Oak Wilt Season
You may have seen warnings in the newspaper or even signs in your neighborhood about not pruning oak trees during the spring months. This is a good rule to follow for the home owner, as your oaks are more at risk of oak wilt during this period. Oak wilt is a caused by a fungus, in turn frequently spread by a burrowing beetle, but it also can be spread through roots and open wounds. It is important when trimming an oak to always make proper cuts (outside the branch collar) and to use a paint to cover the wound. The wound should be painted within a few minutes, or a not at all; it is pointless to paint a wound the day after a cut as the wound will already have been dried and sealed off by the tree.
In the months of spring, it is generally advised not to prune oak trees to avoid spreading oak wilt. It is also ill advised for other reasons, mainly that this is a growing season and the tree needs its stored fuel for this activity. However, there are some reasons to work in oak trees even during this time:
1) Removing Dead Wood- Dead wood is always a liability, both to the tree's health and to the property and people passing beneath the dead wood. The danger of a falling dead limb is obvious. What is less obvious is the threat to the tree. While trees have adaptations to deal with dead wood, it is still valuable to remove the wood; the dead wood can harbor insects and decay organisms that can then move into the live tissue where the dead wood meets the living wood. Removing the dead wood, leaving a minimal amount of dead tissue, minimizes the amount of real estate the decay organism or pests have to proliferate and so reduces the total load of pestilential species in direct contact with the tree.
2) Removing rubbing or broken limbs- Wounds caused by rubbing become vectors for disease. This is true for both the seemingly minor rubbing caused by a vehicle passing and scraping leaves of low hanging limbs, and also the rubbing caused when two limbs have grown too close together. This second case is very easy to miss for somebody not looking for it, but it is a prime reason for removing limbs for a professional tree trimmer. If tree limbs have grown too close to your house or roof, this is not only potentially damaging to your roof, but also to the tree for the same reason. In any case where there is rubbing, the risk of developing disease from open wounds is greater than pruning, and it is appropriate to remove the rubbing limbs as soon as possible.
The prescription to avoid pruning during the spring months is mostly for the tree owner, rather than for a professional, who knows how to properly cut and cover wounds made and minimize danger to the tree. Still, it is always safest to prune at a different time. However sometimes it is more important to prune the tree properly so as to ensure the health of the tree and safety of the property.