What You Need to Know About White Mold on Orchid Roots

White mold on orchid roots can be concerning for any orchid grower. However, there are a few key things you need to know to properly identify, treat, and prevent white mold on your orchid’s roots.

What Causes White Mold on Orchid Roots?

White mold on orchid roots is caused by a fungus known as Sclerotium rolfsii. This fungus thrives in warm, humid environments and can easily infect an orchid’s roots if conditions are right. Sclerotium rolfsii produces white, cotton-like mycelium that covers affected roots. If left untreated, the fungus will rot the roots of the orchid, resulting in loss of vigor, wilting of leaves and flowers, and potentially death of the plant.

There are a few ways that white mold can gain access to infect an orchid’s roots

• Overwatering – Excess moisture allows fungal spores in the potting mix to germinate and attack the roots.

• Poor drainage – Stagnant water and soggy media provides an ideal environment for white mold.

• Root injury – Cuts, scrapes or other wounds on roots create an entry point for the fungus.

• Contaminated potting mix – Spores of Sclerotium rolfsii may already exist in old, reused potting material.

How to Identify White Mold on Orchid Roots

White mold on orchid roots is easy to identify visually, Signs to look for include

• White, cottony or cobweb-like fungal growth on top of the potting medium or lower leaves. This mycelium may spread to cover large sections of the pot.

• White “fuzz” directly on top of or surrounding the orchid’s roots and lower stem. Healthy roots should be firm, plump and green or silver.

• Soft, brown roots under the white fungus, indicating rot and decay.

• Small, round tan or brown sclerotia which are survival structures of the fungus. They allow it to persist in soil.

• Wilting, yellowing or drooping leaves as the roots die off and cannot supply the plant.

How to Treat White Mold on Orchid Roots

If white mold is identified on your orchid, take action right away to treat it:

• Isolate the infected orchid to prevent spread to other plants.

• Cut away all affected roots and stem material with a sterile tool. Remove all potting material.

• Spray remaining roots and plant with a fungicide like thiophanate methyl or copper-based products.

• Repot in fresh, sterile potting mix in a clean container. Allow potting material to dry thoroughly between waterings.

• Apply fungicide drench per label instructions to kill lingering fungus in the plant. Repeat every 7-14 days until resolved.

• Increase air circulation around the orchid by using fans or opening windows.

With prompt treatment, many orchids can recover successfully from a white mold infection. Be sure to continue monitoring for recurrence and adjust care routines to avoid reinfection.

How to Prevent White Mold on Orchid Roots

Prevention is the best cure when it comes to managing orchid fungal diseases like white mold. Here are some tips:

• Water properly – Allow potting mix to dry before soaking again. Discard any water in cachepots.

• Choose suitable potting material – Look for mixes that retain some moisture but still promote drainage and aeration.

• Sterilize pots before reuse – Scrub and disinfect pots to kill any lingering fungal spores and pests.

• Use sterile tools – Clean shears, cutting implements and stakes to prevent spreading diseases between plants.

• Promote airflow – Elevate pots off surfaces, space plants, use fans to keep air moving.

• Avoid root injury – Handle roots gently, trim cleanly and disinfect tools between plants.

• Scout for problems frequently – Inspect roots, leaves, base of plant to catch issues early.

• Isolate new orchids – Quarantine new plants for a few weeks to prevent introducing pests and diseases.

With proper orchid care techniques and cultural controls in place, you can sidestep white mold on orchid roots and maintain a healthy collection. Be observant, act quickly at first signs, and keep environmental conditions from favoring fungal infection.

When to Discard an Orchid with Severe White Mold

In some cases, white mold may be too extensive on an orchid or reoccurs despite treatment. At that point, it is best to discard the infected plant to protect other orchids. Signs it may be time to remove an orchid include:

• Majority of roots are rotted with no viable tissue remaining

• Plant declines rapidly with yellowing or dropping leaves

• Repeated fungus outbreaks continue after multiple fungicide treatments

• Mycelium spreads up into lower stem and leaves

• Small new growths rot at the base indicating systemic infection

While having to part with a treasured orchid can be disappointing, remember you can find healthy replacements to try again! Just be sure to learn from past issues and alter care to support your new orchid’s success.

Common Mistakes that Lead to White Mold on Orchid Roots

Some of the most common mistakes that invite white mold problems include:

• Overwatering or too frequent irrigation

• Poor drainage from dense potting media or lack of drainage holes

• Allowing water to collect and stand in the saucer or pot

• Not allowing enough time for potting mix to dry out between waterings

• Reusing old potting material contaminated with spores

• Crowding plants together with poor air flow

• Failing to sterilize cutting tools which spread fungal spores

• Getting water or debris in the crown of new growths

• Putting an orchid in a pot that is too large, retaining moisture

With greater awareness and a few adjustments to care routines, these pitfalls can be avoided. Be sure to research your specific orchid type and implement the conditions and practices it prefers for strong roots and growth.

When to Seek Diagnosis or Help

If you are unsure about the exact cause of root problems, or if they persist despite your best efforts, don’t hesitate to seek expert input. Reach out to an orchid society, university diagnostic lab, or reputable orchid nursery. They can often identify pathogens through microscopy or lab testing. With an accurate diagnosis, they can also recommend the most effective integrated pest management techniques and products. Getting the right treatment early often means you don’t have to part with your treasured orchid!