Grapevines are not only ornamental; their edible fruit gives them additional commercial and nutritional value. However, sometimes growing grapes can also be a frustrating experience, as they are susceptible to several fungal diseases, including powdery mildew, black rot, downy mildew and botrytis (bunch rot). In some cases, you may be able to control the infection with a plant spray.
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Sulforix is a sulphur-based fungicide, miticide and insecticide. It controls powdery mildew on grapes both in the dormant and growing seasons. However, if the temperature is at or above 29.4 degrees Celsius, wait to apply Sulforix until the weather becomes cooler, or damage to the vine's foliage may occur. This spray works on contact and must cover the entire affected area to be effective.
Liquid Lime Sulfur
Liquid lime sulphur controls Phomopsis cane and leaf spot on grapevines, which cause grape mummification and damage to the vine's foliage. Liquid lime sulphur is a dormant-season spray. It kills the Phomopsis fungal spores overwintering on diseased canes.
Captan 50-WP is sold as a water-soluble powder for use as a spray against several grape fungal diseases: Phomopsis cane and leaf spot, downy mildew and black rot. The manufacturer's label directs you to apply this product at intervals throughout the growing season for as long as the fungal spores are present on the grapevine. In California, Captan 50-WP is also regulated to treat bunch rot on grapes.
Gavel 75-DF is a fungicide containing the chemicals zoxamide and mancozeb. It controls bunch rot, dead arm and downy mildew on grapevines. It is to be applied as soon as you notice the signs of any of these diseases. This formula sticks to the vine's leaves, prolonging its action, says the product label. While this spray is for use in the growing season, you should stop application no later than 66 days before harvesting the grapes. In addition, west of the Rocky Mountains you're only permitted three applications per acre per season. To the east, eight seasonal applications of this product are allowed per acre. This spray isn't registered for use in California.
Copper Soap is a liquid fungicide you spray on grapevines to control powdery mildew, downy mildew, black rot, grey mould and Phomopsis cane and leaf spot. This spray is for use throughout the growing season, starting when new growth reaches ½ inch and reapplied every two weeks. Some grapevine varieties are sensitive to copper and experience leaf burn when treated with this product. Copper soap is not for use with lime.
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