Skip to Content

White Spots On Mint Leaves? Reasons And Solutions

White Spots On Mint Leaves? Reasons And Solutions

Let's grow together!

Does anything smell better than fresh mint? This fragrant herb has many health benefits and adds great flavor to many foods and tea.

But, plants from the genus Mentha have one more great feature; they are easy to grow!

It may seem very surprising when you notice changes in your mint plant, and you may ask yourself what you did wrong.

Although mint is a low-maintenance plant, it doesn’t mean it’s immune to diseases, pests, or other issues.

One such example is white spots on mint leaves. They may have various causes, but the thing is, the sooner you act, the easier it will be to solve the problem.

Don’t worry; I will show you the potential causes of white spots, but I will also show you how to solve the issue and, of course, how to prevent it.

Let’s start!

White Spots On Mint Leaves

A list of possible causes of white spots is pretty long, and some causes are more severe than others.

The reasons may be fungal diseases, pests, viral infections, nutrient deficiency, water hardness, and even dust.

Let’s get into details!

Buy mint herb plant on Etsy

Fungal Infections

Fungal infections are the most common reason for white spots on mint leaves. Most types of fungi work in a similar way.

They use hyphae (branching structures of fungus) to invade the plant. Hyphae’s main function is to ferociously take all nutrients and water away from the plant and transport it to fungus.

Three main fungal diseases that may affect mint plants are sclerotium rot, powdery mildew (the most common), and white rust.

Sclerotium Rot

White mold, commonly known as sclerotium stem rot, is brought on by the fungus Sclerotinia sclerotiorum.

The fungus lives year after year as sclerotia, which are hard, black formations.

Sclerotia are irregularly shaped entities of densely packed white mycelium protected by a dark, melanized layer.

A thick canopy and overwatered soils encourage apothecia to sprout from sclerotia.

Throughout a seven to ten-day period, these creatures, which resemble mushrooms, generate millions of airborne spores practically every day.

When the weather conditions are suitable, these spores are discharged, and air currents might carry them to neighboring areas.

If your mint displays white spots on young and stems leaves first, you should check for this fungal disease.

Powdery Mildew

A humid environment and warmer temperatures may cause one of the biggest nightmares for even the most experienced gardeners; notorious powdery mildew.

Luckily, you won’t have much trouble identifying this disease.

First, you’ll notice chlorotic yellow spots on the mint leaves, and the spots will eventually turn white.

The problem with this disease is that it may affect all foliage and coat it with ash that ranges in color from white to gray.

The longer you leave your mint untreated, the more severe the disease.

The lower leaves are the first ones to suffer. As the disease spreads, the infection spreads all the way to the top.

The spores are developed when humidity is too high, but they spread in low humidity. During summer, daytime and nighttime temperatures differ and change humidity levels. This is a perfect time for fungi to attack.

Some pests such as aphids may transmit this disease. Keep reading to find out more about pests.

White Mint Rust

Another common cause of white spots on the leaves of the mint is a fungal disease known as white rust.

With the exception of the white spots, white rust is comparable to conventional rust in terms of its characteristics and symptoms.

The fungus is concealed below the surface because these spots develop in the subcuticular layer. These white, bumpy areas are visible in the early stages of the disease.

Dense planting and excess water aid in the development of white rust.

Photo from plantvillage.psu.edu

Pest Infestation

White dots caused by insects are considerably simpler to identify than those caused by fungi or viruses.

Many pests may attack your mint, but the ones that cause white dots are mealybugs, spider mites, thrips, whiteflies, and aphids.

Mealybugs

If you notice white lumps on the leaves of your mint, you might want to check if there are any mealybugs around.

They act similar to spider mites in sucking away bodily fluids, making the plant too frail to carry out photosynthesis. Your once-healthy plant develops pale patches and dots as a result.

If you suspect the mealybugs, check the undersides of the leaves. They leave a puffy white mass with their eggs inside.

They may go unnoticed at first, but they reproduce rapidly.

They will suffocate your mint and shift onto another plant in a blink.

