The Wild Side: Oak wilt making its way north
Anyone who drove by my house on a recent Saturday may have seen an odd sight: me teetering on an extension ladder, sawing away on branches in the huge oak tree in my yard. This was not advisable; it was very difficult, and there were phone and power lines nearby that I had to be concerned with. In fact, the power lines were the reason I was up there.
I noticed when I moved into my home two years ago that the oak branches were getting close to the power lines. I wanted to trim them, but felt I had to wait until leaves were off. There is a disease out there, maybe not here yet but close, called oak wilt. This disease looks for an opportunity to infect an oak tree during the growing season. Once it is in the tree, it kills it. This disease is having terrible effects on oak trees further south. It would be ideal to keep it to a minimum up north, but I fear its arrival is inevitable. Probably the best way to protect your oak trees is to limit cutting and pruning during the active leafy time of year, from when the leaf buds start to swell and pop in spring until the leaves are completely turned and dropping in fall. So, this winter, I borrowed a saw and trimmed the branches back so I could have the work done in the tree’s more dormant time period.
Within a day or two of this project, I noticed something different under my tree. Wood chips, big ones, and lots of them, lie all around it on the sidewalk, the snow, everywhere. It took me a couple minutes, but I finally found the source: high up in the oak, a woodpecker had torn my tree a new hole. It was a big one, too, maybe 20 inches long and 6 inches wide. I have had a few folks tell me that woodpeckers kill their trees. I always tell them not to blame the woodpecker; after all, the only reason it is shredding a tree is to consume the insects hidden beneath the bark. If anything, you should blame the insects that are gobbling up the vital tissue beneath the bark and interrupting the flow of nutrients between the roots and the leaves. The woodpecker is merely eating those insects and their larvae in a loud and visible way.
I can’t say what kind of woodpecker did it. We have a few different kinds of woodpeckers in the Northwoods, from the small downy woodpecker to the surprisingly large pileated woodpecker. I suspect the work done on my tree in a short amount of time was from a pileated woodpecker. I thought maybe it was excavating a hole for its nest, but I have seen no further activity since the initial construction work. I will continue to watch. Maybe if the woodpecker does not use the cavity, another bird might. It might even be attractive to a wood duck, except that the entrance hole to the cavity is so large, a smart duck would have nothing to do with it. A wood duck would be willing to lead its young a few blocks to the safety of the water. Mergansers, another kind of tree nesting duck, wouldn’t even consider it because the water is too far away. It is large enough to attract squirrels too, but too small for raccoons.
I am trying to keep a bright outlook on the damage to the tree. Maybe something splendid will happen with this new development. Or, maybe the woodpecker will expose my tree to oak wilt and hundreds of years of life will end with disease. Either way, the damage was done as part of natural processes, and I as a human did my best to minimize the impacts caused by my co-habitation with it in my yard.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.