Banana peppers are a favored crop known for their mild heat and bright yellow color. When the fruit develops dark spots or patches, it indicates the plant is experiencing stress, as browning is rarely a natural part of ripening. Investigating this discoloration is the first step toward diagnosing and correcting the underlying environmental, physiological, or pathological issue.
Browning Caused by Environmental Stress
Sunscald is a common cause of browning resulting from direct physical damage due to intense, direct sunlight, especially during the hottest parts of the afternoon. This excessive radiation damages the pepper’s outer cell walls, causing the exposed area to first appear pale or bleached white. This damage compromises the cell structure, leading the tissue to rapidly dehydrate and collapse into a soft, sunken, or leathery brown-to-black patch.
Banana peppers originate from tropical regions and are highly sensitive to cold temperatures. Brief exposure to temperatures below 50°F (10°C) can cause significant stress even if frost does not form. This sudden chill can disrupt the normal metabolic processes and cellular structure of the fruit wall. This damage may initially manifest as pitting or darkened, water-soaked spots that later turn an irreversible brown or black color.
Physiological Disorders and Nutrient Issues
Blossom End Rot (BER) is a common physiological disorder, not a disease, linked to a localized calcium deficiency in the developing fruit tissue. BER first appears as a small, water-soaked area exclusively at the blossom end (the bottom tip). This spot rapidly enlarges, becoming sunken, dark brown or black, and developing a characteristic dry, leathery texture.
The problem is usually the plant’s inability to properly absorb and transport calcium, rather than a lack of calcium in the soil. Calcium is immobile and must be continuously supplied via the water-conducting xylem to the fruit. Inconsistent watering, such as cycles of drought followed by heavy irrigation, prevents the steady transport of calcium. This causes the cells at the fruit’s end, furthest from the supply, to collapse due to structural failure.
Other soil conditions complicate calcium absorption. If the soil pH is outside the optimal range of 6.0 to 6.8, it can chemically bind available calcium, making it inaccessible to the roots. Additionally, high concentrations of nitrogen fertilizer stimulate rapid foliage growth, which outcompetes the developing fruit for available calcium, exacerbating the deficiency.
Identifying Fungal and Bacterial Problems
Browning can result from bacterial and fungal infections that target the fruit. Bacterial Spot, caused by the bacterium Xanthomonas campestris pv. vesicatoria, initially appears as small, water-soaked spots on leaves and fruit. On peppers, these spots become raised, rough, and develop a crusty, dark brown or black appearance, distinct from sunscald. This disease thrives in warm, wet, and highly humid conditions, often spreading when splashed onto the fruit from infected soil or leaves.
Anthracnose, a fungal disease caused by Colletotrichum species, is another concern. This infection creates distinct, slightly sunken, circular lesions that are dark brown and can expand significantly on the pepper’s surface. These spots often appear as the fruit nears maturity. In moist environments, the center of the lesions may exude pinkish or orange spore masses.
Steps to Prevent Future Browning
Addressing the causes of browning requires a multi-faceted approach focused on environmental management and plant nutrition.
Preventing Sunscald
To prevent sunscald, ensure that the plant has adequate leaf cover by avoiding excessive or early-season pruning of the upper canopy. If your area experiences periods of extreme heat above 90°F (32°C), temporarily using a light, 30% density shade cloth during the peak hours of afternoon sun can significantly protect the fruit from direct radiation.
Managing Blossom End Rot (BER)
Preventing Blossom End Rot relies heavily on maintaining consistent soil moisture levels throughout the growing season, which is crucial for calcium transport. Deep watering is recommended to encourage a stable water supply. Applying a thick layer of organic mulch can help moderate soil temperature and reduce rapid moisture fluctuations. If BER is a recurring problem, a professional soil test can determine if supplementing with calcium amendments, such as gypsum or lime, or adjusting the soil pH is necessary to improve nutrient availability to the roots.
Controlling Pathogens
Managing infectious diseases like Bacterial Spot and Anthracnose involves strict sanitation and environmental control. Always remove and destroy any infected plant debris immediately to prevent spores or bacteria from overwintering and spreading. Avoiding overhead watering, which keeps foliage and fruit wet for extended periods, and spacing plants properly to promote good air circulation are effective cultural controls against these moisture-loving pathogens.