Dutch elm disease killed elms, jackpine budworms killed jackpines and forest tent caterpillars killed basswood, aspen and birch trees.
Now the two-lined chestnut borer, a native beetle, is killing oak trees. The damage is especially visible along Highway 210 in Baxter. Other dead oaks are seen around Gull Lake, Riverside Drive in Brainerd, around Nisswa and Lake Mille Lacs.
The DNR will host a community meeting this fall to discuss the two-lined chestnut borer. Dates and times have yet to be set.
Drought has allowed the borer to thrive and eat through he bark of stressed trees. Earlier the borer infected 15,000 acres of oaks near Grand Rapids. In some areas up to 50 percent of the oaks have been lost.
The first sign that the two-lined chestnut borer has infested an oak tree are dying branches. The beetle lives between the bark and the wood.
» Purchase reprints of this photo.Brainerd Dispatch/Nels Norquist
It usually takes a few years for the borer to kill a tree. But when oaks are stressed or the infestation level of the borer is very high a tree can be killed in one season. The tree is killed when the larvae of newly hatched borers cut through the bark and into the wood. The feeding larvae cut off the conductive tissue that transports water and nutrients from the roots of a tree to its crown.
Early signs that the borer had come the lakes area showed in July. Oaks developed sparse, red-brown leaves. Entire limbs began to die. Some trees have both dead and live limbs, with the crown dying while mid- to lower-level branches remain green. When a tree dies surrounding trees become vulnerable.
Here's what homeowners can do.
- Remove any tree more than half-dead. The borer survives in cut and split wood, so before using that dead oak for firewood wrap it tightly under a plastic tarp. Lack of air will kill larvae. Burn the wood this winter.
Two-lined chestnut borers hit oak trees stressed by drought. Extremely dry conditions the past two summers have put area oaks at risk. When one tree dies, others in the immediate area become vulnerable.
» Purchase reprints of this photo.
Brainerd Dispatch/Nels Norquist
- Water trees by laying a hose at the base of the tree and running it full-throttle until at least two inches of water have soaked into the ground. Do this at least once a week on all infected trees.
- Don't use fertilizer. It makes the lawn green, but it harms trees by building the crown at the expense of the root system. Don't sever roots with utility lines. Don't compact soil near trees, or change the soil grade through addition or removal.
VINCE MEYER may be reached at firstname.lastname@example.org or 855-5862.
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