Brown spots on pepper leaves are the worst thing to happen to them. In any case, their appearance is never beneficial.
Look for other symptoms on your pepper plant to help you pinpoint the cause of the problem.
Brown spots on pepper leaves indicate pest damage and diseases such as bacterial leaf spots, Anthracnose, or bacterial end rot. Eliminate pests with insecticidal soap or neem oil. To combat infections, spray with a fungicide or bactericide; avoid overwatering; thin out your plants; and maintain proper sanitation.
Most causes of brown spots on pepper leaves are simple to recognize, avoid, and remedy for your benefit. Let me walk you through it.
- Why do my pepper leaves have brown spots?
-  Bacterial Leaf Spot on Pepper Leaves
-  Spots on Pepper Leaves Due to Sunscald
-  Phytophthora Blight of Pepper is Causing Brown Spots
-  Blossom End Rot
-  Calcium Deficiency
-  Anthracnose
-  Pest Infestation
- How to Prevent Brown Spots on Pepper
Why do my pepper leaves have brown spots?
 Bacterial Leaf Spot on Pepper Leaves
Bacterial leaf spot is most likely to blame if your pepper leaves develop irregular brown spots.
Bacterial disease caused by the bacterium Xanthomonas campestris pv. vesicatoria, which usually travels on transplants and seeds, is a severe problem.
For this reason, it overwinters in warm, moist environments with poor ventilation.
A bacterial disease can kill your pepper prematurely in some cases, especially if it isn’t caught early and treated promptly.
Bacterial leaf spot symptoms can be found on nearly every part of the plant that is above ground. Stem cankers, fruit spots, and brown, irregular leaf spots are examples of these.
Water-soaked lesions on lower and older leaves are early warning signs. They start out green or yellow but quickly turn a dark brown color.
Warm, humid weather accelerates the growth and darkening of these lesions. They can grow to a diameter of up to a quarter-inch.
The mature spots are light brown or tan in the center, with bumpy, darker edges.
The brown spots may dry out and fall off if the humidity is too low. Leaves that have been hit by this have a tattered or hollow point appearance to them.
Foliage that has been exposed to the problem may turn yellow, then brown, and eventually die.
Even infected fruits are not immune to the disease. They may also get raised, corky, or scabby lesions. Fruits that have been exposed to the fungus will eventually scar or rot.
How to Treat Bacterial Leaf Spot on Peppers
A bacterial leaf spot is nearly impossible to control once it’s a full-blown infection. To add insult to injury, there’s no viable cure for it.
Prevention, good sanitation, and early control are, therefore, your best tools:
- Choose resistant cultivars, although no pepper variety is 100% immune
- Use disease-free transplants and seeds
- Use deep mulch. I prefer organic mulching materials like grass cuttings, straw, or newspaper
- Avoid overhead irrigation
- Reduce humidity levels and boost air circulation to deter the spread of infection
- Trim off badly infected leaves, stems, and fruits. Ensure to discard them safely.
It would help if you also treated pepper seeds before planting:
- Soak the seeds in 10% bleach solution for surface treatment for 40 minutes. Prepare the bleach solution by mixing four parts of water and one part of chlorine bleach.
- For a more profound treatment, consider soaking seeds in hot water pre-heated to 125°F (51°C) for around 30 minutes.
- Rinse and dry the seeds thoroughly before planting.
Spraying with an organic fungicide early in spring can help. I usually spray my peppers every ten to 14 days using copper-containing fungicide (Check the latest price on Amazon here).
This will only help to slow down the infection rate, though.
 Spots on Pepper Leaves Due to Sunscald
Sunscald is often blamed if the affected leaves have brown or white spots. Sunscald, like sunburn, is caused by excessive heat from direct sunlight exposure.
This is a common problem during the hottest, humid summer months, significantly if you quickly move your pepper plant from indoors to outdoors.
Typically, sunscald affects developing fruits and younger leaves. The tender skin on the foliage or fruit cannot withstand direct sunlight’s extreme heat.
