Grapevine diseases - identification, protection and practical tips
A practical guide to identifying and treating the most common grapevine diseases in Polish conditions. What the symptoms look like, when to act and what to spray - from our experience at Winnica Pustkowie.
Anyone growing grapevines in Poland will sooner or later encounter fungal diseases. Our climate - humid, changeable, with large temperature swings - is paradise for pathogens. At Winnica Pustkowie we’ve been fighting them since our first season. This post is a compendium of what we’ve learned in practice.
Downy mildew (Peronospora, Plasmopara viticola)
The biggest enemy of Polish vineyards. It manifests as yellow, oily spots on the upper side of leaves and a white, fuzzy coating on the underside. It attacks leaves, shoots, flower clusters and grape bunches.
When it strikes: May through September, strongest during warm, humid periods. Critical conditions: 18-25°C, humidity above 80%, and rain. First infections usually begin in June.
What it looks like:
- Early stage: round, yellowish-green spots on leaves (“oil spots”)
- Development: white, dense coating on the underside (spores)
- Advanced: spots turn brown, leaves dry out and fall
- On bunches: gray-white coating, berries turn brown and dry out (“leather berries”)
Protection:
- Preventive: copper sprays (Bordeaux mixture) from the 3-5 leaf stage
- During infection: systemic preparations (Ridomil Gold, Acrobat)
- Biological: removing infected shoots, improving ventilation, mulching
- Schedule: every 10-14 days from May to August, repeat after rain
At Pustkowie we base our protection schedule on weather station data. VineyardElf analyzes weather conditions and sends alerts when infection risk is high - so we don’t spray “blindly” every week, but only when it’s truly needed.
Powdery mildew (Oidium, Erysiphe necator)
The second classic problem. Manifests as a white-gray, powdery coating on leaves, shoots and berries. Easier to identify than downy mildew because the coating is on top of the leaf.
When it strikes: May through September, prefers dry, warm days with cool nights. Paradoxically - it prefers dry conditions over wet.
What it looks like:
- White to gray powdery coating on leaves (top and bottom)
- Leaves become deformed and curl
- On berries: gray coating, then skin cracking
- Characteristic smell (some compare it to old cheese)
Protection:
- Sulfur: the oldest and still effective method - colloidal or micronized sulfur from flowering stage
- Products: Topsin, Luna Experience, Vivando
- Schedule: every 10-14 days, especially important from flowering to bunch closure
- Warning: sulfur above 30°C can burn leaves
Gray mold (Botrytis cinerea)
An insidious disease that mainly attacks ripening bunches - right before harvest, when it’s “too late” for aggressive spraying.
When it strikes: from veraison (berry color change) through harvest. Loves moisture and tightly packed clusters.
What it looks like:
- Gray, fuzzy coating on berries
- Berries soften, turn brown, rot
- Spreads rapidly within a cluster - one berry infects its neighbors
Protection:
- Prevention: leaf removal around the fruit zone (better ventilation), thinning excess clusters
- Products: Switch, Teldor - but watch the pre-harvest interval
- At Pustkowie: we remove leaves by hand from veraison and check clusters every few days
Fun fact: Botrytis on Riesling or Furmint is the desirable “noble rot” - it’s used to make the famous Tokaji and Sauternes wines. But on Solaris at Pustkowie, it’s simply destroyed grapes.
Black dead arm (Excoriose, Phomopsis viticola)
Often underestimated because its symptoms are easily confused with normal aging of the vine.
When it strikes: early spring (April-May), infection occurs on young, developing shoots.
What it looks like:
- Black or dark brown spots on young shoots
- Shoots crack and break at infection points
- On leaves: small black dots with a light border
- Overwinters on wood - visible as bark bleaching
Protection:
- Key moment: spray at bud break - this is the only time when the fungus is truly vulnerable
- Products: copper, Folpan
- Prevention: pruning infected wood during winter pruning
Black rot (Guignardia bidwellii)
Rarer in Poland, but increasingly common with climate change.
What it looks like:
- On leaves: round, brown spots with a dark border
- On berries: browning, then mummification - berries dry to black and harden
- Mummies hang on the cluster all winter
Protection:
- Removing mummies (that’s where spores overwinter)
- Same sprays as for downy mildew (copper, mancozeb)
Vineyard protection calendar
For Polish conditions (zone 6b, Mazovia) our schedule looks like this:
- March-April (bud swell): copper spray (Excoriose)
- May (3-5 leaves): first spray for downy mildew + sulfur for powdery mildew
- June (pre-flowering): downy mildew + powdery mildew + monitoring
- July (post-flowering, bunch closure): downy mildew + powdery mildew + Botrytis
- August (veraison): leaf removal, Botrytis control, final sprays with short pre-harvest interval
- September (pre-harvest): mechanical prevention only (leaf removal, removing infected clusters)
Tools we use
Manual weather monitoring and calculating infection risk is possible but tedious. At Winnica Pustkowie we use:
- VineyardElf - disease monitoring - analyzes temperature, humidity, rainfall and leaf wetness duration. Sends alerts when conditions favor downy mildew or powdery mildew infection
- NanoSatelity - satellite monitoring - Sentinel-2 NDVI images every 5 days. A drop in NDVI on a vineyard section can indicate plant stress - including disease - before symptoms are visible to the naked eye
- Ecowitt weather station - data every 5 minutes: temperature, humidity, rainfall, dew point
Varieties and resistance
Not all varieties are equally susceptible. In Polish conditions it’s worth choosing PIWI varieties (fungus-resistant):
- Solaris - good resistance to downy mildew, moderate to powdery mildew. Our main variety at Pustkowie
- Johanniter - very good resistance to both mildews
- Muscaris - resistant to downy mildew, aromatic (muscat)
- Souvignier Gris - outstanding resistance, excellent for white wines
PIWI varieties don’t eliminate the need for protection, but they significantly reduce it - instead of 8-10 sprays per season, 3-4 are enough.
References
- Diseases and pests of grapevines - Prof. Stanislaw Piekut, UP Lublin
- Vineyard protection - training materials from Podkarpacka Wine Academy
- winogrona.org - encyclopedia of vine varieties and diseases
- Grapevine Disease Management - UC Davis Extension