Green mold contamination aka Trichoderma
Green mold in mushroom growing: identification guide, how to prevent and what to do with contaminated mycelium
Trichoderma spp. provide a valuable service in the nature. Many species have found wide practical application in agriculture, food, paper and textile industries.
This mold colonises plant roots and form symbiotic associations that protect plants against fungi diseases. Gardeners around the world like Trichoderma a lot, but things change in the world of mushroom cultivation... Trichoderma spp is the cause of the green mold disease.
What is Trichoderma?
Trichoderma (aka green mold or forest mold) is a common form of mold. It is present in all types of soil and spread all over the world.
- Kingdom: Fungi
- Division: Ascomycota
- Class: Sordariomycetes
- Order: Hypocreales
- Family: Hypocreaceae
- Genus: Trichoderma
- Type species: Trichoderma fuliginoides
- Species: List of Trichoderma species
The genus was discovered by a German scientist named Christiaan Persoon in 1794, but the taxonomy has remained difficult to resolve. For a long time it was considered to consist of only one species, Trichoderma viride, named for producing green mold
According to various estimations, this genus includes from 200 to 400 species. Some of them may turn out to be synonyms of other species, and some of them may belong to other genus. The position of the genus Trichoderma is still debatable. The List of Trichoderma species contains 382 species.
How to identify trich on mushroom mycelium?
Usually it is hard to identify early stage of Trich for newbie growers. Seems like it is mushroom mycelium or bruises, but Trich has typical features for identification.✅ Color. It begins to grow with a white or off-white color at the very beginning, maturing into green as it releases spores
✅ Texture. Trich is powdery and/or marshmallow at the beginning
Trichoderma mold always powdery in active phase of sporulating on spawn, bulk substrate and casing layer
✅ Let's figure out one great example of color and texture differences. Such case can be useful for newbies.
Here Trichoderma contamination is white, but the texture is different to mushroom mycelium. Trich is more dense and powdery like. Mushroom mycelium has thin threads.
The same mushroom cake, closer photo of the same contaminated area. Here you can see greenish tinge
One more example for identification Trich contam on mushroom cake in MonoTub
✅ Smell. Usually hard to feel in home cultivation due to small amount of contamination. On mushroom farm you can feel coconut smell as sign of Trichoderma contamination.
Clear liquid with a typical coconut smell produced by Trichoderma species is called 6-Amyl-α-pyrone
Of course you can use microscope for identification, but it is possible to id on eye. All questionable cases are easier to determine with macro photo (as close as possible) and good light or use simple Magnifying Glass with light on Amazon
Mushroom bruises or Trichoderma contamination?
It's always confused newbie growers, because Trichoderma spp. (T. harzianum, T. viride, T. koningi) have white color at the very beginning and sometimes have even blue tinge.
Green color you can admit only on the latest stage (sporulating phase).
Mycelium bruising and Trichoderma contamination on mushroom spawn
Mycelium bruises and green mold contamination on mushroom cake
🔴 Check out more examples for id: Mycelium Bruises or Mold Contamination
Q-Tip Test or Swab Test for green mold identification
Q-tip test isn't scientific test, but popular life hack among newbie mushroom growers.
Swab test can be used to determine whether your mycelium is just bruised or contaminated with mold (green mold Trichoderma spp. or blue mold Penicillium spp). This test is possible to use during fruiting period only. The test is based on the fact that mold spores are sticky and would be stuck on any surface that comes into contact.
To do this you have to take a clean white cotton swab or a fresh Q-tip and swipe it across the contaminated area.
If your cotton swab rubs the green powder on to it, it is highly likely that you are looking at a Trich contamination.
If your cotton swab comes out clean without any color on it, your mycelium may be simply bruised.
Main causes of Trich mold contamination
⛔️ Contaminated spore syringe or liquid culture
⛔️ Poor sterility of mycological manipulations, especially during inoculation process (also transfer, spawn to bulk, casing etc)
⛔️ Poor grain sterilisation for mushroom spawn. It is well known that substrate is one of the most important contamination sources for green mold disease, especially if it has a high level of carbohydrates, i.e. any grain for spawn
It is supposed that sterilisation treatment due to high temperature and the cooking effect, released nutrients that benefited the green mold. It is also considered that the reduction of the natural microbial flora of the substrate by the sterilization action increases Trichoderma sp. opportunities to colonize the substrate because of a lower presence of competitive micro flora which reduces the possibility of mycelial growth. Bacterial strains can inhibit the growth of Trichoderma sp by production of volatile organic compounds (Mackie and Whetley, 1999) or by releasing antibiotics (Nielsen et al., 2000)
⛔️ Poor bulk substrate pasteurisation. At a temperature 140°F (+60°C) for at least 30 minutes Trichoderma spores die. Pasteurization helps to kill Trich and save useful microflora, that's why pasteurisation method is preferable for bulk substrate. Check out why in Shroomok Community discussion: Sterilization vs Pasteurization for bulk substrate
Trichoderma prefer wood-based fruiting substrate more than manure-based and wheat straw
⛔️ Trichoderma spp. spread by airflows (spores in the air, in air conditioning and ventilation system), water (misting), tools and insects
⛔️ High concentration of Trichoderma spores in the growing room. Especially if you had Trich contamination before. During sporulating phase mold easily spreads in the air when you introducing fresh air and misting growbox or monotube.
