Your graceful, elegant Pothos (Epipremnum aureum) is a resilient plant that will adapt to a variety of indoor and outdoor conditions. Sometimes it is susceptible to diseases, though, and pothos fungal infections top the list.
Fungal spores are everywhere, and when conditions are overly humid and wet indoors or outdoors, the spores can become active and multiply to attack roots, stems, and leaves.
Three pathogens cause most of these diseases: Phytophthora, Pythium, and Rhizoctonia. Each one brings about its own type of infection to the plant, but the treatment for all of them is similar.
The Silent Killer: How Phytophthora Root Rot is Destroying Your Pothos Plants
Phytophthora root rot is the most common fungal disease of Pothos ¹. It is caused by the pathogen Phytophthora nicotianae, a water mold that spreads rapidly by spores that swim through water. It starts in the roots and can eventually move through the stems and the rest of the plant tissue.
Symptoms
The common root rot symptoms above the soil are wilting, yellowing leaves, spongy stems, and stunted growth. Below the soil, the roots become soft, mushy, and black, with an unpleasant odor.
An infestation of fungus gnats in the soil and buzzing around the plant is another indication of possible root rot.
Causes
This disease is triggered by overwatering the plant and poor soil drainage. When water builds up and cannot drain effectively through the soil, it fills up the air pockets, and the roots can’t “breathe” or absorb oxygen. This creates an anaerobic (low oxygen) condition that is a perfect incubator for this disease.
Watch Out for Pythium Root Rot In Your Pothos
Pythium root rot is another water mold that can infect your Pothos. It is caused by various Pythium species of fungi that attack root tips and can move through the pothos roots and up into the stems.
Symptoms
A Pythium infection causes the roots to turn black and have a rotten odor. If the infection spreads throughout the plant, it will cause mushy stems and wilting leaves.
Causes
The same conditions of overwatering and poor drainage as Phytophthora root rot cause this disease. Pythium spores are everywhere ², including potting mix, and they will multiply and move through the water in overly wet soil.
An infestation of fungus gnats can also spread the infection from one plant to another.
Treatments for Phytophthora & Pythium Fungal Infections
If your plant shows unhealthy symptoms and you suspect it has root rot, isolate it from your other plants since fungal diseases spread easily. Then tip the pot to its side and pull out the root ball to look at the roots.
Shake off the soil and wash the roots to get a good look at them. Healthy roots will be firm and light-colored, but your plant has root rot if you see black, mushy roots that smell bad.
Cut off the black roots with clean scissors or shears and discard them well away from your plants. Then, treat the roots thoroughly with a copper-based fungicide or an organic fungicide like Neem oil.
Drenching the roots with a weak 3% hydrogen peroxide solution will also kill any remaining fungus.
Replant the Pothos in fresh soil in a clean pot with at least one drainage hole, and only water the plant when the soil is dry down 1 to 2 inches from the top.
Rhizoctonia Stem Rot & Aerial Blight of Leaves
Rhizoctonia is a soil-borne fungus that lives everywhere outdoors in gardens and fields. The most common species that can attack your Pothos is Rhizoctonia solani on the stems and leaves.
Symptoms
Since Rhizoctonia lives and proliferates in the top layer of the soil ³, it can infect your Pothos at the soil level, where you can see white, fungal webbing in high humidity with stagnant air.
The stems develop brown spots and lesions, shrivel, and become wiry, keeping water and nutrients from moving up to nourish the foliage, resulting in wilting yellowing leaves and eventual death of the plant.
If any leaves come in contact with infected soil, they can develop Aerial Blight, the leaf infection caused by Rhizoctonia. Black fungal leaf spots will form, and heavy infections can cause the leaves to drop.
Causes
Though Rhizoctonia is a fungus that can be dormant for years in the soil, it becomes activated and will grow on plants in moist, humid conditions without much air circulation.
Therefore, if you leave your Pothos outdoors in the summer, be aware that it can easily become infected in shady, moist areas with stagnant air.
Treatments
If the plant is not highly infected, use a combination of a fungicide and better cultural conditions to bring your plant back to health.
Remove the Pothos from its pot and discard the soil. Wash the soil off the roots, and spray or drench your whole plant, including the roots, with a copper fungicide or Neem oil per instructions on the container.
Repot the plant in fresh soil in a clean pot with at least one drainage hole and ensure that none of the leaves are touching the soil. Then set the pot in an area with good air circulation, away from other foliage that could reinfect it.
