Growing banana peppers often leads home gardeners to encounter the confusing sight of black discoloration on ripening fruit. This unexpected color change prompts concern about the health and edibility of the harvest. Blackening is not caused by a single issue, but stems from a range of distinct causes, varying from natural changes to signs of environmental stress or plant disease. Understanding the specific nature of the discoloration is the first step toward successful diagnosis and management.
Harmless Color Changes During Maturation
One of the most common reasons for dark streaks or patches is a natural process tied to the pepper’s genetics and environment. This harmless discoloration is caused by the pepper producing anthocyanin, the pigment responsible for purple and blue colors in fruits like blueberries.
This pigment is a protective response, typically triggered by high light intensity or intense sun exposure, acting like a natural sunscreen for the fruit. The dark areas appear as temporary dark purple or black streaks before the pepper matures to its final yellow, orange, or red color. Since this is a cosmetic change and not a sign of decay or disease, peppers displaying these black streaks are perfectly safe to eat.
Physical Damage from Sun and Water Imbalance
Blackening can be a secondary symptom of non-infectious physical damage caused by environmental factors, primarily sun exposure and inconsistent hydration.
Sunscald
Sunscald occurs when a pepper fruit is suddenly exposed to intense, direct sunlight, often after the plant loses foliage due to pruning or disease. The exposed skin first develops a soft, white, or yellow blistered patch on the side facing the sun. This damaged area then dries out and collapses, becoming thin, papery, and often turning dark brown or black as it becomes colonized by secondary fungi. Unlike disease, sunscald is confined to the exposed surface of the fruit.
Blossom End Rot (BER)
Blossom End Rot (BER) is a physiological disorder caused by the plant’s inability to move enough calcium to the developing fruit. BER is a localized calcium deficiency in the fruit, frequently exacerbated by wide fluctuations in soil moisture. The symptom begins as a dark, water-soaked spot at the blossom end, or tip, of the pepper. This spot enlarges, becoming sunken, leathery, and dark brown to black as the tissue dies.
Identifying Fungal and Bacterial Causes
Infectious black spots on banana peppers are typically caused by specific pathogens, distinguishing them from environmental damage by their appearance and spread. Correctly identifying whether the black spot is a superficial pigment, a dry environmental lesion, or a deep, spreading infectious spot is important for immediate management to prevent further crop loss.
Anthracnose
One common issue is Anthracnose, a fungal disease caused by species of the genus Colletotrichum. This infection produces characteristic sunken, circular lesions on the fruit, which start as water-soaked spots. As the lesions mature, they develop small, dark dots arranged in concentric rings and may exude a pink or salmon-colored, sticky mass of spores in humid conditions.
Bacterial Spot
Another serious problem is Bacterial Spot, caused by the bacterium Xanthomonas euvesicatoria. On the fruit, this manifests as small, raised, warty spots that are initially lighter green but quickly turn brown or black, resembling scabs. Bacterial Spot is often accompanied by lesions on the leaves, which appear as dark, greasy spots. The disease is easily spread by splashing water and touching the plants when they are wet.
Practical Steps for Future Prevention
Preventing blackening requires a multi-pronged approach based on the underlying cause, starting with careful management of water and light.
Managing Environmental Stress
To address Blossom End Rot, maintaining consistently even soil moisture is the most effective action, ensuring steady calcium uptake by the plant roots. Maintaining a soil pH around 6.5 can also support a healthy mineral balance. To minimize Sunscald, ensure the plants have adequate foliage, as leaves naturally shade the developing fruit from intense afternoon sun. Providing a temporary shade cloth during the hottest part of the day can protect vulnerable peppers.
Disease Prevention
Managing infectious diseases requires a focus on sanitation and cultural practices. Avoid overhead watering, which can splash fungal and bacterial spores onto the foliage. Practice crop rotation, meaning peppers should not be planted in the same soil area more than once every three years. Selecting pepper varieties that are specifically labeled as resistant to Bacterial Spot can significantly reduce the likelihood of this disease taking hold.