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Grape Grapes are among the oldest cultivated plants in the world. Human history and grape culture have been intertwined for eons. Leading producers of grapes are ... – PowerPoint PPT presentation

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Title: Grape

  • Grapes are among the oldest cultivated plants in
    the world. Human history and grape culture have
    been intertwined for eons.
  • Leading producers of grapes are Italy, France,
    former Soviet Union, Argentina and U.S.
  • California produces about 90 of US grapes
  • Most grapes are used in wine production
  • 90 of raisin grapes are grown in Fresno County

  • Family Vitis has 11 genera and 600 species
  • Genus Vitis is the only food-bearing genus
  • About 30 species are native to North America
  • There has been much interbreeding to give rise to
    current cultivars

Images and lecture material were not entirely
created by J. Bond. Some of this material was
created by others.
Principal grapes grown in North America
  • European grapesfor wine, raisins and table use
  • American blue grapesfor juice and jelly
  • French American hybridsprimarily for wine in
    areas with cold winters
  • Muscadine grapesin the south

Grape vine anatomy
  • Roots - Grapes root readily from hardwood
    cuttings. Most European grapevines are propagated
    on specific rootstocks
  • Trunk - May be single or split. This is usually
    maintained as part of the perennial structure of
    the vine. It may be trained vertically or in a J
  • Cordon - Horizontal permanent stems. Not all
    training systems have cordons
  • Canes - One year old wood. May have 5-10 nodes.
    Current season growth is also called canes.
  • Spurs - Canes pruned off short, usually 2-3 buds.
    May be fruiting spurs or renewal spurs
  • Tendrils - Twining structures borne opposite
    leaves or clusters. Helps hold grapes to

  • Crown gall
  • Downy mildew
  • Black rot
  • Pierces disease

Crown Gall
  • Caused by the bacterium Agrobacterium
  • This bacterium has the widest host range of any
    plant pathogen. It is capable of causing tumors,
    or "galls," on virtually all plant species,
    except the monocots. A similar bacterium,
    Agrobacterium rubi, causes galls on the canes of
  • Serious problem, freeze injury locations are
  • Rod shaped bacteria non-motile and motile.,
    biovars 3 is found on grape

Crown Gall
  • All fruit crops grown in Illinois are
  • The disease is particularly destructive on
    brambles (raspberries and blackberries) and
  • It can also cause severe problems on apple, pear,
    blueberry, all stone fruits and on ornamentals.
  • The bacteria induce galls or tumors on the roots,
    crowns, trunks and canes of infected plants.
  • These galls interfere with water and nutrient
    flow in the plants. Seriously infected plants may
    become weakened, stunted and unproductive.

  • The disease first appears as small overgrowths or
    galls on the roots, crown, trunk or canes.
  • Galls usually develop on the crown or trunk of
    the plant near the soil line or underground on
    the roots.
  • Above ground or aerial galls may form on canes of
    brambles and highly susceptible cultivars of
  • Although they can occur, aerial galls are not
    common on fruit trees.
  • In early stages of development the galls appear
    as tumor-like swellings that are more or less
    spherical, white or flesh-colored, rough, spongy
    (soft) and wart-like.

  • They usually form in late spring or early summer
    and can be formed each season.
  • As galls age they become dark brown to black,
    hard, rough, and woody. Some disintegrate with
    time and others may remain for the life of the
  • The tops of infected plants may appear normal.
  • If infection is severe, plants may be stunted,
    produce dry, poorly-developed fruit, or show
    various deficiency symptoms due to impaired
    uptake and transport of nutrients and water.

Disease Cycle
  • The bacteria overwinter inside the plant in
    galls, or in the soil. The persists for long
    periods in the soil and plant debris.
  • When they come in contact with fresh, wounded
    tissue of a host, they enter the plant and induce
    gall formation. The bacteria are most commonly
    introduced into a planting site on or in planting
  • Wounds that commonly serve as infection sites
    are those made during pruning, machinery
    operations, freezing injury, growth cracks, soil
    insects and any other factor that causes injury
    to plant tissues.
  • Bacteria are abundant in the outer portions of
    primary galls, which is often sloughed off into
    the soil.
  • In addition to primary galls, secondary galls
    may also form around other wounds and on other
    portions of the plant in the absence of the

  • Obtain clean (disease free) nursery stock, and
    avoid planting clean material in sites previously
    infested with the bacteria.
  • Any practice that reduces wounding is highly
    beneficial. Preventing winter injury (especially
    on grapes) is also beneficial.
  • On grapes, the double trunk system of training
    may be a useful system for minimizing losses due
    to crown gall. If one trunk is infected, it can
    be removed.
  • Galls on the upper parts of the trunk or on canes
    can be removed by pruning.

