trunk diseases compared to conventional pruning. Growth responses, grape composition and morphology, wine quality and labour costs associated with MP have been investigated locally. However, the effect on the incidence and severity of major leaf, fruit and trunk diseases, especially the long-term effect in terms of sustainable production, is unknown.
Apart from an altered canopy structure, MP results in a changed microclimate around the bunch zone, which may favour the development of certain diseases. Depending on the type of MP, a significant increase in the number of pruning wounds can occur as well as wounds with larger surface areas. Trunk pathogens infect susceptible wounds. A build-up of old wood also occurs and even if renewal pruning is practiced on a 3-year rotational basis as prescribed, pathogen fruiting bodies are able to form and release spores that can infect new pruning wounds.
The project will compare the incidence and severity of the following, in MP versus hand pruned vines:
- foliar and fruit diseases (powdery and downy mildew, botrytis and Phomopsis);
- leafroll virus and mealybugs;
- pruning wound infections.
Researchers will also identify and determine the incidence of inoculum (fungal fruiting bodies) on wood, canes and leaves of MP vs hand pruned vines.
The study aims to provide the local grapevine industry with new information on the risks and benefits associated with MP and to make recommendations to prevent inoculum build-up and wound infections. Potentially these recommendations can help to increase the lifespan of such vineyards in order to complement other benefits of MP like reduced labour costs, increased production and acceptable or increased wine quality.
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