Scalding appears as white or black discoloration on the leaves or fruits first. In some cases, they may begin as dark streaks or spots and progress to leave white or brown scars.
The scalded leaves will turn ivory white or brown over time. They’ll also crisp up and feel dry or brittle to the touch.
The affected fruits may split and crack at the scalding points. The scalded areas will become soft and mushy and will begin to rot.
Unfortunately, sunburned leaves and fruits can serve as entry points for diseases and pests. If the problem is not resolved, the affected leaves will fall off prematurely.
How to Treat Sunscald on Peppers
Early detection is crucial to keep sunscald in check
Watch out for leaf-eating bugs, like caterpillars, slugs, and snails, as their feeding action exposes the leaves and fruits to sunscalding.
Install row forms or covers to protect your papers from sunscald
 Phytophthora Blight of Pepper is Causing Brown Spots
The fungal pathogen Phytophthora capsici causes Phytophthora blight on pepper plants. It is also the cause of fruit rot, stem rot, crown rot, and root rot in the majority of pepper cultivars.
Because the soil-borne fungus is typically spread by water splashing, it is common in overwatered, waterlogged, or overhead-irrigated pepper plants.
When the fungus infects your pepper, you’ll notice large dark brown spots on the undersides of the leaves closest to the ground. The margins of the lesions are usually wilted.
Other common symptoms of Phytophthora blight of peppers include:
- Brown or rotten black roots
- Dark brown lesions on stems on the upper parts of the plant
- Black or dark brown tissue on the crown
- Young pepper plants have a soft texture and look watery
- Affected stems may die back and collapse
- Damping-off, often starting from the base of the plant
- Dark, water-soaked patches may show up on infected fruits. You may also see white mold on affected areas of the fruits.
How to Control Phytophthora Blight on Peppers
Phytophthora blight of peppers is an early blight disease. For this reason, early management measures are vital. These include:
- Preventive spraying using fixed copper fungicides in early spring
- Don’t splash water on your pepper plants – so avoid overhead watering
- Promptly remove and destroy affected parts of the plant
- Avoid poorly-drained soil
If your pepper is badly infected, you have no choice but to remove and destroy it completely. Make sure to sanitize your cutting tools to prevent the spread of infection
Good cultural and sanitation practices can help, as well:
- Practice crop rotation in your garden
- Don’t work your plants when they are wet
- Use raised, well-drained beds or pots to grow your peppers
- Apply mulch generously around your peppers to reduce water splashing
 Blossom End Rot
Another common pepper problem is blossom end rot, which causes brown spots to appear on the leaves. The name derives from the fact that the bottoms of rotten peppers.
The primary cause of blossom end rot in peppers is a severe calcium deficiency and mainly occurs in pepper fruit.
Calcium is required for the formation of cell walls. If the pepper fruits or leaves grow too quickly and the plant cannot supply enough calcium, they will rot and develop brown lesions or spots.
This is common when the soil has been depleted of calcium. The same is true if the soil is too acidic or contains high sodium, ammonia, and aluminum levels.
Giving your pepper too much water after a dry spell can also prevent calcium absorption from the soil.
Control and Management of Blossom End Rot on Peppers
Blossom end rot is exacerbated by overwatering and drought conditions. So, keep the soil moist at all times. Mulch can be used to keep soil evenly moist.
Correct acidic soil by liming it to a pH of 6.5-7.0.
Avoid fertilizers containing ammonia or urea. Instead, use a fertilizer that is high in superphosphate and low in nitrogen.
Use a small amount of Epsom salt or calcium chloride solution to spray your pepper.
Amend the soil with bone meal, crushed eggshells, gypsum, or lime to increase calcium content.
 Calcium Deficiency
As noted above, calcium deficiency can result in brown leaf spots and bottom-end rot on pepper fruits.
