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Mold on Mushroom Mycelium (Top 5 Types): Easily Spot & Treat

Top 5 Molds On Mushroom Mycelium Easily Spot & Treat

Even the best mushroom grower cannot guarantee a mold-free mushroom growing experience. Indeed, they will encounter mycelium mold and even mold on mushroom mycelium.

Expectedly, molds are every mushroom grower’s number one enemy mainly because of how fast they can spoil your crop.

From spores, molds grow and become noticeable within 24 hours.

The ideal growing condition for mushrooms invites different types of molds like:

  1. Cobweb Mold (Hypomyces or Dactylium)
  2. Green mold (Trichoderma)
  3. Black mold (Stachybotrys)
  4. Orange-red bread mold (Neurospora)
  5. Black bread mold a.k.a pin head mold (Rhizopus)

Luckily, unlike other contaminations like bacteria and gnats, molds may be the simplest to treat. The key to treating mold on mushroom mycelium is by spotting them early on.

Mostly, all mushroom mold contaminations can be treated the same. That is if you are in the early phases of growing (before the fruiting body phase).

Now, the tricky part is identifying them and not mistaking them as other contaminations or as normal mushroom mycelium.

Do not worry as we will show you below what each mold contamination looks like and the different ways to treat them.

1. How to Spot Mold Contamination on Mushroom Mycelium

1.1 Cobweb Mold (Hypomyces or Dactylium)

How to Spot Cobweb Mold Contamination on Mushroom Mycelium - Molds on Mushroom Mycelium Easily Spot & Treat - Curative Mushrooms
Cobweb mold looks significantly darker and puffier than mushroom mycelium. Also, they love environments with still air, very little oxygen, and high humidity.

Cobweb mold is a fast-growing mold with very fine white strands. For as short as 24 hours, it develops into a stringy gray mass.

Most of the time, it can be tricky to tell apart from the growing mycelium.

Mushroom Mycelium vs Cobweb Mold - How to Tell Them Apart - Curative Mushrooms
Is cobweb mold growing on your substrate or is it mushroom mycelium? Read this article to learn more about cobweb mold.

1.2 Green Mold (Trichoderma)

Identify Green Mold (Trichoderma) - Molds on Mushroom Mycelium - Easily Spot & Treat - Curative Mushrooms
Just like cobweb mold, green mold starts growing into a white puffy mass.

Trichoderma spp., also known as green mold, frequently contaminates any type of mushroom substrates. Most probably, it is the most persistent and aggressive mushroom contaminant.

Usually, green mold begins growing on white mycelium with white or off-white color, maturing into olive color to dark green.

1.3 Black Mold on Mushroom (Stachybotrys)

Identify Black Mold (Stachybotrys) - Molds on Mushroom Mycelium Easily Spot & Treat - Curative Mushrooms

Black mold appears slimy black or highly dark gray, like black crayons on paper.

mushroom grow kit from spores

Also, this mold tends to have definite round splotches with a mottled appearance. Often, you see darker layers of mold over lighter layers.

Black mold is also a common problem in U.S. households. It is often attributed to water damage or leak. When it gets out of hand, homeowners could use some help from mold remediation service providers.

As a matter of fact, who would like to grow mushrooms in a mold-contaminated household? Mold spores are everywhere!

1.4 Orange-Red Bread Mold on Mushroom (Neurospora)

Identify Orange-Red Bread Mold (Neurospora) - Molds on Mushroom Mycelium - Easily Spot & Treat - Curative Mushrooms

Orange and red bread mold appears irregularly cushion-shaped and soon becomes effuse and fluffy. Its color ranges from pale salmon, orange, to red.

1.5 Black Bread Mold, a.k.a Pin Head Mold (Rhizopus)

Identify Black Bread Mold, a.k.a Pin Head Mold (Rhizopus) - Molds on Mushroom Mycelium Easily Spot & Treat - Curative Mushrooms

Rhizopus is a common mold that grows on bread. It looks like a grayish fluffy mass and can be easily confused with Cobweb mold.

Over time, as Rhizopus begins to produce spores, the sporangium (the capsule structure appearing like a pin) becomes black.