⛔️ Plant pots near fruiting chamber. Plants and Trich can form symbiotic associations and support each other, but such neighbouring may be harmful for your mushrooms
⛔️ High temperature. Trichoderma molds enjoy 80–86 °F (27–30 °C)
⛔️ Low pH level (acid soil). Trich likes pH 4-6.
How to prevent Trichoderma Mold contamination?
Basic rules for Trich prevention
✅ Make up your room regularly. Use non-toxic odor-free fungicide, especially on porous surfaces and if you have molds in your accommodation
✅ Treat all your stuff (tub, tools, jars) with bleach if you had Trichoderma contamination before
✅ Keep all mycological manipulations as sterile as possible. Always wear gloves. Use isopropyl alcohol to treat all tools and wipe all surfaces (especially for inoculation process)
✅ Turn off ventilation and air conditioning 1 hour before any mycological manipulations
✅ Control pH level of bulk substrate and casing soil to prevent Trichoderma mold. Use buffering agents for pH level adjusting. We'll figure out this important step in the next paragraph
✅ Sterilise or pasteurise bulk substrate, because it can contain Trichoderma spores. At a temperature 140 °F (+60°C) for 30 minutes Trichoderma spores die. Bulk pasteurisation is easy and cheaper to make by your own. Just pour hot boiled water in coco coir mix in bucket and leave it for few hours to chill.
You can also use ready made pasteurised/sterilised bulk substrate.
Sterile bulk substrate:
✅ Protect air vents in MonoTub with Synthetic Filters or Polyfill or breathable tape
Shroomok's Choice on Amazon:
✅ Wait for 80-100% of top/casing layer colonisation before introducing fresh air and overall fruiting conditions. Trichoderma mold (any mold, for that matter) love and enjoy uncolonised spots
✅ Keeping your fruiting chamber cooler than 80–86 °F (27–30 °C) can discourage Trichoderma growth. Most of mushroom species prefer lower temperature than Trichoderma, there is no conflict with fruiting conditions here
✅ Keep your fruiting chamber on the table or shelf, pick up from the floor. Usually molds flow on the floor with drafts
✅ Good fresh air exchange (FAE)
Trich and all other molds prefer stagnant air in fruiting chamber
✅ Use clean water for humidifier or spray/mister bottle
✅ Keep your gardening projects and plant pots separately from mushroom cultivation projects
Additional recommendations for Trich prevention
✅ Use UV germicidal lamp as additional method for sterilisation tools and air in the room
✅ Use air purifiers for home
✅ Use aquarium air pump for GrowBox and introduce fresh air through water that filter air from spores of contaminants (there is a stone at the end of the aquarium air pump hose; it should be dipped in water. This will filter the incoming air
Shroomok's Choice on Amazon:
✅ Regular cleaning of the air conditioning and ventilation system at least once a year. It's also important for your health. A/C spread spores extremely effective and mold can grow in your A/C system
How soil pH affect Trichoderma
Trichoderma mold prefer acidic soils, pH 4-6. This is a good news, because most mushrooms required neutral or slightly alkaline soil. The optimum pH for actives and edibles is about 6.5-8.5 (except acid-loving edible species, pH 5.5-6.5). This means you can control Trich growing by pH level adjusting.
As the mushroom mycelium colonises the casing layer, its pH gradually falls. During growing cycle the substrate is gradually acidified by mushroom waste products also, which makes it even more vulnerable for Trich mold.
For example, if we applied a bulk substrate and casing layer with pH 7.5, it gradually drops to pH 6.0-6.5 after the 1st-2nd flush of fruiting. If we applied a bulk substrate with pH 5.0-6.5, then after the 1st-2nd flush we'll get acid soil and high risk of Trich contamination
❗️That's why Trich contamination often appear on the 2nd, 3rd or even 4th flush of fruiting when mushroom cake is acidified
pH level of substrate components
Always check the pH level on the pack, it's really useful information.
