Grapevines are grown in many areas of the country, including Oregon and California. These vines produce fruit that is often used to make wine or eaten as a raw fruit. Grapevines are generally healthy, but they are susceptible to a variety of insect infestations that can damage the health of the plant and the grapes it produces.
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Aphids are also known as plant lice and are common pests of grapes. Grapevine aphids are tiny black insects that infest the leaves, fruit clusters and vines on grapevines. Aphid populations flourish in periods of dry weather and can multiply rapidly. The grape flea beetle is another common grapevine pest. These beetles are 1/5 inch in length and are dark green or blue in colour. Both the grape flea beetle and its larvae damage grapevines during infestations. Mealybugs are also a pest of grapevines. Mealybugs are small insects that have a waxy coating on their bodies. This coating is similar to ground meal, which is how the insect received its name. These pests infest all areas of grapevines, including the vines, stems and leaves.
Aphids congregate on the leaves and vines of grapevines, feeding on them and causing stippling. Grapevine aphids usually feed in large colonies and can damage the developing fruit when infesting the clusters of grapes. The adult grape flea beetle feeds on unfolding grapevine leaves and young buds. Infestations are especially heavy if grapevines are growing near wooded areas. The grape flea beetle larvae feeds on the leaves of grapevines, causing them to appear skeletonised or have a lacy appearance. Mealybugs feed on grapevine leaves and stems, removing sap from their tissues. Once the insects ingest large portions of plant sap, they excrete a sticky liquid called honeydew that adheres to the leaves and vines. Sooty mould fungi sticks to the patches of honeydew, causing a black fungus on the surface of the vine and leaves. Grapevines with heavy infestations of mealybugs can suffer reduced growth, lack of vigour and yellow leaves. Untreated grapevines with heavy infestations of mealybugs can die as a result of feeding injuries.
Both the grapevine aphid and grape flea beetle are susceptible to a variety of natural predators that feed on them, keeping their populations low. Lacewigs, lady beetles and parasitic wasps all feed on aphids. The larvae of the grape flea beetle is often eaten by birds and raccoons. Aphids and mealybugs can be removed from grapevines by spraying them with a hard stream of water and knocking the insects from the plant. Repeat this process two or three times each week for the best results.
Since grapevine aphids rarely cause significant damage to grapevines or cause crop loss, there are no chemical methods recommended for their control. If flea beetle larvae are visible on your grapevines, you can remove them by hand and place them in a bucket of soapy water to destroy them. Heavy infestations often require the application of insecticides to reduce their populations and prevent further damage to your grapevines. According to the University of Florida IFAS Extension, flea beetles can be reduced with applications of neonicotinoid insecticides. Aphids and mealybugs are often controlled with applications of horticultural oils. These products work on contact to suffocate insects, causing them to die. Horticultural oils also help remove sooty mould fungi, which is often a result of a honeydew-excreting insect infestation.
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