Rust fungus on monstera often looks worse than it actually is. You can get rid of it and make your plant healthy again in no time at all. Want to find out how?
Read our all-encompassing guide to learn some easy ways to treat rust fungus on houseplants.
- What Causes Rust Fungus on Monstera?
- Frequently Asked Questions
What Causes Rust Fungus on Monstera?
Overwatering, over-humidifying, and not providing enough circulation and lights are the most common predisposing factors why a monstera plant might develop rust.
Rust in this case refers to a group of fungal diseases that often attack the monstera house plant. The plant parts most commonly affected are the leaves, but the disease can also spread to stems, flowers and fruits. They are usually not very fatal diseases, but they do make your plant look unsightly.
Read on to find out the major causes of rust fungus in detail.
– Too Much Warmth and Humidity
All fungi thrive under conditions that are consistently warm and moist. It is true that the humidity requirements of monstera are more than 50 percent and it needs 70 to 80 degrees Fahrenheit temperature at all times for proper growth.
However, if you are overwatering your plant or misting it too much, then these same conditions will lead to the development of this disease.
– Poor Air Circulation
Air circulation is very important for all plants. Leaves that don’t receive adequate light and air are most commonly affected by fungal rust, plant diseases, and pest infestation. That is why pruning your plants is very important. It opens up spaces to let air in and around all parts of the plant.
It is also important not to place your plants in cramped corners. Don’t place two or more plants very close together either.
– Poor Light
This plant needs bright and indirect light for the majority of the day. This light is important not only for photosynthesis but also for the evaporation of excessive water. In conditions of low light, water droplets on the leaves fail to evaporate. This creates the perfect environment for the growth of bacteria.
– Transfer of Infection From Another Plant
This is another very common method by which your plant might get affected. Rust spores have the ability to float in the air and move from one plant to another. That is why you should isolate the affected plant as soon as it starts showing symptoms.
Overwatering the plant will cause its soil to stay excessively wet all the time. Such soil serves as the ideal environment for the growth and rapid multiplication of the various fungal species that are responsible for causing rust. It also leads to more severe problems such as the development of the rapidly destructive root rot.
Make sure that your soil is dry at the top 3 to 4 inches from its surface. Only then should you water it again. When watering, see that the drainage of the soil and the pot is not blocked or compromised in any way. The excess water should flow out of the drainage hole at the bottom.
– Transferred Through Infected Tools
Many a time you might have used gardening tools on multiple plants without cleaning them between each plant. This is a dangerous habit and one of the leading causes behind the transfer of infection from one plant to the next.
Properly cleaning and disinfecting instruments before use will go a long way to prevent rust fungus. Make sure that you wash your instruments with bactericidal and fungicidal soap and water each time.
Also, use a good quality disinfectant solution afterward. Alternatively, rubbing alcohol also works just as effectively. We always use 70 percent isopropyl alcohol for our gardening tools.
– Misting Late in the Day
Misting your plants is sometimes necessary in order to provide it with the required humidity levels. However, improper misting will lead your plant towards rust and other fungal conditions like powdery mildew and leaf spot disease.
Always mist before midday. This will allow the water droplets adequate time to evaporate properly before nighttime. Misting late in the evening leads to the droplets remaining on the plant all night. This, of course, leads to fungi making a home in your plant and infecting it.
Also, make sure to only lightly mist the plant each time. Some people bathe their plants in lieu of misting, which then proves disastrous in the long term.
Treating brown spots with rust fungus is easy. You will first need to isolate the plant, then you can go for home-based remedies like sodium bicarbonate, vinegar, aspirin and neem oil, etc.
Alternatively, you can try commercial fungicides, but do make sure to improve the plant’s cultural conditions first. None of these treatment options will work unless you make sure that your plant’s conditions are not conducive to fungal infections.
Learn how to treat fungus on monstera in great detail in the coming section.
– Isolate the Affected Plant
The fungal spores that cause rust transfer very easily and quickly from one plant to another similar one. That is why it is very important to isolate the diseased plant. Otherwise, you will soon find the rest of your plants being affected by rust as well.
Ideally, you should move the diseased plant to a different room altogether. If that is not possible, then make sure it is a respectable distance from the rest of your collection.
Take great care that any gardening tool or instrument that comes in contact with a plant with brown spots is properly disinfected and cleaned. Only then should you use these tools on another plant.
– Prune the Affected Leaves and Plant Parts
Start treatment of the affected plant with rust spots by cutting off the infected leaves first. You can either chop off the entire leaf or just the part that is most seriously affected. If a majority of your plant is diseased, then it is better to cut the most severe parts only or your plant might have a hard time surviving.
You cannot use the pruned leaves and plant parts for anything else — this includes composting or mulching. Otherwise, you risk spreading rust to your entire pile of compost. It is better to just burn these debrided plant parts off.
Always use sharp gardening scissors or knives for pruning. This will make your work so much easier. Don’t forget to disinfect them thoroughly after use. We recommend using 70 percent isopropyl alcohol for disinfection.
