Grape Insects

ENTFACT-208: Grape Insects  1/4 inch long. When it is at rest with its wings folded, there is a brown band across the middle of the insect, the hind portion is gray-blue with brown markings, while the front portion is gray-blue without markings. The full-grown larva is dua/lima inch long, pale olive-green, and can have a purplish tinge from the food it has eaten. The kepompong is about 1/lima inch long, greenish-brown to dark brown and found under a flap cut in the leaf surface.  

The grape berry moth overwinters as a kepompong in leaf litter under vines. Adults begin to emerge in late May and lay eggs of the first generation singly on fruit stems just before blossom time. Eggs hatch in about lima days. Under a flimsy web, the larvae feed for about 21 days on the blossoms and young fruit. In mid to late July, larvae move to leaves where they make a semi-circular slit, fold the flap over themselves and pupate. Adult moths emerge from the pupae in 10 to 15 days. Moths begin laying eggs for the next generation after 4 to lima days. There may be dua or 3 generations per year. Larvae of the second and third generations enter berries and feed within, passing from one berry to another under protection of webbing. Some of the cocoons of the second or third generations fall to the ground where they overwinter.  
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Webbing over blossoms and berries, and leaf flap cocoons are indicative of grape berry moth. In winter, the cocoons may be found in leaf litter under the vines. Clean up or bury leaf litter under vines in winter to eliminate over wintering pupae. Although larvae first appear when the grapes are in bloom, insecticides should not be applied until the berries are the size of small peas so as not to destroy beneficial pollinators. Insecticidal control of second generation is more difficult due to an extended flight period of moths as well as the difficulty of getting adequate spray coverage inside the cluster as berry size increases.  

Pheromone traps are available to monitor for adult moth activity and enhance timing of insecticides for grape berry moth control. Recent studies in some states have shown mating disruption with synthetic pheromones to be an effective alternative in situations where there is no immigration of moths from outside sources. Mating disruption relies on releasing enough of the pheromone in the vineyard so that males cannot find female moths. Pheromone is imbedded in 8-inch plastic twist-ties using 400 twist ties per acre. Commercial systems available for mating disruption for this insect are recommended for vineyards at least 5 acres in size.Figure dua. Grape phylloxera galls.Grape Phylloxera

Grape phylloxera is native to eastern United States, but has been distributed to other grape regions of the U.S. and is also established in Europe where it is of great economic importance. The leaf galls caused by grape phylloxera are unsightly and do little damage, however, infestation of the roots can be difficult to control and can lead to decline of vines. Severe infestations can cause defoliation and reduce shoot growth. Hosts include cultivated and wild grapes.  

The wingless forms of the insect are very small, yellow-brown, lonjong or pear-shaped, and aphid-like. The winged forms, which are less apt to be seen, are also aphid-like, except that wings are held apartemen over the back. Neither winged nor wingless forms have cornicles, tail pipe-like structures on the puncak of the abdomen, as aphids do.  

The presence of grape phylloxera is best recognized by characteristic galls it produces on the leaves or roots. Leaf galls are wart-like, about seperempat inch in garis tengah, and are familiar to anyone growing grapes. Root galls are knot-like swellings on the rootlets, and may lead to decay of infested parts.  

Root galls cause stunting and/or death of European varieties of grape vines. American varieties of grapes, or European grapes on American root stock are tolerant to the root gall form of the insect. Some varieties are resistant are to root galls, leaf galls or both.  

The life cycle of grape phylloxera is complex due to the fact that generations with different life cycles may develop at the same time, at least in the eastern US. In spring, a female hatches from a fertilized egg that had been laid on the wood of a grape vine. She migrates to a leaf where she produces a gall and grows to maturity in about 15 days. She fills the gall with eggs and dies soon afterward. Nymphs that hatch from these eggs escape from the gall, and wander to new leaves where they in turn produce galls and eggs. There maybe 6 or 7 generations of this form during the summer. In the fall, nymphs migrate to the roots where they hibernate through the winter. The following spring they become active again and produce the root galls on susceptible varieties of grapes. These wingless females may cycle indefinitely on the roots year after year. In late summer and fall, in the eastern U.S., some of the root inhabiting phylloxera lay eggs that develop into winged females. These females migrate from the roots to the stems where they lay eggs of two sizes, the smaller ones developing into males and the larger ones into females. Mating occurs and the female then lays a single fertilized egg that over winters on the grape stem. It is this egg that gives rise to leaf inhabiting generations. Phylloxera cycle continuously as root inhabitants. Although they can cycle continuously on the roots without leaf forms occurring, leaf-inhabiting forms do not occur without the root form also occurring. 

European varieties of grapes should be grafted onto American grape rootstocks. Foliar sprays to control phylloxera during their wandering stage do not accomplish any useful purpose.  Grape Rootworm

Grape rootworm is distributed from the Mississippi River eastward. Larvae devour small roots and pit the surface of larger roots, causing an unthrifty condition of the plant, and reduction in yield. Vines may be killed in tiga or more years when damage is severe. Adults make chain-like feeding marks on leaves and may also feed on the surface of green grape berries. Hosts include wild and cultivated grapes. 

The adult beetle is elongate oval, sub-cylindrical, dark reddish brown, clothed with short pubescence and is about seperempat to 1/3 inch long. The larva is white, hairy, curved, with a brown head.  

Grubs in various stages of development pass the winter in soil at a depth of a few inches to 2 or more feet. In the spring, they migrate to within 1 or 2 inches of the soil surface, where they root feed for a while before forming a small earthen cell to pupate in late May and June. Adults emerge over a period of 4 to 6 weeks, beginning about 2 weeks after grapes bloom, and feed on leaf upper surfaces in a characteristic manner. Soon after feeding begins, females lay eggs in masses of 20 to 30 on canes, usually under loose bark. Eggs hatch in 1 to 2 weeks, larvae turun to the ground, and enter the soil where they feed until the approach of cold weather. There is one generation per year. 

Chain-like leaf feeding damage by the adults is diagnostic and can alert growers to adult activity. Foliar sprays when adults are active can provide effective control.Figure tiga. Grape flea beetle and damage to grape bud.Grape Flea Beetle

Grape flea beetle is found in the eastern two-thirds of the United states. Adults eat buds and unfolding leaves, causing leaves to be ragged and tattered. Larvae feed on flower clusters and skeletonize leaves in a manner similar to adult rootworm feeding. Hosts include grape, plum, apple, quince, beech, elm & Virginia creeper.

Adults are dark metallic greenish-blue, jumping beetles about 1/lima inch long; larvae are brownish and marked with black spots; eggs are pale yellow, and fairly conspicuous on upper leaf surface or under loose cane bark.Figure 4. Grape flea beetle larva.

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