If you’re growing blackberries, seeing white spots on the fruit can be worrying. Those white spots on blackberries are often a sign of fungal infection, which is a common issue for gardeners. Don’t panic, though. This guide will help you figure out exactly what’s going on and, more importantly, what you can do about it.
White Spots On Blackberries
This specific symptom usually points to one of two main fungal diseases. Correct identification is the first step to an effective solution. Let’s look at the most likely culprits.
Common Fungal Culprits Behind the White Spots
The white fuzz or powder you see is actually the fungus itself growing on the surface of the berry. Here are the two primary offenders.
1. Gray Mold (Botrytis cinerea)
This fungus often starts as a small, water-soaked spot that quickly grows a fluffy, grayish-white mold. It thrives in cool, damp conditions. You’ll usually see it after a period of rainy weather or if your plants are overcrowded and lack air flow. The berries will become mushy and inedible.
2. Powdery Mildew (Various Podosphaera species)
This looks more like a fine, white to grayish powder dusted evenly on the berries and leaves. Unlike gray mold, powdery mildew prefers warm, dry, and humid conditions (but not wet leaves). It can cause the berries to be smaller, have a dull appearance, or crack open.
How to Confirm It’s a Fungal Problem
Before you take action, make sure it’s fungus and not something else. Here’s a quick checklist:
- Appearance: Is it fuzzy, powdery, or moldy? If yes, it’s likely fungal.
- Smell: Infected berries often develop a sour or musty odor.
- Touch: Fungal berries become soft, leaky, and collapse easily.
- Spread: Check nearby berries and leaves. Fungal diseases spread quickly to adjacent fruit.
If the spots are hard, dry, or sunken, you might be dealing with a pest issue or physical damage instead. But a soft, white coating is almost always fungus.
Immediate Actions to Take
When you first spot the infection, act fast to save the rest of your crop. Follow these steps in order.
- Remove Infected Fruit Immediately: Carefully pick off any berries showing white spots. Don’t just drop them on the ground! Place them in a sealed bag and throw them in the trash, not your compost pile. This prevents spores from spreading.
- Thin Out the Canes: If your blackberry patch is dense, improve air circulation. Prune out some of the old, non-producing canes and any new growth that’s making the area to crowded. Good airflow is kritical for preventing fungus.
- Adjust Watering Habits: Water the soil at the base of the plants, not the leaves and fruit. Use a soaker hose or drip irrigation if possible. Try to water in the morning so the sun dries the foliage quickly.
Long-Term Prevention Strategies
Stopping the fungus from coming back next year is all about smart gardening practices. Consistency is key here.
Site Selection and Planting
- Plant blackberries in full sun. More sun helps dry leaves faster after dew or rain.
- Ensure the site has excellent soil drainage. Raised beds can be a great option if your soil is heavy clay.
- Space plants according to their variety’s recommendations—usually 3-5 feet apart—to ensure air can move freely between them.
Pruning and Maintenance
Proper pruning is your best defence. It keeps plants healthy and manageable.
- Prune annually to remove floricanes (the canes that just fruited) after harvest.
- In late winter, thin primocanes (first-year canes) to about 4-6 of the strongest per plant.
- Train canes onto a trellis. This keeps them off the ground and vastly improves air circulation around all parts of the plant.
Organic Treatment Options
You can use several organic fungicides as protectants, meaning they help prevent infection before it starts. Apply them early in the season, especially if you’ve had problems before.
- Neem Oil: A natural fungicide and insecticide. Apply every 7-14 days, but avoid spraying during the heat of the day or when bees are very active.
- Baking Soda Spray: Mix 1 tablespoon of baking soda, 1 teaspoon of horticultural oil (to help it stick), and 1 gallon of water. Spray weekly during humid periods. This changes the surface pH of the leaf, making it less inviting for fungus.
- Sulfur or Copper-Based Fungicides: These are classic organic options. Always follow the label instructions carefully, as copper can build up in the soil over time.
Can You Eat Blackberries with White Spots?
This is a very common question. The general rule is: when in doubt, throw it out.
If the infection is very minor—a single tiny spot—you might be able to cut it off plus a generous portion of the surrounding flesh and eat the rest. However, the visible mold is just the fruiting body; its microscopic threads (hyphae) can spread through the berry much farther than you can see. For people with mold allergies or compromised immune systems, it’s not worth the risk.
Berries that are extensively covered, mushy, or smell off should always be discarded. Never use moldy berries for jams, baking, or freezing, as the toxins can survive the heat and the fungus can spoil your whole batch.
Related Problems Often Confused with Fungus
Not every white mark is a fungal infection. Here are a couple other things it might be.
- Sunscald or Wind Scarring: This can cause whitish, dry, papery patches on the side of the berry facing the sun or prevailing wind. The texture will be dry, not fuzzy.
- Redberry Mite Damage: This pest causes individual drupelets (the little bumps that make up the berry) to remain hard, red, or white and fail to ripen. It looks patchy, not uniformly moldy.
FAQ Section
What causes white fungus on blackberries?
White fungus is primarily caused by fungal spores landing on the fruit. These spores germinate in favorable conditions like high humidity, poor air circulation, and wet foliage, leading to diseases like gray mold or powdery mildew.
How do you treat white spots on blackberry leaves?
The treatment is similar to treating the fruit. Remove severely infected leaves, improve air flow through pruning, avoid overhead watering, and apply an organic fungicide like neem oil or a baking soda spray to protect the remaining healthy foliage.
Is it safe to eat blackberries if some have mold?
It is generally not recommended. Mold can produce mycotoxins that may cause illness, and its roots can penetrate deep into the soft fruit. It’s safest to discard any berries with visible mold growth.
Can you wash mold off blackberries?
Washing will remove the visible spores on the surface, but it will not remove the fungal threads that have invaded the berry or any toxins they may have produced. Therefore, washing is not a reliable method for making moldy berries safe to eat.
What is the white stuff on my berries?
The white stuff is most likely a fungal growth. It could appear as a fluffy gray-white mold (Botrytis) or a fine powder (Powdery Mildew). Both are signs of infection and mean the berry is starting to decay.
Final Thoughts for a Healthy Harvest
Dealing with white spots on your blackberries is mostly about prevention. By focusing on a sunny, well-drained site, committed to annual pruning for airflow, and watering carefully at the soil level, you can avoid most fungal issues. If you do see those white spots, act quickly to remove the infected material. With these practices, you’ll be well on your way to harvesting plenty of healthy, juicy blackberries year after year. Remember, gardening is a learning process, and every challenge makes you a more skilled grower.