Common Pepper Plant Diseases and Treatments

Fungus related diseases are the most common in Pepper plants. Plants generally display discoloration, spots, and poor growth. Pepper leaves may yellow and drop off. Many of these diseases of pepper plants can be prevented by:

  1. Planting disease-resistant varieties
  2. Rotating vegetable crops every other year
  3. Implementing proper watering and cultivation techniques.
  4. Keeping the area free of debris and excess weeds
  5. Insect Control

Common Diseases of Pepper Plants


Caused by a fungus [Colletotrichum acutatumi]. Circular or angular sunken lesions develop on immature fruit of any size.

Often multiple lesions form on individual fruit. When the disease is severe, lesions may coalesce. Pink to orange masses of fungal spores forms in concentric rings on the surface of the lesions.

Anthracnose can be introduced into a crop on infected seed. During warm and wet periods, spores are splashed from diseased to healthy fruit.

Anthracnose Treatment

Liquid copper-based fungicide sprays should be applied weekly, starting when the foliage first begins to develop. Spray in the morning, not under the hot sun. Seeds can also be treated prior to planting.

Phytophthora Blight

Phytophthora Blight is caused by the fungus Phytophthora capsici.

Other names applied to this disease of peppers are Damping-off, Phytophthora root rot,crown rot, and Stem and fruit rot.

Diagnosing Phytophthora Blight

All of these names can apply since all parts of the pepper plant are affected. Plants infected at early stages die off rapidly, Plants infected later show an irreversible wilt . Often a number of plants in a row or in a roughly circular pattern will show these symptoms at the same time.

Preventing Phytophthora Blight

Phytophthora blight is soilborne and more common on inadqautely drained soils, and areas where proper cultural practices have not been maintained.

Pepper Plants should not be rotated with related crops such as eggplant, tomato, cucumbers, squash and pumpkin for at least 3 years.

Phytophthora Blight Treatment

Fungicides are of limited value over the long run because the fungus quickly reinvades treated soil and develops resistance to a particular fungicide that can develop rapidly. For short term treatment, Agrigos and Actinovate are registered for the treatment of Phytophthora in its varied forms.

Gray Leaf Spot

Diagnosing Gray Leaf Spot

Circular spots on leaves, the spots are at first brown, later turning to various shades of white with sunken centers, and reddish-brown margins. Spots may appear on stems also.

Gray Leaf Spot Treatment 

Copper-based fungicide sprays should be applied weekly, starting when the fungus is first noticed. Spray in the morning, not under the hot sun.

Gummy Stem Blight Diagnosis and Treatment

Effects the leaves, stems, and fruits of all cucurbits and pepper plants. Circular, tan to dark brown spots appear on the leaves, often first at the margins, and enlarge rapidly until the entire leaf is affected . Satisfactory chemical control is possible with regular applications of protectant fungicides.

Blossom End Rot – Prevention, Diagnosis and Treatment.

See: Plant Nutrient Deficiencies

Blossom End Rot occurs as a slight discoloration or a severe dark sunken lesion at the blossom end; it is caused by temporary insufficiency of water and calcium and may occur under high-temperature conditions when the peppers are rapidly growing.

Blossom End Rot Recommended Treatments

Ripe rot occurs on ripening fruit that is kept in warm, humid conditions. Harvest peppers prior to use and store any unused peppers in a cool area away from direct light.

Sunscald like “ripe-Rot” is not actually a disease, just as the name implies it is the result of too much exposure to direct sunlight. The fruit may become light colored and feel dry and papery.

Alternaria Rot 

The presence of black Alternaria rot, especially on the stem end of the pepper is a symptom of chilling. Discoloration of the seed cavity is another symptom. This rot can also be caused by an injury to the fruit/vegetable itself, not the plant.

There is no effective treatment for this disease other than prevention via proper gardening techniques.

Cercospora Leaf Spot Disease 

A picture of Cercospora disease on a plant leaf.

A fungal disease. It is a common problem in home gardens and can reduce crop yield and cause defoliation. It should be treated promptly and preventative measures are taken to prevent it from recurring in later seasons.

Cercospora leaf spot initially appears as small circular spots on leaves. these spots enlarge as the disease progresses. They vary in color from dark green to murky brown with purple edges. In advanced stages, the leaves become yellow and fall off. Products such as Immunox and Cleary’s 3336 won’t cure an existing infestation but can prevent its spread to other healthy foliage.

Bacterial Spot 

Produces circular scabby spots on immature fruits and on leaves. Tomatoes and Sweet peppers are affected. The bacterium is seed-borne and is often carried on diseased transplants. It can also occur in certain weeds. It overwinters in soil and on old plants and pepper plants. Bacterial spot is favored by warm temperatures, high humidity, long dew periods, and driving rain. Recommended treatment – Potassium Bicarbonate based Fungicides.

Pepper speck 

Appears as spot-like lesions that penetrate the fruit wall; cause is unknown; some varieties are more susceptible than others.

Pepper Insect Problems: Treatment and Prevention

There are many insects that commonly attack pepper plants, sweet peppers more than the hot ones.

Frequent inspection and removal are key to controlling or eliminating infestations. Since many insects overwinter in nearby brush and weed, it is essential that you keep the garden area free of debris.

The major pests that affect peppers include:

  1. Aphids
  2. Mites are prolific plant disease transmitters
  3. Pepper Weevil, which is black colored, gray or yellow marked
  4. Cut Worms
  5. Flea Beetles
  6. Leaf Miners
  7. Tomato Horn Worm
  8. Pepper Maggot See – Plant Maggots

Cultural Practices to Avoid Disease and Ward Off Pests

Purchase vigorous, healthy plants from a reputable supplier. Pepper Plants, being susceptible to diseases, viruses, and insects, some varieties have been bred or hybridized to be resistant to certain pests. Resistance to these pests is usually listed on the plant label using the following abbreviations:

  • V = Verticillium Wilt
  • F = Fusarium Wilt
  • FF = Fusarium Wilt race 1 and 2
  • N = Nematode
  • T = Tobacco Mosaic Virus
  • A = Alternaria (Early Blight)
  • TSW = Tomato Spotted Wilt

Remember that resistance to these problems does not mean they are 100 % immune, good cultural practices are still important.

  1. Crop Rotation in your garden planting area.
  2. Remove and destroy all plant refuse in the fall and use deep cultivation to bury any remaining refuse.
  3. Do not place diseased plants in the compost heap, as this will only serve to carry bacterial or fungal infestation into the next growing season.
  4. Avoid overwatering. Use surface watering methods. Do not handle plants when the vines are wet.
  5. Weeds compete with vegetables for soil moisture and nutrients and also serve as hosts for insects and disease-carrying bacteria and fungus. Control weeds in and around the garden.
  6. Control insect pests such as aphids, which are known to transmit diseases from plant to plant.
  7. Use plastic or organic mulches to reduce disease and blossom-end rot problems.
  8. Choose a sunny location for your tomatoes. Leaf disease problems are much less likely to occur in a sunny location than in a shady one.
  9. Apply recommended fungicides according to label directions at the first sign of leaf spot diseases
  10. Remove abnormal or unhealthy appearing plants as soon as they are observed. To reduce the spread of suspected diseases wash hands and tools with a mild detergent after handling suspect plants.