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Grapevine diseases and symptoms: How to recognize four of the most common diseases of leaves & grapes.

As much as you take care of your plants, there is no guarantee that they will never get sick, because sometimes it is simply unfavorable weather conditions that favor certain diseases. So, of course, the vine can be affected. If you have noticed something atypical on your plants, you should try to find out what it is as soon as possible. Because in many cases, diseases can still be stopped if you act in time. We have compiled a few of the most common grapevine diseases and pests to help you diagnose them.

Recognizing and combating black rot on the vine

Grapevine diseases and damage patterns to identify black rot on the grapes.

This fungal disease should be taken seriously, because it can destroy the entire harvest and does not occur infrequently. If a plant and specifically the grapes were already infected in the previous season, the fungal spores can conveniently overwinter in the fallen and mummified fruit to cause damage again in the new year. Released the spores already at the first rains, while spreading with prolonged wetness and temperatures above 10 degrees. Young shoots are particularly susceptible, while in grapes, susceptibility continues for six to seven weeks after flowering.

Black rot on the vine leaves and branches with dry spots and holes

Grapevine Diseases and Damage Patterns: On leaves, infection is manifested by light brown spots of regular to irregular shape that may turn reddish brown after some time. In turn, the spore-producing bodies can form black spots, which are arranged in a ring shape. Stems, in turn, acquire dark-colored depressions that prevent the inflow of liquid, causing the leaves to dry out and die. Grapes acquire small, round spots of light brown color surrounded by dead tissue, which continues to spread until the fruit becomes hard and dark. The spores remain contained and continue to pose a threat to spread again.

Control black rot as grapevine diseases:

  • Remove and destroy fallen, infected fruit and those still attached to the plant.
  • Thin out the canopy sufficiently to improve airflow and thus aeration so moisture dries more quickly.
  • Cut off and discard diseased plant parts.

Grapevine diseases – powdery mildew on the vines.

Both downy mildew and powdery mildew can affect plants. Both fungal diseases are common in gardens and are weather related. Here are the differences:

Powdery mildew in pictures.

This fungal disease attacks all green parts of the plant and can easily overwinter in the bark of the plant. Temperatures from 10 degrees (ideally between 22 and 30 degrees) and wetness in combination with high humidity create the best conditions for the spread of the fungus, whose spores are blown onto other parts of the plant. The first infections of powdery mildew usually occur two weeks before flowering or at the latest 30 days after flowering.

Powdery mildew on leaves with white coating and cane in the form of brown spots

Grapevine diseases and symptoms: Visually, the pattern of damage varies as it depends on factors such as leaf age, fungal age, and source of infection. Usually, however, a white coating appears on the leaves in the form of round spots, which then turn gray (in young fungal colonies). Older fungi usually cause dead leaf tissue right away. Sometimes spots similar to those of downy mildew also develop. Infections are also visible on the stems, initially resembling those of the leaves, but later turning dark. A white coating also appears on the grapes.

Powdery mildew on the fruits with white coating

What can you do:

  • Thin out the canopy sufficiently to improve airflow, and thus aeration, so moisture dries more quickly.
  • Ultraviolet light kills these fungal spores. Proper foliage canopy also ensures proper sun exposure.

Grapevine diseases and symptoms – downy mildew

Downy mildew on the leaves with different symptoms - yellow, brown or white spots

Warmth and wetness (from rain or dew) are necessary for downy mildew to spread, with as little as 10 degrees being sufficient. Rain splashes and also winds spread the spores to the plants, where they continue to spread under optimal conditions. Thus, the first infections occur two to three weeks before flowering or two weeks after flowering at the latest, and on all parts of the plant.

Grapevine diseases and symptoms of downy mildew on grapes

Grapevine diseases and pests: On the leaves, shiny spots first appear on the upper surfaces, which appear oily and later turn yellow. These circular to irregularly shaped spots then turn brown over time, indicating that the leaf tissue has died. Spore-producing fungal bodies may be visible on the lower surfaces, with a cottony, whitish-colored texture. The grapes usually turn gray.

Preventive measures you can take include the following:

  • Thin out the canopy sufficiently to improve airflow, and thus aeration, so moisture dries more quickly.

Anthracnose on fruit and other parts of the plant

Recognizing and combating anthracnose on grapes

Anthracnose is a fungal disease that can occur primarily during wet seasons, but is rare in our latitudes. Cold does not kill the spores, instead they overwinter on the fallen fruit and canes infected during the previous season. A moisture period of only 2 weeks at temperatures around 2 degrees (4 days at 32 degrees) is sufficient for spores to reappear and continue to spread.

Grapevine diseases and symptoms - anthracnose on leaves and stems

Grapevine diseases and symptoms: Visually, the disease is recognized by spots on the leaves , which initially appear reddish, enlarge over time and then sink in, after which they turn brown with a gray center. The center of these spots disappears over time, creating holes. The grapes also get reddish-brown spots that get larger and sink in, and then get a gray center.

Here’s what you can do about these grapevine diseases:

  • Immediately cut off and destroy infested wood.
  • Discard infested and fallen fruit.
  • Thin out the canopy sufficiently to improve airflow and thus aeration so moisture dries more quickly.
  • If necessary, apply a fungicide.

Grapevine diseases and pictures of damage to recognize the most common problem