Peppers are among the most popular garden vegetables, and seeing fruit change color normally signals approaching harvest. When the color change is an unwelcome brown instead of the expected red, yellow, or orange, it indicates a problem with the plant or the fruit itself. Browning on peppers stems from one of three primary causes: issues with the growing environment, physical damage from pests, or the presence of a microbial disease. Diagnosing the specific pattern of discoloration is the first step toward saving the rest of your harvest.
Environmental Stress and Nutritional Deficiencies
Sunscald is a common physiological disorder resulting from environmental factors, occurring when fruit is suddenly exposed to intense direct sunlight, especially during periods of high heat. This exposure causes large, bleached, or pale spots on the side of the pepper facing the sun. These spots dry out, becoming thin, papery, and light brown or white in color. Although the heat-damaged spot itself is not a disease, it frequently becomes an entry point for secondary fungi that cause the entire pepper to rot.
Blossom End Rot (BER) frequently causes browning, affecting the bottom or blossom end of the fruit and creating a dark, sunken, leathery patch. This disorder results from the plant’s inability to move calcium to the rapidly developing fruit tissue. This localized deficiency is triggered by fluctuations in soil moisture, such as alternating between dry spells and heavy watering, or by excessive nitrogen fertilization. Maintaining a consistent watering schedule and using mulch stabilizes soil moisture, allowing the plant to absorb calcium properly.
Extreme temperatures also contribute to browning, particularly on the foliage and fruit tips. Cold damage or chilling injury from frost can cause necrotic, brown discoloration on the exposed plant tissue. This damage is often widespread across the plant, affecting the tips of leaves and fruit that have not been adequately protected from the elements.
Damage Caused by Pests
Browning on the pepper surface can be a secondary symptom of mechanical damage caused by pests. The Pepper Weevil, a small, dark beetle, causes damage when its larvae tunnel into the fruit near the core. The initial puncture site from the adult laying eggs or subsequent feeding damage leads to discoloration and premature fruit drop, as the fruit tissue dies around the wound.
Smaller pests, such as Thrips and Mites, feed by rasping or piercing the surface cells of the pepper fruit. This feeding damage creates a symptom called “flecking,” which appears as tiny, silvery, or bronzed speckles. These speckles may merge, giving the fruit a rusty or brown, scarred appearance. Thrips can also cause fruit deformity and spread viruses that lead to further discoloration and distortion.
Larger pests like slugs and snails may also cause browning, particularly on fruit resting on or near the ground. Slugs use rasping mouthparts to chew irregular holes in the pepper skin. While the initial damage is a feeding wound, the damaged area often turns brown or necrotic as the plant attempts to heal. The presence of a silvery mucus trail on the plant or surrounding soil indicates these mollusks are the culprit.
Identifying Pathogenic Infections (Fungal and Bacterial)
Discoloration presenting as distinct, isolated spots or lesions often indicates a microbial pathogen. Bacterial Spot, caused by Xanthomonas bacteria, thrives in warm, humid conditions. On the fruit, it appears as small, water-soaked spots that become rough, raised, and scab-like, eventually turning dark brown or black. Since the bacteria are easily spread by splashing water, growers must avoid overhead irrigation and working with wet plants.
Fungal infections also cause browning, with Anthracnose being a common concern, particularly on ripening fruit. This disease, caused by Colletotrichum species, begins as small, water-soaked areas that quickly become sunken, dark, and circular lesions. A distinguishing feature is the development of masses of salmon-pink or orange spores within the sunken area, which can coalesce and lead to complete rot. Management involves removing infected material, using plastic mulch to create a barrier between the soil and the fruit, and ensuring good air circulation to reduce humidity.