White spots on plant stems are a worrying feature when you see the plant has changed from what it used to look like to how it has dots all over the stems. Powdery mildew is just one thing causing those spots, but not the only one.

White Spots on Plant Stems

We are here to help you discover the exact situation on your plant stem and how to deal with them and get rid of them.

What Are the Causes of White Spots on Plant Stems?

The causes of white spots on plant stems are powdery mildew, downy mildew, and blight. In addition to this, it would also be due to wilt infestation, aphids, and mealy bugs. Moreover, this matter would also be caused by spider mites, molds, and nutrient deficiencies.

– Powdery Mildew

It seems that powdery mildew will be your main culprit, but many other plant diseases will cause spots on plant stems. You’re probably upset by the sight of that ugly white stuff, and you’re probably wondering if it’s powdery mildew, as it is just the most usual disease around and no plant is resistant to it, because, on the stems, they will look strange.

Note that its spores are air and water-transmitted onto the leaves and stems. You can easily identify powdery mildew as being a superficial white powder, and if you run your fingers through it, this will leave a smudge. They will be on the stems with a powder or velvet-like texture that will cover the bases of the plant, and just by the look of it, you will feel this disease is growing.

To elaborate further, those white spots are commonly found all across the board in the plant world. Most gardeners will usually connect these to white powder features to mildew, but this isn’t the only thing causing white stuff on plant stems. Turns out that powdery mildew is the least of your worries, as there are some more dangerous.

– Downy Mildew

Downy mildew is one such disease where symptoms are similar to those of a powdery counterpart. This is the type of issue that will only likely affect the bottom sides of the leaves and will typically occur in spring and fall because due to the conditions met, they will grow much faster.

In short, it is a fungal disease that first begins as superficial powdery clumps before it bites into the tissue and leaves it weak and weird in color, which is beige or off-white.

– Blight

Algal leaf spot and blight are another set of common fungal diseases that dye your plant stems white, as they would spread quickly. However, the difference between these fungi to others is that they are dangerous to the health of the plant; these will bite into plant tissue and infect it from the inside, and develop from there.

They first begin as small spots that will quickly turn brown and black at the edges, especially if the plant’s stem is a little hairy, they will appear more white on the edges and then slowly turn brown as they are harming the stem.

These fungi thrive in moist conditions and are typically spread by water and air. They simply love humid and stale conditions and which means that they could come if the water you are irrigating with was constantly on the stems and stayed there for a prolonged period of time.

– Wilt Infestation

The reason why you have white dots would also be an issue with wilt infestation. This one will often infest your plant stems when conditions are rainy, humid, and hot, spreading rapidly and coloring your stems white, yellow, and brown, and when this happens you will see that the chlorophyll level is decreasing. In short, wilt will typically infect leaves, making them curl up and mushy, but it can be transmitted to stems too if left unattended.

– Aphids

Aphids are probably the most common of all insects that would be on the stem of the plant. They are tiny and pear-shaped insects that often look like moving mildew, quickly running about the stem and leaves in search of a perfect spot where they’ll be eating that plant sap undisturbed.

Causes of White Spots on Plant Stems

They latch themselves on your stems and leaves and suck out nutrients from plant vessels often leaving the plant wilted when they’re finished with it. They get their source of food from the stems and the being of a plant.

Now, insects are going to be your next worst thing to deal with after diseases. In addition to this, note that those sap-sucking insects especially will be too hard to see lurking about if no serious infestation is present. But when they go ballistic is when there are thousands of them creating those small white bumps on your stems.

– Mealy Bugs

Mealybugs are another specie that will hoard your stems and leaves. These wingless insects aren’t white, but they produce a white sap in their trace. The insects will often cause stunted growth, causing leaves and stems to curl up. Also, they will often transition from your stems and into the soil if it’s porous enough.

– Spider Mites

Spider mites are the tinniest and thus, the trickiest of them all, as they are spiders that have webs. At the same time, these are the least visible and do the most damage, because they are often connected by their webs, and they would thrive around the leaves and steps at the same time.

These white webs will help you tell that you have a problem with mites. Be careful, as spider mites can go into the ground and mess with the root of the plant, too, when they develop even further. You should inspect your plants regularly for signs of insect activity. Check your spots often to see if they’re a part of the bark or if they are moving.

