Troubleshooting guide: Why is there black on my pepper plant?

Pepper plants are a delightful addition to any garden or vegetable patch, but when they start turning black, it can be a cause for concern. Blackening on pepper plants can be attributed to various factors, ranging from minor issues to more severe problems that can negatively impact the plant’s health. 

In this troubleshooting guide, we will explore the different causes of blackening on pepper plants and provide insights on diagnosing and addressing them promptly. 

Causes of blackening on pepper plants

Understanding the reasons behind blackening on your pepper plant is crucial for maintaining its health. Several potential causes can lead to this phenomenon, ranging from harmless natural occurrences to more severe issues that can negatively impact your plant’s well-being. By identifying these causes, you can take appropriate measures to address the problem and ensure the optimal growth of your pepper plant.

Pepper fruit is turning black

When your pepper fruit starts to turn black, it could be due to various factors, some of which are normal occurrences, while others may require attention. Let’s explore the different causes and what you can do about them.

Natural coloration

In some instances, the blackening of peppers is simply a natural part of their color progression as they ripen. Some varieties, such as jalapeƱos, transition from green to a very dark color that may appear black, eventually turning red. Additionally, peppers like black pearl and purple jalapeƱos naturally exhibit a dark purple or black color. If the fruit seems firm and healthy apart from the color change, there is likely no cause for concern.

Sunscald

Blackening of pepper fruit can also result from sunscald. This occurs when the fruit is exposed to excessive sunlight, causing minor discoloration on the surface. However, severe sunscald can soften the skin, making the fruit susceptible to mold growth. To prevent sunscald, consider using a shade cloth with up to 50% shade cover to shield your plants from intense sunlight.

Bottom of the fruit turning black

If you notice the bottom of your pepper fruit turning black and becoming mushy, it could signify blossom end rot. This condition is typically caused by issues related to calcium uptake in the plant. Contrary to common belief, blossom end rot usually does not result from calcium deficiency in the soil, so adding calcium-rich supplements like crushed Tums or eggshells around the base of your plant or using calcium fertilizers won’t effectively address the issue.

Blossom end rot is often associated with watering problems, such as extended periods of drought followed by heavy watering. Additionally, imbalances in soil pH can contribute to this condition. To minimize the risk of blossom end rot, it is essential to water your plants consistently without overwatering and ensure that the soil maintains a balanced pH, preferably neutral to slightly acidic.

Leaves turning black

When you observe blackening of the leaves on your pepper plant, it is important to identify the underlying causes. Here are several factors that could contribute to this issue:

Overwatering or excessive moisture 

Black leaves on pepper plants can indicate overwatering or excessive moisture. Watering your plants from above and the leaves remaining wet for prolonged periods can lead to blackening. Similarly, extreme rainfall or high humidity levels can contribute to this problem. To address this, water your plants appropriately, allowing the soil to dry out slightly between waterings. Additionally, consider adjusting your watering technique or providing adequate drainage to prevent excessive moisture accumulation.

Cercospora leaf spot

Cercospora leaf spot is a fungal disease that causes dark brown spots on the leaves with lighter grey centers. If you notice these characteristic spots on your pepper plant leaves, it is likely due to this disease. To prevent its spread, promptly remove any foliage that appears infected. If your plants are in pots, separating infected plants from healthy ones is advisable to avoid further contamination. Practicing crop rotation can also help reduce the risk of this disease affecting your plants in the future.

Overfertilization

Overfertilization can result in blackening of the leaves on your pepper plants. If you have used excessive amounts or overly strong fertilizers, it can cause stress to the plant and manifest as blackened foliage. Refrain from fertilizing for a few weeks to allow your plants to recover. During this time, reassess your fertilizer regimen and ensure you use a balanced fertilizer at the appropriate strength, following the recommended guidelines.

