With their tall stems and large, deep green leaves, rubber plants can be a striking addition to any home. Rubber plants are generally easy to grow, but just like other plants, they are not invincible!
One of the most common issues in rubber plants is the appearance of white spots on their leaves. It is an indication that there is a problem that you need to address immediately.
Oedema, powdery mildew, sunburn, and pest infestation can all cause white spots on rubber plants. They can also indicate malnutrition, disease, fertilizer issues, or frost damage. They could, however, be nothing more than dust that can be wiped away!
In this article, I’m going to walk you through the causes of white spots on your rubber plant and how you can address each to bring back the health of your endeared houseplant.
- How to Identify White Spots on Rubber Plants
- Why Does My Rubber Plant Have White Spots?
- Powdery Mildew
- Pest Infestation
- Lack of Nutrition
- Fertilizer Problem
- Frost Damage
- Dust on Leaves
- Final Words
How to Identify White Spots on Rubber Plants
As the leaves of rubber plants are dark green in color, you may think that it is easy to spot any white spots.
However, spots start as small and can begin to develop at the undersides of leaves, which is not usually noticeable.
As such, it is important to examine your plant carefully for early signs of white spots.
Look for light gray to white powdery growth forming on the surfaces of the shoots or leaves, as these can be powdery mildew.
Meanwhile, if you’re seeing brown leaves or white-like corky growths, you may be dealing with oedema.
Thick, cotton-type wax on plants, on other hand, can mean your rubber plant has been infested with mealybugs.
Let us now delve deeper into the causes of white spots and how you can cure each.
Why Does My Rubber Plant Have White Spots?
Container-grown rubber plants require frequent watering, combined with humidity and cool temperatures, which can result in edema.
Oedema is a condition due to physiological upset in the water balance of your plant.
This occurs when the roots absorb water faster than a plant can transpire through its leaves.
Too much water creates pressure that causes the cells in the leaves to expand and burst.
When this happens, water-soaked spots appear to be swollen areas (looking like blisters!) on the epidermis of the leaves.
These blister-like areas then erupt and result in tan, brown, or even white spots on the leaves.
What’s concerning is that if this condition continues, the leaves turn yellow and eventually fall off the stem!
How to Fix
As oedema usually happens due to reduced transpiration on the surfaces of the leaves and a high level of soil moisture, you need to cut back on watering your rubber plant.
This is especially true during cool temperatures in the late winter. It’s also important to promote higher transpiration by keeping your humidity low.
You can do this by moving your rubber plant away from your other houseplants, as placing them together promotes humidity.
Doing this also improves airflow. You can also improve air circulation by pruning your rubber plant.
- Do not let oedema develop in your rubber plant by maintaining an environment that does not favor the condition.
- Avoid overwatering your plant and always aim for humidity levels that are below 70 percent.
- Always promote good airflow and ensure that your plant gets enough sunlight. When you provide your rubber plant with a more favorable growing condition, you’ll surely see it recover from oedema.
You will find Lithocysts on your rubber plant leaves at some point. It is identical to white spots on your leaves. The interesting part is
that it is not harmful to plant.
The white spots or the crystals you see are calcium carbonate which is an outgrowth of the cell wall of leaves. It is a natural process of your rubber plant, so don’t panic about it.
Just like other plants, your rubber plant can attract powdery mildew fungal pathogens that manifest as white spots, negatively affecting its growth.
Powdery mildew is a common disease of plants worldwide. As the name suggests, this disease causes “powdery” or talc-like growth on plants.
Powdery mildew is caused by different fungal species. When the fungus takes over your rubber plant, you’ll notice a layer of mildew with many spores form on the top of its leaves.
These spores spread to other parts of your plant and may transfer to other houseplants. High humidity levels combined with low moisture favor powdery mildew.
This disease thrives in warm, dry climates and affects plants in shady areas. Powdery mildew can result in stunted plant growth.
The powdery mildew disease can be divided into three stages:
- First Stage: A light and almost unnoticeable silver-colored coating appear. This sign starts from the bottom of your rubber plant and spreads to the top.
- Second Stage: Besides the leaves and stem of the plant new shoots and leaves are also infected.
- Third Stage: You may lose your plant at this stage. The leaves start curling and wilting and the root system itself dries.
How to Fix
- Spray the infected parts with an organic fungicide. Organic fungicides that can be effective for treating powdery mildew are sulfur, lime-sulfur, potassium bicarbonate, and neem oil.
- You can also spray your plant with a bicarbonate solution by mixing one teaspoon of baking soda in 1 quart or four cups of water. It’s important to spray the surfaces of the affected parts thoroughly to ensure that it comes in contact with the fungus.
- If your rubber plant is heavily infected, it can be hard to get rid of powdery mildew, so prevent the disease from spreading further to your other houseplants.
- Trim all infected parts and, to get rid of the fungi, burn these or dispose of them properly.
- Never compost the diseased parts as powdery mildew can still thrive even in composted materials!
