Pepper plants are a warm-weather vegetable that can be affected by a number of growing conditions and pests. Pepper plant leaves will turn white as a consequence of extremes in growing conditions, plant infections or pest infestations. Diagnosing the cause of white leaves on the pepper plant require you to look for other symptoms or be aware of dramatic shifts in growing conditions.
Suddenly cool temperatures or a quick drop in temperature will affect pepper plant leaves, turning them white. Pepper plants do not tolerate even a light frost. This problem with pepper plants happens most frequently when pepper plants have not been hardened off before they are transplanted outdoors. Hardening off is the gradual process of introducing pepper plant seedlings to the outdoors so there is less of a shock when they are transplanted.
Powdery mildew is an infection that can affect the entire pepper plant, including the fruit. Powdery mildew most often begins as small white spots on the leaves of the pepper plant but can spread quickly to cover entire leaves as well as the stem and fruit. Powdery mildew prefers humid climates, so plant your pepper plants in well-draining soil that receives plenty of direct sunlight.
Pepper plants require significant amounts of sunlight to grow properly, but too much strong or direct sunlight can create sunscald in your pepper plants. Sunscald produces brown to white blotches on the leaves and fruit of your pepper plants. Sunscald occurs when there is too much and too intense of direct sunlight. Do not over-prune your pepper plants when they are outdoors as the foliage provides protection to the pepper plants.
Aphids are small, orange pests that live on the underside of the pepper plant leaves. Aphids live in clusters and secret a sticky substance. Aphids affect the pepper plant by sucking the nectar from the leaves, creating light brown to white dots and holes. Eventually, aphids will cause the pepper plant leaves to become light brown to white and paper thin. If left untreated, aphids will eventually kill a pepper plant.