Do you have an apple tree or a crabapple tree? Are some of its leaves turning brown and almost look burned? There’s a good chance that your tree has FIRE BLIGHT, which is a bacterial disease that can kill the tree.
Here is some of the information from CSU:
Pruning: Remove and destroy newly infected young twigs as soon as possible. Do this on a dry, sunny day, when there is no chance of rain for 48 hours. It may be best to leave pruning until winter when the bacteria are not active.
Make cuts at least 12 inches below the visible edge of infection.
CAUTION! After each cut, surface sterilize all tools used in pruning. Dip tools in household bleach or ethyl alcohol, or use household spray disinfectants.
During pruning, take care to avoid unnecessary wounds to the tree. Put all blighted twigs and cankered branches in the trash. Do not compost them!
For complete information, refer to this helpful document on FIRE BLIGHT from the CSU Cooperative Extension. Call a tree care company if you are unsure of what to do.