Okay, as a Certified Arborist I may be able to shed some light on what is going on with the Birch trees in your area. The links that lin has listed are very helpful. To begin:
1- Birches drop their leaves during really hot weather. Even if it is short lived- it is a way the tree manages its resources for self preservation. This is true even with a wet spring.
2- Birches will shed damaged leaves from Jap beetles, Spring leaf miner, and for any other leaf damaging insects. Once again, self preservation management.
3- Bronze head Borer lays its eggs in weaker brich stems or plants. The eggs hatch in the furrows of the bark and the larvae burrows into the wood and feeds on the cambial tissues beneathe the bark. This usually happens in the early parts of the summer. The borers will kill trees in parts or entire plants if the infestation is really bad. call your local Certified Arborist for treatmnt suggestions.
4-Watering weak trees or in dry times will help the tree defend itself against the borers as it increases the wood fluid density making it harder for borers to penetrate into the cambial tissues under the bark. Look for copper colored leasions on the trunks with dead tops to help you Id the pest.
5- My suggestions for your trees is to begin supplemental watering if possible to boost plant hydrology. Call a certified arborist in your area to help diagnose more serious problems and to protect the trees. Also consider a fall fertilization to boost plant vigor for next year.
|