Cause Drought or heat stress may cause leaf scorch. In general, there is not enough water reaching the leaf margin to keep up with transpiration. An interruption of the vascular system, as with cankers or squirrel damage, can also produce these symptoms. Or, too much salt (from over-fertilization) has been translocated to the leaf margins. In the Southeastern United States, the bacterium Xylella fastidiosa has been associated with these symptoms in red maple, elm, oak, and sycamore. Based on periodic testing, this bacterium has never been found on maple trees with scorch symptoms in the PNW.
Symptoms Leaf margins and areas between veins turn brown. Twig dieback may follow. Symptoms can be severe in eastern Washington when bright, hot days follow cool, moist weather during leaf emergence. Sun or heat related stress will occur primarily on the south side of plants.
- When irrigating, wet the entire root zone infrequently during the summer. Avoid over-watering.
- Provide good drainage and avoid soil compaction.
- To avoid reflected heat, do not plant close to buildings or paved surfaces, and avoid rock and black plastic mulches.
- Avoid root and trunk injury.
- Do not over-fertilize.