Many people ask us, "When can I prune my tree?" With some trees, it is not as crucial to time pruning perfectly, however with Oak trees it could mean life or death.
If you have an oak tree, it is extremely important to avoid pruning between March (mid-January for large branches) and November. You may ask, "Why is this so important?" In Iowa, there is a very infectious fungus that causes a disease called Oak Wilt. This fungus has been in Iowa for several years and can kill even the oldest tree in less than a few months from infection. In Iowa, red, black, and pin oak are the most susceptible, however any oak can become infected.
How does the oak become infected?
The fungus can infect a tree in two ways. The first is through open wounds (fresh cuts) during the growing season (April-September). A small beetle carries the fungus from an infected tree to the open wound in the healthy tree, which then causes the fungal infection. The second way the disease is transmitted is through the root system. If an infected tree is within 50 to 100 feet of a healthy tree, that healthy tree could become infected if the roots are touching.
How do I prevent Oak Wilt?
The easiest way for prevention is by only pruning the tree between Late December until the beginning of February. If you have very large limbs to cut and the temperatures are seasonably warm, you may consider painting the open wound with a household latex paint to protect the open wound. Remember, when pruning any tree, it is important to properly clean your tools with alcohol or bleach between cuts. Pruning during the winter months will give the tree time to heal the wound before the fungus is able to be transmitted. Another form of prevention is checking your oak trees (if you have several in close proximity). If you notice you have an oak tree that has brown leaves in early to mid-summer, it may be necessary to form a trench around the tree to avoid the disease from spreading through the root system.