Spider Mites

Spider mites are close relatives of spiders, scorpions, and tics. These small insects feed on the leaf tissue causing the small holes.

These arachnids suck out the chlorophyll from the leaves, leaving tiny white spots.

If you spot a few spider mites, you shouldn’t worry much. But, if you run upon a larger colony, prepare for a battle.

They will cover your mint with a net of white trails. They also make bedding for their eggs out of webbing. In addition, a severe infestation on your plant could be lethal.

Thrips

Thrips are tiny insects that like to eat the tasty mint leaves. These pests may encourage the spread of viruses on the leaves.

Thrips will lay their eggs on the tissue of leaves and feed on the sap. This implies that these insects will use the nutrients your plant needs to grow healthy.

If the thrips are the culprits, you will notice silver spots and streaks on the leaves-

You should be cautious of further indicators in addition to white (or silver) spots.

Nutrient Deficiency

Your mint needs nutrients necessary for chlorophyll development, such as magnesium, iron, manganese, phosphorus, or calcium.

If your mint lacks some nutrients, it may display white spots. For example, a lack of iron and magnesium is a very common cause of white dots.

Iron Deficiency

Iron is necessary for producing enzymes and chlorophyll, essential to several processes in your mint.

Chlorosis results from a lack of green pigment, which is caused by a lack of chlorophyll.

You can clearly identify if the mint leaves turn pale-white, but the main vein remains green.

The deficit in manganese is correlated with a deficiency in iron, and manganese plays a crucial role in photosynthesis.

The signs are essentially the same as those of iron chlorosis, with the exception that the absence of manganese is more obvious on the younger, top leaves since it is immobile throughout the plant.

Magnesium Deficiency

Iron deficiency causes spots on younger leaves, whereas magnesium deficiency causes spots on older leaves.

This nutrient enhances mint enzymes to produce major energy sources, such as carbohydrates and lipids.

In the cases of severe deficiency, a mint growth rate and leaf size decrease, and its lower leaves fall off.

Water Hardness

Calcium compounds, as well as a number of other metals, contribute to water hardness.

Your mint plant consumes both beneficial and harmful minerals through the water.

Using hard water results in the buildup of white limescale. Hard water is defined as having a high calcium content, which settles on the surface of leaves after water evaporation.

Viral Infections

Multiple viral infections are common in mint plants. Mosaic viruses are a distinct class of viruses that leave a recognizable pattern of leaf spots.

You may find spots caused by mosaic viruses in various colors such as light green, white, or yellow.

If the mint leaves are discolored, it could lead to chloroplast disintegration (chloroplast is a green structure on the leaf’s surface).

Why is this important? Mint leaves need chloroplast to transform sunlight into energy; without it, the leaves quickly turn pale.

Viral infections do not consume food and liquids through the plant’s digestive system. Their goal is to kill cells so that their DNA may be used to make more viruses (how brutal!).

It’s difficult to identify which virus strain infected your plant because there are numerous virus types.

White spots on mint leaves photo from Pinterest

Types Of Viral Infections

Here is a list of prevalent types of viruses that cause white spots.

  • Cucumber mosaic virus (CMV): This virus affects hundreds of plant species (not only cucumbers). Apart from white spots, you may notice stunted growth, thinning, or mosaic.
  • Tobacco Ringspot Virus (TRSV): May affect a wide range of plants causing wilting, delayed maturation, and white spots.
  • Tomato aspermy virus (TAV): Very common virus that may attack shrubs, flowers, or garden plants. It causes mottling and leaf curl (usually upwards).

The most common transmitters of plant viruses are pests such as aphids, thrips, or whiteflies.

Remember that the mint roots may already be infected before planting. We can also transmit these viruses if you use unsterilized tools or dispose of the affected plants incorrectly.

Dust

Don’t panic immediately after seeing some white spots on your mint, as they are frequently caused by dust.

Dust can gather if you don’t frequently clean, leave your home for a while, or place your mint in a pretty hard-to-reach spot.

When you see some white spots on the leaves of your mint, don’t jump to a conclusion; maybe it’s just dust!

