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Vineyard Pests

by Staff Writer - B. Shaughnessy | January 29, 2012

The grape vine, like any other plant is subject to attack from a vast array of insect based life. Many insects feed on the various parts of the grape vine including leaves, berries and root systems. An outbreak of an insect attack ranges from small limited attacks to large aggressive attacks. The abundance of the insect and its attack on the grapevine depends on numerous factors, including the species of insect. The good news is that many insect attacks occur infrequently. This fact leads to the conclusion that the vintner must be fully aware of any signs and symptoms of insect attack. Correctly identifying the symptoms of an insect based attack allows the vintner to manage the problem before a crop is damaged or destroyed.

When systematically viewing insect pests, it helps to classify the insect by the damage inflicted on the plant. With this notion in mind, grape pests can be classified by direct and indirect damage. Direct damage pests are insects that cause damage to the berries of the grape vine. Indirect damage pests are insects that cause damage to the grapevine itself. The following paragraphs briefly describe some of the direct damage pests, signs of attack and general management procedures. Indirect damage pests are briefly reviewed as well.

One of the most destructive vineyard pests is the grape berry moth. Several different species of the grape berry moth exist with different species affecting different regions of the world. The primary damage of the grape berry moth comes from the larvae feeding on berries. Additional damage can be found in feeding on grape leaves, however this is minor compared to the berry damage. The larvae will eventually tunnel into the berries and feed on the pulp and seeds. The resulting fruit is reduced to a shriveled grape skin with most of the crop suffering a similar fate. The presence of the grape berry moth can be detected by the use of a pheromone trap. If the grape berry moth is detected early on in the vineyard, management controls can be used to disrupt potential damage. Procedures such as mating disruption, burning of fall leaves, soil cultivation and insecticide spraying can prevent significant destruction.

The grape flea beetle is another pest of great concern for vineyards. This small (about 0.2 inches/5millimeters) insect presents its greatest threat in the adult stage of the grape flea beetle. In grape flea beetle's adult stage, the insect eats holes in the side of grape buds and gouges out the center of the bud. This effectively destroys the mechanism responsible for the creation of a grape. Secondary damage in the larval stage of the grape flea beetle includes chain-like pattern damage of grape leaves. The use of insecticides and vineyard cleanup are methods of controlling the grape flea beetle. With the use of insecticides it is important to remember that insecticides target specific pests. Therefore the proper identification of the grape flea beetle is important for selecting the proper insecticide.

Climbing cutworms are caterpillars of several different species of moths. Roughly the length of a United States dime, the climbing cutworms live in the soil and weeds below the trellis during the day. At nighttime, the climbing cutworms climb the vine and feed on the primary grape buds of the grapevine. Damage is similar to the grape flea beetle with the grape bud being destroyed. Solutions to the problem of the climbing cutworm include good weed control under the vine trellis.

Wasps present yet another pest to the vineyard. During the beginning of the growing season, wasps can be considered important to the vineyard, as they are predatory insects of other pests. However toward the end of the growing season wasps will turn to feeding on ripe grape berries. Wasps will tear open the grape berries and feed on the insides of the sweet berry. Yellowjackets, hornets and paper wasps all fall within this pest category and must be controlled. Controlling wasp problems is confined to destroying wasp nests and killing overwintering queens. Insecticide use may not be desired as important and non-threatening honey bees would also be killed.

The banded grape bug is a small insect that is only destructive in its non-adult life cycles. In the early life cycles of the banded grape bug, nymphs feed on vine shoot tips as well as grape clusters. The end result is that the numbers of grape clusters are reduced with berry weight being negatively affected. Insecticides are available to control the banded grape bug.

Insects that create a grape vine condition known as a gall are known as gallmakers. Gallmakers are small midges that attack various parts of the grapevine. Galls themselves are outgrowths located on the surface of the grape plant. Identifying the specific pest responsible for the gall can be achieved by observing the growth of the gall. Galls occurring on tendrils and buds can cause considerable damage to a grape vine. Galls occurring on other areas of the grapevine usually do not pose a threat. Management of galls is confined to removing the gall from the vine and destroying it.

The rose chafer is a grape pest very similar to the Japanese beetle, with feeding occurring on a number of different plants. The grape vine remains one of the rose chafer's preferred targets. The rose chafer can be considered a general feeder as it feeds on leaves, blossoms and fruit. Management of the rose chafer is limited to the use of specific pesticides.

Another grape pest that feeds on grape berries is the grape curculio. This pest is a small black weevil of about 0.1 inch (2.5 millimeters) long. The grape berry's destruction begins when the female of the weevil chews a hole in the skin of the grape and lays her egg. The resulting larva eats the flesh and seeds of the grape. While the grape curculio is responsible for the destruction of grape berries, the economic destruction is low when compared to other pests.

The redbanded leafroller is a pest of grape plants and in its various lifecycles it damages the grape plant in different ways. In early life cycles, the redbanded leafroller's feeding is confined to leaves and fruit clusters. In later life cycles the redbanded leafroller chews holes in the side of berries. It is interesting to note that the redbanded leafroller will not enter the berry after chewing a hole in the side of the berry. Mating disruption techniques as well as insecticides are used to control the redbanded leafroller.

The multicolored Asian ladybug is an interesting pest with respect to grape plants. As a predatory insect, the multicolored Asian ladybug does not eat or damage the berries of the grape plant directly. The threat of the multicolored Asian ladybug comes from lifecycle patterns. Typically great numbers of this pest will bunch up in tight places for overwintering. Multicolored Asian ladybugs therefore can be found in grape bunches during harvesting time. When crushed during grape processing, the remains of the multicolored Asian ladybugs produce a foul taste in the resulting juice. The end result is grape juice that cannot be made into wine.

Additional pests exist that feed on different parts of the grape plant. Grapes leaves, shoots, canes, trunks and roots are all areas where certain pests enjoy foraging for food. Unlike the direct damage pests, these indirect damage pests do not eat the grape berry. The end result however is a grape plant that is weakened to the point where grape berry production is jeopardized. Management programs including insecticide use, mating disruption techniques and cultural controls are effective at controlling these pests. Specific indirect damage pests include: the Japanese beetle, European red mite, green june beetle, two-spotted spider mite, phylloxera, grape leafhoppers, potato leafhopper, grape mealybug, grape plume moth, eightspotted forester, grapevine looper, hawk moths, spotted pelidnota, grape erineum mite, grape leaffolder, grapeleaf skeletonizer, grapevine aphid, grape colaspis, grape cane girdler, ambrosia beetles, grape cane borer, grape cane gallmaker, grape scale, European fruit lecanium, periodical cicada, grape root borer and grape rootworm.

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