Dry Bubble aka Verticillium contamination in mushroom cultivation

Dry Bubble disease is a danger to mushroom farms, especially for those growing edibles like white button mushrooms (Agaricus bisporus).

Even though, it's quite 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, spread disease and eat contaminated fruit bodies.

In mushroom cultivation this contamination caused by the fungal pathogen Lecanicillium fungicola, formerly known as Verticillium fungicola or just Verticillium or Dry Bubble disease in every day use

The best way to show you what is Dry Bubble — is a real case 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...

Penis Envy mutation or dry bubble disease verticillium

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 and mushroom stems and caps;

2) shapeless blobs like dry bubbles with some brown color later — that's why it is actually called Dry Bubble disease;

Deformed blob-like mushrooms - Dry Bubble disease

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

Mushroom caps contaminated by verticillium

4) dull gray-white color with powdery /velvety /web-like texture on the mushroom caps. While mycelium on caps is snow-white and looks fluffy and/or thread-like, not powdery;

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

6) and the most important — the mushrooms begin to bend and resemble a question mark "?" shape

It is also called "hair lip" defect when mushrooms grow crooked due to infection on one side of the mushroom body. Here is one more example:

7) Later damaged tissue becomes more brown and may begin to rot — typically it's dry rot

8) 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

Verticillium is one the worst enemies on mushroom farms! It is also appears on plant leaves, sometimes on fruits and veggies. However, contaminated mushrooms or plants are not toxic.

They considered harmless to people, but better to avoid eating mushrooms, vegetables and fruits that shows signs of this disease!

Infected mushrooms are also carriers of disease, as the pathogen's spores remain on the mushroom's body and wait for an opportunity to spread. So that you can spread the contamination on other mushroom bags, cakes, blocks. Or you can transfer disease from infected to healthy mushrooms.

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:

airflow, drafts, A/C and ventilation air currents — spreading by air is the main vector of contamination in home cultivation
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
spores in bulk substrate or casing layer due to poor pasteurization
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 plants nearby
contaminated vegetables and 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, but I hope your case will help other growers.

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 and stems are straight

3) Mushroom mycelium on caps. Dry Bubble has graish powdery cover, while mycelium on caps is snow-white and looks like dots: Cool little specks of mycelium on mushroom cap - Penis Envy

Mycelium on cap may be fluffy and/or thread-like, not powdery at all:

Quite often mycelium dots on caps accompanied with fuzzy feet:

4) Features of mushroom strain - when kind of discoloration, velvety texture on the caps and odd shapes is a specific of a strain you grow. You should know about it in advance!

If you grow ordinary original strains and their isolations like Golden Teacher, Pink Buffalo, Cambodian, B+, Z strain etc. they won't show you any strange shapes or discolorations.

If you grow mutated strains - Albinos or Leucistic strains - expect unusual colors, textures and mutated shapes. Here are a few photo examples: