Food Gardening Network

Growing Good Food at Home

Dealing with Bell Pepper Diseases

Red bell pepper damaged by Anthracnose disease

Red bell pepper damaged by Anthracnose disease

Like all food crops, bell peppers are susceptible to various fungal diseases. Your best weapons against these are best planting practices, which help prevent disease in the first place.

This is especially important, as there are no fungicides approved for home use for many diseases.

These best practices are aimed at producing strong, healthy plants that can withstand disease, and at avoiding situations that contribute to the development of disease. They involve keeping plants clean, dry, and undamaged.

Companion Planting: Each crop has a garden buddy that helps out in some way: repelling pests, attracting pollinators, contributing nutrients to the soil. We discuss this in more detail in the Planting section of this guide. You can also review our Food Gardening Network Companion Planting Chart for a full list of good planting partners for your garden.

Crop Rotation: As tempting as it might be, it’s best not to grow the same crops in the same soil—open garden, raised bed, or container—for more than one growing season. Each plant takes certain nutrients from the soil and leaves others behind. Some crops are susceptible to soilborne diseases or particular pests. For these reasons, you want to rotate your crops from growing season to growing season. This will help ensure better soil health and healthier, more productive harvests. This practice applies primarily to annual crops; perennial crops can usually continue to grow where they’re planted.

Now, in a perfect gardening world, you would be able to implement a crop rotation plan that spans decades. There are some soilborne diseases that can live in the soil for up to 20 years!

Even so, it’s a good idea to switch things up from season to season. Here’s a list of vegetable crops by category. The general rule of thumb here is to plant crops from one list in the growing space of the crops in the following list in the next growing season. So, you would go from List 1>List 2>List 3>List 4> and then back to List 1.

  1. Root, Solanaceous (nightshade), & Tuberous Crops

    • bell peppers
    • carrots
    • celery
    • eggplant
    • parsnips
    • potatoes
    • bell peppers
    • sweet potatoes
    • taro
    • tomatoes
  2. Brassicas

    • broccoli
    • Brussels sprouts
    • cauliflower
    • kale
    • kohlrabi
    • mustard
    • radishes
    • rutabaga
    • turnips
  3. Legumes and Pod Crops

    • broad beans
    • lima beans
    • okra
    • peas
    • runner beans
    • snap beans
  4. Alliums

    • bulb onions
    • garlic
    • leeks
    • oriental bunching onions
    • scallions
    • shallots
    • welsh onions

Here’s a short example of common crop rotations:
potatoes>corn>cabbage>peas>tomatoes>beans>root crops>squash/potatoes>onions

If you can’t do a complete crop rotation, consider alternating what you grow from one season to the next—a virtual crop rotation of sorts. With containers and raised beds, you have the option of changing out the soil, depending on what you want to grow there. Some container soil, especially, will be severely depleted of nutrients at the end of the growing season and should just be replaced.

Mulch: Mulch can help with water retention—but be vigilant and check for insect or fungal activity.

Watering: Water your bell peppers deeply about once a week (check the soil for dryness). Do not over-water. Soggy soil invites disease.

Other best practices include:

  • Buy healthy, disease-free seeds from reputable sources.
  • Plant your bell peppers in full sun.
  • Plant in sites with good drainage; if planting in open ground, choose a higher spot for better drainage.
  • Check plants regularly for signs of disease.

Common Bell Pepper Diseases

Here are some of the usual culprits that might infest your bell pepper plants. Remember, it’s important to remove infected plant material (leaves, roots) to prevent the spread of disease once it’s found its way onto your plant.

Anthracnose

Cause:Fungus

Symptoms:

  • leaves turn yellow at the tips, eventually turning brown all around
  • browned, dying leaves
  • dark, sunken lesions on fruit and/or stems

How it Spreads:

  • spores spread by rain and splashing water
  • wind

Treatment:

  • remove all infected parts
  • clear ground of leaf and twig litter
  • apply liquid copper fungicide to reduce recurrence

Prevention:

  • prune plant to provide good air circulation and access to sunlight
  • provide proper water and fertilizer

Bacterial Leaf Spot

Cause: Bacteria

Symptoms:

  • leaves have circular spots with irregular edges
  • spots may turn yellow and water-soaked
  • leaf drop

How it Spreads:

  • water
  • wind
  • garden tools
  • thrives in warm, moist conditions

Treatment:

  • remove and discard infected leaves
  • if infection becomes serious, discard entire plant
  • do not compost infected plant material

Prevention:

  • mulch around plants to prevent water from splashing onto leaves
  • avoid overhead watering; water at soil level
  • make sure plants have good air circulation and lots of sun
  • sterilize garden tools before each use
  • spray plants weekly with neem oil or a commercial fungicide such as Bonide Revitalize
  • rotate crops annually

Blossom-end Rot

Cause: Calcium deficiency

Symptoms:

  • water-soaked area on end of fruit where the flower was
  • lesion on side of fruit
  • lesion enlarges and turns brown and leathery

How it Spreads:

  • caused by a calcium deficiency in the soil

Treatment:

  • keep soil pH between 6.5 and 6.8
  • lime soil to increase calcium content
  • mulch to retain soil moisture

Prevention:

  • test soil before planting
  • water consistently
  • avoid excessive amounts of nitrogen fertilizer

Cercospora Leaf Spot

Cause: Fungus overwinters in infected plant material and emerges in warm, humid weather, most commonly after a rainy spell. It does not affect the fleshy root of the plant. In the U.S., this infection is most prevalent in the southeastern states.