  • A biological control agent for crown gall is
    available for apple, pear, stone fruit,
    blueberry, brambles and many ornamentals. It is
    not effective on grape.
  • The agent is a nonpathogenic strain of bacterium
    (Agrobacterium radiobacter strain 84) that
    protects the plants against infection by the
    naturally occurring strains of pathogenic
    bacteria in the soil.
  • Nursery stock is dipped in a suspension at
    planting time. The antagonistic bacteria act only
    to protect disease free plants from future
    infection by the crown gall bacterium they
    cannot cure infected plants.

Downy mildew
  • A major disease of grapes throughout the eastern
    United States.
  • The causal agent Plasmopara viticola, causes
    direct yield losses by rotting inflorescences,
    clusters and shoots.
  • Indirect losses can result from premature
    defoliation of vines due to foliar infections.
    This is a serious problem because it predisposes
    the vine to winter injury.
  • It may take a vineyard several years to fully
    recover after severe winter injury.

Symptoms and Signs
  • On leaves, young infections are very small,
    greenish-yellow, translucent spots that are
    difficult to see. With time the lesions enlarge,
    appearing on the upper leaf surface as irregular
    pale-yellow to greenish-yellow spots.
  • On the underside of the leaf, the fungus mycelium
    (the "downy mildew") can be seen within the
    border of the lesion as a delicate, dense, white
    to grayish, cotton-like growth.
  • Infected tissue gradually becomes dark brown,
    irregular, and brittle. Severely infected leaves
    eventually turn brown, wither, and drop.
  • The disease attacks older leaves in late summer
    and autumn, producing a mosaic of small, angular,
    yellow to red-brown spots on the upper surface.
    Lesions commonly form along veins, and the fungus
    sporulates in these areas on the lower leaf
    surface during periods of wet weather and high

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Symptoms and Signs - Fruit
  • Most infection occurs during 2 distinct periods
    in the growing season.
  • The first is when berries are about the size of
    small peas. When infected at this stage, young
    berries turn light brown and soft, shatter
    easily, and under humid conditions are often
    covered with the downy-like growth of the fungus.
  • Generally, little infection occurs during hot
    summer months.
  • As nights become cooler in late summer or early
    fall, the second infection period may develop.
    Berries infected at this time generally do not
    turn soft or become covered with the downy
    growth. Instead, they turn dull green, then dark
    brown to brownish-purple. They may wrinkle and
    shatter easily and, in severe cases, the entire
    fruit cluster may rot.
  • These infected fruit will never mature normally.

Symptoms and Signs - Fruit
Symptoms and Signs Shoots and Tendrils
  • Early symptoms appear as water-soaked, shiny
    depressions on which the dense downy mildew
    growth appears.
  • Young shoots usually are stunted and become
    thickened and distorted.
  • Severely infected shoots and tendrils usually die

Disease Cycle
  • The fungus overwinters in infected leaves on the
    ground and possibly in diseased shoots.
  • Oospores germinates in the spring and produce a
    sporangium. These sporangia are spread by wind
    and splashing rain.
  • The sporangia release zoospores, which also are
    spread by splashing rain, either will produce a
    germ tube and enters through stomates.
  • Once inside the plant, the fungus grows and
    spreads through tissues. Infections are usually
    visible as lesions in about 7-12 days.
  • At night during periods of high humidity and
    temperatures above 55 degrees F (13 degrees C),
    the fungus grows out through the stomates and
    produces sporangiophores on the lower leaf
  • The small sporangiophores and sporangia make up
    the cottony, downy mildew growth.
  • Sporangia cause secondary infections and are
    spread by rain.
  • The optimum temp. for disease development is 64
    to 76 degrees F.

