The appearance of brown spots on jalapeño peppers is common for growers and consumers. These blemishes range widely in origin, from harmless, natural scarring on the fruit’s skin to indicators of serious underlying plant distress. Identifying the specific visual characteristics of the spot determines the cause, which can be an environmental stressor, a nutritional imbalance, or a transmissible pathogen. Understanding the root cause is necessary to effectively manage the issue and protect the harvest.
Corking: Natural Skin Scarring
The most frequent and least concerning form of browning is corking, which is essentially the pepper’s version of a stretch mark. Corking appears as a network of thin, horizontal, tan-to-brown lines across the pepper’s surface. These lines are scar tissue that forms when the fruit’s internal pulp grows faster than its outer skin can expand.
This rapid growth is often triggered by fluctuations in water uptake, such as a dry period followed by heavy irrigation or rainfall. Corking is a non-pathogenic process, meaning the fruit is safe to consume. Many pepper enthusiasts seek out corked jalapeños, as the phenomenon is associated with higher capsaicin levels, suggesting a spicier flavor.
Physiological Stressors
Brown spots can also arise from non-infectious environmental and nutritional issues, grouped under physiological disorders. These problems are localized to the affected fruit and do not spread from plant to plant.
Blossom End Rot (BER)
Blossom End Rot (BER) begins as a small, water-soaked spot on the blossom end of the pepper, quickly enlarging into a sunken, leathery patch that turns dark brown or black. BER is caused by the plant’s inability to translocate adequate calcium to the developing fruit. This problem is exacerbated by inconsistent soil moisture or excessive nitrogen fertilization.
Sunscald
Sunscald is a common physiological disorder, presenting as light, dry, or papery patches on the fruit’s side most exposed to intense sunlight. This is essentially a sunburn, causing the tissue to become bleached white or tan. Sunscald often occurs when the pepper plant has lost too many leaves, leaving the fruit vulnerable to solar radiation.
Infectious Diseases Causing Lesions
Pathogenic organisms represent the most serious cause of brown spots, as these conditions are transmissible and can rapidly spread throughout a garden. The appearance of these spots is usually distinct from corking or sunscald.
Bacterial Leaf Spot
Bacterial Leaf Spot, caused by the bacterium Xanthomonas campestris pv. vesicatoria, initially manifests on the leaves as small, water-soaked lesions that turn dark brown or black. On the fruit, the bacteria cause small, raised, scab-like spots that give the surface a rough texture. The bacteria thrive in warm, wet conditions, often leading to premature leaf yellowing and defoliation.
Anthracnose
Anthracnose is a fungal disease caused by species of Colletotrichum. This infection creates water-soaked, circular, and often sunken lesions on the fruit that eventually turn dark brown. A distinguishing feature of late-stage Anthracnose is the development of concentric rings within the spot, which may contain a wet, gelatinous mass of salmon-colored spores. The fungi often infect the fruit when it is small, but symptoms may not become visible until later in the season, particularly during periods of high humidity and frequent rainfall.
Managing and Preventing Brown Spots
Implementing targeted cultural practices is the most effective way to prevent and manage brown spots.
Managing Physiological Disorders
For physiological disorders like Blossom End Rot, maintaining consistent soil moisture is paramount, as water fluctuation impedes calcium uptake. Applying a nitrate-based calcium supplement to the soil can help correct a mineral deficiency, but consistent watering remains the primary fix.
Preventing sunscald requires promoting a dense canopy of foliage to shade the developing fruits. This is achieved by avoiding heavy pruning and managing leaf-destroying pests or diseases. If the fruit is affected by minor sunscald or corking, it is safe to consume after cutting away the damaged portion.
Controlling Infectious Diseases
Controlling infectious diseases relies heavily on sanitation and chemical intervention. For Bacterial Leaf Spot, practices include treating seeds with hot water or a dilute bleach solution before planting, and applying copper-based bactericides at the first sign of infection. Managing Anthracnose involves avoiding overhead watering to prevent the splash dispersal of fungal spores and applying fungicides containing copper or mancozeb during the growing season. Any fruit showing signs of extensive bacterial or fungal rot should be immediately removed and discarded to prevent the disease from spreading.