🔷 Usually coco coir (coconut coir bricks) about pH 5.5-6.5. In fact each pack has different pH.
Peat soil acidity is different, depends on the type of peat:
🔷 Sphagnum peat is acid - pH 2.5-3.5
🔷 Transitional or prepared acidified peat - pH 5.0-6.5
🔷 Lowland peat has a neutral pH 6.5-7.0 due to its high calcium content
Additives for bulk substrate and casing for Trichoderma prevention
For pH level adjusting of bulk substrate and casing we need to add buffering agents on the base of calcium carbonate (CaCO3): Limestone flour (CaCO3), Limestone grit (CaCO3), Dolomitic limestone flour (CaCO3-MgCO3), Marl, Chalk, ground oyster shell.
What is the best to use?
Limestone flour is the best and fast de-acidifier additive for substrate. It consists of 95-100% calcium carbonate (CaCO3). Just add it to the substrate mix, it's ready to use.
Limestone grit is the same Limestone, the difference is the fraction size.
Limestone saturates the substrate with oxygen, promotes mushroom metabolism and reproduction of beneficial microorganisms, reduces the growth of Trichoderma mold. Hence, increases the yield of mushrooms and fruiting period.
✅ Dolomitic limestone flour (CaCO3-MgCO3) - consists of 50-75% calcium carbonate and contains about 25-50% magnesium carbonate (MgCO3)
Some researchers have reported depressed mycelial growth in casing high in magnesium
✅ Marl. Dredged from dry lake bottoms, marl is a soft lime similar to chalk but has the consistency of clay. It is a composite of clay and calcium carbonate (50-75% and 25-50% insoluble residue (SiO2 + R2O3) with good water holding capacity.
✅ Chalk (CaCO3) is a kind of limestone, consisting of 75-95% calcium carbonate and about 5-25% magnesium carbonate (MgCO3). But it isn't the chalk type used for boards.
✅ Oyster Shell. Comprised of calcium carbonate, ground up oyster shell is similar to limestone grit in its buffering action and ifs structural contribution to the casing layer. Oyster shell is not recommended as the solo buffering agent due to low solubility in water and substrate.
🔴 Gypsum is not a buffering agent. It is non-pH affecting salt. Gypsum has a neutral pH 7.0. The base of gypsum is calcium sulfate (CaSO4) instead of calcium carbonate (CaSO3) in limestone.
❗️ Gypsum provides looseness (particle separation) to reduce soil compaction and increase drainage, aeration in soils. Gypsum provide mineral salts, especially sulfur and calcium, essential elements for mushroom metabolism
🔴 Gypsum (calcium sulfate) may affect pH by half of a point initially. Its pH-altering ability is minor until the sulfur evolves into sulfuric acid. Calcium and sulfur are essential elements in mushroom metabolic processes. If the substrate is lacking in these essential elements, yields are adversely affected
Gypsum is totally not about trich, but can be added as additional ingredient to the basic buffering agent 50/50.
💡 If you find products like "Trich preventer additive" it's mostly marketing. In fact the main content of such products is simple calcium carbonate (CaCO3) aka limestone or gypsum+lime, which are 10 times cheaper. Save your money ;)
Shroomok's Choice on Amazon
Limestone, calcium carbonate (CaCO3):
Gypsum, calcium sulfate (CaSO4):
How much limestone to add to mushroom substrate or casing
It depends on the current pH of soil, it vary from 2.5 to 7.0.
Usually on eye for coco coir bulk substrate add about 5% from DRY weight. Or 5% of Lime and 5% of Gypsum.
For more acidic soils you need to add more limestone and check the soil pH.
How to check soil pH level?
✅ Accurate method is Soil pH meter or Digital soil tester
Insert the tester tip into substrate and in a few minutes check the result. Such simple device may be useful in gardening.
Shroomok's Choice on Amazon:
Digital, Luster Leaf, Soil pH Meter - $23.25
✅ Cheap and easy way is pH Paper Test Strips. Such tests may be useful in gardening as well
Use distilled water and mix it with the soil in 1:1 ratio. Use paper test strips to determine the pH level based on the color chart.
Shroomok's Choice on Amazon:
Soil pH Tester, 10 Tests $8.03
✅ Improvised amateur method to determine pH level is acetic acid or vinegar.
Take a sample of wet soil and add a few drops of vinegar. If bubbles and foam appear, then soil is alkaline. If the amount of bubbles is small, then neutral, if no bubbles at all - soil is acidic.
