Phomopsis Cane and Leaf Spot of Grape

FACT SHEET

Agriculture and Natural Resources

HYG-3031-11

or many years, the Eastern grape industry rec-

ognized a disease called “dead-arm,” which was

thought to be caused by the fungus Phomopsis viticola.

In 1976, research ers demonstrated that the dead-arm

disease was actually two different diseases that often

occur simultaneously. Phomopsis cane and leaf spot

(caused by the fungus Phomopsis viticola) is the new

name for the cane- and leaf-spotting phase of what

was once known as dead-arm. Eutypa dieback (caused

by the fungus Eutypa lata) is the new name for the

canker- and shoot-dieback phase of what was once

known as dead-arm. We now propose that the name

dead-arm be dropped. Growers should remember

that Phomopsis cane and leaf spot and Eutypa dieback

are distinctly different diseases, and their control

recom mendations vary greatly.

Disease incidence of Phomopsis cane and leaf

spot ap pears to be increasing in many vineyards

throughout the Midwest. Crop losses up to 30 per-

cent have been reported in some Ohio vineyards in

growing seasons with weather conducive to disease

development. Phomopsis cane and leaf spot can affect

most parts of the grapevine, including canes, leaves,

rachises (cluster stems), flowers, tendrils, and berries

and can cause vineyard losses by:

•Weakening canes, which makes them more suscep-

tible to winter injury.

•Damaging leaves, which reduces photosynthesis.

•Infecting cluster stems, which can result in poor

fruit development and premature fruit drop.

•Infecting berries resulting in a fruit rot near har vest.

Phomopsis Cane and Leaf Spot of Grape

Daniel J. Anco, Omer Erincik, and Michael A. Ellis

Department of Plant Pathology

Symptoms

Spots or lesions on shoots and leaves are com-

mon symptoms of the disease. Small, black spots on

the in ternodes at the base of developing shoots are

probably the most common disease symptom. These

spots are usually found on the first three to four

basal internodes (figure 1). The spots may develop

into elliptical lesions that may grow together to form

irregular, black, crusty areas. Under severe condi-

tions, shoots may split and form longitudinal cracks.

Although cane lesions often appear to result in little

damage to the vines, it is important to remember that

these lesions are the primary source of overwintering

inoculum for the next growing season.

Leaf infections first appear as small, light-green

spots with irregular, occasionally star-shaped margins

Figure 1. Spotting and cracking of grape cane caused by Phomopsis.

These typical cane symptoms are usually present only on the first

three to four internodes.

Phomopsis Cane and Leaf Spot of Grape—page 2

(figure 2). Usually only the lower one to four leaves

on a shoot are affected. In time, the spots become

larger, turn black, and have a yellow margin (figure

3). Leaves become distorted and die if large numbers

of lesions develop. Infections of leaf petioles may

cause leaves to turn yellow and fall off.

All parts of the grape cluster (berries and rachises

or cluster stems) are susceptible to infection through-

out the growing season; however, most infections

appear to occur early in the growing season. Lesions

developing on the first one or two cluster stems

(rachises) on a shoot may result in premature wither-

ing of the cluster stem. Infected clusters that survive

until harvest often produce infected or poor-quality

fruit.

If not controlled early in the growing season,

berry infection can result in serious yield loss under

the proper environmental conditions. Berry infec-

tions first appear close to harvest as infected berries

develop a light-brown color (figure 4). Black, spore-

producing structures of the fungus (pycnidia) then

break through the berry skin, and the berry soon

shrivels. At this advanced stage, Pho mopsis cane

and leaf spot can be easily mistaken for black rot.

Growers should remember that the black rot fungus

only infects green berries and will not infect berries

after they start to mature. Berries become resistant

to black rot infection by three to four weeks after

bloom. Fruit rot symptoms caused by Phomopsis

generally do not appear until close to harvest on

mature fruit. Severe fruit rot has been observed in

several Ohio vineyards.

Research has shown that berry infection can occur

throughout the growing season; however, most fruit

rot infections probably occur early in the season

(pre-bloom to two to four weeks after bloom). Once

inside green tissues of the berry, the fungus becomes

inactive (latent), and the disease does not continue

to develop. Infected berries remain without symp-

toms until late in the season when the fruit matures.

Thus, fruit rot that develops at harvest may be due

to infections that occurred during bloom.

Causal Organism and Disease Cycle

The fungus overwinters in lesions or spots on old

canes and rachises infected during previous seasons

(figure 5) and requires cool, wet weather for spore

release and infection. The fun gus produces flask-

shaped fruiting bodies called pycnidia in the old

diseased wood. These pycnidia release spores in early

spring and are spread by splashing rain droplets to

Figure 2. Symptoms on young leaves early in the season.

Figure 3. Symptoms on older leaves late in the season.

Figure 4. Symptoms of fruit infection.

Phomopsis Cane and Leaf Spot of Grape—page 3

developing shoots, leaves, and clusters. In the pres-

ence of free water, the spores germinate and cause

infection. Shoot infection is most likely during the

period from bud break until shoots are six to eight

inches long. The opti mum temperature for leaf and

cane infections is between 60 and 68 degrees F, and at

least six hours wetness duration is required at these

temperatures for infection to occur.

As the wetness duration increases, the oppor-

tunity for infection greatly increases. Lesions on

leaves appear at seven to ten days after infection.

Fully expanded leaves become resistant to infec-

tion. Lesions on canes require two to four weeks to

develop. The fungus does not ap pear to be active

during the warm summer months, but it can become

active during cool, wet weather later in the growing

season. Pycnidia eventually develop in infected wood

and will provide the initial inoculum for infections

Figure 6. Disease cycle of Phomopsis cane and leaf spot. We wish to thank the New York Agricultural Experiment Station for use of this

fig ure. Figure taken from Grape IPM Disease Identification Sheet No. 6.

Figure 5. Phomopsis fruiting bodies (pycnidia) on a dormant cane.

during the next growing season. Infected canes

and rachises do not produce additional inoculum

during the same growing season in which they

were infected.

Phomopsis Cane and Leaf Spot of Grape—page 4

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Control

1. Select planting sites with direct, all-day sunlight

(avoid shade). Good soil drainage and air circula-

tion are also very important. Orient rows to take

full advantage of sunlight and wind movement.

Cultural practices that increase air circulation and

light penetration in the vineyard will reduce wet-

ting periods and should be beneficial for control.

2. While dormant pruning, cut out infected or dead

canes and destroy them. Remove or destroy all

rachises. Select only strong, healthy canes that are

uniform in color to produce the next season’s crop.

3. Proper timing of early-season fungicide sprays is

im portant for control in commercial vineyards.

For the most current spray recommen dations,

commercial growers are referred to Bulletin 506-

B2, Midwest Commercial Small Fruit and Grape

Spray Guide, and backyard growers are referred

to Bulletin 780, Controlling Diseases and Insects in

Home Fruit Plantings. These publications can be

obtained from your local OSU Extension office or

OSU Extension’s online bookstore at

http://estore.

osu-extension.org/

More information about plant diseases and online versions of Ohio

State Univer sity Extension plant disease fact sheets and bulletins,

with color figures, are available on the following websites:

http://plantpath.osu.edu

http://ohioline.osu.edu