Leaf Spot Disease Philodendron [Causes & How to Fix]

Leaf spot disease is one of the most common diseases that attack philodendrons. It weakens your plants by messing with the process of photosynthesis, rendering your philodendrons unable to absorb light energy through their leaves.

Leaf spot disease Philodendrons can cause water-soaked lesions and reddish-brown margins to appear on philodendron leaves. These lesions can spread and cover the entire leaf, especially under extreme temperatures. As a result, the leaves can fall off and adversely affect the plant’s growth.

The rest of this article will further discuss leaf spot disease in philodendrons, its symptoms, and its causes. I will also explain how you can treat and manage it.

What Is Leaf Spot Disease?

Leaf spot disease is a condition caused by bacteria or fungi that attack the flowering plants in the philodendron genus. This disease commonly attacks philodendrons that grow in Connecticut, Florida, and Pennsylvania, causing tan, black, and brown water-soaked lesions to appear on the leaves.

There are many symptoms of philodendron leaf spot disease you should look out for, so you can identify, manage, and treat the condition. These symptoms vary depending on the pathogen causing the infection — specifically, bacteria and fungi.

Bacterial Leaf Spot

Bacterial leaf spot is most often caused by three types of bacteria: Erwinia, Pseudomonas, and Xanthomonas.

Some of the characteristic symptoms of bacterial leaf spot are:

Small brown to black water-soaked lesions on the leaves that enlarge with age
Irregularly shaped spots
Lesions on the stalk and stem
Unpleasant fishy smell from the leaves
Reddish-brown margins on the edges of the lower leaves with yellow halos around them
Protruding leaf veins around the lesions
Leaves dropping too often

Fungal Leaf Spot

Phytophthora and Dactylaria fungi are often responsible for fungal spot disease. This form of leaf spot disease is characterized by:

Irregularly shaped lesions that are water-soaked and dark brown
Lesions with depressed centers
Leaves that turn yellow due to a lack of chlorophyll

What Causes Leaf Spot Disease in Philodendrons?

Bacteria and fungi cause leaf spot disease in philodendrons during severely moist and hot conditions. The excess moisture allows them to thrive, while the warmer temperatures cause the spores to germinate and penetrate the leaves, infecting them.

Since these organisms stay invisible until the signs of leaf spot disease appear on your plants, it can be difficult to control the infection with fungicides. The disease has already become contagious at this stage, and surrounding winds can quickly spread the disease to other, healthier plants.

Therefore, your best option is to prevent leaf spot disease from infecting your philodendrons in the first place.

Some tips to prevent leaf spot disease in philodendrons are:

Avoid overwatering your philodendrons.
When watering your philodendrons, spray the water directly on the soil to prevent it from wetting the leaves.
Keep your house well-ventilated and use devices such as fans and dehumidifiers to keep the temperature and humidity low, respectively.

How To Manage Leaf Spot Disease on Philodendrons

You may not be able to “cure” leaf spot disease once it gets bad enough, but you can keep it from getting out of control and spreading to your other plants. Below are some of the ways to do just that.

Remove Infected Leaves

Removing infected leaves is the first line of defense against leaf spot disease. Do this as soon as you notice symptoms of the disease on your philodendron since the infection tends to spread quickly and affects all the leaves on the plant.

However, this method only works on mildly infected plants. If the infection is more severe, you have to take more drastic measures.

Handle Plants With Care

The bacteria that cause leaf spot disease can be spread by careless handling of philodendrons. Therefore:

Always wash your hands after defoliating the diseased plants to prevent the spread of the infection to healthier plants.
Don’t touch the leaves when your hands are wet. Otherwise, the moisture will transfer to the leaves and encourage the growth of harmful pathogens.

Avoid Overhead Watering

Water your plants in a way that ensures water doesn’t touch the leaves and stalks. As I mentioned earlier, leaf spot disease thrives in highly moist conditions. Also, overhead watering can cause droplets from the affected leaves to splash on the healthy ones and infect those.

Isolate the Plants

Move the infected plants away from the healthy ones as soon as you notice the leaf spot symptoms on them. Since the disease is highly infectious, keeping the affected houseplants far away from others will prevent the healthy ones from getting contaminated.

