9 Philodendron Diseases to Watch for This Season
Is your beloved philodendron looking less than its best this season? There might be an underlying reason that needs addressing. Gardening expert Melissa Strauss walks through some of the diseases common to this type of plant and what to do about them.
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Philodendrons make excellent houseplants, and in warm climates, they are fabulous in the garden landscape. They are not without their problems, though. These tropical lovelies need just the right balance of conditions to stay healthy.
Many philodendrons are epiphytic or hemiepiphytic, which means they grow on trees with exposed roots. They are similar to orchids in this sense. As a result, it’s easy to overwater them, and that opens them up to fungal diseases. There are also some bacterial diseases that are common in this group.
If your plant isn’t looking its best lately, there could be an underlying issue. Once you’ve ruled out care issues, like proper watering and adequate light and humidity, it’s time to look at diseases. Let’s take a look at some of these and discuss how they manifest, as well as how to treat them.
Stem Rot
Stem rot and root rot go hand in hand, but it’s possible to have one without the other, depending on humidity. When this happens, it’s a product of sclerotia, which are bodies of a fungal pathogen covered with a melanized protective coating. These break open, releasing spores, and they can find their way to your garden.
This is mainly an issue in outdoor plants. Stem rot in your indoor philodendron is going to be related to root rot. It happens most often when overwatering, excessive rainfall, or high humidity are present. The proximity of other plants is another factor. Less airflow and sunlight means more fungal issues.
How to Fix It
Preventatively, keep some space around your plants for air to circulate, and be careful about overwatering. Good watering practices will prevent most fungal diseases. Once it is present in small amounts, a fungicide can be helpful.
In advanced cases, if left untreated, it will kill the plant. The best thing to do here is to take as many healthy cuttings as possible. Cut portions of the unaffected stem with at least one node per cutting. Use these to propagate new plants so you don’t lose yours altogether.
Root Rot
Root rot is a major issue for houseplants, especially epiphytic ones. In their natural environment their roots are exposed to the elements with a lot of air circulation. That means there is nothing holding soil around them, so pathogens in the soil can’t affect them.
Many philodendrons are epiphytes, so their roots are highly sensitive to fungus and overwatering. A soil-borne pathogen called Phytophthora sojae causes this disease. It is most active in moist soil and warm temperatures (above 60%).
Indications of root rot include yellowing of leaves and a mushy crown or stems. You may also detect an unpleasant odor coming from the soil. Fungus gnats may also be present.
How to Fix it
If you suspect root rot, it’s imperative that you re-pot the plant as soon as possible. Remove it from its container, rinse the soil out of the roots, and inspect them for dark, mushy spots. If the roots are predominantly rotten and it has moved into the crown, your philodendron is on its way out.
In the event that your roots are no longer able to support the plant, and it has moved up into the crown and stems, there is only one solution. Take cuttings from the healthy tissue and propagate. Many philodendrons are easy to propagate.
If you manage to catch the root rot before it affects the entire system, that’s wonderful. Just trim away the affected tissue and re-pot the plant in a fresh potting mix. Using a mix with large particles like bark and perlite will increase drainage. This helps to keep air flowing through the soil and makes it more difficult to overwater.
Fungal Leaf Rot
Another fungal disease you may come up against is leaf spot caused by one of several fungal pathogens. This manifests as dark, watersoaked lesions on leaves that are sunken in and darken with time. It is a common disease caused by water splashing from an infected plant onto a healthy one.
If you notice these spots, isolate the affected plant away from others to avoid spreading it. I’ve seen this show up on newer plants that came in contact with it at the nursery, where watering practices tend to be utilitarian. The pathogens flourish in the humid environments that philodendrons love, like a greenhouse.
How to Fix It
Good watering practices are the best prevention. Keep air circulating, and don’t overdo the humidity. Sometimes, it pops up through no fault of your own. When this happens, cut off any affected leaves to help control the spread. Then treat with a copper-based fungicide or neem oil every seven to ten days for a month or until you are certain it’s gone. Keep the plant isolated during this time.
Fungal Blight
Fungal blight, also called southern blight, is another issue that tends to manifest as a result of poor plant hygiene. Initially, it might look like other types of rot, but over time, it will take on a more distinctive appearance. Masses of white mycelia will form on the stems and leaves and will spread over time.
How to Fix It
Prevention is the best control. Make sure that you inspect your plants before you bring them home. When potting, always use clean tools, soil, and containers. If it’s present in or on these things, the plant is at risk. Prune away damaged leaves as they crop up to prevent spread to healthy plant tissue.
