At this time of year the Ziplocs start to change from a preponderance of "Bug Bags" to "Leaf Bags". While we are still seeing signs of tomato horn worms, aphids, ladybug larvae and squash beetles ...we are also seeing large amounts of gardeners with leaf scorch. The best way to describe it is a brown area around the outside of the leaf. Most of the time you will see this on young trees that do not yet have a good root system established. However, Sycamores are one tree that suffers from this until they are 3 or 4 years in the ground. The good thing is it that you probably won't lose the tree over this. It might make it unsightly though. Our recommendation is to check the watering ~ see if it needs to be stepped up in this heat ~ and then mulch...mulch....mulch the root zone area. There are all different kinds of mulch you can use from grass clippings to leaf mold. Bagged products come in an assortment from redwood to cedar, cocoa mulch to compost. We do not ever recommend rock be placed around your trees or shrubs. Think about how you feel when you stand in an asphalt parking lot with no shade....your feet get HOT! The roots of your trees are the same. They like their roots cool too. Also keep in mind, plants already stressed from lack of water are more vulnerable to diseases, insects and other environmental factors that can further damage them.
Of course you could have a bug eating on your plant. If you are concerned about the way your tree is looking, bring us a leaf and we will do our best to diagnose the problem for you....that's what we are here for.
See you soon, Susan.