Remember, calcium is an essential element for:
- Developing and producing quality pepper fruits
- Promotion of the health of a pepper plant
- Preventing blossom end rot, a condition in which the pepper fruits rot at the bottom. It is a physiological disorder.
- Ensuring the integrity of pepper fruits by the formation of solid cell walls
Common signs and symptoms of calcium deficiency in peppers include:
- Sunken, water-soaked yellow areas on the bottoms of affected fruits
- Brown spots on foliage
- Affected areas may be infected by fungus or bacteria
- Mold may grow in affected areas
Calcium deficiency in peppers is caused or exacerbated by:
- Soil has too much aluminum
- Soil has excess sodium
- Too acidic growing medium
- Heavy leaching due to sandy or light soil
- Overwatering after allowing the soil to become completely dry
- Excess nitrogen, potassium, or ammonium in the soil
How to Treat Calcium Deficiency in Peppers
Check the soil to ensure it isn’t too acidic or too low in calcium.
If the soil is too acidic, lime, sulfur, aluminum sulfate, or crushed limestone must be applied to raise the pH to around 6.5-7.0.
To increase calcium supply, consider using a foliar spray containing dissolved Epsom salt or calcium chloride.
Increase the calcium content of your soil by adding gypsum, ground eggshells, bone meal, or lime.
Use a low potassium and nitrogen fertilizer to add calcium to the soil. It should not be urea or ammonia-based.
Another common fungal infection that causes brown spots on the plant’s foliage is anthracnose of peppers. Colletotrichum spp. is the pathogen responsible for the spots.
The Anthracnose fungus thrives in warm, moist environments with little air circulation. Fungal spores enter your plant via irrigation or rain splashes.
Low light and overwatering conditions can aggravate the situation.
Symptoms can be found on nearly every part of the above-ground pepper. However, the leaves and fruits bear the brunt of the damage.
The disease manifests as small, water-soaked circular lesions on older leaves and those near the soil’s surface. The color of these sunken spots can range from orange-yellow to brown.
The spots become dark brown as they mature. They can also be found on newer leaves, shoots, and stems.
Affected pepper fruits develop circular, sunken lesions. As the infection progresses, the lesions enlarge and develop pink or salmon-colored spore coatings. This gives the fruits a gelatinous or wet appearance on the surface.
How to Control and Manage Anthracnose in Peppers
- Plant your peppers using disease-free seeds
- Ensure the soil is well-drained and control weeds
- Control water splashing by avoiding overhead irrigation and applying a thick mulch
- Use disease-resistant varieties of pepper
- Apply fungicide preventively in early spring
(Source: University of Florida)
 Pest Infestation
If you suspect pests are to blame for the brown spots on pepper leaves, you most likely have a soft-bodied aphid infestation.
These insects are small, pear-shaped, and have long antennae. They drill small holes into the foliage with their sharp mouthparts.
They leave tiny brown spots on the foliage as they suck the sap from the leaf tissues.
The spots are usually seen along the veins.
Other symptoms of an aphid infestation on a pepper plant include:
- Clusters of aphids on the backs of the pepper leaves. They are usually black, pink, or pale green to yellow or red.
- Curled leaves
- They cause foliage to turn yellow
- Sticky honeydew on the foliage
- Presence of sooty black mold and ants on leaves with honeydew
How to Get Rid of Pests from your Peppers
- Spray down your pepper plant with a strong stream of water from a garden hose. This should be enough to dislodge the aphids off your pepper.
- Attract natural predators, such as parasitic wasps, lacewings, or ladybugs
- Spray your pepper using insecticidal soap or neem oil
- Sprinkle your pepper with diatomaceous earth
How to Prevent Brown Spots on Pepper
- Minimize water splashing by applying mulch and avoiding overhead irrigation
- Maintain consistent soil moisture- Don’t overwater or underwater your pepper plant.
- Use disease-free seeds and transplants.
- Apply preventive fungicide early in the growing season
- Embrace good gardening hygiene
- Practice crop rotation in your garden