Cause Heat stress is the primary cause of leaf scorch. Drought stress and use of excess fertilizer can also cause a leaf scorch symptom.
Symptoms Leaves affected by heat stress will show symptoms shortly after an exceptionally hot, sunny day that has been preceded by more moderate temperatures. The leaf tissue becomes bleached looking, especially those portions of leaves that were facing the sun. Affected tissue is paler green than usual, tending toward yellow. Leaves underneath those on top will be less affected or completely unaffected. Occasionally there will be a leaf with a darker green patch where the leaf above protected it from the sun. Severely affected leaves will become necrotic where the heat injury was the most intense. Leaves scorched from excess fertilizer or from insufficient water will have marginal necrosis.
Cultural control Provide adequate water during the summer for plants affected by drought stress. There is no remedial action that can be taken once leaves are scorched by the sun, but effects are not fatal and new leaves will soon cover damaged ones.