Trichoderma - Killing Bad Fungus with a Good One

[Anglo]

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.