Of course, this method will be rough and approximate. You won't be able to adjust accurately the pH level in this way
Rehydration in pH adjusted water to prevent Trichoderma contamination
One of the methods to reboot pH level for mushrooms after harvesting is rehydration in alkaline water pH 8.0 - 9.0. The main ingredient we use here is hydrated lime (soluble in water):
Shroomok's Choice on Amazon:
💡 Check out details: Soaking mushroom cake in alkaline water
Reapply casing layer to prevent green mold contamination (optional step, but may be beneficial if you catch contam often)Adding new layer of pH adjusted casing (about 0,5 cm) after rehydration help to manage pH and protect mycelium.
⛔ We don't scrap mushroom cake and previous casing layer! We just add new thin layer to reboot pH, thus protecting mycelium
Casing layer is non-nutrient substrate. It is based on peat moss, vermiculite and pH adjusted. That's why casing content is unattractive for molds, but beneficial for mushrooms.Moreover casing top layer retains moisture extremely great and acts as a security guard for shrooms.
💡 Check out details: Casing layer for growing magic mushrooms
What do I do if I see green mold growing?
Trichoderma spp. grow quickly and spread spores like wildfire. That's why isolation is a key.
🔴 Get contaminated mushroom cake/block/spawn/agar out of your house immediately! Keep healthy spawn bags/jars, tools, substrates, fruiting chambers, mushrooms far away from contaminated.
🔴 Don't open the spawn jar/bag with contaminated spawn indoor, because you can spread mold spores in your room. It's a high contamination risk for your future cultivations.
🔴 Treat affected tools/tubs and surfaces with a bleach solution and wipe with alcohol to kill the mold spores. You need to bleach and alcohol everything you think you touched, change the clothes and take a shower.
This will at least prevent the Trichoderma from infecting more of your current and future crops. You can bury contaminated mushroom cake and spawn in the garden.
💡 Contaminated cakes/blocks/spawn buried in the garden can produce healthy mushroom fruiting outdoor
Is it possible to treat Green Mold contamination on mushroom cake or spawn?
Trichoderma species are resistant to most agricultural chemicals, including fungicides. It is extremely aggressive and fast growing mold.
Trich spores easy spread in the air. Once you had green mold contamination you have high risk of contamination for the future cultivations and be ready to fight for a long time...
⛔️ No sense to treat contaminated spawn jars/bags. Throw them away without opening in the room. Open contaminated jars outdoor only!
Even such tiny contamination should be tossed!
⛔️ No sense to treat contaminated mushroom cakes/blocks when green color detected on top layer.
Even if you see small green area. Throw it away immediately or bury in the garden
Green mold powder (spores of Trich) and such huge area of contamination is a dangerous sporulating phase. Don't let it get to such critical state!
⛔️ Don't use mushroom caps for making spore prints from contaminated mushroom cake. Trichoderma spores may be on mushroom stems and caps as well and you'll get contaminated spore print from the very beginning.
⛔️ Any treatment for Trichoderma mold is impossible and risks of future contamination increases greatly. I still recommend to throw away contaminated cakes/blocks to avoid INEVITABLE spreading of spores and work on prevention
Preventive measures are always the best treatment!
⛔️ If you decide to cut contaminated green area it won't work, after 2-3 days Trichoderma will say hello again, even more than before, because you pushed spores during cutting process on the entire mushroom cake ⛔️ If you decide to spray contaminated area with alcohol or hydrogen peroxide (H2O2) you'll spread the spores of Trichoderma with aerosol flow and Trich will appear again soon
🔥 Keep in mind wildfire example as an analogue of spreading Trichoderma spores
Can I save mushroom culture on agar contaminated with Trichoderma mold?
Yes, you can save mushroom culture on agar by transferring healthy part of mycelium to new agar plate. Sometimes it takes 5-10 transfers to get clean culture. It makes sense for rare expensive mushroom cultures or if you have a patience and great desire to play with it.
How to treat Trichoderma mold on the early stage?
Any recommendations on treatment green mold isn't professional advice.
If you are newbie grower toss contaminated cake immediately and forget about this paragraph
You can save the flush if you have pins or small shrooms on the cake and suddenly early stage of Trich contam happen.
It is possible to stop mild green mold contamination on the early stage of Trichoderma development only. If you see green color, it's too late to bother about treatment. Throw it away immediately or you'll have to burn down your house, because it's too hard to fight with green mold after sporulating and spreading in the air
Again, this applies to small areas on the early stage (totally white!) of Trich contamination and it doesn't mean you can stop it for sure!
