Plant Disease Management Handbook

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Cause A physiological problem that has not been explained fully. Frequent attempts to isolate pathogens from necrotic tissue have not resulted in any fungi or bacteria. The disorder is associated with cool and/or wet weather just before bloom. Excessive vigor, shade just before bloom, and general stresses have also been associated with symptoms. The disorder resulted in low yields 4 out of 10 years in the 1980s in Oregon.

Image related to Grape (Vitis spp.)-Inflorescence Necrosis (Bunch Stem Necrosis)

Necrotic flower and pedicel tissue extending into the rachis on this cluster.

Jay W. Pscheidt, 2016.

By R. Martin and J. Pscheidt

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Grape (Vitis spp.) - Virus Diseases

Image related to Grape (Vitis spp.)-Grapevine Red Blotch Disease

The discolored areas on the leaves expand and coalesce with time to become reddish or reddish-purple blotches that are strikingly apparent towards the end of the season. Although this leaf may be confused with the virus disease leafroll, it tested negative for leafroll and positive for red blotch.

OSU Plant Clinic Image, 2013.

Symptoms of red blotch on Pinot Noir (upper two images) from Willamette Valley and Merlot (lower two images) from Rogue Valley.

Bob Martin, 2014 and 2016.

Cabernet Franc infected with red blotch in the Rogue Valley of Oregon.

Bob Martin, 2016.

Achala KC, 2016.

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Grape (Vitis spp.) - Botryosphaeria Dieback

Grape (Vitis spp.) Relative Disease Susceptibility and Sensitivity to Sulfur

Notice the poor shoot growth and chlorotic, cupped leaves on right side of this trunk.

Photo by Jay W. Pscheidt, 1996.

This is the symptom of stunted shoot growth and cupped leaves, sometimes occuring only on one side of the vine.

Jay W. Pscheidt, 1996.

A canker is revealed in cross section and when the bark is peeled away near a large, old pruning wound.

Jay W. Pscheidt, 1996.

Image related to Grape (Vitis spp.)-Eutypa Dieback

Other fungi, such as Botryosphaeria, can cause similar cankers and wedge shaped symptoms.

Plant Clinic Collection, 2011.

Cause Many fungi have been associated with these diseases, although the cause of esca continues to be disputed. Esca (black measles) is considered a disease of older vines.

Image related to Grape (Vitis spp.)-Esca, Young Esca, and Petri Disease

Viewing this 'Syrah' trunk in cross-section shows dark brown to black streaking in the vascular elements due to plugging of individual or aggregates of xylem vessels with amber to black gum (gummosis) and formation of tyloses. These symptoms alone are not enough for a definitive diagnosis.

OSU Plant Clinic Image, 2013.

Petri disease, Phaeomoniella chlamydospora, was found on this 'Pinot Noir' vine. Much of the trunk is dead with only a small portion on the right side to provide water and nutrients to the vine.

OSU Plant Clinic Image, 2013.

Trunk diseases usually are due to multiple problems. The vascular streaks here are due to Phaeoacremonium viticola while the dark streaking in the center was due to P. viticola and Fusarium. Diplodia was found on the exterior several inches above the graft union.

OSU Plant Clinic Image, 2013.

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Boston Ivy (Parthenocissus tricuspidata) - Downy Mildew

Top side of leaf (left) with chlorotic spot sometimes called an "oil spot" and a similar lesion on the underside of the leaf (right) with the white sporulation of downy mildew.

Jay W. Pscheidt, late 1980's.

There are numerous white areas on this leaf, but most of these are due to the grape erineum mite. Erineum mite damage is often confused with downy mildew. The larger, whitish more diffuse area on the right-side of the leaf is downy mildew.

Photo by Jay W. Pscheidt, 1996

Image related to Grape (Vitis spp.)-Downy Mildew

Notice the white, downy appearance of infections on the berries

Photo by Ed Hellman, OSU

Early infection due to downy mildew can destroy grape clusters.

Jay W. Pscheidt, late 1980's.

Notice the chlorotic spots on the upper-surface of the leaves.

