Several types of insect pests eat the leaves of grape vines, but a few cause far more damage than others. It is important to identify the type of pest with which you are dealing before starting treatment, as you can deal with many pests through simple practices such as handpicking, reducing the need for the application of insecticides.
Rose chafers appear around the time grapes begin to bloom and eat the buds of blossoms. They also skeletonize leaves. These pests can have a negative effect on production, as adult rose chafers emerge from May to early June, appearing all at once in overwhelming numbers. The insects prefer light, sandy soils, and the larvae overwinter in the soil. Rose chafers attack many common yard and garden plants. The adults have tan bodies with red to brown heads and black undersides. If you find an average of two rose chafers per grape vine, you can use Japanese beetle traps with a pheromone lure for rose chafers to trap these pests. The traps also give you an early heads-up to emergence of the insects. A combination of handpicking and traps can spare you the need for pesticides.
Grape Flea Beetles
Grape flea beetle adults live through the winter in the soil or in wood near grapevines. Upon emergence in spring, the adults consume buds, and later, their larvae consume grape leaves, skeletonizing the leaves and leaving ragged-shaped foliage. The adults that emerge in late July also feed on leaves. The adults and their larvae feed on both upper and lower surfaces of leaves. While the damage is usually limited, adults emerging in spring do the most damage, as their feeding can compromise future yields. The beetles have a metallic blue appearance with purple and green facets. Use good maintenance practices, including clearing of litter around vines, as a first step to control these pests. Insecticide treatments are used in early spring, and you should check for the presence of grape flea beetles in April. Applications of carbaryl, esfenvalerate or pyrethrin must be timed properly for effectiveness.
Japanese beetles emerge in June and July to feed on grape foliage. The beetles skeletonize the leaves, eating away the tissue present between the veins of leaves, which can cause leaf death. Their larvae survive the winter in the soil. Japanese beetles are metallic-colored beetles with green thorax areas and heads and copper wing covers. Because the beetles tend to select certain grape varieties, avoid planting French hybrids if you live in an area where the beetles are a problem. Handpick the beetles and deploy Japanese beetle traps to fight infestation. Permethrin, carbaryl and malathion insecticides are recommended for control of the beetles.
Two kinds of leafhoppers feed on grape leaves: potato leafhoppers and grape leafhoppers. Both feed by sucking. During feeding, potato leafhoppers inject toxins that cause leaves to develop a misshapen appearance. These bright green, wedge-shaped insects travel north on air currents. The three types of grape leafhoppers present with varied colors and markings, but the same body shape as potato leafhoppers. Feeding by these leafhoppers can cause leaf drop, and it affects fruit production and quality. The adults shelter in plant debris, and when temperatures rise in spring, they lay eggs on the undersides of leaves. The nymphs then feed on grape leaves upon emergence, causing the foliage to develop a mottled appearance.
Good maintenance practices, including cleaning up plant litter and removing weeds around the site, can help. Late-producing cultivars, wine and table grapes are most affected, while these pests target more vigorous vines. Check for the presence of pests 10 days after bloom and during the third week of both July and August. Shake the vines and watch for adults to flee, and look for the stippled leaves that mark an infestation. When the threshold of five leafhoppers per leaf is reached, use captan and malathion for control.
- University of Minnesota Extension; Grape Insect Pests of the Home Garden; Jeff Hahn, et al.; 2008
- Michigan State University Extension; Pest Control in Small Vineyards; Thomas J. Zabadal; April 1999
- Ohio State University Extension: Midwest Grape Production Guide: Grape Insect Pests
- University of Kentucky College of Agriculture; Entomology: Grape Insects; Ric Bessin; January 2010
- University of Florida IFAS Extension; Insect Pests of Grapes in Florida; Oscar Liburd, et al.; 2009
- Photo Credit Thinkstock/Comstock/Getty Images
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