Dry Bubble disease in mushroom growing

Verticillium spp. is one the worst enemies for mushroom farmers, especially for those growing edibles like white button mushrooms (Agaricus bisporus). And gardeners as well, since it affects plant leaves, stems, roots, fruits and veggies.

Note: Verticillium spp. that affect plants (Verticillium dahliae, V. albo-atrum) and mushrooms (Lecanicillium fungicola, formerly known as Verticillium fungicola) are different species!

Even though, it's relatively rare contamination in hobby home growing, it is worth to be aware of it! Why? Because it's easy to mess up with mutated mushrooms and spread disease.

The best way to show you what is Dry Bubble — is a real cases from real grower's life. Here we go!

Hello friends! Does anyone have any idea why these Penis Envy mushrooms are mutating? The crack in the cake is new. Although the surface is moist. Also any idea as to why the tops of their caps are white?

The top of the cake is very moist and even have droplets here and there. The cake is densing, and pulling away from the sides now. I have side pins. The darker areas, I can address with peroxide just to be safe...

Shroomok answers:

Hey! This case is a prime example of Verticillium contamination aka Dry Bubble disease. I've been waiting for the case like this to explain its features. Sorry, my dear grower!

Dry Bubble disease symptoms

At first glance and early stages of disease it does look like Mutation

But why I think it's Verticillium, rather than mutation:

1) distorted deformed pins, mushroom caps and/or stems;

2) shapeless blobs like dry bubbles. Later on brown necrotic lesion appears on them — that's why it is actually called Dry Bubble disease;

3) damaged caps on bigger mushrooms. It seems like a snail has eaten a layer;

4) split stems

5) dull gray-white color with powdery /velvety /web-like texture on the mushroom caps and deformed pins;

6) dry brown cracks on the mushrooms and on the cake while top layer is wet enough;

7) the most significant symptom — the mushrooms begin to bend and resemble a question mark "?" shape due to infection on one side of the mushroom body;

8) "Hair lip" defect due to infection on one side of the mushroom body. Here is one more example:

8) Later damaged tissue becomes more brown and may begin to rot — typically it's dry rot, necrotic dry lesion on stems and caps.

9) Dry Bubble disease does not cause wet rotting or unpleasant smell, like it's happen with Wet Bubble disease (Mycogone)

Is Verticillium harmful to people

Mushrooms contaminated by Verticillium fungicola are not toxic. Inhaled spores rarely causes diseases in humans, mostly in immunocompromised individuals.

However, it is best to avoid mushrooms that show signs of pathogen spores and necrotic damage, just as you would avoid rotten and moldy apples.

Also keep in mind that infected mushrooms (fresh or dry) are carriers of disease, as the pathogen's spores remain on the mushroom's body and wait for an opportunity to spread. They can wait for years! So that you can transfer disease from infected mushroom to healthy mushrooms, cakes and bags.

Very interesting case study! I'll look into this disease. Is there any way to save the cake? Also causes the disease?

Main causes of Dry Bubble disease

Verticillium spreads as the most of other pathogens or mold spores:

• spores in bulk substrate or casing layer due to poor pasteurization — this is the main vector of contamination in home cultivation

• airflow, drafts, A/C and ventilation air currents — second vector of contam in home growing

• flies, mites, springtails that carry spores on their legs - not only Verticillium, but other pathogens as well - but this vector of contamination is more common for mushroom farms

• unsanitized tools and surfaces

• spores on your cloth

• spores on your hands, especially after your close contact with contaminated mushrooms

• water splashing or fog

• contaminated mushrooms, plants, vegetables, fruits in your home

• waste with organic matter that wasn't tossed in time

Regarding your next question...

Is there any way to save the cake with Dry Bubble contamination

Unfortunately NO! You can work on prevention only.

On mushroom farms on early stages of the disease it is possible to remove a few contaminated mushrooms in order to avoid transferring Verticillium from contaminated to healthy mushrooms. Sometimes it works, sometimes not.

