The Online Gardener's Handbook
Chapter 5: Fruit
Table of Contents
- Berry Moths
- Black Rot
- Grape Flea Beetles
- Downy Mildew
- Powdery Mildew
- 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 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
Remove nearby wild grapevines. Bury leaf debris.
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
Remove infected debris before the start of the growing season.
Cultivate early in season to bury infected mummies and remaining
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.
Examine vines in May. If practical, knock the adults off into a
pail of soapy water.
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.
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
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.
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.