Trichoderma - Killing Bad Fungus with a Good One
 

Trichoderma is a genus of fungi found in soil and decaying wood. These molds play some very important roles in the natural world. For one thing, Trichoderma kills other fungi, thereby keeping them in balance within the ecosystem. They are an enemy to mushroom farmers, but a friend to most other gardeners. Aside from killing harmful fungi, they grow on the roots of plants in a symbiotic association that stimulates root growth and boosts resistance to drought and disease.

Trichoderma fungus has a number of horticultural and even medicinal applications, and is very easily put to use. You don’t use it directly, but rather with a medium in which it grows. The best medium is whole-ground or stone-ground cornmeal -- not the refined stuff that contains just starch, but the kind with the corn germ and bran left in.

You can get this at some grocery stores or in health-food stores or you can get horticultural cornmeal at a garden center or feed store. The fungus is either present in cornmeal to begin with or the cornmeal is quickly inoculated by airborne spores. I don’t know which, but it becomes active soon after the cornmeal is wetted.

I first started using cornmeal to treat black spot on rose bushes. Just spreading it around the plants now and then provides permanent protection. It was later that I tried using it on orchids.

To use it on orchids, you first put some into a bowl and add enough water to turn it into a soupy paste. I consider it ready to use after sitting overnight and better after 24 hours. That’s not based on anything scientific, but just what seems to work for me. Plants can be soaked in the slurry or covered with it and then be maintained in a humid environment for a day or two such as in a plastic bag so the cornmeal will remain moist. A moist environment would also be beneficial to the fungus you want to kill, but that won’t matter.

Before using the cornmeal, it’s okay to use hydrogen peroxide first to kill or reduce at least some of the harmful fungus. The hydrogen peroxide can then be rinsed off or given a little time to break down so that it won’t inhibit the Trichoderma. I’ve done this with bad fungal infections, but it might not be necessary. In my experience, hydrogen peroxide alone has not always eradicated fungal infections anyway, but Trichoderma has.

I have used cornmeal to eliminate a variety of fungal infections of orchids including an aggressive black rot infection of a rescued Cattleya. So far, it has always worked.

You might want to give it a try sometime. Meanwhile, there are lots of interesting references to Trichoderma fungus on the internet, if you’re interested in learning more about it.

Angelo this is an excellent post. Suprised that more people have not commented on it. Wonder if anyone (scientist) has tried mixing it with Salacilic Acid (SAR)
The internet searches on Tricoderma are really interesting.

Anglo,
I haven't used Trichoderma on my orchids but I have used Trichoderma inoculants on several potted non-orchidaceous plants with a lot of success. I agree it's great stuff. The only reason I haven't used it on orchids is because a lot of my orchids are mycorrhiza dependant so I'm reluctant to risk killing the fungi off.

I haven't used cornmeal to promote the growth of Trichoderma, though. I know that many people use cornmeal in the garden but do you know to what extent Trichoderma occurs in non-soil based media (bark, CHC, sphagnum, etc)? It would seem that that usefulness of cornmeal vs direct inoculation would depend on the fungi being present in soilless media.

Thanks for the comments.

Orchids3,
I have not heard of any attempts to mix Trichoderma with salicylic acid. If works as a pesticide, maybe it would be toxic to the fungus also.

Andrew,
Trichoderma fungi attack pathogenic fungi, but evidently coexist with mycorrhizal fungi. Even though I have not found a scientific reference that specifically states this, I have not seen anything to the contrary either. I have seen some horticultural products on the market that contain both mycorrhizal and Trichoderma fungi along with beneficial bacteria that reportedly all "work together" to the benefit of plants. And it seems logical to me that if the beneficial fungi have a common interest in promoting the health of plants, they would not be in conflict with each other.

As for the natural presence of Trichoderma in organic orchid mediums, my uneducated guess would be maybe in decaying bark, but probably not in Sphag or CHC.

I have never tried treating an orchid medium with it, but I'm sure you could. I'd probably try it by running water into the medium through the prepared cornmeal contained in a filter. Or maybe spreading just a little dry or prepared cornmeal on the surface. Too much cornmeal in the medium could obstruct aeration.

I read that the Trichoderma grows best between 25-30 degrees C and smells a little like coconut when it is cultured. Maybe I could put the corn meal with the culture in an old sock and hand it in the 55 gal barrel where I mix my fertilizer and pump it onto the orchids. Somewhere I read that cornmeal could be used to control fungus some time ago but the sock of cornmeal was added to the barrel without culturing the Trichoderma first. It was questionable wheather there was a benefit at that time. Will look for the corn meal tomorrow and wait for the weather to get warmer so the greenhouse will be at 80 degrees during the day for a few days.

Very interesting post, thanks for posting!
Trich spores are everywhere, and they will appear as a fast growing white mycelium patch that turns dark, forest green when it sporulates. If you leave a cup of coffee out for a couple of weeks, watch what moulds grow on it. If a dark green mould grows which spreads to take over the surface of the liquid (patching over other moulds in the process) then that might be Trichoderma.

The problem is that there are also green spored moulds that look completely identical to the naked eye that are very poisonous, causing respiratory illnesses. The only way to tell them apart for certain is under a powerful microscope.

So i'd be very careful before growing just any green mould on corn meal. You're likely to germinate a whole bunch of molds on the corn meal and some of them could be be dangerous.

A far safer way of doing it would be to take cornmeal (or brown-rice flower, wild bird seed or rye grain), mix it with water so that it's just moist without dripping wet (squeeze the excess moisture out), pile it into a jam jar, close the lid and seal it off.