For such cases mushroom farmers use salt application (or baking soda application, or garden lime application). It is more popular method for Cobweb disease treatment, parasitic pathogen Mycogone or Wet Bubble disease and possible to use for Trichoderma as well
❗️Edge of tissue should be totally sealed with salt!
This way you can seal and stop contamination development and possible spores spreading. But it doesn't mean it won't show up elsewhere on the cake. Trich can grow deep inside mushroom cake. ❇️ One more method is acid 30% hydrogen peroxide solution. Spray directly on contaminated area as soon as you noticed bright white area. Don't wait till it turns green!
❗️30% H2O2 is very acidic, protect your skin (wear gloves) and eyes!
Usually both methods works for one flush you are waiting for. It is not recommended to soak such mushroom cake in water after harvesting to avoid possible mold spreading all over the cake.
Such manipulations (salt/soda/lime application) helped me to save the Panaeolus cake that produced 3 more flushes after treatment (size of early Trich was like a coin). Also helped to save Oysters block. So, it works for cultivators! However mycologists don't do this and don't recommend any treatment, because they prefer to work on prevention. Although mushroom farmers and home growers don't hesitate to use treatment for saving harvest. Just keep balance between two points of view!
Can I reuse jars and tubs after contamination?
Yes, it is possible to reuse jars and fruiting chambers after washing them in bleach solution to kill mold spores. Wipe fruiting chamber (shoebox/growbox/monotub) with isopropyl alcohol for additional treatment before spawn to bulk.
Mushroom Mycelium vs Trichoderma battle
Mushroom mycelia not so defenseless. Mycelia have immunity and always struggle with any kind of contamination. Sometimes can literally eat bacteria or mold contamination.
This battle between mycelium and green mold contamination was shared by Mycelia P in Shroomok Growers Community on Discord.
Who will win this time!? Take a look day by day fighting
Is Trichoderma useful for anything?
Many species have found wide practical application: for food production, pulp and paper production, textile industries, for disposing of waste and especially in agriculture as biocontrol.
Being a mycoparasite, the Trichoderma viride are very popular natural anti-fungal treatment for plants and bio-fertilizer for seed preparation. Trich creates a protection for plant roots against other fungi. It is natural antifungal treatment for plants. It is also antibiotic producers, especially of wood-rotting fungi. Trich promotes the growth of the plants and plant defense responses.
Trichoderma harzianum is also well-known species and is widely used as a biocontrol agent and for enzyme production.
Trichoderma reesei is a highly efficient producers of many extracellular enzymes. They are frequently used in the food and textile industries for these purposes. For example, cellulases from these fungi are used for denim fabrics (soft, stone-washed effect denim).
So funny, isn't it? Trichoderma is useful... if you’re not trying to grow mushrooms!
Is Trichoderma toxic for people?
Human infection by species of Trichoderma (T. atroviride, T. harzianum, T. koningii, T. longibrachiatum, T. viride, T. citrinoviride, T. pseudokoningii, T. reeseiis) limited to individuals with severely weakened immune systems, provoke allergic reaction, coughing, sneezing, sore throats, and asthma.
However, some species are producers of potent mycotoxins.
Trichoderma longibrachiatum (produces small toxic peptides trilonginsis) often found in air conditioner filters, window filters, natural carpets, cabinets, on water-saturated wood items, wallpapers, gypsum walls, mattress dust, bathroom corners, and kitchen.
It can cause adverse health effects in immunocompromised individuals: mycosis, invasive sinusitis (inflamed sinuses), brain abscess, liver infection, necrotizing stomatitis (inflamed mouth), hypersensitivity pneumonitis, skin infections.
Trichoderma viride can produce gliotoxin, that inhibit immunity system and can also be neurotoxic.
Normally, we are capable of fighting off any inhaled or ingested Trichoderma spp. spores. We don't live in a sterile environment, we contact with thousands of molds every day and our immunity system manage it every day. Don't be paranoid! Illness related to Trichoderma is rare in healthy people but common in those with compromised immune systems.
Regular overall cleaning, regular ventilation of the property, cleaning air conditioning and ventilation filters, using air purifiers, regular monitoring of your property/furniture for signs of moisture and stagnant air are preventing measures to combat mold and protect both your health and your shrooms
Mold spores concentration (any mold, for that matter) differ from house to house. It also depends on the climate conditions and season of the year greatly. This can influence your growing cycles planning and preventive measures
I know how contamination cases hurts, especially on the first try. In fact contamination happen to all cultivators, even experienced ones.
Don't regret throwing away the contaminated mushroom cake/jar/bag. Don't afraid to start again. Don't give up, my dear grower. Keep learning and keep growing!
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Have a happy growing and healthy shrooms!