However, please remove the dust as it may prevent your mint from getting enough sunlight and, in that way, weaken the plant.

Solutions To White Spots On Mint Plant Leaves

Now that you know the possible causes, it’s time to solve the problem. You can use chemical substances to treat some issues, but I always recommend natural solutions if possible.

After you find the final cause, you also need to determine the severity of the damage.

Now, let’s see the best ways to solve this issue.

Solution To Fungal Infections

It’s true that fungal infections may severely affect your mint and may even be lethal.

However, don’t lose hope and try your best.

Let’s see how to get rid of the nasty fungi!

Sclerotinia Rot

The biggest problem with the fungus Sclerotinia sclerotiorum is that it moves quickly from one plant to another.

What was once a mint problem only could easily be a problem for all your plants.

Severely diseased plants should be removed.

You can prevent Sclerotinia rot from spreading to other parts of the plant by using fungicides that contain vinclozolin or thiophanate methyl.

If you grow your mint in greenhouses, chemicals may work well. Still, if you grow mint indoors, I highly recommend natural methods.

Powdery Mildew

You can use a traditional method for curing fungal diseases, such as copper fungicide. Many gardeners also suggest using wettable sulfur as a fungicide.

If you decide to use sulfur as a treatment, mix it with water (follow the instructions on the label) and spray over your mint using a pressure sprayer.

You can apply fungicide twice a month and expect the results after about 6 treatments.

I have to mention that these fungicides work best in the early stages of fungal diseases. You can dust the leaves as a preventative measure.

Wettable sulfur is very effective in the case of powdery mildew.

Use a cooper fungicide like sulfur, but avoid spraying it near aquariums as it is poisonous to fish.

You can use baking soda as a natural remedy. Add 1 tbsp of baking soda with 1 tbsp of vegetable oil and 1 tsp of dish soap to a gallon of water and spray your mint leaves.

Another great combination for removing powdery mildew is mixing one part milk and three parts water. Spray the solution over mint leaves.

White Mint Rust: Azoxystrobin & Myclobutanil Fungicide

You can use azoxystrobin and myclobutanil fungicides if your mint suffers from white rust.

These products work well for treatment and are less likely to cause fungus to become resistant.

Avoid planting mint plants near each other; these plants really like to have some space, and by dense planting, you increase susceptibility to diseases.

Solution To Pests

Pests shouldn’t surprise you; who could resist such a delicious plant as mint?

Luckily, there are many ways to control pests during flowering.

Here are the most common and effective methods to help remove pests.

Spray Off The Pests

Before choosing a specific, likely more effective strategy, you should try spraying off pests first.

I recommend this method each time you face an infestation. Although it may not remove all pests, it will significantly reduce the number.

After spraying off, you should, of course, apply pesticide.

Don’t forget to spray the undersides of the leaves as these places work as pest shelters.

Use Neem Oil

Neem oil includes azadirachtin, which prevents pests from growing and consuming plant tissue. It’s a completely safe and natural way of removing pests.

Neem oil may be applied the day before harvest if necessary. This kind of essential oil functions as both fungicide and insecticide.

Spray the mixture of water and neem oil over the plant.

Use Insecticidal Soaps

Insecticidal soaps include salts of fatty acids that destroy the outer shell of the pests. They won’t leave any traces and are completely safe for people.

Be mindful of covering and reapply insecticidal soap frequently.

Nevertheless, I advise avoiding spraying buds because it can alter the flavor or odor of the crops.

The best thing about insecticidal soaps is that they work well against a variety of pests, including mealybugs, leafhoppers, aphids, whiteflies, and others.

These soaps are also very effective at fighting off and eliminating fungus gnats.

Attract Beneficial Insects

Beneficial insects consume bugs and pests, although they might not be effective on extensively infested plants.

Ladybugs remove soft-bodied pests like mealybugs, spider mites, or whiteflies. Ladybugs may destroy pests in every stage of their life cycle.

This method is really simple to “implement”; just release the ladybugs onto your mint, and the pests will disappear.

Of course, you can use this technique outdoors or in greenhouses.

