Pepper plant leaves turning white

Pepper Leaves Turning White: Treating Peppers With Powdery Mildew

Pepper leaves turning white is an indication of powdery mildew, a common fungal disease that can afflict nearly every kind of plant under the sun. Powdery mildew on pepper plants can be severe during the warm days of summer, and can significantly affect quality and yield at harvest time. What can you do about that nasty white powder on pepper leaves (or sometimes brownish-yellow)? Read on for helpful information.

What Causes Powdery Mildew on Pepper Plants?

Powdery mildew on pepper plants spreads primarily by wind, but also by splashing water. The disease is also transmitted by humans, and sometimes by insects such as aphids, thrips and whiteflies.

Certain weather conditions favor the disease, particularly weather fluctuations such as warm, dry days followed by cool, moist nights. Plant crowding is also a contributing factor, as is excessive use of high-nitrogen fertilizer.

Mature plants are most susceptible to pepper powdery


What to Do About Peppers with Powdery Mildew

Treating pepper powdery mildew in the garden is certainly possible, although prevention is even better.

Monitor plants closely, especially the undersides of leaves. Fungicides may provide some level of control, but only when applied as soon as the disease appears, or even before symptoms are visible. Complete coverage is critical, and repeat applications are usually required.

Avoid conditions that promote wet foliage, including shade and overcrowding. Plant peppers in full sunlight and allow plenty of space between plants. Also, keep weeds under control, as weeds can foster disease pathogens.

Water at the base of the plant and avoid overhead sprinklers whenever possible. Irrigate early in the day to allow time for the leaves to dry completely before evening. Avoid high-nitrogen fertilizers, which make plants more susceptible to infection.

Home remedies for powdery mildew on pepper plants are sometimes employed as well, especially in organic gardens. It is usually recommended to alternate these remedies, however, for them to be most effective.

Some research suggests that milk may be as effective as chemical fungicides. Fill your sprayer with a solution of 1 part milk to nine parts water.

In some cases, baking soda is effective against powdery mildew, especially when mixed with horticultural oil. Fill a one-gallon sprayer with water, then add a tablespoon of baking soda and 2 ½ tablespoons of horticultural oil.

Try a garlic extract consisting of two entire garlic bulbs blended with a few drops of liquid dish soap. Strain the mixture through cheesecloth and store it in the refrigerator. Combine the mixture in a sprayer at a rate of one part garlic extract and ten parts water.

Why Do Pepper Leaves Turn White When Outside?

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Pepper plants are a warm-weather vegetable that can be affected by a number of growing conditions and pests. Pepper plant leaves will turn white as a consequence of extremes in growing conditions, plant infections or pest infestations. Diagnosing the cause of white leaves on the pepper plant require you to look for other symptoms or be aware of dramatic shifts in growing conditions.

Cooler Temperatures

Suddenly cool temperatures or a quick drop in temperature will affect pepper plant leaves, turning them white. Pepper plants do not tolerate even a light frost. This problem with pepper plants happens most frequently when pepper plants have not been hardened off before they are transplanted outdoors. Hardening off is the gradual process of introducing pepper plant seedlings to the outdoors so there is less of a shock when they are transplanted.

Powdery Mildew

Powdery mildew is an infection that can affect the entire pepper plant, including the fruit. Powdery mildew most often begins as small white spots on the leaves of the pepper plant but can spread quickly to cover entire leaves as well as the stem and fruit. Powdery mildew prefers humid climates, so plant your pepper plants in well-draining soil that receives plenty of direct sunlight.

Excessive Sunlight

Pepper plants require significant amounts of sunlight to grow properly, but too much strong or direct sunlight can create sunscald in your pepper plants. Sunscald produces brown to white blotches on the leaves and fruit of your pepper plants. Sunscald occurs when there is too much and too intense of direct sunlight. Do not over-prune your pepper plants when they are outdoors as the foliage provides protection to the pepper plants.


Aphids are small, orange pests that live on the underside of the pepper plant leaves. Aphids live in clusters and secret a sticky substance. Aphids affect the pepper plant by sucking the nectar from the leaves, creating light brown to white dots and holes. Eventually, aphids will cause the pepper plant leaves to become light brown to white and paper thin. If left untreated, aphids will eventually kill a pepper plant.

Pepper Plants With Yellow Leaves


Pepper plants can suffer from any number of nutrient deficiencies that cause issues. Two common deficiencies will express themselves in yellowing leaves. The first is a Magnesium deficiency. This affects the oldest leaves first and causes yellowing in intravenous sections of the leaves.

This can sometimes happen from an excess of potassium, or particularly hot and dry weather. Correct magnesium deficiency by mixing an Epsom salt solution and feeding it to your pepper plant. Also, reduce any applications of potassium.

Yellowing accompanied by slow growth, low fruit set, and brittle leaves is a sign of phosphorus deficiency. This is correctable but should be noted as a possible larger soil-related problem. Phosphorus comes from organic matter in the soil: plant material, manure, compost.

