Grape Plant Problems

Disease

• Grapes are susceptible to numerous fungal, bacterial and viral diseases, including powdery mildew and crown gall. To prevent and control these diseases, you may need to counter environmental conditions, alter maintenance practices or curb pest populations. Viral diseases present perhaps the most complex problem, because some plants -- like those suffering with grapevine leafroll disease -- may show no symptoms or develop symptoms late in the season. Washington State University Extension suggests you plant only certified grape stock to prevent the introduction or spread of pathogens.

Pest Damage

• Insect pests of grapes include Japanese beetles, leafhoppers, thrips, cutworms and borers. Depending on the pest, you may see localized damage, severe internal damage or stress that affects the health of the entire plant. Voles are known to eat the bark from grapevines during the winter. Root knot nematodes and dagger nematodes cause direct damage through feeding on the roots of grapevines, but their feeding also creates an opening for disease-causing microorganisms to enter the plants. You should test the soil for nematodes before planting new vines. Keep the area around the vines free of snow and apply several inches of mulch to deter voles. Treat for individual pests as recommended by your local extension agent.

Environmental Damage

• Environmental extremes can lead to damage of grapevines or a reduction in fruiting. Water stress and drought can affect the vines during their early season growth or cause poorly developed fruits. Shaded vines may experience reduced production since grapes require a daily eight hours of full sun. Developing buds are sensitive to late frosts and cold snaps. To prevent damage, North Carolina State University Cooperative Extension suggests planting grapes on north- or east-facing slopes. You may also plant varieties with greater cold tolerance.

Damage from Herbicides

• Take care not to damage vines when applying herbicides for weed control. Washington State University Extension recommends avoiding the use of the same equipment to apply both pesticides and herbicides, avoiding bringing herbicides in contact with grapevines, and not combining herbicides unless the mix of products has been tested and declared safe. Damage can also occur from herbicides sprayed in the area of grapevines; grapes are extremely sensitive to 2,4-D, an herbicide used for dandelion control. The plants cannot tolerate fumes or traces of the formulation in the air. Contact can also occur if the herbicide leaches through the soil from applications made nearby.