– Use Baking Soda
Sodium bicarbonate is a common household kitchen ingredient that you can use to treat rust. It is quite a potent fungicide and will surely get rid of the fungal leaf spots from your rust-affected plant with consistent use.
– Different Types of Soda Foliar Sprays
You can make several different types of baking kitchen soda mixtures, then apply them as foliar sprays on the affected leaves.
Mix one teaspoon of soda in one-quarter of a gallon of water. Also, add some common dishwashing soap to it. Pour this mixture in a spray bottle. You can now use this mixture for months on end.
Alternatively, you can mix four teaspoons of soda with one ounce of horticultural oil and one gallon of water. Both these solutions have proven to be quite effective.
– How Often To Use Foliar Sprays
Spray the above-mentioned mixtures on your diseased plant on a weekly basis. It is better to spray lightly but make sure that no part remains unmedicated. Adding a bit of white vinegar to this mixture will also help.
You will need to spray your plant with this spray for at least three to four months. Only then will it start to show any progress. Dedication is the key here!
Remember that sodium bicarbonate is quite basic in nature. This product has a tendency to cause chemical burns to the plant if you are careless with it. Only use these foliar sprays once a week and in moderate amounts.
– Use Chamomile Tea
Chamomile is another natural antifungal agent. You can easily use it if you don’t want to expose your plant to harsh chemicals like sodium bicarbonate. It is also available in most kitchens and if not, you can simply purchase it from your local grocery store.
Simply boil some chamomile in water. Allow the tea to cool until it reaches room temperature, then put it in a spray bottle. Lightly douse your plant with this tea daily, and you should begin to see a marked improvement in symptoms soon enough.
Like all-natural remedies, chamomile tea will also take several weeks before you see any improvement. Often, leaves turn yellow due to fungal rust and take months before they regain their color back.
– Apply White Vinegar
White vinegar can also be a great help against this problem. All you have to do is to mix one part vinegar with one part water. Apply it to the diseased Monstera deliciosa plant every second or third day.
Keep in mind that we are talking about common household vinegar here. This one contains about 20 percent acetic acid and even this one needs to be diluted so that it is safe enough for the plant.
You can also opt for store-bought vinegar that has higher concentrations of acetic acid in it. These are obviously going to be more potent, but they will also need to be diluted more.
– Spray With Aspirin
Rust disease is another type of headache that Aspirin is a fantastic cure for. You can just use over-the-counter aspirin for these brown spots. The aspirin tablets preferably should be uncoated to produce the maximum effect.
Now, how can you use aspirin properly? Dissolve two to four tablets of aspirin in one gallon of water. Fill a spray bottle with this fungicidal mixture and spray every other day until you begin to see some improvement.
Aspirin can also be dissolved in water and applied directly to the affected monstera leaves. However, we do not recommend this method. Aspirin burn is a common phenomenon, and trust us, you do not want to subject your plant to it.
– Use Neem Oil
Neem oil for rust fungus is a time-tested household item that is a very strong antifungal agent. It is a completely natural ingredient that gets rid of rust without harming your plant. It is a multi-purpose plant saver, solving all sorts of problems ranging from fungal infections and spider mites infestations to plant leaves turning yellow.
Cotine reaading to find out the various ways you can use neem oil.
- First of all, decide on the type of neem you want to use. You can either buy pure neem oil or use a store-bought mixture containing some quantities of neem oil in it. We recommend buying pure neem oil to go the all-natural route.
- Take a Q-tip and wet it with one or two drops of neem oil. Apply this Q-tip directly on the spots on the leaves once a week. One major disadvantage of this method is that it is very time-consuming and needs a lot of effort.
- Alternatively, you can also make a DIY foliar spray using neem oil. Just take one liter of water and add one teaspoon of neem oil and half a teaspoon of dishwashing soap to it. This solution is now ready for use.
- Spray this mixture on the affected plant on a weekly basis until symptoms resolve. Afterward, you can decrease the frequency of spraying to only once fortnightly. This way, neem oil can also be used as a preventative measure against rust.
– Purchase Commercial Fungicides
Commercial fungicides are very effective when it comes to rust fungus treatment. There are a lot of these available in the market. You can buy and use any one of them, just make sure that you are following the instructions given on the back of the label to the tee.
Make sure that the fungicide you use has four important active ingredients present. These four ingredients are chlorothalonil, mancozeb, myclobutanil and trifloxystrobin. Carry on reading to learn two of the best commercial fungicides in use these days.
– Liquid Copper Fungicide
This is of the most widely used fungicides and bactericides in the plant world today. They get rid of not only rust, but also a large majority of fungal and bacterial diseases.
- Copper is a most useful substance when it comes to killing fungi. However, in large quantities, it also begins to kill plant cells.
- Always buy this fungicide from a trusted manufacturer and strictly follow the instructions on the label.
- Make sure to spray it every week without fail, or at least once every ten days at the very least. Spray no sooner than 7 days.
