Fungal diseases come in two main categories — those that infect trees from the inside out, which are usually fatal, and those that mainly affect the exterior of the tree, such as leaves and branches. Proper care and trimming techniques can minimize the damage from the latter type, and in many cases can eradicate the infection. 

1. Air Circulation

Poor air circulation is the primary cause of foliar fungal issues in trees, but it's also an easy one to avoid.  Fungus thrives in damp, humid conditions in an overcrowded tree crown. Good air circulation prevents these conditions from occurring. Your tree service can thin out the crown by removing some of the excess branches in the crown so that sunlight and air can penetrate. Thinning also prevents branch wounds from wood rubbing together, which also minimizes the chances of fungal pathogens entering the trunk.

2. Nursery Branches

Some branches almost act like a nursery to a fungal pathogen. A weaker branch can become infected initially, while stronger, healthier wood seems untouched. The fungus then breeds extensively on the weaker "nursery" branch until there is enough to over-power and infest nearby healthy wood. Branch tips are often affected first in this manner. Trimming out any wood that shows signs of fungal infestation prevents them from becoming a nursery branch. 

3. Underbrush 

Underbrush growing around the tree can provide a safe harbor for a fungus to lurk, and then it will move into the tree during times of weakness -- such as if the tree experiences drought stress. Keep nearby plants pruned back so they aren't in direct contact with the tree trunk. The same goes for mulch, as it should be pulled back so it doesn't touch the trunk. Any scrubby growth around the base, such as suckers, should also be cut off the trunk. 

4. Entrance Points

Wounds on the tree can provide an easy entrance point for fungal pathogens. Branch stubs left behind from bad pruning or breakage must be trimmed flush to the branch collar, which is the raised ridge of wood where the branch joins a larger branch on the trunk. This encourages quicker wound sealing so fungus can't get in. Your tree service will also trim any ragged bark around wounds on the trunk, as smooth bark edges also encourage quick sealing and prevent infection.

Contact a tree trimming service for more information. They can assist you!