Plant Health Management
for Backyard Grape
Plantings
Prepared by
Mike Ellis
Professor and Extension Specialist
and
Omer Erincik
Graduate Research Assistant
Department of Plant Pathology
The Ohio State University
OARDC/OSUE
Wooster, OH, 44691
Black rot
Symptoms:
On leaves
 Brown to reddish brown lesions with
irregular margins.
 Minute, black, spherical fungal fruiting
bodies (pycnidia) form within the
lesions.
 Pycnidia often are arranged in a ring
pattern just inside the margin of the
lesions.
 Similar lesions also develop on young
shoot, cluster, stems and tendrils.
Black rot
Symptoms:
On Fruit
 Small, round, light-brownish
spots develop on fruit.
 Tissue in the spot softens and
becomes sunken.
 Spots enlarge quickly rotting the
entire berry in a few days.
 Infected berries eventually shrivel
into small, hard, black and
wrinkled (mummies).
Black rot
Disease Development:
Caused by the fungus Guignardia
bidwellii.
The fungus overwinters on infected plant
parts in the trellis or on the ground.
In spring, the fungus produces spores on
plant parts infected the previous year.
The fungus spores are spread by
splashing rain, and a film of free water on
the vine surface is necessary for infection.
Black rot
Disease Development:
Berries are susceptible to infection from
bloom until several weeks after bloom.
Berries become resistant to infection as
they begin to ripen. Ripe berries are
resistant.
The disease can result in complete crop
loss under warm, humid environmental
conditions.
Downy mildew
Symptoms:
On leaves:
Early season infections:
 Irregular pale-yellow to grayish-yellow
spots appear on the upper leaf surface.
 White to grayish cotton like fungal
growth develops within the border of
the lesions on the lower surface.
Late season infections
 Small, angular, yellow to red-brown
spots develop on the upper surface.
 Lesions commonly form along the
veins.
 The fungus sporulates (produces
downy growth) on these infected areas
Downy mildew
Symptoms:
On fruit
 Infected young berries turn brown
and soft, shatter easily, and often
are covered with a downy like
growth of the fungus.
 Late season infection results in
berries that are dull green, then dark
brown to brownish –purple. They are
generally not covered with the
fungal growth.
Downy mildew
Disease Development:
 Caused by the fungus, Plasmopara viticola
 The fungus overwinters on infected plant parts
in the trellis or on the ground.
 The fungus is spread by wind, splashing rain,
and by handling wet plants.
 When plant parts are covered by a film of water,
the fungus infect leaves through stomates
(natural openings) on the lower leaf surface.
 All common species of wild and cultivated
grapes are susceptible.
Powdery mildew
Symptoms:
On leaves:
 Small, white or grayish-white
patches of fungal growth appear
on the upper or lower leaf surface.
 These patches usually enlarge
until the entire upper leaf surface
has a powdery, white to gray
coating.
On shoots:
 Dark-brown to black patches
develop on young shoots and
dormant canes.
Powdery mildew
Symptoms:
On fruit:
 Infected berries are misshapen or
have rusty spots on the surface,
and are usually covered by a
powdery growth of the fungus.
 Severly infected berries often
split open.
 Late in the season tiny black
specks may develop on the
surface of infected areas.
Powdery mildew
Disease development:
 Caused by the fungus, Uncinula necator
 The fungus overwinters in bark crevices on the
vine.
 The fungus is spread by wind throughout the
growing season.
 Unlike most other grape diseases, powdery
mildew is considered a “dry-weather” disease,
and does not require free water on the plant
surface to infect.
 The disease is generally more severe in dry
areas or during dry seasons at temperatures
between 65 and 80 °F.
Phomopsis cane and leaf spot
Symptoms:
On leaves:
Small light-green irregular spots with star-shaped
margins develop in early spring.
Later in the growing season, these spots turn
black and have a yellow margin.
Usually only the lower 1 to 4 leaves on a shoot are
affected.
On shoots:
 Small, black spots develop at the base
of developing shoots.
 These spots may grow together to
form irregular black crusty areas.
 Under severe conditions, shoots may
split and form cracks in the cortex.
