South African table grape producers continue to expand the use of overhead netting to protect their crops as, during the past decade, the number of hectares of table grapes under netting have increased from 13 000 hectares to 21 000 hectares. Growers report that the increased growth and improved harvests achieved through implementing this risk mitigation infrastructure makes it possible for them to recoup the cost of net installation within six to seven years.
The overhead nets protect the table grapes from climatic threats, including sunburn, hail, wind, dust, and birds. According to Francois Rossouw Jr of Mooigezicht Estates in the Hex River Valley, the installation of overhead netting provides growers with a way to manage the quality of their table grapes more intensively and thoroughly. He explained that this made it possible for them to differentiate their quality product in an oversupplied market.
White netting is used above the vineyards as this allows sufficient light for optimal growth to pass through the net. The white net also allows for good light dispersal under the nets, reducing the risk of sunburn on varieties that are sensitive to sun damage. In addition to the white overhead nets, in areas with strong winds, growers use the thicker and stronger green nets on the sides of the net construction to protect the crop from wind damage. The green nets along the sides of the net construction and the white overhead netting also further assist with creating a protective microclimate for grapes under the netting.
While the overhead nets minimize climate risks, they also create other production challenges such as humidity in the net house. If the humidity in the microclimate under the nets becomes excessively high, this creates the ideal circumstances for Botrytis fungal rot to develop and spread on the grapes.
Article by Jacques Burger
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