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7 Causes of Yellow Spots on Pepper Leaves (With Treatment)

Yellow spots on the leaves of a vibrant pepper plant are the last thing you want to see in your garden.

So whether growing a small ornamental pepper or hoping for a bumper crop of crisp fruits, it’s critical to protect your plant’s foliage.

Diseases or pests are the most common causes of yellow spots on pepper leaves. It is critical to prevent disease by heavily mulching, watering appropriately, and providing adequate ventilation. Yellow spots are also caused by nutritional deficiencies, excessive sun exposure, and poor watering technique.

Let’s look at what might be causing your issues and what you can do to fix them.

Pepper Plant Leaf Diseases

The disease is the most common cause of yellow leaf spots in pepper plants.

They are particularly susceptible to fungal infections because the plant thrives in the same warm, moist conditions that promote the growth of pathogenic fungi.

Phytophthora Blight

The Phytophthora capsici fungus causes Phytophthora Blight. It lives in garden soil all year and usually gets to the leaves through splashed water.

Yellow spots will be blotchy and will appear primarily on lower leaves. The disease causes the leaves to turn brown or black.

On the stems, flowers, and fruit, the plant may also have black or brown lesions or patches of softness.

Treatment

When it comes to Phytophthora, it’s often best to be proactive. For example, you can avoid splashing the plant by applying water directly to the soil rather than the leaves.

It’s also good to mulch heavily around the plant to keep mud from splattering onto the leaves.

Remove infected plant parts and destroy them. Composting infected leaves are not permitted. Finally, consider directly applying a copper-based fungicide to the infected plant.

Because fungicides are incredibly potent, always read the label and wear protective clothing when using them. (Check out the Amazon prices here)

Anthracnose

Anthracnose is another common fungal infection caused by the fungus Colletotrichum spp.

This species prefers warm, damp conditions and is especially common in areas with poor ventilation. Overwatered plants in poorly draining soil are particularly vulnerable.

Anthracnose causes water-soaked lesions on the leaves that are closest to the soil. They are soft and frequently have a slimy texture.

Lesions will also appear in other parts of the plant, like fruits and, particularly, near the ground.

Treatment

Remove infected leaves, stems, and fruit and adequately dispose of them. If the infection is severe, the last line of defense is a copper-based fungicide.

If your infected plant is in a container, consider repotting it in a better-draining medium and a larger pot. At least three drainage holes are required; the more, the merrier.

Make sure to mulch your pepper plant if it is bedded thoroughly. This will prevent the Anthracnose fungus from entering your plant’s leaves and stems from the soil.

Bacterial Leaf Spot

Bacterial leaf spot is indicated by tiny yellow speckles that spread and become more prominent brown spots. It is caused by the bacteria Xanthomonas campestris pv. Vesicatoria, which is commonly found in soil.

Cankers and lesions on stems, particularly near the soil, are other symptoms. The spots may dry out as time passes and leave holes in the pepper’s leaves. Fruit frequently has corky, brittle areas.

Treatment

Bacterial Leaf Spot, like Mosaic, has no cure. If your plant becomes infected, it is best to destroy it thoroughly to prevent the spread of the disease.

Toss the potted peppers, pot and all, into the garbage. Remove and discard bedded peppers, and avoid planting food crops there for a year or longer.

Powdery mildew

As a disease that affects nearly all crop plants, powdery mildew is highly annoying and widespread. It spreads quickly through the air and thrives in dark, damp places with little ventilation.

The leaves develop silvery dust on their surface and crisp, yellow spots on their margins as the disease progresses.

Somewhat unexpectedly, ladybugs can be a sign of mildew. Outdoors and mildew are indicated if you see many tiny ladybugs scurrying around the pepper plants.

Many ladybugs have larvae that only eat mold, making them valuable allies in the fight against that fungus.

Treatment

Fortunately, several simple home remedies exist for dealing with powdery mildew. I’ve had great results spraying my peppers with whole milk diluted to about 10% in clean water.

The mildew can be eradicated without harming your peppers or the beneficial insects you’ve attracted, thanks to the chemicals released as the milk deteriorates in the sun.

Another obvious choice is:

  • A gallon of water mixed with one tablespoon of baking soda and two tablespoons of horticultural oil was sprayed all over the plant.
  • A garlic tincture is made by blending two whole heads of garlic and mixing them with a few drops of dish soap. After straining, dilute to 10% and spray over the foliage.

You can always use a commercial fungicide if you prefer, but I’ve found that natural remedies are far more convenient to use.

In addition, you don’t need any special tools, and most people have milk or baking soda on hand in an emergency.

Root and Stem Rot

This is a catch-all term for a variety of similar conditions, the majority of which are caused by Pythium fungi:

  1. The pepper begins to rot from the roots, with blotchiness and darkening tissue spreading upward from the ground.
  2. Wet green lesions appear and quickly turn brown or black.
  3. Yellow patches appear on the leaves, especially the older ones.

