How to Identify and Treat White Mold on Orchid Roots

White mold on orchid roots can be a concerning discovery for any orchid grower. This common orchid disease appears as a fuzzy white growth on the roots and potting medium. If left unchecked, it can spread throughout the plant and wreak havoc. However, with some knowledge and preventative care, white mold on orchid roots can be effectively managed.

What Causes White Mold on Orchid Roots?

White mold, also known as Sclerotinia sclerotiorum, is a fungal pathogen that affects over 400 species of plants. It thrives in cool, wet environments. For orchids grown indoors, the main causes of white mold on the roots include:

• Overwatering – Excess moisture in the potting mix encourages fungal growth Orchid roots need a wet/dry cycle.

• Poor drainage – Waterlogged potting mix creates an ideal habitat for white mold

• Inadequate air circulation – Stagnant, humid conditions prevent drying out between waterings

• Overcrowding – Plants spaced too closely impede airflow.

• Temperature – White mold develops in cooler temps, ideally 59-68°F.

• Old potting mix – Broken down media retains moisture and promotes mold.

How to Identify White Mold on Orchid Roots

Detecting white mold early is key to saving affected orchids. Watch for these signs:

• White, powdery or cobweb-like growth on roots and potting mix.

• Mushroom-like odor coming from the potting mix.

-FIRM roots that feel mushy or hollow in the center when squeezed.

• Yellowing, wilting, or dropping leaves.

• Small black dots (sclerotia) scattered within white mold.

• White mold originating at base of plant or crown.

• Slowed growth.

How to Treat White Mold on Orchid Roots

If white mold is spotted on one or several of your orchids, take action right away to avoid it spreading further. Follow these treatment steps:

• Isolate infected plants away from healthy orchids.

• Remove orchid from pot and discard all potting mix, cleaning roots.

• Prune any rotted roots back to healthy tissue; dip pruning shears in alcohol.

• Spray a 3% hydrogen peroxide solution on the roots and plant to kill spores.

• Allow plant to dry completely before repotting in fresh, sterile mix.

• Apply a organic fungicide like cinnamon powder or clove oil to root area.

• Repot in new container with drainage holes, using fresh potting material.

• Move orchid to spot with improved air flow and light.

• Allow more time between waterings and ensure pot drains fully.

• Continue using fungicide until orchid shows improvement.

How to Prevent White Mold

While even the most careful grower may occasionally encounter white mold, there are preventative steps to reduce its occurrence:

• Water thoroughly but allow pots to dry out a bit between waterings.

• Use well-draining potting mixes, changing out every 2-3 years.

• Ensure plenty of air circulation around plants.

• Space orchids at least 12 inches apart to prevent overcrowding.

• Maintain daytime temperatures 65-85°F and nights above 60°F.

• Water early in the day so plants dry out by night.

• Sterilize pots and tools with dilution of bleach or isopropyl alcohol.

• Apply fungicides like cinnamon or hydrogen peroxide as a preventative.

• Inspect roots when repotting for signs of rotted roots or mold.

• Isolate and promptly repot any plants showing white mold.

While managing white mold takes diligence, it is very possible to enjoy beautiful, healthy orchids by following sound watering, potting, and preventative practices. Inspect roots frequently and address any signs of mold growth right away. With proper care, your orchids will continue thriving and flowering for years to come.