By Linda Williams, DNR Forest Health Specialist, Woodruff; Linda.Williams@wisconsin.gov or 920-360-0665
Scattered balsam fir trees in some areas of northern Wisconsin have suddenly turned a rusty red or brown color and are dying. These trees are not being impacted by spruce budworm and typically die with a full complement of needles.
These symptoms are similar to those observed in 2018 and 2020. So far, the number of impacted trees reported is smaller than what was seen in 2018 or 2020. While reports of affected trees are still coming in, they seem to be concentrated in northern areas of the state that experienced extensive snowfall in late winter.
Similar to what was seen in in 2018 and 2020, balsam fir trees of all sizes have been impacted and trees that have suddenly died can be found next to other trees that are green with normal growth rates. Dead trees can be completely dead, or the top half to two-thirds of the tree may die. No pathogens or pests that could have caused mortality have been observed in affected trees, although bark beetles are occasionally seen attacking the dying trees. On trees that are only partially dead, there are no clear margins between live and dead portions that would indicate a fungal canker. The balsam fir that suddenly died this spring don’t seem to pose a risk to other nearby trees. Trees could be removed, and no special handling of the wood is required
In 2018 and 2020, the mortality was attributed to dramatic swings in weather during late winter and early spring of those years, and it is suspected that this year’s balsam fir mortality is due to the same phenomenon. From April 10-15, 2023, some areas of northern Wisconsin had several feet of snow on the ground when temperatures first reached the 70s during those dates. With warm temperatures and sunny days, conifers were losing water from their needles, but their roots were not able to replenish that water due to the deep snow still on the ground.
Additionally, after a week of very warm temperatures in mid-April, much of the Northwoods experienced a low temperature in the teens on April 26, which may have been too much of a shock for some trees, but not others. What makes one tree more susceptible to these mortality events than another is still unknown.
Watch for more information later in the season as additional locations of mortality are reported and more information is collected.