The roots will be black, brown, or even orange, soft, and rotting when dug up. They also occasionally smell like rotting eggs.

Treatment

Although a copper-based fungicide may be effective, it is often too late to save the plant when the disease has spread to the leaves. The plant can’t survive without healthy roots.

Check the pepper plants’ roots if they’re in containers. Remove the diseased roots, and repot the plant in fresh medium if there is still a sizable amount of pale, healthy rootstock.

Use a fungicide that contains copper as a final step. Your pepper might make it with some TLC.

If your plants are in a bed, you should remove them and replant them elsewhere.

Then, take a year off from growing edible crops there and think about making some of the above soil amendments.

Verticillium Wilt

Verticillium wilt is a fungal disease of the plant’s veins caused by Verticillium dahliae and V. albo-atrum.

It develops inside the pepper’s vascular tissue and completely shuts down its ability to transport oxygen and nutrients.

Wilting and eventual death result from water and nutrients being blocked from reaching the leaves from the soil.

The plant wilts unevenly, with one side looking weak and thirsty while the other seems unaffected by the disease.

In addition, you may notice brown veins or yellow spots on the leaves. As the vascular tissue within the stems becomes blocked, the plant may suddenly lose its leaves and die.

Treatment

First, ensure that your pepper plant is well-watered. Wilting is a common symptom of dehydration, so address it first. Your pepper’s dejected appearance might soon brighten.

If watering the plant doesn’t help and only one side or part of the plant is dying, you’ll have to throw it away.

Fungicides containing copper can alleviate symptoms, but the disease is always fatal in the long run.

Mosaic Virus

The mosaic disease is a true assassin. First, it is caused by several viruses that affect food crops, with viruses from the Potyviridae family being the most common in pepper infections.

Then, insects, particularly aphids, spread it. The virus causes the disease’s name by causing patchy, interconnected areas of discoloration on the leaves.

The mosaic virus can also be identified by the pests it attracts, which can be in staggering numbers.

Treatment

It isn’t much you can do about the Mosaic virus. Even in commercial agriculture, the only cure is to destroy the entire plant.

If you grew your pepper in a pot, throw it out. The soil and pot cannot be reused because doing so risks infecting any new plants. Sometimes it’s better to accept defeat and move on.

The infected pepper must be removed entirely if it is in a garden bed. Don’t plant food crops in that part of the garden for at least a year because the soil will still be infected.

I’d also recommend adding well-rotted manure and mulch to the soil. This will replenish the soil with beneficial microbes and organic matter.

Preventing Disease in Pepper Plants

You probably already know that most diseases that affect pepper plants are fatal to them. Therefore, the most effective strategy is prevention.

Good air circulation and moderate watering are essential whether growing in a container or a garden.

By allowing air to circulate the leaves and avoiding muddy sprays, you can stop disease-causing organisms from ever reaching the plants in the first place.

Mulching can also be helpful, particularly for plants that are in beds. It’s worth noting that, due to the importance of food crops, a lot of effort has been put into creating disease-resistant varieties.

To reduce risk, you can plant a type of pepper that has been bred to survive even in the presence of harmful pathogens. There is a wide variety, with a cultivar available to suit any environment or taste. (Source)

Bugs on Pepper Causing Yellow Spots

Insect pests are well aware of the deliciousness of peppers. They nibble holes in the plant, which soon turn yellow.

It’s essential to take action when you notice sap-sucking insects because they weaken the plant and can spread disease.

Mealybugs

Mealybugs are tiny, scale-shaped insects that can be any shade of white, cream, or gray.

These bugs are sap suckers, congregating around pepper’s veins and stems to drain the plant’s vital fluids.

They frequently appear fluffy because they sweat a sweet substance called honeydew, which crystallizes into fine fibers.

Spider Mites

Spider mites are about the size of a sesame seed and congregate in nooks and crannies to suck the sap from your pepper plant. They are frequently bright red but can also be brown, black, or pale green.

Keep an eye out for thin threads on the pepper – the spider’s web is often the first and most obvious sign of a problem.

Scale

Scale beetles are tiny insects that look like brown or black bumps on your plant. They prefer stems and veins, which allow them to suck sap from the pepper.

They are frequently accompanied by ants, who enjoy the honeydew produced by these pests.

Aphids

Aphids, another sap sucker that loves to form tight groups on veins and stems, are one of the garden’s most prolific pests.

They are also small and come in various colors ranging from translucent whites and greens to browns and black.

Treatment

The first step in dealing with insect pests is to hose them down. In warm, dry weather, there’s no harm in blasting the pests off the leaves with a shower head or a garden hose.

If the infection persists, a neem oil spray on the leaves will deter insect diners from feasting on your pepper plants.

Edema

Edema on Pepper leaves
Edema on Pepper Leaves

Edema occurs when a healthy plant receives too much water. As a result, the pepper’s ability to regulate moisture levels is lost, allowing water to accumulate in the tissue.

Consequently, it forms a blister-like growth in the leaf. When the blisters rupture, a yellow patch with sharp edges remains.

