The intense heat and sun exposure can cause a burning or browning of plant tissue called sunscald. This is an abiotic stress. Even the most heat seeking plants can get too much of a good thing. Pepper sunscald is common when the plants are forming fruit in the late summer heat. Sunscald on pepper plants primarily affects the fruit, although the foliage may get white streaks and dry edges. White scars of tougher tissue are formed at the burned sites. In immature peppers, the affected areas are light green. The areas can also appear dry and sunken. The fruit may crack and split where the scald occurs. Sometimes, cracking can allow bacteria or fungi into the fruit. In these cases, the fruit will soften and the burnt areas will become rotten. Sunscald on pepper plants can cause the fruit to get woody and tough and ruin it cosmetically.
There are some pepper varieties that are resistant to sunscald. Planting these will reduce the chance that the peppers get damaged.
The best prevention is to encourage lots of foliage by growing healthy robust plants early on. Fertilize with an organic fertilizer prior to fruit set and after fruit set for better leaf growth to shade the peppers. Preventing sunscald on pepper fruit may require mechanical intervention. Row covers or forms erected with shade cloth have the ability to deflect much of the intense light and protect the plants from pepper sunscald. Providing optimum pest control is another way to reduce the problem. Defoliation amplifies the sun’s effects. Watch for pests and begin a treatment program right away.
Most of the damage on sun scalded peppers is cosmetic and the fruit is perfectly good to eat. Remove any fruit that has been affected before it gets soft. You may want to pare out the affected areas, especially where the fruit has gone mushy or is tough. Sometimes only the skin has been damaged and you can roast these peppers and pull off the skin.