How to control powdery mildew in vineyards

When it comes to managing powdery mildew in grape orchards, prevention is better than cure, and the key lies in taking action early in the season. Glenneis Kriel reports.

- Glenneis Kriel

FAST FACTS

Powdery mildew is a fungal disease that can drive up production costs and have a damaging effect on wine grape yields.

Before signs of the disease begin to appear, farmers should take preventative action against the fungus by starting a spraying programme early in the season.

In order to prevent powdery mildew from building up a resistance to a single fungicide, farmers are advised to use four or five products from different chemical groups, and to rotate them.

Over the 2021/22 season, wet spring and summer conditions resulted in an explosion of powdery mildew infestations on wine grape farms in various regions in the Western and Southern Cape.

Not only did the fungal disease negatively affect yields, it also drove up production costs, as farmers were forced to use more fungicides than usual in an attempt to combat the disease.

In addition, before harvesting could take place, they also had to send workers into the vineyards to remove infected berries by hand, or risk them having an undesirable effect on wine quality.

De Wet du Toit, a crop protection specialist at Winfield United South Africa, told farmers at a Winetech Vinpro information day held in May in Rawsonville, Western Cape, that early action was key to the successful management of powdery mildew.