For the treatment of fungal diseases. Here are the fungicides I recommend:
|Name of The Fungicide||Amount||Amount of Water|
|Garden Safe Brand Fungicide3||2 tablespoons (1 fl oz)||1 gallon of water|
|Bonide 811 Copper 4E Fungicide||1-4 tablespoons (.05-2.0 fl oz)||1 gallon of water|
|Southern Ag – Liquid Copper Fungicide||3-4 tablespoons||1 gallon of water|
- Prevent dealing with powdery mildew by ensuring that your rubber plant is receiving enough light. Powdery mildew develops more often on plants sitting in shadier areas.
- Regularly prune overcrowded areas in your rubber plant to promote good airflow. This also helps to reduce humidity levels.
- Water your plant in the morning. This makes sure that it dries properly by the end of the day.
Rubber plants can thrive in areas of your home that have bright light, but not direct sunlight.
When you expose your plant to the heat of the sun, it will develop white spots caused by sunburn.
This is especially true if your plant has been growing in an area with subdued lighting and you suddenly move it to a spot that is directly hit by the sun.
How to Fix
- If you’ve been growing your rubber tree plant in a southern or western window, immediately move it to an area with a lesser light exposure to stop further damage.
- Southern windows get strong, bright natural light which can be magnified to dangerous levels by the glass in most windows. West windows can also be harsh to your rubber plant as they get full afternoon and evening sun.
- If the plant lost some leaves due to sunburn, reduce watering. Your rubber plant will not need the same amount of water that it requires before.
- When watering, apply water slowly. You’ll know that you’ve watered your plant properly when the water has dropped out of its pot’s drainage holes.
- You also need to reduce fertilizing your plant especially if it loses leaves because of sun damage. Maintain the same schedule you had before your plant got sunburned, but provide only half the amount of fertilizer.
How to Prevent
Grow your rubber plant in a bright spot that gets indirect light. You can still place your plant in your windows, but make sure you are filtering the sunlight.
You can filter light through the use of window treatments such as sheer curtains or combi blinds.
Rubber plants can attract the common houseplant pests — spider mites, scale, aphids, and mealybugs.
These pests typically attack tender foliage located at the top of the plant and suck nutrient-containing sap from the leaves.
Other pests, specifically cottony cushion scale and mealybugs, cause white spots by leaving a cotton-like appearance on the surface of leaves.
How to Fix
If your plant is infested with spider mites, you can knock the pests off using a water hose. Insecticidal soaps and neem oil can also be effective in removing this pest.
For scale insects, which can be resistant to chemical pesticides, your best weapon is rubbing alcohol. Wipe scales off using cotton swabs soaked in rubbing alcohol.
If aphids have infected your rubber plant, you can squish them with your fingers or simply prune the infested areas.
You can also kill aphids by spraying them with liquid soap. For mealybugs, you can shake the plant to knock the pests off or spray them with water.
- Inspect your rubber plant carefully before bringing it inside your home. When buying houseplants make sure to examine the foliage from top to bottom to ensure you’re not bringing any pest home, as they can easily spread to all your houseplants.
- While you may think your new rubber plant is free of pests after inspection, it is still best to isolate the plant. Pests may have laid eggs in the hidden parts of the plant and they may not be visible to the naked eye.
- Keep your plant away from the rest of your houseplants for a few weeks to ensure it is pest-free. This can help you keep early signs of pest infestation under control.
- Examine your plants regularly and watch for any signs of pests. Areas to check to include the surface and undersides of leaves, the stems, and even the soil.
Lack of Nutrition
As is the case with humans, nutrient deficiencies can cause serious trouble for rubber plants also.
When plants lack nutrients, they cannot properly manufacture important molecules, such as chlorophyll, proteins, and lipids, among many others.
This can result in stunted growth, susceptibility to different diseases, and in conditions called chlorosis or necrosis.
In rubber plants, the development of white spots, along with other symptoms, is among the telltale signs of nutrient deficiency.
How to Fix
Here is a table showing the different types of nutrient deficiencies on plants and what you can do to address each:
Deficiency Symptoms: Leaves of young plants are chlorotic, with the yellowing starting at the veins. As the deficiency gets worse, chlorosis turns white. In some instances, veins may also lose their green color.
Solutions: Add Iron chelates on the soil or mix them with water and spray on the plant’s surfaces. Iron chelates are organic molecules that are readily available and suited for plant use. Another option is to give the plant seaweed fertilizer.
Deficiency Symptoms: New leaves have necrotic tissue. They are also brittle and irregularly shaped.
Solutions: Add lime to the soil of your rubber plant. You can also simply crush some eggshells and add these to the soil. Eggshells do not only boost calcium; they can also aerate the soil.
Deficiency Symptoms: Older leaves are chlorotic; you’ll see the yellowing starting at the edge of the leaves. The plant looks pale. Other than yellow, purplish pigment may also develop on leaves.
- Treat magnesium deficiency by adding dolomite fertilizer, which is rich in magnesium. You can also use Epsom salts.
- Dissolve two tablespoons of the salt with a gallon of water.
- Transfer the water to a spray container and spray the solution directly to the surface of your plant.
Deficiency Symptoms: The plant is severely stunted. Foliage is dark green. You’ll also notice wilting in older leaves.