But when you have relatively small mushroom cake compared to farms' scale it won't help.

And it 100% won't help if Verticillium spores and their sclerotia live in your cake, I mean in bulk or casing substrate.

Interesting. Thank you so much! I feel a little better now that I know 😊

Glad to help! I'm really sorry you caught this contaminant. I hope your case will help other growers. Thanks for sharing!

Cases NOT related to Dry Bubble

1) Rosecomb mutation — caps turned inside out or gills are present on the cap. But the cap is clean, without powdery white-gray cover. The stem is not distorted and without brown necrotic signs.

2) Abnormal mutated growth on caps — buboes mutations on caps or another mushroom growth on the cap, while caps are clean, without graish powder, and stems are straight without brown spots

3) Mushroom mycelium on caps. Dry Bubble has graish powdery cover, while mycelium on caps is snow-white and looks like dots:

Mycelium on cap may be fluffy and/or thread-like, not powdery.

Quite often mycelium on caps accompanied with fuzzy feet due to lack of FAE (fresh air exchange) and quickly disappear within 1-2 days.

4) Merged mushroom fruit bodies with signs of white mycelium dots on caps is NOT a Verticillium contamination.

5) Features of mushroom species and strains - when kind of discoloration, velvety texture on the caps and odd shapes is a specific feature of the species and strains you grow. You should discover it in advance! Let me show you a few examples.

• Mycelium blobs formation that is a specific of Psilocybe ochraceocentrata (formely Psilocybe Natalensis) species.

If you grow ordinary original P. Cubensis strains they rarely show you any strange shapes or discoloration — e.g. Golden Teacher, Pink Buffalo, Cambodian, B positive, Amazonian etc.)

If you grow mutated strains — any Albinos especially from TAT lineage and APE lineage — e.g. APE (Albino Penis Envy), TAT Ghost, Clockwork Orange etc. — expect unusual color, texture, blobs and other odd mutations. Here are a few photo examples:

• APE (Albino Penis Envy) blob mutation is NOT a Dry Bubble disease. Why? Because these bubbles is a common mutation type for this strain. These blobs look clean without necrotic damages and powdery cover. No signs of dry rot on blobs at all!

• Different tint of beige/yellow/white color and slightly velvety caps is a feature of P. Cubensis Clockwork Orange strain. But it's not a Verticillium contamination, because caps and stems are solid. No signs of deformations or brown dry rot on caps and stems.

• Velvety and pointed darker center of the caps is a specific feature of P. Cubensis TAT Ghost strain. But there is no Verticillium on them, because caps and stems are solid and weren't cracked or deformed. No signs of dry rot on fruit bodies.

And many many other crosses and mutated isolations have extraordinary appearance that can be identify as a disease. Know your species and strains. Label matters!

Challenging cases of identification Dry Bubble disease

If you grow Penis Envy or Melmak you may face with the issue called Dino Eggs mutation. Ideally your blobs should look clean, without powdery cover and without dry brown spots like here:

Such mutated blobs are safe!

But it is also possible that such distorted blobs with brown dots can be due to Dry Bubble disease. And it's hard to tell for sure!

Or you can see mix of good white blobs (the biggest 2 blobs) with blobs that have gray powdery cover like here (the top left blob) :

To make sure it is not a Dry Bubble disease you can do the next:

1) Q-tip test. Verticillium spores are sticky. So take a clean sterile cotton swab and swipe the blobs/caps.

Do you see gray powder on it? If no — it's mutation. If yes — probably Verticillium spores on blobs.

2) Agar test. The next step can be testing a swab on agar. Prepare agar plate and swipe with a swab you used for a "Qtip test" before. Within the next few days you may notice white growth with yellow circles or yellow border — this is a sign of Verticillium growth. If zero growth — it's fine.

If you find this write up helpful treat me with a cup of coffee on buymeacoffee

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Have a happy growing and healthy shrooms!