Potting mixes custom-tailored to fight plant diseases can work much better than systemic fungicides, according to the US Agricultural Research Service.
Plant pathologists made the finding for a mix of peat, compost and the beneficial fungus Trichoderma hamatum strain 382.
In a test with begonias, the scientists found that the mix reduced Botrytis grey mold, caused by the Botrytis cinerea fungus, better than the standard fungicide chlorothalonil did. Botrytis grey mold is the most common disease of greenhouse floral crops such as begonia, carnation, chrysanthemum, cyclamen, geranium, impatiens, petunia and marigold.
The beneficial Trichoderma fungus seems to enter the plants through the roots and spread through the entire plant internally. One advantage of systemic biocontrol - as opposed to spraying the plant leaves with a solution containing beneficial fungi - is that it doesn't leave a residue on the plant that harms plant market value.
Begonias grown in this mix had much fewer gray mold symptoms and much higher market value that those grown in straight peat and sprayed with chlorothalonil. The improvement in plant quality and market value makes the Trichoderma-compost mix very promising for greenhouse operations. Also, Botrytis has developed resistance to several fungicides.
The Trichoderma fungus thwarts Botrytis on more than one front. It prevents Botrytis from infecting fresh wounds, and produces compounds that keep Botrytis spores from germinating.
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