Put the jar in a dark place and wait for the molds inside to grow. In theory, a whole bunch of white, green, black, grey and pink molds will grow from spores throughout the jar. Over time though, the dark green Trich should compete favourably and colonise the entire jar.

You can then open up the jar when it has been fully colonised by the green Trich. And hopefully by then, the pathogenic molds will have been killed off. You can smell the jar, make sure it doesn't smell sickly or sweet. If it does, seal it and chuck it. If it smells like coconut or mushrooms, it could be safe to use.

(Note italic emphasis, playing with random molds can be dangerous, don't consider this a foolproof method, i take no responsibility for giving people advice on how to grow mold!)

That would be a far safer way to grow Trich in my opinion, if the alternative is just to grow it openly.

Mold does need to grow on something organic though, and i don't think it would work for inert mediums. But the whole point of inert mediums is to avoid fungi in the first place so i don't know if Trich would help anyway.

But if what they say about Trich is true, then it could work well for bark...

Undergrounder, thanks for your informative response. Since you obviously know something about molds, maybe you can offer an opinion on the Trichoderma-cornmeal relationship.

When using cornmeal as a fungicide, it isn't necessary to wait for a visible sign of mold before it becomes effective. So could this mean that Trichoderma is already present in dry cornmeal in an inactive state? I have not been able to find a firm answer to this question by searching the web.

I really don't know Anglo, is it just regular store-bought cornmeal or specially prepared? Trichoderma is already present everywhere, i don't know whether its specially present in cornmeal but you would think that plenty of molds would be there too.

There might be something in the cornmeal that makes it tasty to Trichoderma without being attractive to other molds and fungi. Different molds prefer different substrates - woody debris, grains and carbohydrates, sugary substances, forest soil, etc. So it might be the case that cornmeal attracts Trich without attracting some of the more dangerous molds - or something.

But i don't know... i'll have a look.

It would be an interesting experiment to chuck 3 cupfuls of cornmeal and 1 cupful of wet vermiculite into a sealed jar and just watch what grows. If only green mold grows then i guess that suggests there is something special about it.

Thanks this is good information for both my chids and the roses ....I will be using it on roses for sure

Having had a quick look online, it seems like Trich would grow happily on any grain, not just cornmeal. So you can probably use anything 'gluteny': brown rice flour, rye, bran, wheat meal, etc.

And as far as i can tell, you're just putting out 'mold food' into the soil, which when it becomes wet, would slowly quickly become colonised by molds of all kinds. And then if there's Trichoderma spores in there too (which there probably is), then they might germinate, eat the grains and move on to attacking the root pathogenic fungi. I think that's how the corn meal is working.

I don't see why or how it would work to kill bacterial rots, it only parasites onto fungi as far as i've read. So i don't see why it would work on leaf spots and soft rots. I might be wrong. You said that you used it in combination with H202 for bad rots as well, didn't you? I wonder whether that is doing the job, because in my experience, 3-6% H202 is great for dealing with specific bacterial and fungal infections.

Thanks for posting an interesting thread, i don't think i'll be using Trich in my orchids, as Andrew mentioned i'd be worried about killing of mycorrhizal partnerships, and i don't use a media that would work very well with it anyway. But i might use it in the soil around my roses!

Undergrounder, just for clarification on the diseases I mentioned, black spot on roses and black rot of orchids -- they’re both fungal infections. You’re probably thinking of bacterial brown rot.

Yes i was thinking of bacterial rots, although they can be black as well.

Have read that tricoderma is used on corn corps both on seeds before they are planted and as a spray after growth. Could that be the reason it is common in corn meal? It is said to promote root growth and encourage Nitrogen uptake as well as preventing bad funus attack.
Have found a Biotech company that offers tricoderma both in the liquid and powdered form. They are sending me a sample. Have a covered test of wet corn meal in the greenhouse - my wild bird seed got moldy due to wet conditions so added a sprinkling of that to the corn meal. When the tricoderma gets here and the corn meal gets moldy will spray the surface and see what develops. Also have a few orchids that would go in the trash - there are culls from a flask. Will apply the tricoderma and observe the result.
Am seeing some opinions that tricoderma may attack other pathogens than just fungus.

Thanks for posting this very interesting thread. Plant-fungi relations are one of my specific interests and this might make an interesting topic or project in one of my horticulture classes.

Very interesting stuff, but the thought of putting something into the medium that absolutely will decompose quickly (compared to the medium) would seem to be a concern for limiting root zone aeration.

Can't wait to find out what happens with those experiments, orchids3!

I don't know about the Trich on cornmeal thing, but i would hope that there isn't green Trich. mold spores all through the cornmeal we are eating? I know its supposed to be harmless, but ... blleeccchhh!

Florida is full of mold spores. We are a wet humid semi tropical to tropical place. A lot of people have respatory problems due to this condition. Organic matter decomposes so fast in gardens that the only way to get nutrients to plants is with fertilizer addatives. Even gardening in the ground! A chemist friend of mine says we really use hydroponics. Organic matter decomposes very quickly and is useless as a soil ammendment. To try to understand the process that is going on is only natural.

Trichoderma harzianum in orchids
 

Hi there! I have been using weekly trichoderma harzianum for the last 2 years and I have seen a really better performance in survival, height and root zone of my cattleyas seedling including those recently deflasked.

Trichoderma have good effect on controlling fungus diseases，promoting root growth and improve soil contion. Especially Trichoderma harzianum T-22, testing reuslts is very good.

That species is well known for its effects, but that does not mean that all trichoderma species are beneficial.

Relying on ubiquitous species is playing Russian Roulette.

I agree with you, It's very important to choose the right strain of trichoderma.