All across the internet I’m seeing photos of green grass with pollinator-friendly people warning “leaves the leaves!” and “don’t clean up your gardens yet!” I chuckle jealously at those posts while watching another few inches of heavy wet snow come down. Here in the Northwoods, we’re dreaming about spring alright, but we’ve got a few more weeks of mud season to endure first.
In the case of the leaves and gardens, the issue is the bees, butterflies, fireflies, and other beneficial insects who have snuggled down in the duff or holed up in hollow flower stems for the winter. They aren’t eager to come out of their warm hiding spots until they’re sure it’s going to be sunny and warm. So, cleaning up your flower gardens—especially if you have lots of perennial native species you planted with pollinators in mind—will need to wait until tomato-planting weather. That way you know that the days and evenings are consistently warm enough for the insects to have emerged.
Warm weather also warns us that a not-so-beneficial insect may have emerged already.
Sap beetles in the family Nitidulidae are one of the main vectors for oak wilt. Oak wilt is a fungal pathogen that kills trees in a single season. While it’s already widespread in southern Wisconsin, it only arrived here in the north in 2018.
When an oak tree is injured—by a bulldozer, trail groomer, windstorm, pruning cut, logging, etc.—sweet juices begin oozing from its wounds, and that scent lures in hungry beetles. If those beetles have already been eating from a tree infected by the oak wilt fungus, they will transport spores and inoculate a new infection.
These beetles begin flying around as early as April and continue through July. They can’t chew their own holes, but any sort of wound can be the entry point for oak wilt into your forest, and your neighbor’s forest, too. That’s why this reminder is an early spring tradition—if you need to do some work in your yard, do it now while we’re still in “third winter”…or wait until fall.
In order to curb the spread of the fungus, land managers must cut all the potentially affected oaks and quarantine the wood under a tarp for a year so that beetles can’t spread the fungal spores. That can take up a lot of space.
This winter, Paul Cigan, a forest health specialist with the Wisconsin Department of Natural Resources (WDNR), teamed up with Max Wolter, a fisheries biologist with the WDNR, to dispose of oak-wilt-infected wood in a creative way. “So far, the DNR’s Hayward Fish Team has created a total of 16 fish cribs from oak wilt trees on Windigo, Little Sissabagama, and Placid (Tiger Cat Chain) Lakes,” reported Max. “The crew worked hard to construct some really impressive cribs that anglers may find in their next trip to one of these lakes.”
Although this project started with the tragic loss of several oak trees, it ends with a win-win. “There is no link to oak wilt spread through water,” Paul reassured me. “The point of submersion is to get the wood (and its spore mats) away from beetles that like to visit them.” Additionally, since oak logs are solid and long-lasting, they will provide fish habitat for many years. Max would like me to remind you that installing cribs often requires a permit.
While those fish cribs—built on the ice—sink into the lakes over the next few weeks and take the oak wilt fungus with them, we have a job to do on dry land: keep an eye out for oaks with wilting leaves. When caught early by observant landowners and reported to your local WDNR office, infections can be contained.
Foresters from the counties, the WDNR, and the United States Forest Service are working together on their large-scale oak wilt detection and mitigation operations. Aerial surveys with planes and drones, and satellite imagery with computer analysis that can spot sick trees are at the forefront.
Oaks are a major component in our forests, and they are important ecologically, economically, and aesthetically. Preventing oak wilt will be a team effort.
Author’s Note: Portions of this article are reprinted from March 2020 Natural Connections.
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