No matter how much you pay attention to your plants, there is no guarantee that they will never get sick, because sometimes it is simply unfavorable weather conditions that promote certain diseases. Of course, the grape vine can also be affected. If you have noticed anything unusual about your plants, you should try to find out what it is as quickly as possible. In many cases, illnesses can still be stopped if you act in time. We have put together a few of the most common grapevine diseases and damage patterns to help you diagnose them.
Recognize and combat black rot on the vine
This fungal disease must be taken seriously because it can destroy the entire harvest and is not uncommon. If a plant and specifically the grapes were already infected in the previous season, the fungal spores can easily overwinter in the fallen and mummified fruits in order to cause damage again in the new year. The spores are released with the first rainfall, while they spread during persistent wet conditions and temperatures above 10 degrees. Young shoots are particularly susceptible, while grape susceptibility lasts six to seven weeks after flowering.
Grapevine diseases and damage:The infection appears on the leaves as light brown spots with a regular to irregular shape, which can turn reddish brown after some time. The spore-producing bodies can in turn form black pimples that are arranged in a ring. Stems in turn develop dark-colored depressions that prevent the inflow of liquid, so that the leaves dry out and die. The grapes develop 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 risk of renewed spread.
Black rot as a grapevine disease control:
- Remove and destroy fallen, infected fruits and those still attached to the plant.
- Thin out the canopy sufficiently to improve air flow and thus ventilation so that moisture dries more quickly.
- Cut off and discard diseased plant parts.
Grapevine diseases – mildew on the vines
As well asDowny mildew and powdery mildewcan affect the plants. Both fungal diseases are common in gardens and are weather-related. These are the differences:
Powdery mildew in pictures
This fungal disease affects all green parts of the plant and can easily overwinter in the bark of the plant. At temperatures of 10 degrees and above (ideally between 22 and 30 degrees) and wet conditions in combination with high humidity, the best conditions are created for the spread of the fungus, whose spores are blown onto other parts of the plant. First infections occurin powdery mildewusually two weeks before flowering or no later than 30 days after flowering.
Grapevine diseases and damage:Visually, the damage varies as it depends on factors such as leaf age, fungal age and source of infection. Usually, 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. Sometimes spots similar to those of downy mildew appear. Infections are also visible on the stems, initially resembling those on the leaves but later turning dark. A white coating also appears on the grapes.
What can you do:
- Thin out the canopy sufficiently to improve airflow and thus ventilation so that moisture dries more quickly.
- Ultraviolet light kills these fungal spores. The right canopy also guarantees the right amount of sunlight.
Grapevine diseases and damage – downy mildew
Warmth and moisture (from rain or dew) are responsible for the spreadof downy mildewnecessary, although 10 degrees is sufficient. Rain splashes and winds distribute the spores to the plants, where they spread further under optimal conditions. The first infections occur two to three weeks before flowering or at the latest two weeks after flowering, and on all parts of the plant.
Grapevine diseases and damage:Shiny spots first appear on the upper sides of the leaves, which appear oily and later turn yellow. These circular to irregularly shaped spots then turn brown over time, which is a sign that the leaf tissue has died. Spore-producing mushroom bodies may be visible on the undersides, with a cotton-like, whitish-colored structure. The grapes usually turn gray.
To prevent this, you can do the following:
- Thin out the canopy sufficiently to improve airflow and thus ventilation so that moisture dries more quickly.
Anthracnose on fruits and other parts of plants
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 fallen fruits and canes infected in the previous season. A moisture period of just 2 weeks at temperatures around 2 degrees (4 days at 32 degrees) is enough for the spores to spread again and further.
Grapevine diseases and damage:The disease can be recognized visuallySpots on the leaves, which initially appear reddish, enlarge over time and then sink in, whereupon they turn brown with a gray center. The center of these spots disappears over time, creating holes. The grapes also develop reddish-brown spots that become larger and sink in, then develop a gray center.
This is what you can do about these grapevine diseases:
- Cut off and destroy affected wood immediately.
- Discard affected and fallen fruits.
- Thin out the canopy sufficiently to improve airflow and thus ventilation so that moisture dries more quickly.
- If necessary, use a fungicide.
