Diseases of Grapes

Diseases of Grapes: Common Problems and How to Tackle Them

Grapes are a fantastic fruit. They make for sweet snacks, fine wine, and even raisins when left to dry out. But just like us, grapevines can get sick. And when they do, it’s not pretty. Imagine investing months in growing a vineyard, only to see your grapes covered in weird spots or rotting on the vine. Heartbreaking, right? Well, fear not. In this guide, we’re going to talk about the most common diseases of grapes , what causes them, and—most importantly—how to keep your vineyard healthy.

1. Diseases of Grapes: Powdery Mildew (Erysiphe necator)

This is one of the most notorious grape diseases. If your grapevines look like they’ve been sprinkled with baby powder, you’ve got a case of powdery mildew.

Symptoms:

White or grayish powdery coating on leaves, shoots, and grapes.
Leaves curl and distort.
Infected grapes might crack and fail to ripen properly.

Causes:

Warm, dry climates encourage its growth.
Poor air circulation.
Lack of proper pruning.

How to Control It:

Choose resistant grape varieties if possible.
Prune your vines regularly to increase airflow.
Apply sulfur-based fungicides before the disease appears.
Remove infected leaves and grapes to prevent further spread.

2. Diseases of Grapes: Downy Mildew (Plasmopara viticola)

Powdery mildew’s evil twin—downy mildew—makes its mark with yellowish-brown spots rather than white dust.

Symptoms:

Yellow or brown oil-like spots on leaves.
White cotton-like fuzz underneath leaves.
Premature leaf drop.

Causes:

Wet, humid conditions.
Poor drainage and lack of airflow.
Overcrowded grapevines.

How to Control It:

Keep the vineyard well-ventilated.
Spray with copper-based fungicides.
Remove and destroy infected leaves.
Avoid overhead watering, as wet leaves invite trouble.

3. Diseases of Grapes: Botrytis Bunch Rot (Botrytis cinerea)

Also known as gray mold, this disease can either be a nightmare or a blessing. In some cases, winemakers love it when it’s called noble rot, but for table grapes, it’s a disaster.

Symptoms:

Soft, brown, or gray moldy grapes.
Shriveling and decay of fruit.
Grayish spores covering infected clusters.

Causes:

Humid and warm conditions.
Wounds on grapes from insects or damage.
Overripe grapes.

How to Control It:

Ensure good air circulation.
Harvest grapes promptly.
Use fungicides during bloom and before harvest.
Don’t let grapes get overripe on the vine.

4. Diseases of Grapes: Black Rot (Guignardia bidwellii)

Black rot is like that one uninvited guest who shows up, ruins the party, and doesn’t leave.

Symptoms:

Dark brown spots on leaves.
Small, black, shriveled grapes.
Black, pimple-like spots on stems and tendrils.

Causes:

Wet and humid weather.
Spores spread by wind and rain.
Infected plant debris left on the ground.

How to Control It:

Remove and destroy infected vines and leaves.
Apply fungicides early in the season.
Space vines properly for good air circulation.
Avoid overhead watering.

5. Diseases of Grapes: Esca (Black Measles)

Esca is a slow-moving but deadly disease that affects old grapevines, often leading to a gradual decline.

Symptoms:

Leaves with tiger-stripe patterns yellow and brown streaks.
Dark streaks inside the wood.
Grapes shrivel or become speckled with brown spots.

Causes:

Fungal pathogens infecting vine wood.
Poor pruning practices.
Warm, dry conditions.

How to Control It:

Prune carefully and seal wounds.
Remove and burn infected wood.
Avoid excessive stress on vines.
Use healthy planting materials.

6. Diseases of Grapes: Phomopsis Cane and Leaf Spot

This disease primarily attacks young grapevines, making them weak before they even get started.