Like grapes grown in any other region, South African grapes can be susceptible to certain diseases. However, it's important to note that the prevalence and severity of diseases can vary depending on factors such as climate, grape varieties grown, farming practices, and disease management strategies implemented by growers.
South Africa has a diverse climate, ranging from Mediterranean in the Western Cape to subtropical in certain regions, which can create different disease pressures. In some areas, such as the Cape Winelands, the conditions are well suited to grape cultivation, with dry summers and low humidity, which can help reduce the incidence of certain fungal diseases.
However, certain grape diseases, including downy mildew and powdery mildew, can still pose challenges, particularly in regions where cool, wet conditions prevail during the growing season. Botrytis bunch rot can be a concern in areas with higher humidity, which can promote the development and spread of the fungus.
Despite these challenges, the industry's commitment to research, innovation and best practice mitigates the risks and helps to maintain a competitive grape sector.
FUNGAL DISEASES DOWNY MILDEW
Downy mildew (Plasmopara viticola) can cause significant damage to grapevines. According to the Michigan State University: Integrated Pest Management (MSU), downy mildew is widespread. The fungus thrives in cool, humid conditions. The spores are wind-borne.
Initial symptoms include light green to yellow spots. The MSU explains that these 'oil spots', as they are called, can appear greasy in appearance. "Under humid conditions, white downy spore masses can be seen on the lower leaf surface." The MSU says that these lesions appear five to 17 days after infection, eventually turning brown as the infected tissue dies.
この記事は Farmer's Weekly の June 30, 2023 版に掲載されています。
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