Orchid Fungus

Beneficial Fungus

• Some orchid species rely on fungus to help them to obtain nutrients and germinate their seeds. In return, the fungus gets nutrients from the plant. This sort of symbiotic relationship is not usually harmful to the orchid. In fact, as reported in the February 2011 issue of "Scientific American," South African orchid species remain loyal to one species of fungus throughout their lives. This is usually a different species than that used by any neighboring plants, which allows the orchids to avoid competition.

Black Rot

• Black rot fungus can infect the roots and leaves of orchids. This fungus shows itself on the orchid's leaves first, giving new foliage a rotted yellow or purple-brown appearance. Leaves later turn black. Black rot can spread to the roots in its later stages so infected orchids should be treated promptly by removing infected areas with a sterilized knife. Apply fungicide, and avoid overwatering while the orchid is recovering.

Root Rot

• Root rot will cause an orchid to look sickly for a few months before it eventually dies. Leaves turn yellow and brown, and black splotches appear on the plant's roots. The orchid will look generally wilted and droopy. Root rot should be treated by cutting off the infected areas of the roots (those with brown and black splotches), with a sterile knife. Then treat the orchid with fungicide and repot it.

Fungus Prevention

• Fungus grows well in moist environments, so be careful not to overwater your orchids. Skip watering on cool, cloudy days or when it is raining. When growing orchids inside, use fans or open windows to keep the air in the room moving. Stuffy environments also encourage fungal growth. Treat fungus promptly when you discover it. If you are growing multiple orchids, you may want to move the infected orchid away from other plants so that the fungus will not spread while it is being treated.