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  • Any practice that speeds the drying time of
    leaves and fruit will reduce the potential for
  • Sanitation is important. Remove dead leaves and
    berries from vines and the ground after leaf
  • It may be beneficial to cultivate the vineyard
    before bud break to cover old berries and other
    debris with soil. Cultivation also prevents
    overwintering spores from reaching developing
    vines in the spring.
  • To improve air circulation, control weeds and
    tall grasses in the vineyard and surrounding
  • Grape varieties vary greatly in their
    susceptibility to downy mildew. In general,
    vinifera (Vitis vinifera) varieties are much more
    susceptible than American types, and the French
    hybrids are somewhat intermediate in
  • A good fungicide spray program is extremely
    important. Downy mildew can be effectively
    controlled by properly timed and effective

Black rot
  • Caused by the fungus Guignardia bidwellii
  • The the most serious disease of cultivated and
    wild grapes in Illinois and is one of most
    important disease of northeast US, Canada, EU, SA
  • The disease is most destructive in warm, wet
  • Crop losses range from 5 80
  • The fungus attacks all green parts of the vine
    the leaves, shoots, leaf and fruit stems,
    tendrils, and fruit. The most damaging effect is
    to the fruit.

Black Rot
  • Infections early in the growing season destroy
    blossom clusters or cause developing berries to
    "shell off" the cluster and fall to the ground.
  • Later infection periods can destroy a high
    percentage of the berries, turning them into
    hard, black, shriveled "mummies."
  • Unsprayed fruit on very susceptible varieties may
    become almost completely rotted by harvest time

Symptoms - Leaves
  • Reddish brown and circular-to-angular spots
    appear on the upper surface of the leaves
    starting in the late spring.
  • As spots coalesce, they form irregular blotches
    that are reddish brown. The number of spots or
    lesions per leaf varies from 1 to more than 100
  • The center of the leaf spot turns tannish brown
    and is surrounded by a black margin.
  • Pycnidia that are speck sized and black are
    arranged in a definite ring just inside the
    margin of the spot.
  • Only young, rapidly growing leaves are

Symptoms - Leaves
Symptoms - Fruit
  • Fruit infections can take place shortly after the
    calyx (flower petal) falls, but most infections
    occur when the fruit is half to almost full size.
  • A small spot appears that is circular and whitish
    tan, often surrounded by a brown ring.
  • The spots rapidly enlarge, darken, and may cover
    half or more of the berry within 48 hours.
  • The center of the spot rapidly becomes sunken,
    wrinkled, and dark. Within a few days, the entire
    berry becomes coal black, hard, and mummified.
  • The diseased fruit 'shell' or shatter and drop
    early. The surface of the withered fruit is
    covered with minute, black pycnidia that are
    often arranged in circular zones.

Symptoms - Fruit
Symptoms - Shoots, Leaf and Fruit Stems, and
  • The lesions on these parts are dark purple to
    black, oval to elongated, and somewhat sunken.
  • The speck-sized black pycnidia are scattered over
    the surface of the lesions.
  • As the canes grow, the bark tends to split along
    the length of the lesion. If the berry stem is
    infected early, the flow of sap is shut off, and
    the berry shrivels and fails to develop.

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Disease Cycle
  • Overwinters in canes, tendrils, and leaves on the
    grape vine and on the ground.
  • Mummified berries on the ground or those on
    vines become the major infection source the
    following spring. During rain, ascospores are
    shot out of numerous, perithecia and are carried
    by air currents to young, expanding leaves.
  • Ascospores slowly germinate, often taking 36 to
    48 hours, penetrate the young leaves and fruit
    stems (pedicels).
  • The infections become visible after 8 to 25 days.
    Spots appear first on the lower leaves. When the
    weather is moist, ascospores are produced and
    released throughout the entire spring and summer,
    providing continuous primary infection.
  • The fungus requires warm weather for optimal
    growth cool weather slows its growth. A period
    of 2 to 3 days of rain, drizzle, or fog is also
    required for infection.

Disease Cycle
  • Each older leaf spot contains a number of
    pycnidia, each of which produces hundreds of
    summer conidia that ooze out in winding tendrils
    during wet weather.
  • Raindrops spreads these spores to other leaves
    and to young fruit. The conidia germinate in 10
    to 15 hours and penetrate young tissue.
  • New infections continue into late spring and
    summer during prolonged periods of warm, rainy
    weather. The conidia are capable of germinating
    and causing infection several months after being
  • During August, the pycnidia are transformed into
    an overwintering sclerotia that, in turn, gives
    rise to perithecia which produce ascospores in
    the spring.