Solution

Cautionary watering can effectively prevent edema. Water pepper plants only if the top inch of soil is dry.

During the heat of the summer, this may be as often as once a day, especially for peppers grown in beds with insufficient mulch.

On the other hand, a pepper plant in a pot may only need water once a week during the winter.

Sunscald

Sunscald on Pepper Leaves
Sunscald on Pepper Leaves

While pepper plants thrive in direct sunlight, too much light can bleach the leaves. As a result, it will first turn yellow, then ivory, and finally white.

The damaged area will eventually dry out and become papery. It may even flake away entirely.

Solution

With potted peppers, the solution is simple: relocate the plant to a more shaded location. Ornamental peppers do not require direct sunlight, with early morning light ideal.

Consider using shade structures directly above the plants for bedded peppers. This will shield them from the midday sun’s heat without reducing their light levels. (Check out the prices on Amazon here)

Improper Watering

Your pepper plant suffers from wet leaves. Splashing water around a garden bed is a great way to transmit soil-borne pathogens to the leaves, but it also has other risks.

Water on leaves can act like tiny lenses, focusing sunlight and causing speckled burns. The little spots, similar to sunscald, turn yellow at first, then dry out as the burn ages.

It’s also an excellent way to end up with a dried plant. Water that evaporates from the leaves never reaches the soil. So a dry plant, like one that is rarely watered, will eventually develop yellowing leaves.

Solution

Water your plants by sprinkling the soil rather than the leaves. Because the pepper plant draws moisture from the ground rather than its foliage, this is a simple problem to solve.

It also helps to water in the morning so that your pepper plant has plenty of water throughout the day.

Nutrient Deficiency

Pepper plants are notorious for nutrient deficiencies, particularly nitrogen, magnesium, and calcium. They’re heavy feeders, especially when fruiting, and they’ll need a lot of help as they grow.

The pepper plant cannot form strong leaves when malnourished.

Therefore, they are more susceptible to all the abovementioned problems, including disease, pest damage, sunscald, and physical damage that can appear as spots or speckles.

If the yellow spots spread to produce completely yellow leaves and are part of a general pattern of poor growth, you may be deficient in nitrogen or magnesium.

Calcium deficiency is more difficult to detect until the pepper has fruit.

Peppers with soft, mushy ends that smell like mold suffer from blossom end rot and a condition lacking calcium that results in weak, fragile fruit. 

Solution

The soil in potted peppers should contain enough nutrition to sustain the plant for only two weeks. Afterward, you should begin fertilizing once weekly, preferably with a general-purpose balanced fertilizer.

Flowers indicate a change in the pepper’s metabolism, so keep an eye out for them. In addition, flowers are a fruit that requires a shift in fertilization.

A specialized pepper fertilizer is ideal because it contains the proper balance of nitrogen, calcium, and magnesium to promote a large number of flowers and fruit.

Before scattering fertilizer around for peppers grown in beds, figure out what’s missing. Soil testing kits are simple to use and tell you which nutrients you need to add to your garden bed. (Check out the Amazon prices here)

However, before planting, I recommend enriching the soil with plenty of compost and bone meal.

Bone meal is high in calcium; incorporating it into the soil before planting can help prevent end rot. In addition, you can fertilize your pepper plants with eggshells; read another article here.

Fertilizer Burn

If fertilizing peppers sounds complicated, that’s because too much nitrogen in the soil causes chemical burns to the peppers’ root system.

As a result, the edges of the leaves begin to brown, and patches of yellow appear along the margins.

This is especially true for peppers in pots. Too much fertilizer in a pot has nowhere to go and will accumulate in the soil. It eventually forms mineral salts that scald the roots, causing them to stop working.

Solution

For a potted pepper, the best approach is to flush the soil with lots of fresh, clean water. To do this: 

  1. Fill the pot with water until puddles form on the surface, and place it in a large basin or tub.
  2. Allow a few minutes for soil-trapped salts to dissolve.
  3. Allow the water to drain from the pot.
  4. Allow water to flow freely through the medium by watering deeply for a few minutes.
  5. Allow the pot to drain completely before replacing it with saucers or trays.

You’ll have to wait for bedded peppers. Peppers are such heavy feeders that larger varieties, such as bell pepper vines, will quickly consume the excess.

Water as usual, and they’ll be fine in no time. You can speed up the process by adding fresh soil from another part of the garden.

Another option is moving your pepper to a less stressed garden area or even a container. But, again, fresh soil represents a new beginning.

How to Prevent Yellow Spots on Pepper 

  • Use mulch to keep plants healthy and disease-free, as well as proper watering and ventilation.
  • Fungicides or home remedies can be used to treat disease as it appears.
  • Remove any pests that appear.
  • Water when the top inch of soil is dry, preferably first thing in the morning.
  • Avoid regularly wetting leaves.
  • Shade vulnerable plants from the midday sun.
  • Use a balanced fertilizer to fertilize.