2. How to Treat Contamination: Mold on Mushrooms

2.1 Spray Hydrogen Peroxide ( H2O2)

Undeniably, hydrogen peroxide is an effective way to treat the early stages of mold. That is within 24 hours since visible mold contamination.

Oftentimes, mushroom cultivators advise spraying the surface mold with 3% hydrogen peroxide.

Fortunately, you do not need to create your solution since you can just buy over-the-counter. Hydrogen peroxide is sold in concentrations of 3 to 12 percent at most drug stores and online stores.

For this, you may use a clean spray bottle. Simply spray the whole surface area of your infected substrate or fruiting block with the solution.

mushroom grow kit from spores

In a blink of an eye, molds dissolve as they come in contact with the solution.

2.2 Isolate and Scoop Out the Contaminated Area

Desperate Move (to Save Your Mushroom) That Might Work - Curative Mushrooms

Before scooping any contaminated area of your crop, the first best thing to do is separate the mold-contaminated kit from healthy ones (supposing you have more than one grow kit).

However, scooping out the contaminated area of your crop seems like a desperate measure. Mold spores like Trichoderma are hard to contain once it gets ahold of your crop.

But if you’d like to take a chance with your mold-contaminated kit, you can try the following:

  1. Prepare your spoon (clean it with 70% isopropyl alcohol).
  2. Spray hydrogen peroxide on the surface of the crop.
  3. Put a clean damp paper on the mold blotch.
  4. Scoop it with your clean spoon.

If the mold on mushroom mycelium is smaller than a coin, your chance of saving your kit with the scoop-out method is higher.

2.3 Throw Your Mushroom Mycelium Block… Under a Tree

Contaminated Mycelium Block Can Grow Back Under a Tree - Curative Mushrooms
Disclaimer: We do not advise cooking mushrooms for human consumption if they are infested with molds. Further, eating mushrooms that have molds is unsafe.

This may sound silly, but it sometimes works. Well, since you’ll throw it, you might consider giving it some dignity. lol

So instead of putting your contaminated mushroom block in a garbage can, you may put it in a proper resting place, under a tree or a pile of wood in your backyard.

Try to think of it. Mushrooms that grow in the wild need not have careful babysitting. They just thrive amidst all environmental challenges. Thus, the same thing may happen with your spoiled mushroom block.

Besides, if you give it a chance to flourish in its natural habitat, it may have a bigger chance of surviving. So just toss it under a tree and come back a week later to see if it has returned to life. ;)

Your Contaminated Mushroom Block Might Grow In the Forest - Curative Mushrooms
mushrooms in the wild growing unbothered

Now, you have an idea of spotting these silly mold contaminants.

As a recap, the most common are green mold, black mold, orange bread mold, pinhead mold, and cobweb mold.

mushroom grow kit from spores

In addition, you can treat your contaminated block by spraying hydrogen peroxide, scooping out contaminated areas, or tossing it with dignity under a tree.

Always remember: once you spot contamination, immediately separate the healthy blocks. Also, in using any tools that will touch your substrate, sterilize them first with isopropyl alcohol or flame.*

Happy Mushroom Growing! :)


Mushroom Contamination Guide - Identify & Treat Top 3 Types
Do you notice other unusual growths in your mushroom kit? Do they look like slimy wet spots? Is anything moving in your substrate? You might want to check if they’re not some other types of contamination like Sour Rot, Soft Rot bacteria, or some naughty pests.



Curative Mushrooms has to post the standard FDA Disclaimer…The statements made regarding medicinal mushrooms have not been evaluated by the Food and Drug Administration. The efficacy of these products has not been confirmed by FDA-approved research. Curative Mushrooms is not making claims intended to diagnose, treat, cure or prevent any disease. All information presented here is not meant as a substitute for or alternative to information from healthcare practitioners. Please consult your healthcare professional about potential interactions or other possible complications before consuming the medicinal mushrooms. The Federal Food, Drug and Cosmetic Act requires this notice.


This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Curative Mushrooms nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement or lifestyle program.


Jess is a feature writer and a Psychometrist by profession, exploring emerging mental health and wellness trends. She came across the fantastic world of medicinal mushrooms through the Curative Mushrooms online community. Since then, she has taken an interest in growing medicinal mushrooms, exploring their medicinal and therapeutic potential and the current ethical and legal issues surrounding them.

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