The Online Gardener's Handbook 2010
Chapter 5: Fruit

Table of Contents

  1. Introduction
  2. Berry Moths
  3. Black Rot
  4. Grape Flea Beetles
  5. Downy Mildew
  6. Powdery Mildew
  7. Learn More


In this chapter, a description of various grape pests will be provided along with suggested management options. These management options will not include the use of pesticides. Some biopesticides and certain reduced risk pesticides are still available to the homeowner for controlling weeds and pests in lawns and gardens. For more information, refer to Chapter 2 of this handbook and the Ministry of the Environment's website. For suggestions on managing specific weeds and pests, consult local horticulturalists, Master Gardeners or your local garden supply centre.

Berry Moths

Berry moths are a problem only in areas where grapes are grown commercially. The adult is a 6 mm brown-bodied moth with blue-grey wings that have cream spots near the tips. The larvae are initially cream-coloured with a brown head but become green and then purple when mature. The first generation larvae web together buds, flowers and newly set berries and chew them. The second generation burrow into green berries near the stem. Berries usually shrivel or fall off.

Management Options

Remove nearby wild grapevines. Bury leaf debris.

Black Rot

Black rot can be a serious problem on many grape varieties including Catawba, Concord, Agawam and Niagara. Raised black lesions develop on clusters and leaf stems and on new shoots. Infected berries develop a reddish-brown ring and shortly before harvest shrivel into blue-black mummies.

Management Options

Remove infected debris before the start of the growing season. Cultivate early in season to bury infected mummies and remaining debris.

Grape Flea Beetles

The grape flea beetle is a shiny, metallic, greenish-blue beetle that attacks opening buds in spring. It is 4-5 mm long and jumps when disturbed. The adult chews through the ends and sides of swelling buds. Larvae are black-spotted grubs which feed on leaves.

Management Options

Examine vines in May. If practical, knock the adults off into a pail of soapy water.

Downy Mildew

Downy mildew appears early in the season and affects leaves, tendrils, shoots and fruit, covering these with heavy, white, downy fungus underneath and localized pale yellow areas on top surfaces. Fruit clusters may curl or be completely destroyed. The disease is more serious in wet seasons and in sheltered areas with poor air movement.

Management Options

Prune to allow good air movement. Collect and destroy infected plant material. Cultivate in spring to bury any remaining infected tissue. Agawam, Delaware, Fredonia, Niagara and Van Buren varieties are especially susceptible. Plant less susceptible varieties if possible.

Powdery Mildew

Powdery mildew usually appears later than downy mildew but may be present just after bloom. Blossoms wither and drop, whitish patches appear on upper leaf surfaces in shaded areas of the vine, and fruit may crack and fail to ripen. If the fruit stem is infected, berries drop. Prolonged humid conditions favour its growth.

Management Options

Prune to allow good air circulation and to reduce shading. Agawam, Buffalo, Concord, DeChaunac, Fredonia, Foch, New York Muscat and Seneca varieties are especially susceptible. Plant more resistant cultivars if possible.

Learn More

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