Destroy the Plants

If the leaf spot disease is severe enough (meaning the water-soaked lesions cover all the leaves and cause them to fall off), there’s not much you can do other than destroy the affected plants. Specifically, you need to uproot the infected plants and burn them ASAP.

Avoid Reusing Infected Soil

After you’ve destroyed the severely affected plants, you should also get rid of the soil they were planted in. Otherwise, if you use the infected soil for new plants, they may suffer from leaf spot disease as well. Instead, use new soil.

You can opt for potting mix as new soil. It’s the best place for potted plants to grow since it’s usually sterile and free of diseases.

Use Raised Benches

Leaf spot diseases caused by fungi and Xanthomonas bacteria are commonly contracted from ground beds. Therefore, you should plant your healthy philodendrons in sterilized soil and place the containers on raised benches.

You can sterilize the soil via one of the following methods:

Steam the soil

Pour water into a pressure cooker.
Place the soil in shallow pans on top of the rack before covering the pans with foil paper.
Close the lid and leave the valve slightly open to allow some steam to escape.
Steam the soil for at least 30 minutes to ensure that it’s well-sterilized. You should allow the soil to cool before reusing it in the pots.

Sterilize in the oven

Fill an oven-safe container, such as a metal baking pan, and cover it with foil.
Place a food thermometer in the middle of the soil.
Bake the soil for about 30 minutes at 180-200 °F (82-93 °C).
Let the soil cool before using it.

Sterilize using a microwave

Pour moist soil into a microwave-safe container. Note that if you have a big microwave, you can add more than one container inside it.
Cover it with a lid that has ventilation holes.
Heat the soil at full power for around 90 seconds before turning off the microwave.

Use a Polypropylene Bag

Place it in the microwave with the upper part open for ventilation.
Microwave the soil on full power for about 2 minutes.
Leave it to cool before reusing it.

Plant With Disease-Free Seeds

Avoid using infected plants as a cutting source (i.e., growing plants from sources other than seeds) because you’ll have more diseased flora. Instead, use fresh and clean seeds to produce more plants or propagate with disease-free varieties.

Spray the Plants

Since most fungicides don’t work on bacterial leaf spot disease, using organic copper-based products can help you to stop the spread of the disease. For instance, you can use Cueva, Badge, and Cuprofix Ultra Disperses to spray the leaves, stalk, and stems and get rid of harmful bacteria.

As for fungal leaf spots, you can use thiophanate-methyl and chlorothalonil-registered fungicides to treat the disease.

Maintain the Right Temperature

Sweltering conditions also accelerate the spread of leaf spot disease, so always maintain the right temperature in the areas where your philodendrons grow. For example, you can use a dehumidifier or fan to regulate the temperature on days when you can feel the scorching heat of the sun.

Can Leaf Spot Disease on Philodendrons Be Cured?

You can treat leaf spot disease on philodendrons using fungicides if the symptoms are still mild and have not appeared on new leaves. However, chemical control can be ineffective for the disease when it is already at an advanced stage.

Also, you should first get an accurate diagnosis from an expert to know which type of leaf spot disease you’re dealing with and what chemical sprays will work best on it.

For example, you can use Bonide 775 Copper Fungicide Rtu Natural 1 Qt (available on Amazon.com). It’s easy to use, as all you have to do is spray it — and it’s safe for organic gardening as well.

To ensure that your fungicides work, follow the instructions on the labels describing the diseases they treat, dosage, and precautions to take while spraying the plants with them.

Alternatively, you can use organic products that contain copper like Kocide 3000, or mix a quarter teaspoon of baking soda in a gallon of water and spray the solution on the leaves and their stems.

Final Thoughts

Since leaf spot disease can affect your philodendron plants’ growth and cause them to get destroyed, it’s better to prevent it from happening in the first place. Use clean containers with sterilized soil to grow the plants and ensure that the philodendrons get the right amount of water.

Additionally, you should maintain the proper humidity and temperature inside your home since this disease thrives under extreme conditions.