The hot, dry weather of the last few weeks has been stressful for peppers, resulting in the appearance of blossom end rot, especially in early fruit sets. Blossom end rot is the result of plant stress brought on by periods of dry vs moist soil. Calcium deficiency in the plant is the cause but applying calcium to the foliage won’t help. Calcium is relatively insoluble and plants under stress can’t move it to flowers and developing fruit. It is a vital component of plant cell walls and the matrix that holds the cells together. When fruits start to form without sufficient calcium the tissues soften and die. Secondary molds often colonize the dead tissue.
Blossom end rot becomes less problematic with more consistent soil moisture and as the plants grow and develop their root systems.
Another fruit problem reported recently and related to hot, sunny weather is sunscald. Sunscald can appear similar to blossom end rot – it appears on the part of the fruit exposed to the sun. Sunscald spots are tan in color, and eventually become dry and papery. There isn’t much that can be done about sunscald except to encourage good foliage coverage by appropriate fertilization.
Anthracnose also causes lesions on pepper fruit, but the disease is caused by a fungus dispersed by rainsplash (or overhead irrigation); it is less severe in dry than rainy weather. This disease is managed by application of fungicides.
Thanks to Carri Jagger for the blossom end rot and sunscald photos.