Phomopsis cane and leaf spot
Symptoms:
On cluster stem:
Small black spots develop on cluster
stems, eventually the entire cluster
stem may be blighted.
On Fruit:
A light-brown fruit rot develops close
to harvest.
Black spore-producing structures
(pycnidia) develop on the surface of
infected berries.
Fruit rot develops only on ripening or
ripe fruit. Green fruit are resistant to
fruit rot.
Phomopsis cane and leaf spot
Disease development:
 caused by the fungus, Phomopsis viticola
 The fungus overwinters on infected plant parts in
the trellis.
 The fungus produces spores in early spring, and
the spores are spread by splashing rain; thus,
spreading the disease.
 Most infections occur early in the season under
cool and wet conditions.
 Fruit rot symptoms do not develop until fruit starts
to ripen.
Botrytis bunch rot
Symptoms:
Infected berries first appear
soft and watery.
Later, they become covered
with a grayish brown, dusty
mass of fungus spores.
Rotted berries generally
shrivel with time and turn
into hard mummies.
Botrytis bunch rot
Disease development:
Caused by the fungus, Botrytis cinerea.
Berries are usually infected by the fungus
during bloom or near harvest.
 Disease is favored by warm and moist
weather.
Any wound on the berry provides an
excellent infection site for the fungus.
Management of leaf and fruit
rot diseases of grape
(Black rot, Downy mildew, Powdery mildew,
Phomopsis cane and leaf spot, Bortytis
bunch rot)
Free water (wet conditions) is required for
most fungal pathogens (except Powdery
mildew) to infect plants. Any practice that
promotes faster drying of fruit and foliage
is beneficial for disease control.
Many cultural disease control methods are
aimed at promoting faster drying of plant
parts.
Management of leaf and fruit rot
diseases of grape
 Site selection
 Plants grapes in sunny, open areas that allow good air
movement.
 Do not plant in shaded areas
 Maintain good weed control beneath vines
 weeds can reduce air movement and result in slower
drying time.
 Proper pruning practices,
 opens the canopy for increased sunlight penetration
 creates good air circulation for faster drying.
 Sanitation
 Destroy fruit mummies and remove all diseased plant
parts during dormant pruning, or early in the spring
before bud break.
Management of leaf and fruit rot
diseases of grape
Use of disease resistance varieties:
Unfortunately, the grape varieties that
are commonly grown in the midwest do
not have good resistance to most
diseases. Disease management for
grapes depends mostly on the cultural
practices previously mentioned, and the
use of fungicides (chemical control) if
necessary.
Using Fungicides For Grape
Disease Control
 Fungicides are very important for disease
control in commercial grape production, and
can be useful in backyard grape vineyards;
however, the emphasis for disease control in
backyard vineyards should be placed on the
use of the various cultural practices
previously mentioned.
 Effective fungicides are usually difficult or
impossible for backyard growers to obtain.
 If not used properly, they are generally not
effective.
Using Fungicides For Grape
Disease Control
If diseases such as black rot or
downy mildew become established in
the vineyard, fungicides may be
required in order to “clean up” the
planting.
There are a few fungicides available
for homeowners that should be
useful in backyard vineyards.
For backyard growers
that do wish to use
fungicides in the disease
management program,
fungicide recommendations
are available for grapes in
Bulletin 780 “Controlling
Disease and insects In Home
Fruit Planting”.
Selected literature for backyard fruit
production and plant health
management:
 Bulletin 591. “Growing and Using Fruit at Home”
 Bulletin 780. “Controlling Diseases and Insects in
Home Fruit Planting”
 Bulletin 815. “Grapes Production, Management
and Marketing”
 Bulletin 861. “Midwest Small Fruit Pest
Management Handbook”
These can be obtained through your county extension
agent or the Extension Publications Office, The Ohio State
University, 385 Kottman Hall, 2021 Coffey Road, Columbus,
Ohio, 43210-1044
To get more information about plant
diseases visit the websites below.
http://www.ag.ohiostate.edu/~plantdoc/extension.php
http://www.ohioline.ag.ohio-state.edu