Hello. My name is Gina and I live in Troy, MO. We have a mature crabapple tree that is having limbs turn brown at the tips and seems to be movving up the branches. Its random around the tree and seems to be getting worse. Wondering if this is a fungus or insect? Not sure what to do. Also we have noticed an oak tree in the back yard doing the same thing.
Thank you.
Gina

Crabapple trees, particularly older mature ones are susceptible to Scab disease. You may have some other soil condition. Have an arborist look at it.