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  • Space vines properly and choose a planting site
    where the vines will be exposed to full sun and
    good air circulation.
  • Prune the vines each year during the dormant
    period. Remove the prunings, excess growth,
    diseased and overwintering berries, leaves, and
  • Keep the fruit planting and surrounding areas
    free of weeds and tall grass.
  • Where feasible, cultivate the vineyard before
    bud-break to bury the mummified berries.
  • Use protective fungicide sprays, which are needed
    in wet seasons, to protect the developing new

Pierce's Disease
  • A lethal disease caused by the bacterium Xylella
  • First detected in 1880s when it decimated
    vineyards in the LA Basin and again in the 1930
    and 1940s.
  • Pierce's disease is only known from North America
    through Central America and has been reported
    from some parts of northwestern South America.
  • It is present in some California vineyards every
    year, with the most dramatic losses occurring in
    Napa Valley and in parts of San Joaquin Valley.
    During severe epidemics, losses may require major

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Pierce's Disease
  • The bacterium that causes Pierce's disease lives
    in the xylem and is spread from plant to plant by
    sap-feeding insects that feed on the xylem.
  • Symptoms appear when a significant amount of
    xylem becomes blocked by the growth of the
  • Insect vectors for Pierce's disease belong to the
    sharpshooter and spittlebug families. The
    blue-green sharpshooter the green sharpshooter
    and the red-headed sharpshooter are important as
    vectors of this disease.
  • Other sucking insects, such as grape leafhoppers,
    are not vectors.

Pathogen in Host
Voracious, aggressive flyer and feeds and breeds
on 133 host Spreads Pierces disease with
astonishing speed.
Spring Symptoms
  • In vines that are infected in spring, symptoms of
    Pierce's disease first appear as water stress in
    midsummer, caused by blockage of the
    water-conducting system by the bacteria.
  • New leaves on PD vines are stunted, more yellow
    than normal, and deformed in shape.
  • Interveinal areas of leaves may be more yellow
    than normal leaves, much like zinc deficiency

Spring Symptoms
Summer Symptoms
  • The combination of these three symptoms is a
    definitive indication that PD is present
  • 1) Leaves become slightly yellow or red along
    margins in white and red varieties respectively.
    As the disease advance leaf margins progressively
    dry or die (turn brown) in concentric zones.
  • 2) Scorched leaves dry down and the blade falls,
    leaving the petiole attached to the cane.
  • 3) Wood on new canes matures irregularly,
    producing patches of green, surrounded by mature
    brown bark.

Type and extent of symptoms vary
  • 1. Grape variety
  • Highly susceptible are Barbera, Chardonnay,
    Fiesta, and Red Globe.
  • Less susceptible varieties are Chenin blanc,
    Flame Seedless, Riesling, and Thompson Seedless.
    Cabernet sauvignon, Merlot, are intermediate" in
  • 2. Date when the vine was infected.
  • 3. Vine age -   The younger the vine, the faster
    severe symptoms will appear and the less chance
    that it will recover over the next winter.
  • 4. Climate
  • 5. "Variability".
  •    For unknown reasons, different vines of the
    same age, location, and variety will develop
    somewhat different symptoms.
  • 6.Other constraints mimicking Pierce's Disease
  • Zinc deficiency, measles, salt burn

  • Removal of wild grapevines, immaculate weed
    control and establishing a weed-free perimeter
    around a vineyard provide the best strategy to
    manage Pierces disease.
  • Sharpshooters need water to survive and
    reproduce. Avoiding sites adjacent to creeks,
    streams, ponds or even depressions that retain
    rainwater will reduce the likelihood of
    consistently high leafhopper populations.
  • By creating a large (at least 150 ft.) buffer
    zone around vineyards, growers can either
    chemically or mechanically create an environment
    that is not favorable to insect populations.
  • Growers should also understand that when hay
    fields adjacent to a vineyard are cut, large
    numbers of insects will be seeking alternative
    habitat and feeding sites.
  • Insect monitoring and insecticide applications
    should be considered when insects move into the