Cause Drought or heat stress may cause leaf scorch. Not enough water reaches the leaf margin to keep up with transpiration. Or, too much salt (from overfertilization) 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. No work has been done in the Pacific Northwest on the bacterium's association with scorch symptoms on these trees.
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.
- When irrigating, wet the entire root zone. 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 overfertilize.