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Common Causes for White Spots on Indoor Plants (Plus the Solution)

Common Causes for White Spots on Indoor Plants (Plus the Solution)

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Taking care of indoor plants is a tricky maneuver. One day they’ll look fine, and the next day they’ll be drooping like there’s no tomorrow. 

They also show adverse reactions at the slightest change in their watering schedule or amount of direct light, so you’ll have to be as punctual as they come.

Though most symptoms that appear on indoor plants require easy fixes, other symptoms are signs of underlying causes that need ongoing treatment. For example, seeing white spots on your indoor plants may be a sign of mildew, mealybugs, or some kind of disease.

Luckily for you, I’ve had my share of sick indoor plants, and I’ll help you identify the problem and fix it.

Powdery Mildew

Ss - Powdery Mildew

Powdery mildew looks like talcum powder, but it’s actually not. It’s a fungal disease that can affect a number of different plants, and it’s caused by a wide variety of fungi.

Luckily, the symptoms of powdery mildew are easy to distinguish and appear right away. You’ll notice white spots appearing on the stems and the leaves of the plants as soon as it’s affected.

The mycelium that forms on the fungal spores is what causes the fluffy white substance on the plants. These spores tend to spread out in the air, especially when water splashes on the plants.

More often than not, the lower leaves are more affected by the powdery mildew, though it won’t take long before the symptoms take over the entire plant. Any part of the plant above the ground will be covered in that white powdery substance if you don’t start treating it.

How to Fix the Problem

You need to understand that powdery mildew is usually caused due to the conditions surrounding the plant.

If you can eliminate those conditions and make the place favorable, you won’t have to worry about using any chemicals. The first step that you need to take is to improve the air circulation in your house.

This is essential as it breaks up the life cycle of the powdery mildew. Most people place their indoor plants in corners of the room.

Fiddle Leaf Fig In Corner Of Room

Powdery mildew is often a result of the conditions surrounding the plant.

If you can eliminate those conditions, you won’t have to worry about using any chemical treatments. 

For example, most people place their indoor plants in room corners. The air tends to stagnate in these areas, providing the perfect conditions for the white spots to appear. 

So, the easiest fix here is to move the plants. More importantly, if you’re keeping several potted plants close to each other, you need to space them out.

Other than breaking up the life cycle of the powdery mildew, this also prevents the spread of mildew because the leaves won’t touch one another.

Aside from air circulation, you’ll also want to make sure the soil is well-draining. 

The top half inch of the soil of most of your indoor plants must dry properly before you water them again. If the soil is still wet, don’t water the plant because excess moisture encourages the growth of fungi.

On top of that, make sure to empty the saucers under the plants regularly. If you leave them full of water, they may cause the soil to get waterlogged.

To fix the problem once and for all, there are different kinds of horticultural oils that you can find in the market, like Bonide’s All Seasons Horticultural Oil. Even neem oil is a great choice, especially when you consider the many benefits that it offers. 

These oils are incredibly effective in getting rid of the stubborn mildew that develops on the plants.

However, before you start spraying the plants with these horticultural oils, you should always move them away from the window.


Ss - Mealybugs

Another issue that may result in white powdery substances developing on your indoor plants is the presence of mealybugs.

Mealybugs can leave a thick, cotton type wax on your plants. This wax will usually accumulate on the foliage of the plant, and you might even notice it on the crotch of the branch.

These insects are usually pink or gray in color, and they leave behind a velvety appearance in areas where they feed. You might notice the leaves turning yellow if the infestation of mealybugs only grows, and the plant may begin to die as well due to the infestation.

The problem is that these bugs tend to produce honeydew, which tend to attract ants and can also lead to the creation of mold colonies throughout the branches and the stems of the plant. To identify these plants, you need to look for small patches of cottony wax on the plants.

If the white powdery substance is all over the plant, it might be powdery mildew. However, if it starts by appearing in thick patches on different areas of the plant, you are probably looking at a mealybug infestation. They usually lay their eggs in these white areas.

You might even notice their cluster on the underside of the leaves, as well as where the leaves connect with the stems.

Keep in mind that a few mealybugs won’t cause any damage to your plants, but once they begin to grow and start feeding in earnest, your plants are going to die very soon.

How to Fix the Problem

Thankfully, taking care of mealybugs is as simple as you might think. You can fix a light infestation by just picking the bugs off the plants.

If you want, you can use rubbing alcohol to kill them first. If the infestation has grown, you might need to spray a mixture of insecticidal soap or even horticultural oil.

In some plants, you can also apply imidacloprid. It spreads throughout the plant, killing the pests that feed on it.


If the white spots on your indoor plants are constantly moving, they’re probably aphids. These insects are tiny, translucent, and white. When there’s an infestation, these bugs move together in groups, so they look like white spots on the leaves of your indoor plant.

You can identify them by tracking their movements. They’re also sometimes dark near the edges, but that’s not always clear to the naked eye.

The way aphids work, they keep moving around the plant to suck its sap, and then they go dormant by clinging to the leaves. That’s when you should try to get rid of them because they’ll be at their most vulnerable.

How to Fix the Problem

The best way to treat aphids is to use horticultural oil sprays. These sprays will suffocate the aphids, getting rid of them once and for all. You can also use insecticidal soap if you don’t have horticultural oil. 

Apply it to your indoor plant two to three times daily. Keep doing so for five days, then watch the results. If the aphids are still there, start another round of treatment for five days.

If all else fails, you can use chemical insecticides, but make sure first that they’re safe for your plant.

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