Symptoms:

  • yellow and brown spots on the underside of leaves
  • leaves may curl and turn upward

How it Spreads:

  • fungus overwinters in infected plant material
  • wind, insects, and birds

Treatment:

  • removed and destroy infected areas

Prevention:

  • liquid copper fungicide
  • if necessary, sulfur-based fungicide
  • plant disease-resistant varieties
  • remove plant debris
  • rotate crops annually; see crop rotation guidelines above

Damping-off

Cause: Fungi

Symptoms:

  • water-soaked, decomposing seeds
  • infected roots are gray and water-soaked
  • seedlings grow but then collapse and die
  • older plants that get infected are severely stunted

How it Spreads:

  • spores thrive in moist soil and cool temperatures

Treatment:

  • liquid copper fungicide, if infection is severe
  • remove and discard infected parts

Prevention:

  • minimize soil moisture
  • plant in well-draining areas
  • avoid overhead watering; water at soil level
  • treat seeds with fungicides before planting
  • rotate crops annually

Fusarium Wilt

Cause: Fungus

Symptoms:

  • leaves wilt and turn yellow

How it Spreads:

  • splashing water (rain, irrigation) disturbs spores
  • warm temperatures favor growth

Treatment:

  • destroy infected plants

Prevention:

  • purchase disease-free plants
  • plant in well-draining areas
  • homemade fungicides
  • choose planting sites with good air movement

Gray Leaf Spot

Cause: Fungi present in the soil

Symptoms:

  • small red-brown spots on leaves
  • lesions expand and turn lighter in the middle
  • mature lesions have white or gray centers and dark margins
  • leaf drop

How it Spreads:

  • splashing water
  • contact with other infected plants

Treatment:

  • remove and discard infected plant matter

Prevention:

  • buy disease-free seeds
  • avoid overhead watering; water at soil level
  • make sure plants have good air circulation and lots of sun
  • rotate crops annually

Mosaic Virus

Cause: Viruses

Symptoms:

  • small, light-colored spots on the youngest leaves of the plant
  • leaves turn pale yellow between the veins
  • leaf death
  • stunted roots

How it Spreads:

  • aphids

Treatment:

  • disease is not treatable
  • discard all infected plant material
  • do not compost

Prevention:

  • keep aphids away from plants; once aphids appear, plants are at risk of infection
  • use floating row covers with hoops to accommodate plant growth
  • use companion plants like asters, nasturtiums, and nettles to attract aphids away from bell pepper crop
  • plant repellent plants like catnip, dill, and marigold
  • interplant cilantro, cosmos, and geraniums to attract ladybugs—which love aphids
  • spray plants with a mixture of 4 parts mineral oil to 1 part dish soap to smother any insects that land on the leaves
  • do not save seeds from infected plants
  • avoid planting in cool, wet weather
  • avoid overhead watering; water at soil level
  • make sure plants have good air circulation and lots of sun
  • rotate crops annually; see crop rotation guidelines above

Southern Blight

Cause: Fungi present in the soil

Symptoms:

  • leaves wilt and turn brown
  • fungus visible on plant stem and surrounding soil
  • discolored stem

How it Spreads:

  • fungus living in the soil
  • disease emerges in times of high temperatures, high humidity, and acidic soil
  • most frequently found in southern U.S.

Treatment:

  • remove and discard infected plant matter

Prevention:

  • buy disease-free seeds
  • avoid planting in cool, wet weather
  • avoid overhead watering; water at soil level
  • make sure plants have good air circulation and lots of sun
  • rotate crops annually

Powdery Mildew

Cause: Fungus overwinters on infected plant debris and emerges in warm, humid weather

Symptoms:

  • white, powdery patches on leaves
  • leaves may curl and turn upward
  • new shoots appear stunted
  • older infections look like a tan or reddish-brown felt covering; these contain spores
  • heavy mildew infections can stunt a plant’s growth

How it Spreads:

  • fungus overwinters in infected plant debris
  • spores do not need moisture to germinate; often called a “dry weather disease”
  • wind, insects, and birds

Treatment:

  • removed and destroy infected plant matter

Prevention:

  • liquid copper fungicide
  • if necessary, sulfur-based fungicide
  • plant disease-resistant varieties
  • remove plant debris
  • rotate crops annually

This is not an exhaustive list of the ailments that may plague your pepper crop. Other potential bacterial/fungal/viral infections include:

  • Bacterial Canker
  • Verticillium Wilt
  • Magnesium Deficiency
  • Nitrogen Deficiency
  • Tomato Spotted Wilt Virus
  • Phytophthora Blight

If you’re not sure what’s wrong with your pepper plants, take good close-up pictures and contact your local garden center or extension center for advice. Many diseases present with similar symptoms, but the treatment for them may vary. In general, you can reduce the likelihood of fungal infections with careful, consistent watering. It’s not a failsafe, but it’s good gardening practice.

Which diseases have you had to treat on your bell peppers? Please tell us how you prevent and handle diseases. If you spot other symptoms on your bell peppers that are not mentioned here, contact your local extension center or garden center for a consult—and please let us know what you discover.

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