– Mold

Apart from white webbing in the case of spider mites, there’s another thing you can look for to determine insect infestation, especially the sooty mold. Because this is the type that will grow when the texture of the place, in this case, the stem, is high in its moisture.

You may ask, where they come from, the truth is, sooty mold is a fungal occurrence that germinates on sap excrement from insects. It, too, can be colored white and found on your stem and everywhere below from where the insects were feasting.

– Nutrient Deficiencies

Fertilizers are often salt-based, which means that the fertilizer that didn’t get used by the plant will crystallize over time. This process will leave white crystals all over the soil and your plant stem, especially if you’ve gone overboard with fertilization.

The crystals can also come from the water, so always try to use purified or filtered water if the crystals are there, and you’re sure that you’ve done fertilization properly. Also, the white from the water will look somewhat different from fertilizer, much like chlorine at times as well, and this would indicate that the feeding process was not done efficiently.

Sometimes plants will begin to develop spots when they’re lacking certain nutrients or are finding too much of one or more. The essential plant nutrients are nitrogen, phosphorus, and potassium and any of these can cause a color disturbance on the plant leaves and stems.

How To Eliminate The White Spots of Stems on the Plants?

To eliminate the white spots on the stems of plants you must trim the infected parts, and use some fungicide on the stem. You may also spread some organic pesticides to get rid of the pests, brush or evaporate the crystals, and use a balanced fertilizer.

– Trim the Infected Parts

We have mentioned powdery mildew as the primary culprit behind those spots, but other fungal and bacterial diseases can be to blame. Luckily, they’re all easily dealt with in a somewhat similar way. After noticing the disease, you can control powdery mildew by quickly removing parts of the stem and leaves that are too infected. If you take prevention steps soon enough, you may just skip this removal step.

– Use Some Fungicide

To use a good consistency of fungicides you must mix two or three tablespoons of soda powder with water and spray heavily over your plants. Baking soda will create an oxidative layer on the skin which will prevent the fungi from germinating. If there are any parts of the plant still infected, you can remove them with the same mixture rubbed in with some cloth.

If you’re growing your infected plants in containers, you can freely move them to an isolated quarantine spot for a few weeks, just to prevent powdery mildew from spreading to other indoor plants nearby.

– Spread Organic Pesticides

We usually fight insects with pesticides, but those small critters don’t have to be dealt with the use of those harsh chemicals. You can mix your own, highly effective pesticide with the things you likely have in the kitchen. Neem oil, baking soda, horticultural oil or even rubbing alcohol are all great when fighting insects.

Eliminate The White Spots of Stems on the Plants

Make a simple mixture of baking soda, some neem oil, and even any other previously-mentioned ingredients with water and spray all over the plants. These will all act as a suffocating medium for the insects and will kill them off within a day. After this, you can wipe your highly infested areas clean with watered-down alcohol or hand soap.

Some sap-sucking insects can find their way into the soil. If that’s the case with your plant, then you should think about replanting your container-grown plant.

– Brush or Evaporate the Crystal

To remove those salt crystals you can scrape them with a toothbrush. Just dip your toothbrush in some distilled water and scrape away. If your plant stem is too fleshy and not hardwood, you may want to use a gentler method. One of these can be taking your plant into a shower room for a few days — steam and hot temperature from the shower will cause those crystals to evaporate and go into thin air.

– Use a Balanced Fertilizer

To prevent nutrients from forming those white crystals is to use a balanced mineral fertilizer as prescribed on the packaging label. This way, the plant will not show you its deficiency on the stems or even through the leaves; on the contrary, the right fertilizer will correct the vibrancy and color of the foliage as well.

Control Powdery Mildew to Protect Stems


White spots on those plants’ stems make for an unsightly show, but depending on the issue, some things are simple to tackle. Here’s what we discussed in this article:

  • Always avoid placing and growing your plants in humid and stale environments, as these will enable fungal diseases to form.
  • Another issue will be caused by sap-sucking insects which will probably be far worse, as they will eat your plants all over.
  • You can almost always safely assume that you’re dealing with powdery mildew spread; however, you would also check how vast they have grown.
  • Insecticides and pesticides are always good options to deal with these diseases and pests, but try to go with more natural options.
  • If you have proper watering and fertilization regimes established you likely won’t have too many troubles.

Getting up close will help you determine your problem quite better than just doing basic guesswork. In addition to this, knowing the right issue further helps you with how to deal with the specific issue in the right way.

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