Sunscald is caused by intense concentration of the sun’s heat on plant tissue. Sunscald is not considered to affect yields. Injury often occurs when bright sunny days follow cloudy, warm and humid conditions.
Sunscald can occur on leaves, stems or pods and most often affects new, tender leaf tissue at the top of the plant. Affected leaves can exhibit brown scorched leaf tissue or white discolouration of upper exposed leaves. Leaf tissue becomes necrotic and crumbles easily, resulting in a ragged leaf appearance. Serious sunscald may cause many leaves to drop.
On pods, sunscald starts as tiny brown-reddish spots that gradually lengthen. Shaded plant parts within the canopy should not exhibit symptoms. Symptoms on pods may be mistaken for bacterial disease, but should not damage the beans within the pods as is often seen with bacterial disease.
Plants that are rapidly growing, such as areas that have excess nitrogen fertilizer, may be more prone to sunscald if weather conditions are conducive to sunscald injury. Sunscald is not considered to affect yields.