Pay attention to the ladybug varieties; purchase the ones native to America, as the Asian ladybugs are invasive.

Solution To Nutrient Deficiency

If your mint suffers from iron deficiency, you will need to improve the soil quality.

First, you’ll need to ensure that mint soil is well-draining as the roots need it for nutrient absorption.

Another thing that may obstruct iron transmission is the fertilizer with high phosphorus concentrations.

Therefore, you’ll need fertilizers with lower phosphorus concentrations (the second number in the npk ratio).

On the other hand, if the soil lacks magnesium, you’ll need a fertilizer with lower concentrations of potassium (the third number in npk ratio).

Solution To Water Hardness

If you conclude that the white spots on mint leaves are caused by water hardness, you can clean the affected leaves using a mixture of vinegar and water (1 tablespoon of vinegar per 1 gallon of water).

If you only use tap water, leave it to sit overnight as it will allow the chlorine to evaporate.

However, it would be best if you thought of a long-term solution. I strongly recommend checking water quality.

Remember that the best water for mint plants is rainwater or melted snow.

Solution To Viral Infections

Unfortunately, there is no remedy for viral infections in cases of the heavily infected plant.

If only a few leaves displayed white spots due to some viral disease, you could remove them.

The most important thing to remember when removing affected leaves is that you should sterilize your shears both before and after using them.

This is the best way to prevent viral infections from spreading.

Bear in mind that any affected plant may transmit the disease, so inspect all your plants regularly (including houseplants).

In the cases of the heavily infected plant, you’ll need to discard it. Please wrap it in the paper bag and then throw it.

Never add infected or diseased plants to your compost pile (if you have one).

Also, disinfect the pot of the mint and discard the old soil.

Solution To Dust

I know it seems obvious, but you should clean mint leaves regularly.

You can wet a soft sponge with lukewarm water and rub it on the leaves of the mint.

If you pledge to use it gently, a dust brush will work too.

What Is The Best Way To Prevent White Spots On Mint Leaves?

You know what they say, prevention is the best remedy!

If you pay close attention to mint plant care, you’ll avoid many issues.

One of the ways to prevent issues is by regularly inspecting mint leaves (and plants). The smaller number of white spots indicates that the issue isn’t serious yet.

Therefore, it will be way easier to fix it.

You may conclude that many issues are caused by high humidity, overwatering, or too warm temperatures.

Here are some tips for mint care.

  • Humidity: Mint thrives in moderate humidity and requires good air circulation.
  • Temperature: When it comes to the temperature, you should keep it between 60 and 70 degrees Fahrenheit.
  • Watering: Pay close attention to avoid overwatering. Mint despises waterlogged soil as it attracts fungus and may cause many issues. This plant needs about 1-2 inches of water per week.
  • Fertilizing: To avoid nutrient deficiency, you’ll need a complete fertilizer.
  • Soil: Your mint needs well-draining and fertile soil, so loam based compost will do wonders.

Can I Use My Mint Leaves If They Have White Spots?

Generally speaking, the answer is “yes.” You can consume mint, use it to make a drink, or use it to flavor tea.

However, before eating it, determine the cause of the white tint spots; in the cases of pests, fungi, or spider webs, it would be best to cure your mint before using it.

Also, pay attention to the smell of the mint; a spoiled mint smells unpleasantly primarily because of the fungi in the soil.

Additionally, your mint’s flavor changes due to fungi, and it could be more bitter than usual.

Wrapping Up

Even though we take good care of our plants, the issues may occur.

The fungal disease, viral infections, or pests spread quickly and may cause different issues, including white spots on mint leaves.

Additionally, water hardness, nutrient deficiency, or plain dust may also cause the abovementioned issue.

It may seem that the list is too long and you’ll have a hard time determining the cause; trust me, it isn’t.

Although it takes time to identify the culprit, it’s worth it!

Fortunately, now you have many ways to solve the problem with your mint.

Good luck and until next time!

Meta: Find out the reasons for white spots on mint leaves. Learn how to solve the issue and see some tips on how to grow a healthy mint plant.

Let's grow together!