Blackberry Penicillium Fruit Rot: What Causes Fruit Rot Of Blackberries?

The fungus that causes blackberry fruit rot is called Penicillium roqueforti. It’s a common type of fungi found all over the world, but it tends to grow best in warm climates where there are lots of moisture and sunlight. You may have seen it growing on your own backyard orchard. It grows best in moist soil with lots of organic matter (like compost) and good air circulation. If you live in a dry climate, like I do, then you’re probably not going to see any signs of Penicillium roqueforti anywhere near your garden.

In the summertime when there’s plenty of sunshine and humidity, Penicillium roqueforti thrives. But during the winter months, when there’s less light and humidity, Penicillium roqueforti dies back. That’s why you often get blackberry fruit that looks like they’ve been dusted with snow.

Penicillium roqueforti is one of the most common types of fungi found in our gardens. It usually grows on things that have gone bad: like bread, nuts, and fruit. If you leave a piece of fruit out long enough you’ll see it start to rot and develop a fuzzy coat of Penicillium roqueforti.

But even though the fungus causes the mold that’s all around your blackberries, it doesn’t actually cause any harm. In fact, if you’re not careful, you might even mistake the mold for signs of ripeness! It can be tricky to tell the difference between mold and rot, but there are a few things you can look for…

What The Mold Looks Like On Blackberries

When you see white fuzzy stuff on your berries, it’s probably Penicillium roqueforti. You’ll notice that the mold is “cottony” and it tends to grow in patches or spots. It doesn’t grow in strands like other kinds of mold. The berries might be partially covered or entirely covered with it.

The mold doesn’t pose any danger to the plants or the person eating the fruit. It’s not toxic. It won’t make you sick. It won’t make you trip.

It won’t make you hallucinate.

It’s just mold.

But some people are allergic to it, so if you’re one of those folks then you’ll want to take action right away. (More on that in a minute)

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You can usually spot Penicillium roqueforti by its color. It’s got a very distinct blue/green shade to it. I’m tempted to say that it looks like blue/green paint that’s beginning to crack and peel. It can also look grayish or even yellowish in some instances.

Does Penicillium roqueforti rot directly cause my blackberries to fall off the vine?

No, that’s a result of a fungus called Monilinia . You won’t be able to tell the difference between the mold and the rot without taking a closer look, but you can be relatively sure that it’s one or the other.

So how do you get rid of blackberry mold?

You cut it off and dispose of it. And this is the tricky part for some folks.

How To Get Rid of Blackberry Mold

You can’t just pick the moldy berries and throw them out because you run the risk of spreading the mold to other, non-moldy berries. You also have the potential of promoting additional mold growth if you’re not careful.

One of the best ways to get rid of blackberry mold is to pick it off. I say this because it’s the most direct way of getting rid of the mold and it requires the least amount of effort on your part.

I’m not joking when I say that you can spend hours trying to carefully cut out all of the moldy portions without damaging the rest of the berry. It’s a tedious process that will cause you to lose valuable berry time with your children or your spouse.

Instead of doing that, why not just pick the moldy portions off by hand?

You can dispose of them in the trash or compost pile and keep your other berries relatively intact.

You’ll also want to make sure that you wash your berries really well before you eat them. Mold can’t hurt you, but it makes sense to get rid of as much of it as possible. To do this, fill a pot of water and bring it to a rolling boil. Add your berries and let them soak for at least 60 seconds.

Drain the berries in a colander and then place them in a clean tea towel. Gently rub the berries together inside of the towel in order to wipe off any remaining mold or spores. At this point you can either eat them or refrigerate them for later.

How to Prevent Blackberry Mold in the Future

As with all fruits and vegetables, you can take steps in order to prevent mold from occurring in the future. While you can’t do much about the weather, you can improve upon the conditions within your garden.

Choose a plant site that has excellent air circulation . You don’t want to plant your berries in a low-lying area where water is prone to pool. Likewise, you also want to avoid planting them on a incline as this will cause water to pool as well.

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Next, add some additional light if possible. Blackberries generally require at least 6 hours of sunlight in order to produce the best yields. If you’re planted in the wrong spot, try moving your plants or make adjustments to their position in order to receive the amount of sunlight that they need.

Finally, mulch your plants . Blackberries tend to put down deep roots and therefore break up the soil around them. By mulching, you’re helping to limit this effect and also preventing the soil from becoming waterlogged.

While these steps won’t eliminate all instances of mold and rot, they can certainly prevent a large amount of it from occurring.

What If I’ve Already Eaten Some?

Don’t worry, moldy berries aren’t going to kill you. They may make you sick to your stomach and possibly cause some diarrhea and vomiting, but you’ll be fine if you just brush your teeth afterward.

While it’s not life-threatening, moldy berries can still pose a serious problem because they’re really, really hard to get rid of.

If you’ve ever tried to remove mold from something like a piece of bread, you already know that it’s not an easy task. When you introduce this to your digestive system, you’re asking for a whole host of problems.

Even after rinsing the berries off really well, you’re probably not going to be able to get them completely clean. As a result, you’re almost certainly going to experience some of the symptoms mentioned above.

The other aspect of this is that mold is a living organism by nature and it will continue to grow if given the right conditions. Ingesting large quantities of it can cause additional and more severe problems.

The overall point here is that it’s just not worth it to risk eating moldy berries and it’s better to prevent and remove the mold as soon as possible.

Blackberry Moldy Plants

Since mold is an issue with any crop grown outdoors, it’s still possible for your blackberry plants to become infected even if you do everything right.

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In most cases, this is going to result in the death of the individual plant.

That’s not to say that you should give up on it altogether because there’s a chance that some of the roots may still be healthy. If this is the case, you can simply pull up the entire plant, cut off as much of the roots as you can (since these are probably moldy as well), and re-plant it in a new area.

If your soil is good then it should be able to sustain a new plant. But again, even with the best care, there’s no guarantee that it’s going to survive.

If you’re really concerned about the possibility of getting moldy berries, you can try to prevent it by always washing your hands before harvesting. Mold is less likely to grow on the skin and by keeping it off of the fruit, you’ll greatly reduce your chances of it developing.

This isn’t foolproof but it’s worth a try.


Blackberry plants are fairly hearty and don’t require much maintenance as far as weeding and pest control. They also have a fairly long growing season so you can expect a good harvest.

Of course, this is assuming that you take all the proper steps of planting in the right location with proper sunlight and nutrients and keeping an eye on the plants to make sure they’re free from disease and infestation.

If you don’t want to mess around with all that, then you can always buy your berries at the store. At least then you’ll know that they weren’t infected with mold!

Sources & references used in this article:

Ozone storage effects on anthocyanin content and fungal growth in blackberries by MM Barth, CEN Zhou, J Mercier… – Journal of Food …, 1995 – Wiley Online Library

Mould and yeast flora in fresh berries, grapes and citrus fruits by VH Tournas, E Katsoudas – International journal of food microbiology, 2005 – Elsevier

Evaluation of post-harvest disease resistance in blackberry genotypes by JP Kidd, JR Clark, P Fenn… – Discovery, The Student …, 2004 –



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