Potential impact of climate change on grapevine diseases of economic importance to South Africa.
Bonnardot, V M F
Climate change, and more specifically global warming, is a scientifically based reality and the impact thereof needs to be addressed in the South African wine industry. Recent research has shown that climate change has already had an impact on viticulture in the Western Cape Province with an increase in annual temperature, as well as a shortening of the winter season. With an estimated increase of 2º C predicted for the global wine producing regions over the next 50 years, this effect might even increase. Research indicates that some local wine regions are already at their upper level of climatic limits, whilst other areas will change to warmer groups. From a viticultural point of view this means that the suitability of cultivars in certain areas will have to be re-investigated, or that more heat tolerant varieties be planted. New wine regions will also have to be investigated, especially cooler areas next to the coast, at altitude, or towards the eastern part of the Western Cape Province where rainfall is more evenly distributed.
All of these scenarios will have an impact on grapevine diseases. There are three basic components of disease, often referred to as the ‘disease triangle’, namely the host plant, a pathogen and a set of environmental conditions. A change in one component will have a direct effect on the other two, although there might be considerable variability within each component. However, for disease to develop, a set of environmental conditions within a favourable range must occur. Many grapevine diseases are associated with very specific environmental conditions. Favourable conditions will increase disease pressure and could lead to the need for more fungicide applications. In a world where consumer resistance against chemicals are growing, management strategies will be under severe pressure if proactive measures are not put in place before it is too late. The alternative of introducing grapevines to new environments might also subject them to unknown or unfamiliar pathogens.
The objectives are:
- To determine the potential effect of climate change on grapevine diseases (foliar-, trunk, as well as soil borne diseases) in the main grape growing areas in its current form. Including:
- The effect of vector activity on grapevine diseases.
- Potential change in management strategies.
- To determine the potential effect of climate change on grapevine diseases in newly established grape growing areas.
- To determine the potential effect of the relocation of grape growing areas to new areas being considered for future development as a consequence of climate change, and the risk thereof in terms of grapevine pathogens.