Water your Pothos in the morning when the soil is dry, 1 to 2 inches from the top. That way, it will have the light and heat of the day for the stems and leaves to dry out before nightfall.
Best Practices to Prevent Pothos Fungal Infections
Your Pothos needs a balance of light, temperature, humidity, soil, and water to grow well. If one or more of these conditions are out of balance, the plant could become susceptible to disease.
Fungal infections in plants are mainly caused by humid conditions, insufficient air circulation, and overly wet soil with poor drainage. If you can remedy these conditions and give your Pothos what it needs, you should have a healthy plant for years to come.
Light
The right amount of light is essential to the life of the plant. Too much light can burn Pothos leaves, and too little can slow the plant’s growth, keep the soil from drying out, and invite disease.
Pothos plants need bright indirect sunlight to photosynthesize reasonably and make food energy for their growth. When there is more light, the plant uses up water more quickly from the soil than when there is low light.
In low light, the soil will tend to dry out more slowly, creating an environment for fungal growth.
Even though they are adaptable plants and can survive in moderate to low light, it’s healthiest for Pothos to have bright light but not in direct sunlight.
Temperature
Temperature is another factor in the health of the plant. Pothos grow best at 65 to 75 degrees F, which are average household temperatures. After that, they wilt and shrivel above 90 degrees and will not grow at all below 50 degrees.
Warmer temperatures will increase the rate of photosynthesis and dry the soil out more quickly. However, it will also activate fungal spores if too much water is present and the soil is overwatered and not allowed to dry out.
Humidity
Humidity levels must be watched, especially if your plant is outside for the summer and has high humidity levels.
Pothos plants are native to tropical rainforest conditions and love high humidity. But fungi easily get a foothold in humid conditions, so there needs to be enough air circulation around the plant to discourage fungal growth.
As houseplants indoors, Pothos grow best in 40 to 60 percent humidity. However, the household levels are usually about 30 to 40 percent during the winter when the heat is on. This is too low humidity for Pothos, and they will need a boost from a pebble tray of water, a humidifier, or misting.
The humidity levels should remain healthy as long as there is plenty of air circulation around your plant indoors or outdoors.
Soil
Your potting soil provides the structure for your Pothos to sit in and absorb oxygen, water, and nutrients. Above all else, it needs to be loose and well-draining to physically maintain air spaces for the roots to stay healthy and disease-free.
You can use a good commercial potting mix that you amend with perlite, coco coir, orchid bark, or peat moss. This will allow water to drain through the soil and let the roots “breathe.” Fungal diseases will not grow when the soil has plenty of air.
Water
Watering correctly is perhaps the most important thing you can do to keep your Pothos from developing a fungal disease.
You need to allow the soil some time to dry out and the Pothos to absorb the water already in the soil. When you do this, the amount of water will stay balanced with the other growth conditions, and your plant will stay healthy without any fungal problems.
When the soil is dry, 1” to 2” down from the top, it’s time to water. Water thoroughly so that it runs through the soil and out the drainage holes in the pot. Let it drain, then empty any remaining water in the dish or tray underneath the pot.
Then monitor the soil moisture and water again only when the soil is partially dry. A moisture meter can help you determine when it’s time to water.
Note: In addition to watering correctly, it’s very important to choose a pot with at least one drainage hole so that the water will not build up and cause root rot.
Providing healthy conditions for your Pothos will go a long way toward the best growth and prevention of disease.
Fungal Diseases Aren’t The Only Threat To Your Pothos: Bacterial Leaf Spot
Fungal diseases of Pothos is highly relevant to the issue of bacterial leaf spot. While a bacterial pathogen causes pothos bacterial leaf spot, the conditions that lead to fungal infections, such as overwatering and poor soil drainage, also make the plant more susceptible to bacterial diseases.
Therefore, following the best practices outlined in the article, such as watering correctly, maintaining healthy soil, and providing sufficient air circulation, you can help prevent fungal and bacterial diseases in your Pothos plant.
References
1: Leahy. (n.d.). Phytophthora Blight of Pothos. Retrieved April 5, 2023, from https://www.fdacs.gov/content/download/11407/file/pp401.pdf
2: Pythium. (2014, June 12). Pythium. https://extension.psu.edu/pythium
3: Rhizoctonia. (2014, June 12). Rhizoctonia. https://extension.psu.edu/rhizoctonia
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Nancy has been a plant person from an early age. That interest blossomed into a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Nancy worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.