A phosphorus deficiency points to a soil with low quantities of organic matter which will cause further problems if left alone. Apply rich, living compost as a mulch and water through it.


The three most common pepper pests all can have a yellowing effect on plant leaves.

  • Aphids
  • Flea Beetles
  • White Fly

If the yellowing appears in tiny dot patterns it could be from insects. Turn the leaves over and examine them. Aphids and white flies will be clustered on the undersides of the leaves. Flea beetles are fairly easy to spot and look exactly as they sound. These pests won’t kill pepper plants right away, but they will weaken them until they die or contract a disease.

Combat pest problems a few ways. For an immediate remedy spray the plants with neem oil over the course of a week or two until they appear to recover. In the long run, encourage predatory insects and birds into the garden by planting friendly plants and creating habitat for them.


A disease is the worst possible cause of leaf yellowing because it is almost impossible to correct. Leaf spot, wilt, and blight can all cause yellowing of the leaves and the only thing to do is pull the affected plants.

It’s better to take preventative measures when it comes to disease. Avoid soluble fertilizers that can swell plants and make them weak and vulnerable to disease. Use organic composts and worm castings instead. Keep pepper plants from being exposed to extreme temperatures and moisture extremes which can also render them susceptible.

Common on many plants and easily recognized, powdery mildew is a fungal disease found throughout the United States. It is caused by a variety of closely related fungal species, each with a limited host range. (The fungi attacking your roses are unlikely to spread to your lilacs). Low soil moisture combined with high humidity levels at the plant surface favors this disease.

Symptoms usually appear later in the growing season on outdoor plants. Powdery mildew starts on young leaves as raised blister-like areas that cause leaves to curl, exposing the lower leaf surface. Infected leaves become covered with a white to gray powdery growth, usually on the upper surface; unopened flower buds may be white with mildew and may never open. Leaves of severely infected plants turn brown and drop. The disease prefers young, succulent growth; mature leaves are usually not affected.

Fungal spores overwinter inside leaf buds and other plant debris. Wind, water and insects transmit the spores to other nearby plants. Zucchini, beans, cucumbers, squash, pumpkins, tomatoes, roses and zinnia are especially susceptible.


  1. Plant resistant cultivars in sunny locations whenever possible.
  2. Prune or stake plants to improve air circulation. Make sure to disinfect your pruning tools (one part bleach to 4 parts water) after each cut.
  3. Remove diseased foliage from the plant and clean up fallen debris on the ground.
  4. Use a thick layer of mulch or organic compost to cover the soil after you have raked and cleaned it well. Mulch will prevent the disease spores from splashing back up onto the leaves.
  5. Milk sprays, made with 40% milk and 60% water, are an effective home remedy for use on a wide range of plants. For best results, spray plant leaves as a preventative measure every 10-14 days.
  6. Wash foliage occasionally to disrupt the daily spore-releasing cycle. Neem oil and PM Wash, used on a 7 day schedule, will prevent fungal attack on plants grown indoors.
  7. Water in the morning, so plants have a chance to dry during the day. Drip irrigation and soaker hoses will help keep the foliage dry.
  8. Use a slow-release, organic fertilizer on crops and avoid excess nitrogen. Soft, leafy, new growth is most susceptible.
  9. Destroy all plant debris after harvest (see Fall Garden Cleanup). Do NOT compost.

If disease symptoms are observed, treat plants with one of the following approved organic fungicides:

  • Apply sulfur or copper-based fungicides to prevent infection of susceptible plants. For best results, apply early or at first sign of disease. Spray all plant parts thoroughly and repeat at 7-10 day intervals up to the day of harvest.
  • Green Cure Fungicide contains a patented formula of potassium bicarbonate — commonly used in food products — that kills many plant diseases on contact and provides up to 2 weeks of residual protection. At first sign of disease, mix 1-2 Tbsp/ gallon of water and apply to all exposed surfaces of the plant. Monterey® BI-CARB is a similar product containing micro-encapsulated potassium bicarbonate as the active ingredient. Mix 4 tsps in 2 gallons of water to thoroughly cover foliage.
  • Effectively treat fungal diseases with SERENADE Garden. This broad spectrum bio-fungicide uses a patented strain of Bacillus subtilis that is approved for organic gardening. Best of all, it’s safe to use — you can treat and pick crops the same day!
  • SNS 244 and Zero Tolerance Herbal Fungicide are made from 100% pure, food-grade ingredients that work fast to kill existing plant diseases and prevent new fungal problems from starting.
  • Indoor growers may want to consider using a Sulfur Burner/ Vaporizer which turns sulfur prills into a fine dust and changes the pH of leaf surfaces. Fungal spores and mold can’t get established on this plant coating. As an added benefit, studies have shown that this dust will eliminate spider mites.

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