- Spray adequately both under and over the leaves. You want it to reach all the fungal spores and kill them.
- Make sure you are wearing protective clothing when spraying this on the plants. Wear eye goggles as well as tough leather gloves. Your clothes need to be full-sleeved and made of a thicker material.
– Sulfur Plant Fungicide
Sulfur-based fungicides are best for those who are invested in organic gardening. They are great for treating rust on monstera plants.
- This is another type of commercial fungicide that is pretty effective. The sulfur in its composition prevents the growth of fungal spores.
- Sulfur-based fungicides come in two forms. One form is simple powder. Take the dry powder and then sprinkle it all over the infected plants. Don’t leave anything out, especially the undersides of the leaves.
- It also comes in a powder form that is meant to be mixed with water. This is then sprayed on the plant according to the manufacturer’s instructions.
- Sulfur fungicides are relatively safer. They are non-toxic to both plants and humans. We can also say that it is the best fungicide for rust fungus.
- Take note that they are toxic to aquatic life, so take care not to pollute any bodies of water with them.
– Choose Rust-resistant Varieties of Plants
Plant hybridizers are constantly creating new varieties of plants that are resistant to common diseases. The same goes for monstera varieties. If you are sick and tired of having to deal with and treat this disease year after year, then maybe it’s time to get rid of your rust-susceptible monstera.
Contact a monstera expert near you and ask them to give you a cultivar that has been modified to resist this disease.
Still, you must keep in mind that even with resistant varieties, you must not neglect the basic requirements of fungus prevention. Make sure your plant has adequate drainage and air circulation.
– Improve Cultural Care
Before you learn how to treat rust fungus on plants, you must improve the plant’s cultural conditions. Otherwise, all your efforts will go to waste. All fungi thrive under dark, moist and humid conditions.
Keep your precious monsetras in a room that is lit brightly with plenty of light received indirectly. Make sure this room is also well-ventilated. Pruning the plants regularly also helps in improving the circulation of air around all parts of the plant.
Water only when the top one to two inches of the soil dries up. Even then, make sure that extra water drains out without any impediment. Maintain high humidity but don’t mist the plant late in the day.
Frequently Asked Questions
We bet you still have some important questions to ask regarding this fungal disease affecting your monstera deliciosa plant. Read below to learn the answers to some of them.
– What Does Fungus Look Like on Monstera?
First of all, this disease causes discolored spots to appear all over the leaves of the affected plant, and these spots can be brown, red or black in color. This is followed by leaves that become yellow in color. They also start to droop and fall down at a rather disturbing rate.
After the passage of some time, these spots develop into structures called pustules. These are bigger in size and contain a large number of spores. These pustules commonly form on the lower sides of the leaves, but they can also spread to the stems and petioles.
With prolonged disease, the plant will start to weaken. It will lose its strength and its ability to resist other infections, diseases and pest attacks. In extreme cases, the poor plant might even die.
– What Kills Rust Fungus?
Hydrogen peroxide is a very good and quite potent anti-fungal that easily kills fungi that cause fungal rust in household plants within a span of several days.
All you have to do is take some of this chemical and dilute it with clean, filtered water, then apply it on the affected plant every day. You will only need to apply hydrogen peroxide for three to four days maximum. This time should be enough to treat the plant of rust.
However, be very careful that the chemical is properly diluted as it can be very harsh and kill the plant as well.
– Is Plant Rust Harmful to Humans?
No, rust fungus is not particularly harmful to humans. You cannot get infected by the fungi causing this disease in plants if you take care of them. This is strictly a disease that only affects plants.
However, humans can serve as the means by which the fungal spores of rust can be transmitted from one plant to the next. Always wash your hands after dealing with a plant suffering from rust.
– Should I Cut off Leaves With Rust?
Yes, as soon as plant rust is detected in a plant, the best thing to do is to immediately cut off all the affected leaves and stems and dispose of them safely.
Technically, leaves affected by rust can be composted. However, this is often strongly not recommended because of the risk of transferring the disease to the entire composting pile.
If you have decided to add such leaves to your pile, make sure that the temperature of the pile is raised up to at least 140 degrees Fahrenheit. This temperature should be enough to kill the fungal spores and sterilize the leaves.
Jump down below to read a brief summary of this article.
- Monstera species, especially monstera deliciosa, are prone to getting rust infections if they are kept in moist, warm and cramped locations.
- Usually, brown-colored spots appear all over the leaves. They then enlarge to form spore-forming pustules over and below the leaves. The leaves can also become yellow and begin to fall off.
- Treating rust is not that difficult. First of all, isolate the diseased plant. Use household remedies like sodium bicarbonate, chamomile tea, neem oil, or aspirin to treat it, or you can go for commercial fertilizers. It totally depends on your own personal choice.
- Some other conditions that mimic rust are mildew, fungal rot, deficiency of calcium and magnesium, as well as certain pests.
Now you are well-versed in the A to Z of fungal rust on monstera house plants. The next time you see brown-colored spots on the leaves of your plant, you will definitely know what to do.
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