Solutions: Add fertilizer with copper sulfate or copper oxide to the soil.
Deficiency Symptoms: Similar to iron deficiency, there’s yellowing that starts at the veins. But it’s not as prominent or distinct as is the case with lack of iron. You’ll also notice that the parts of the plant are not growing in their standard sizes.
Solutions: Treat manganese deficiency by adding zinc chelates to the soil. You can also add fertilizers with zinc sulfate, which has higher zinc content.
Prevention of Nutrient Deficiency In Rubber Plant
- Nutrient deficiencies happen when you neglect the soil of your rubber plant. As pH levels change rapidly, you need to check the pH levels of your soil regularly.
- Bring a sample of your soil to a laboratory for testing. This way, you’ll know if it lacks any nutrients.
- Adding organic matter and keeping it mulch can also help improve the nutrients in your soil.
While there are no serious problems associated with rubber plants, it is important to still keep an eye on plant diseases that might affect the foliage.
Rubber plants can attract fungal and bacterial pathogens that can cause leaf spots.
If you’ve noticed some light spots with a dark rim on the leaves or some tiny, water-soaked spots, your rubber plant may be suffering from bacterial leaf spots.
A common leaf spot disease among rubber plants is Xanthomonas, which is caused by bacterial plant pathogens that use wounds or natural openings, like stomata, to enter plants.
How to Fix
As there are no available bactericides that can combat Xanthomonas pathogens, cultural methods are your best resort to save your rubber plant.
Water is the medium that transmits the bacteria, so use a drip irrigation system or a microjet to water your plant.
Water in midmorning so the plant can dry before the evening.
When it comes to preventing diseases among houseplants, sanitation is key! Always disinfect the tools that you use when pruning.
Make sure that you store your new pots in clean, sanitized areas.
You can disinfect tools and potting containers by submerging them in a 1:3 ratio of bleach to water for a minimum of 10 minutes.
You can also use pesticides as a primary defense to prevent the disease on the plant.
Rubber plants do not require much fertilizer, but they can benefit from regular feeding throughout the growing season.
Fertilizer helps produce and maintain the big, glossy leaves of your rubber plant.
Overfertilizing your rubber plant, however, can harm the foliage, as is the case with other houseplants.
Overfertilization can cause a buildup of salts in plants, which can burn their young roots.
When this happens, the plants will not be able to absorb nutrients and water. This results in burned or scorched leaves and stunted growth.
For rubber plants, a sign of fertilizer problem is the development of white spots on their leaves.
How to Fix
Heal your overfertilized rubber plant by following these steps:
- Remove the excess fertilizer on the soil of your rubber plant. If there are crusts of fertilizer on the soil’s surface, remove them carefully.
- Remove the damaged foliage.
- Drain away the fertilizer from the soil with distilled or filtered water. Don’t use tap water as it contains chemicals like chlorine which can further harm the plant. Do this step three to four times to ensure that the fertilizer has been removed properly.
- If you have overfed your plant severely, wash it properly and transfer it to new, fresh soil.
- Do not fertilize your rubber plant for several weeks.
Prevent overfertilization by applying fertilizer only during the growing season.
Plants, including your rubber plant, go into dormancy during winter, so do not fertilize them during this season.
Use water-soluble fertilizer for your rubber plant and apply it only once a month.
Plants can survive better with less fertilizer than more, so it’s fine if you’ve missed feeding your plant for a month or two.
Frost can cause devastating damage to your rubber plant. As the water in the plant freezes, it expands and bursts the cells open.
Plants suffer further damage due to dehydration when the temperature warms up.
For rubber plants, frost or cold damage can manifest through white spots on their leaf surfaces.
Frost-damaged plants are susceptible to insects and diseases, so if you want to revive your plant, you need to act fast.
How to Fix
Move your plant away from direct sunlight, as the excess sun can make the condition of frost-damaged plants worse.
Let the plant rest and resist pruning frost-damaged parts of your plant. Trimming leaves before your plant recovers can further damage it.
Keep the soil moist but not saturated with water and avoid fertilizing the plant unless it’s actively growing.
Protect your plants from freezing conditions by covering them with plastic sheets, drop cloths, bed sheets, or even blankets. (Source: University of California)
Use stakes to keep plastic and other materials from touching the leaves of your plant.
You can remove the coverings the following day, but only if the temperature has risen.
Another way to promote warmth is through the use of artificial lights. Place a 100-watt lamp in the interior of your rubber plant to shield it from frost damage.
Dust on Leaves
As I have discussed in this article, white spots on the leaves of your rubber plant can have several causes.
In some instances, however, white spots are simply dusted on your leaves! Your rubber plant’s large leaves can easily catch dust because of their big surface area.
How to Fix
Take your rubber plant outside and use a water hose to dust it off. You can also use baby wipes or cotton swabs with alcohol to wipe the dust.
This is especially effective if the grime on the leaves is a little thick.
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There are many different causes of white spots on the leaves of rubber plants. But despite these, they are really easy to grow!
If you follow the right cultural practices and provide an environment favorable to their optimum growth, you’ll have a beautiful thriving rubber plant that enlivens your living space.