While most pest and disease problems that plague vegetables are treatable with some form of chemical or organic spray, black spot on pepper plants are caused from an environmental disorder. Subsequently, altering the growing area and conditions of a pepper plant will significantly lower the odds of black spot from affecting your pepper plants. Black spot is also sometimes referred to as bottom rot, but whatever you choose to call it, treat it quickly to avoid a complete outbreak.
Buid Up Calcium in the Soil
Amend the soil to alter the calcium deficiency. Add lime by sprinkling it to the base of the pepper plant to increase calcium content. (Lime is readily available at garden centers or nurseries.) Maintain a soil pH of 6.5 to help curb future outbreaks.
Use Proper Watering Techniques
Water the plant thoroughly and evenly. Allow the roots to absorb the added calcium and transfer it to the pepper plant. Strive for even soil moisture during the day and night. (Additional watering may be necessary during the hotter parts of the day.) Provide 1 inch of water each week for proper development.
Mulch Pepper Plants
Mulch the area to help moderate soil temperature which will optimize root function, better enabling the pepper plant to absorb calcium. Use black polyethylene mulch in the spring and silver polyethylene mulch in the summer and fall. Apply a 1-to-2 inch layer of the material around the base of the plant.