Big Darby Tree Services LLC

We'll be at the Green Columbus Earth Day Celebration all day! Come check out the tours and talks at Scioto Audubon Metro Park!
11am-7pm

Thanks to Adventure Films ltd. for these awesome in-canopy shots!

Know when to prune oak trees

Oak wilt symptoms on red oak leaves. Photo: D. W. French, University of Minnesota, Bugwood.org Prune oak trees in the right time of year! While many trees respond fine to pruning any time of year, oaks need special care so as to not spread a fatal vascular disease called oak wilt. The origin of Oak wilt (Bretziella fagacearum) is unknown, but is found in North America including all 88 counties of Ohio. Oak wilt gets its name from the effect it has on oaks. The pathogen plugs the living tissue of the tree, the sapwood. This limits water uptake and causes the leaves to wilt. While trees can somewhat control how much water they uptake, oak wilt stops up these vessels longer than the tree can tolerate. Oaks can be divided into two groups, red oak and white oak. Red oak leaves typically have bristle tips and white oak typically have rounded tips. Affected red oak leaves turn yellow versus white oaks show more general symptoms. Leaves from the top of the tree generally wither first and work its way down. The leaves will eventually fall from the tree. Other signs of the disease include vertically cracking bark and fungal mats. All oaks are effected, but white oaks hang on longer. Red oaks can die within a few weeks once infected, but white oak can last 1-2 years longer. When needing to prune an oak tree it’s important to understand the disease’s cycle. Sap feeding beetles carry spores while feeding on sap from oak trees. Oaks typically only excrete sap when an injury occurs i.e pruning cuts. Sap sucking beetles are attracted to this sap and travel from tree to tree acting as a vector for the disease. Thus we look at the life cycles of sap sucking beetles that are known to interact with oak trees. That is generally from spring to early October. So the best advice is to limit oak pruning to being performed from October – February when the beetles are least likely to be active. Now, rising temperatures affect an insect’s life cycle, so ideally oaks are pruned when it’s cold outside, at least for here in Ohio.