Potting Mix May Replace Fungicide United States Department Of
Agriculture (USDA) researchers have discovered a way to make
potting mixes more successful than fungicide in reducing
Botrytis gray mold, the most common disease affecting greenhouse
floral crops such as begonia, carnation, chrysanthemum,
cyclamen, geranium, impatiens, petunia and marigold. In a test
with begonias, plant pathologists Leona Horst, James Locke and
Charles Krause found that a mix of peat, compost and the
beneficial fungus Trichoderma hamatum strain 382 reduced
Botrytis gray mold better than the standard fungicide
chlorothalonil did. Beneficial Trichoderma seems to enter the
plants through the roots and spread through the entire plant
internally. One advantage of systemic biocontrol is that it
doesn’t leave residue on the plant, harming plant market value.
Begonias in this mix had fewer gray mold symptoms. The
improvement in plant quality and market value makes the
Trichoderma compost mix promising for greenhouse operations.
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