White mold, also known as Sclerotinia sclerotiorum, is a devastating fungal disease that can infect orchid roots. It appears as a fuzzy white growth that can quickly spread, robbing the plant of nutrients and eventually killing it. While orchids of all types are susceptible, Phalaenopsis and Dendrobium orchids seem especially prone to infection. If you suspect your orchid has white mold, prompt action is required to save your plant. Here is everything you need to know about identifying and treating white mold on orchid roots.
How to Identify White Mold on Orchid Roots
The first signs of white mold on orchid roots are subtle. You may notice some slowdown in growth or slightly yellowed lower leaves. Take a close look at the roots and base of the plant to spot early symptoms:
- White fuzzy growth around roots and lower stem
- Soft, mushy roots that appear melted
- Roots pulling away from the plant when gently tugged
- Dark water-soaked lesions on stems near the soil line
As the disease progresses you’ll see more distinctive symptoms
- Rapid wilting and yellowing of leaves
- White mold covering most of the roots
- Dark brown or black roots that are very mushy
- Severe rotting at the plant’s base
- White fungal growth spreading up stems
If your orchid exhibits these advanced signs, the likelihood of saving it is low At this point, the mold has damaged or destroyed much of the root system.
What Causes White Mold on Orchid Roots
Sclerotinia sclerotiorum fungus thrives in cool, moist environments. Some common causes that allow it to take hold include:
- Overwatering – Excess moisture in the potting mix breeds fungus
- Insufficient air circulation – Stagnant air encourages mold growth
- Low temperatures – Below 60°F (16°C) favorable for fungus
- Unsterilized potting tools – Transfers fungal spores to cuts
- Contaminated potting mix – Mold spores present at potting
The fungus produces resilient structures called sclerotia that can survive in soil or potting mix for years. Even just a few sclerotia mixed in with your orchid’s potting material can lead to infection.
How to Treat White Mold on Orchid Roots
If caught early, white mold can be conquered with prompt treatment. Here are the steps to treat an orchid with mild to moderate white mold:
1. Isolate the infected plant. Keep it quarantined in a separate area away from other orchids to prevent spreading spores.
2. Remove the orchid from its pot and detach all potting mix. Discard the old medium, as it likely harbors mold spores.
3. Prune off any severely infected roots or stem areas. Use sterilized, sharp pruners to make clean cuts. Throw away the trimmings immediately.
4. Spray remaining roots and stem with hydrogen peroxide 3% solution. This will kill lingering mold spores. Let sit 5 minutes before continuing.
5. Dust cinnamon powder on any cuts or questionable spots. Cinnamon has anti-fungal properties that inhibit mold growth.
6. Repot the orchid into fresh, sterile potting mix. Choose a pot with ample drainage holes.
7. Move the orchid to an area with good air flow. Turning on a fan nearby will help dry things out.
8. Hold off watering until roots appear silvery green. Let the plant dry out slightly between waterings going forward.
9. Apply orchid fungicide weekly per label directions. Treat for 2-3 weeks minimum to eradicate the mold.
With aggressive treatment, you can rescue an orchid in the beginning stages of white mold. However, if the fungus has already damaged the root system extensively, the plant likely cannot be saved.
How to Prevent White Mold on Orchid Roots
While treatment is difficult, preventing white mold in the first place is easier. Here are some tips to reduce the risk of this orchid disease:
- Water only when potting mix is nearly dry
- Provide plenty of air circulation
- Keep temperatures above 65°F (18°C)
- Use sterile pruning tools and pots
- Allow potting mix to dry out between waterings
- Pot in an orchid bark mix, not moss
- Inspect roots and base routinely for early signs
- Isolate and treat immediately if mold appears
- Apply preventative fungicide drenches
Good cultural practices that create an unfavorable environment for fungal growth are key. Be vigilant about air flow, moisture levels, and temperatures around your orchids. Check roots frequently, and act fast at the first sign of white mold to maximize your chances of saving infected plants. With proper prevention and early detection, you can help keep your orchid collection mold-free.
Frequently Asked Questions
What does white mold look like on orchid roots?
White mold first appears as a fuzzy white growth surrounding orchid roots and lower stems. As it spreads, roots turn brown or black and become very mushy and melted. Advanced cases will show white fungal growth covering most roots and spreading up the stems.
What orchids get white mold?
While all orchids are susceptible, Phalaenopsis (moth orchids) and Dendrobium orchids are especially prone to white mold infections. Taking preventative measures is important for these varieties.
Is white mold on orchids contagious?
Yes, white mold is very contagious between orchids. Spores can travel on air currents or shared tools. Isolate any infected plants immediately to avoid spreading.
Can you save an orchid with severe white mold?
If the mold has already damaged a large portion of the root system, the prognosis is poor. However, orchids in early stages of infection can be saved with aggressive sterilizing and fungicide treatment.
Does hydrogen peroxide kill white mold on orchids?
Spraying a 3% solution of hydrogen peroxide directly on infected roots can help kill white mold. Combine with other sterilization methods for most effectiveness.
How do you prevent white mold on orchid roots?
Allow potting mix to dry between waterings, provide good air circulation, use sterile tools and pots, keep temperatures above 65°F, and inspect roots routinely. Isolate and treat any infection early.
With vigilance and prompt treatment, you can protect your orchids from devastating white mold infections. Be on the lookout for early symptoms, and be prepared to take action at the first sign of fuzzy white mold growth. A little extra care will help ensure your orchids stay happy and healthy.
Orchids are gorgeous houseplants, but they are prone to disease – even when you are trying your hardest to look after them.
If you spot a white, fluffy mould-looking patch near the roots of the orchid, your houseplant is in danger of dying.
Everything Orchid warned: “There are a variety of different types of fungi that can begin forming on your orchids.
“Fungus can be extremely harmful and even deadly to orchids. It is important to immediately take action if you notice any signs of fungus forming on your orchids.”
One of the best methods to get rid of the mould as soon as you spot it involves the use of a natural essential oil.
You will need to try tea tree oil, which contains natural anti-bacterial properties that can effectively remove the harmful mould growing on the houseplant.
READ MORE: Orchids will produce ongoing gorgeous blooms if pruned at the correct time
“You won’t ever have to worry about tea tree oil killing your orchid,” Everything Orchid promised, which should be used for a “mild infection”.