Bacterial Leaf Spot
Bacterial leaf spot is similar to fungal leaf spot, but different pathogens cause it. This disease is the result of contact with the bacteria Xanthomonas campestris pv. dieffenbachiae. It travels best in spaces with high humidity and warm temperatures.
You may notice translucent spots on leaf margins, which gradually turn to reddish brown. A yellow halo will form around the edge of these spots. Eventually, the spots will turn into holes.
How to Fix It
Avoid overhead watering that can splash water from one plant to another. This is how the bacteria spreads. Isolate the offending plant and remove any affected leaves. Inspect any new plants you bring into the home and garden.
Bacterial Blight
You may see the use of leaf spot and blight used interchangeably. But for our purposes, I will differentiate by the name of the pathogen that causes each one. The causes of this disease are the bacterias Erwinia carotovora and Erwinia chrysanthemi.
This bacterial disease manifests as small, dark green spots on the leaves, which grow rapidly, spreading to petioles. Ultimately, the leaves will collapse into a mushy, rotted state and have an unpleasant odor.
How to Fix It
Treat this similarly to bacterial leaf spot. Isolate it and remove all affected foliage. Even if there is only a small spot, take off that leaf. If it recovers, make sure to establish good watering practices. Don’t water overhead where water will splash on the leaves and petioles. Water only at the soil level, or from underneath.
Tip Curl
Tip curl is more of a condition caused by external factors than disease. However, it is something to watch out for, as it indicates an underlying issue. If the ends of your leaves are curling up, it’s usually a sign of stress or malnutrition.
The primary cause of curling leaf tips is a lack of moisture. This can be the result of under-watering or a lack of moisture in the air. In other words, not enough humidity. Philodendrons are tropical and their native habitat is humid. Their foliage needs moisture as much as their roots do.
Curling tips can also be the result of malnutrition. Essential nutrients like nitrogen, magnesium, and potassium are necessary for proper growth and health. Curling leaves with an anemic appearance may be the result of a nutrient deficiency.
How to Fix It
If the issue is moisture, that’s easy to fix and should be obvious. Make a habit of checking the soil more often to establish when and how much to water. Likewise, if the room has dry air, you should move the plant to a more humid room or increase the moisture in the surrounding air. Making these changes should quickly remedy the problem.
If the issue doesn’t resolve with the additional moisture, make sure your philodendron is getting enough fertilizer. In spring and summer, fertilize every two weeks with a liquid formula. In fall and winter, when growth slows, slow fertilizing to every six to eight weeks.
Cold Injury
This, again, is not a disease, but if you’re looking for a reason your philodendron is suffering, it’s an important thing to consider. These tropicals are sensitive to cold temperatures. They are not cold tolerant, and fluctuations can cause damage.
Cold damage manifests as browning of the leaf margins and wilting of foliage. The youngest leaves will be first and more severely affected. The older leaves are stronger and will tolerate some cooler weather.
How to Fix It
If your plant is outdoors, there are only two options: bring it in, if possible, or protect it from the weather. In the cooler part of their range, many of these plants lose leaves in the winter and will come back in the spring.
For indoor plants, location is important, particularly in the winter. Keep your philodendron away from cooling vents, doors, and drafty spaces. If you expect freezing temperatures overnight, consider moving these away from the window for a bit. It can get cold on the inside near your windows.
When you see this damage, make sure that to minimize any other stressors. Make sure the soil is moist, and don’t give it any fertilizer. Then, gently remove the affected tissue to encourage it to focus energy on recovering.
Chlorosis
Chlorosis is the loss of color in the leaves caused by environmental factors. It will manifest as leaves that turn yellow between veins that remain green. Some causes of this include poor soil, low light, overwatering, or nutrient deficiency. All but one of these has nutrient deficiency as the root cause.
Poor soil with depleted nutrient content can be a problem. Overwatering can dilute the nutrients in the soil and wash away fertilizer. Commonly, this is a result of not fertilizing, though. Lack of light is a possibility, as well. Philodendrons like bright but indirect sun exposure.
How to Fix It
If it’s been a while since you last re-potted the plant, go ahead and do that. Use fresh potting mix, and discard the old. You can also top-dress it with some compost or worm castings, but this takes longer to have an effect.
If you don’t fertilize regularly, this is a good time to start. Make sure to use a formula that contains iron and magnesium. These are micronutrients that are important to philodendrons.
Key Takeaways
When it comes to most philodendron diseases, prevention is the best solution. Practice good watering habits, and keep your plant fertilized and healthy. Always inspect new plants when you bring them into the home or garden and isolate at the first sign of a problem.