Natural dark foliage 

Some pepper varieties naturally exhibit dark foliage that may appear black or purple. Examples include black pearl peppers and black olive peppers. If your pepper plant has this characteristic dark foliage and the leaves are healthy, there is typically no cause for concern.

Black streaks on the stem, nodes on the stems are black

If you notice black streaks on the stem or nodes of your pepper plant, there may not be a cause for alarm. In some cases, such as with bell peppers or purple cayenne, it is natural for the stems to develop dark purple or black streaks and the nodes to exhibit a darkened color. As long as the rest of your plant appears healthy, there is usually no reason to be concerned.

These natural colorations of the stem and nodes do not indicate any underlying issues with the plant’s health. However, it’s always a good practice to closely monitor the overall well-being of your plant if you have any concerns. If the darkened nodes or vertical streaks on the stem are the only symptoms present, your plant is likely perfectly fine and exhibiting its unique natural characteristics.

Remember to observe the plant for any additional signs of distress or disease, but rest assured that the presence of blackened nodes or dark streaks on the stem alone is typically nothing to worry about.

Black nodes and other symptoms

When you observe blackening of the nodes/joints on your pepper plant, accompanied by other symptoms such as black, mushy fruit, yellowing, and wilted leaves, it may indicate the presence of Fusarium wilt, a fungal disease. Fusarium wilt is a soil-borne disease, which means it can be challenging to eradicate, and planting nightshade plants (peppers, tomatoes, eggplants, tomatillos) in the same soil for several years can risk the spread of the disease.

Tomato plant with fusarium wilt
Tomato plant with fusarium wilt. Image credit: F.D. Richards (CC BY-SA 2.0)

Unfortunately, there is currently no known cure for Fusarium wilt. If there is still time, purchase new pepper starts and plant them in a different location free from the disease. In future growing seasons, it is recommended to only plant varieties that are resistant to Fusarium wilt in the affected area.

If your pepper plants are in pots or grow bags, it is crucial to discard the soil and thoroughly sterilize the containers before planting any other nightshade plants in them. This will help prevent the disease from persisting and affecting future crops.

Fusarium wilt is a severe concern for pepper plants and other nightshade crops. Taking proactive measures to avoid further spread and selecting resistant varieties are essential steps in managing the disease and preserving the health of your plants.

Black ring around the stem

If you notice a black ring around the stem of your pepper plant, it may be a sign of Phytophthora blight. Phytophthora blight is a fungal disease that can have severe consequences for your plants, especially young ones. Mature plants may continue to grow, but dark lesions may develop on the stem near the soil.

As the disease progresses, these lesions spread, causing the plant to wilt and turn yellow. Additionally, the lesions can extend to the leaves, resulting in the formation of dark spots. The infection may also affect the fruit, causing blackening and shriveling. Phytophthora blight obstructs the cells in the stem, preventing the plant from effectively transporting nutrients and water from the roots to the leaves and fruit.

pepper plants that are wilted and dried because they have blight
Wilted pepper plants infected with blight

Preventing the occurrence of blight is crucial. Implementing crop rotation practices is essential, avoiding planting nightshade crops in soil known to be infected with blight. Overwatering and overhead watering, which can lead to prolonged moisture on the stems and leaves, can contribute to blight development and should be minimized.

It’s important to note that there is currently no known cure for blight. Once your plant is infected, it is challenging to control the disease. Therefore, prevention and early detection are key. Taking proactive measures, such as practicing proper crop rotation and minimizing conditions favorable to blight development, can help safeguard your plants from this destructive fungal disease.

While blackening on pepper plants can be worrisome, it is important to approach the issue with optimism and determination. By identifying the specific causes and taking swift action, you can effectively address the problem and restore your pepper plants to their vibrant and fruitful state.

Remember, some blackening may be completely natural or harmless, while others may require intervention. You can overcome these challenges with proper care, attention to watering, disease prevention strategies, and a proactive approach and enjoy a thriving pepper garden.

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