Why are my grapes dying? : common grape diseases

Описание: black rot of grapes

SCIENTIFIC NAME : Guignardia bidwellii
The signature symptoms of black rot are small, reddish-brown circular lesions on infected leaves. Tiny black dots are visible in the center of the lesion. These dots are spherical fruiting bodies called pycnidia where spores for further dispersal are produced. Older lesions have margins with a black line while the inner area of the spot is tan. Elongated black lesions on the petioles of affected leaves result in wilt. Cane infections result in black lesions, weakening the stem.

Fruit infection is the most damaging stage, resulting in small, light-colored lesions with black borders. Darkening regions of fruit develop masses of black pycnidia on the surface. Infected berries shrivel and turn into hard black bodies called mummies.

BIOLOGY:
After mummies fall to the ground, the pathogen is able to overwinter in the dead fruit. The fungus can also survive in cane infections on the vine. Survival can extend for at least 2 years within lesions on the infected shoots retained as canes or spurs. Ascospores, the spore stage dispersed in the late winter and spring, can be disseminated from the mummies to spread the disease. Another spore stage, called conidia, are spread from the pycnidia over short distances by splashing rain or water.

MANAGEMENT METHODS:
Practices to control black rot with cultural methods include managing vineyards to optimally grow healthy grape crops. For example, choosing the correct cultivar for a growing region is recommended, as well as considering which cultivars are more susceptible to the pathogen. Proper orientation and pruning of the grape vines is essential to optimize light and aeration, as well as keeping vines off the ground

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Choosing the Right Grape Varieties
Not all grapes thrive in Texas heat and humidity, so choosing the right variety is half the battle. Some grapes struggle with the diseases that come with our warm, sometimes wet climate.

Here are the best options for North Texas:

Bunch Grapes
Champanel – This variety was practically made for Texas. It handles heat, drought, and clay soil like a champ. The grapes have a strong, old-fashioned flavor, great for juice or fresh eating.
Black Spanish (Lenoir) – A disease-resistant, tough-as-nails grape with deep red juice, perfect for making wine or jelly.
Blanc du Bois – If you’re into making white wine, this grape is an excellent choice. It’s resistant to Pierce’s disease (a bacterial infection that can wipe out grapevines in the South).
Victoria Red – A relatively new variety with large, sweet grapes that work well for fresh eating.
Concord – Yes, you can grow the classic jelly grape here, but be prepared for a little extra disease management in humid years. I had a neighbor that grew Concords and made them into jelly.
Muscadine Grapes for East Texas
Muscadine Grapes
Muscadines, native to East Texas, are the toughest, most disease-resistant grapes, thriving in acidic soil (pH 5.5–6.5). They tolerate heat, humidity, and pests better than bunch grapes and have a rich, unique flavor. A standout variety, “Southern Home”, is clay-tolerant, drought-resistant, and doubles as an ornamental vine with striking, maple-like leaves.


Where and How to Plant Grapes
Grapes are one of those crops that reward a little extra effort up front. If you plant tem in the right spot with a strong support system, you’ll save yourself a lot of trouble later.

1. Location, Location, Location
Grapes need full sun—at least 6 to 8 hours per day. The best spot is on a gentle slope or a raised area where air can circulate well. If you plant them in a low spot, they’ll be more prone to fungal diseases due to lingering humidity.

3. Soil Prep

Much of North Texas has heavy clay soil, so good drainage is key. If your soil is dense, consider amending ground soil with good compost and expanded shale or planting your vines in a raised bed.

4. Spacing & Trellising
Space grapevines 6 to 8 feet apart.
Use a strong trellis system—grapevines are vigorous growers, and a flimsy setup will collapse under their weight. The most common system is a single wire trellis at about 5 feet high or a two-wire system at 3 and 5 feet.
You can also grow grapes along fences, arbors, or other vertical support structures.
Caring for Your Grapevines
This is where things can get a little tricky if you’re new to grapes, but don’t worry—I’ve made all the mistakes so you don’t have to.

1. Watering

Grapes need deep watering when they’re young, but once established, they’re quite drought-tolerant.

Instead of frequent, shallow watering, wait until soil is dry to a depth of two inches and then water deeply. Drip irrigation or watering by hand is best. Overhead watering from sprinklers encourages disease.

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