Mold on Orchid Roots

Snow Mold

• Snow mold, also called potting fiber mold, is a fungus of the Ptychogaster species that grows within the soil where an orchid is planted. It often covers the roots and grows several inches thick at the pot’s base. As it spreads throughout the soil, it reduces the plant’s vigor and may eventually kill it.

Snow Mold Management

• As the snow mold on orchid roots thickens, it deprives the root system of oxygen, water and nutrients. Fungicides are available that control this disorder and must be applied at least twice during a two-week period if the mold is especially thick. Hand pick as much mold as possible off the roots. Repot the orchid after treatment.

Mealybugs

• Mealybugs are orchid pests that dig deep into the soil where they cling to the plant’s root system. The insect is covered with a white, waxy secretion and often leaves behind what appears to be cottony balls of fuzz. Because of this secretion, an infestation of mealybugs is easily confused for mold growing on orchid roots and within the soil. The pest moves easily from plant to plant.

Root Rot Mold

• Several fungal and bacterial diseases produce mold on orchid roots with Phytophthora root rot and Pythium root rot the most common. These root rots decay the root system, preventing it from properly absorbing and delivering sufficient supplies of water and nutrition to the rest of the plant. Symptoms initially display as brown or black spots on the foliage. As the rot worsens, the entire plant may die. Excessive watering and overly moist soil contribute to root rot.