See:
Maple (Acer spp.) - Leaf Scorch
Cause Many possible causes. Plants under stress (such as from drought or heat) may not provide sufficient water to their leaves. Trees placed near heat-reflecting surfaces such as buildings or pavement often suffer from heat stress. Other possible causes of scorch include damage to roots or stem, soil compaction (which can reduce drainage, resulting in root damage), or excessive salts from overuse of chemical fertilizers. In the Southeastern United States, the bacterium Xylella fastidiosa has been associated with these symptoms in oak as well as red maple, elm, and sycamore.
Symptoms Leaves edges turn bronze, then later brown and dry. In severe cases, the scorch may spread to areas between veins or entire twigs may die back. Sun or heat related stress will occur primarily on the south side of plants.
Cultural control Prevention is the key as 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 eventually cover damaged ones.
- Avoid injury to roots and trunk.
- Do not over-fertilize.
- Do not pave over the root zone of established trees.
- Do not plant trees directly against the sunny sides of buildings.
- Heavy foot traffic, construction, and heavy equipment can compact soil and damage roots.
- Irrigate affected plants during dry periods. Wet the entire root zone but do not overwater. Water oaks deeply but infrequently.
Chemical control Use before hot summer weather. Always follow pesticide label directions. Anti-transpirants or anti-desiccants are not recommended since they have not been shown to be effective at preventing heat or cold-induced desiccation of plants beyond their normal adaptations.
- Surround CF at 6.25 to 37.5 lb/A plus a surfactant. A dry white film will result on all treated plant parts. 4-hr reentry. O
Reference Gould, A. B., and Lashomb, J. H. 2007. Bacterial leaf scorch (BLS) of shade trees. The Plant Health Instructor. APSnet Feature, St. Paul, MN. 18p.DOI: 10.1094/PHI-I-2007-0403-07
Chalker-Scott, L. 2010. The myth of antitranspirants, pp. 183-189. In The Informed Gardener Blooms Again, University of Washington Press, Seattle, WA.