Photo by Jay W. Pscheidt, 1996.

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Grape (Vitis spp.) Relative Disease Susceptibility and Sensitivity to Sulfur

Fleshy, hard galls are typically found midsummer on the trunk, located at the root crown and on the first 2 ft of the vine above the soil line.

Jay W. Pscheidt, 2014.

Image related to Grape (Vitis spp.)-Crown Gall

The crown gall has a cauliflower-like growth and is solid when cut into with a pocket knife.

Photo by Jay W. Pscheidt, 2000.

Pinot Noir with crown gall.

Melodie Putnam, 2010.

Galls can develp at the graft union of young plants.

Melodie Putnam, 2010.

Cause Several classes of herbicides and pesticides can cause damage to grapevines. Some of the most damaging chemicals are 2,4-D herbicides. Grapes are very sensitive and frequently are damaged by chemical drift from nearby applications. Grapes are most sensitive from bud break through bloom but can become damaged anytime during the growing season. The ester form, commercially available as Crossbow, Brush Killer, and other trade names, is more volatile than the amine form.

Image related to Grape (Vitis spp.)-Chemical Injury

Grape showing continued 2,4-D injury the year AFTER exposure. Vines can show injury for several years due to one exposure.

Jay W. Pscheidt, 2012.

Note that the leaf from the main cane is deformed by 2,4-D but that the summer lateral is fine.

Robert Pool, 1976.

When applied during high temperatures, sulfur can burn leaves.

from Robert Pool.

Roundup injury to potted grapes. Chemical was applied to the soil.

Robert Pool, 1977.

Classic 2,4-D injury to grape leaves.

Photo by Iain MacSwann, 1963.

Injury to grape leaves due to a single application of boron at 1 lb/per acre.

Jay W. Pscheidt, 2003.

Cause Diaporthe ampelina (formerly Phomopsis viticola), a fungus. The disease has been not been found frequently in vineyards west of the Cascade Range and rarely in Oregon. The fungus overwinters in last year's cane growth. Fruiting bodies of the fungus (pycnidia) develop in the periderm and produce many spores in the spring. These spores are exuded during rain events when the bark is wet. Spores are then rain splashed to developing shoots.

Lesions look like little tears along the cane of this Chancellor grape.

Photo by Jay W. Pscheidt, 1988.

Image related to Grape (Vitis spp.)-Cane and Leaf Spot

Fruit rot is rarely seen in the PNW.

Jay W. Pscheidt, 2006.

Scaring occurs on both the canes and rachis as on this Concord vine.

Photo by Jay W. Pscheidt, 1981.

Leaf spots are chlorotic and slightly puckered.

Jay W. Pscheidt.

When canes are wet pycnidia of the fungus ooze spores out of a small hole in the top. If it is just humid the spores form what is called a cirrus (it is kind of like a Play-dough fun factory).

Jay W. Pscheidt.

This same fungus has also been found infrequently as a trunk pathogen causing cankers, interior wood discoloration, poor vigor, and die-back.

OSU Plant Clinic Collection, 2015.

See:

Grape (Vitis spp.) Relative Disease Susceptibility and Sensitivity to Sulfur

Cause This disease is common on the west side of the Cascade Range but a sporadic problem in the arid viticulture regions of the PNW.

Symptoms in red cultivars may be subtle with off colors, shriveled or leaking berries, and/or the gray sporulation of the fungus.

Jay W. Pscheidt, 2009.

One cluster of green grapes with leaves around

Infection can spread from leaves to fruit or visa versa (not sure in this case).

Jay W. Pscheidt, 2010.

Botrytis sporulating on these infected berries.

Jay W. Pscheidt, 1987.

Note the brown sporulation typical of this fungus.

Photo by Jay W. Pscheidt, 1998.

Note the tattered leaf due to hail injury, and the water soaked margin of necrotic tissue.

Photo by Jay W. Pscheidt, 1998.

Spores can be found all year long from many sources such as this old rachis from the previous year.

Alexander Wong, 2021.