Pine beetles and oak wilt can cause further damage in affected forests



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"DNR News"



May 1, 2025
Contact: Cheryl Nelson <[email protected]>, 231-287-1714 or Simeon Wright <[email protected]>, 906-203-9466

After the storm: DNR recommends prioritizing forest health in tree management

The recent ice storm has left an overwhelming tangle of downed and damaged trees across northern Michigan and the eastern Upper Peninsula. For those working with damaged trees in this region or across the state, the Michigan Department of Natural Resources is providing guidance in prioritizing work to reduce the impacts of tree pests and diseases now and in the future.

Prioritize pine

Five specimens of different bark beetles.

Pine species are widespread in storm-affected areas. Downed pine trees develop a fungal stain quickly, losing their value as timber. Stressed or damaged pines and fresh pine debris in early spring can attract native pine bark beetles. If left for several weeks, pine logs and downed branches can become breeding grounds for bark beetles, leading to population explosions. Beetles can emerge to attack stressed trees and even overwhelm the defenses of healthy trees.

Take these steps to reduce the impact of pine bark beetles:


* Salvage and clean up as much affected pine as possible before June to reduce beetle regeneration.
* Avoid piling logs and branches. Piles reduce drying time and invite increased beetle production.
* Prioritize removal of debranched and tipped trees, followed by those that are severely bent, and then those with the fewest intact branches.


Conifers, especially red pines, are also susceptible to Heterobasidion root disease [ [link removed] ], or HRD, spread by fungal spores that enter from cut stumps and travel through root connections to other, nearby pines, creating pockets of dead trees. In the ice-storm-damaged area, HRD is known to be present in several locations in Emmet County and one location in Montmorency County. Locations can be viewed or reported using the online HRD Viewer [ [link removed] ]. If working within a 5-mile radius of known HRD infection, pine stumps within plantations should be treated with approved chemicals to prevent new infections.

Delay oak pruning and management

Due to the threat of oak wilt, a fatal fungal disease introduced through oak tree wounds, oak salvage and cleanup should be postponed wherever possible until after the high-risk period of April 15 to July 15. There is less urgency to harvest damaged oak because deterioration of storm-damaged oak and other hardwoods will occur more slowly than pine, providing up to two years to complete salvage.

Oak wilt infection seen in a cluster of four oak leaves that are brown on the outer edges but still green in the center.

April 15 through July 15 is the high-risk period for oak wilt spread because that is when oak wilt fungal spores are most abundant and when sap-feeding nitidulid beetles are most active and likely to spread spores from infected trees to newly damaged ones.

Oak wilt is fatal to trees in the red oak family, which includes black oak, northern red oak and northern pin oak – all identifiable by their pointed leaf tips. White oaks, those with rounded lobes or leaf tips, are susceptible to oak wilt but may survive for several years or succumb more slowly before dying. Once infected, oaks can spread the disease to other oaks through underground root connections or grafts, creating an expanding circle of dead trees.



Important considerations for protecting oak trees:


* Trees that were wounded or damaged in the late March storm are at less risk of infection than trees sustaining fresh wounds later this spring.
* If you must work around oaks during the high-risk period, take precautions to avoid hitting or damaging them.
* If oaks are pruned or damaged during the high-risk period, immediately coat wounds with latex paint.
* Oak wounds are only vulnerable to oak wilt infection for three to four days. It is not necessary to coat wounds or stumps of previously damaged trees.

Learn more about oak wilt and prevention strategies at MichiganOakWilt.org [ [link removed] ].

Future forest health concerns

Many trees have been damaged or weakened by the storm. In some areas, drought or infestations like spongy moth may have already stressed trees, making recovery more difficult. Stressed and damaged trees are more susceptible to a host of native and invasive insects and diseases that may strike in the future.


* Armillaria root disease [ [link removed] ], a mushroom-producing fungus that slowly kills trees, may become evident in one to three years in impacted trees and stands.
* Native two-lined chestnut borer [ [link removed] ] may attack damaged or stressed oak trees. Heavy infestations can stop the flow of sap, killing branches and entire trees.
* Native white spotted pine sawyer beetles will also attack dead and dying pines and may be confused with the invasive Asian longhorned beetle. Michigan State University’s Spot the Difference guide [ [link removed] ] can help distinguish between the two beetles.

Newly opened forest canopy and cleared landscape areas invite invasive trees and shrubs. Look for and remove common invaders like autumn olive, buckthorns, invasive honeysuckles, Norway maples and Scotch pines. Early action can improve native forest regeneration and rebuild wildlife habitat. More information on invasive trees and shrubs is available at Michigan.gov/Invasives/id-report/plants [ [link removed] ].

Proper debris disposal

To help with cleanup efforts, 17 public debris disposal sites have been opened to serve the 12-county disaster area. A map of these locations is included in the 2025 Northern Michigan Ice Storm dashboard [ [link removed] ] at Michigan.gov/MSP [ [link removed] ]. Check the location listing for hours of operation and permissible items. Some locations are accepting tree debris only, and others will accept all vegetative debris.

Note that it is unlawful to dump or dispose of debris on public lands or property. Be aware that moving vegetative debris can spread invasive insects, plants and diseases.

Don’t move firewood

Tree insects and diseases don’t move far on their own, but when people move firewood, these species can move hundreds of miles. Though the storm has created a lot of potential firewood, it is important to use it on-site or locally to prevent the spread of invasive pests and tree diseases to new locations.

Help for forested lands

The U.S. Department of Agriculture’s Farm Service Agency can provide payments to eligible owners of nonindustrial private forest land for emergency measures to restore land damaged by natural disasters through its Emergency Forest Restoration Program [ [link removed] ]. The program is available in areas affected by the recent ice storm. Landowners are encouraged to contact their local FSA office to determine eligibility.

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*Note to editors:* Accompanying photos are available below for download. Caption information follows.


* Bark beetles [ [link removed] ]: A number of bark beetle species can actively reproduce in pine logs and debris then attack and harm live trees. Photo courtesy of Gerald J. Lenhard, Louisiana State University, Bugwood.org.
* Oak wilt [ [link removed] ]: Oak wilt, a disease deadly to red oak, causes leaves to turn yellow or brown around the edges and fall prematurely in the summer. Photo courtesy of D. W. French, University of Minnesota, Bugwood.org.



"Following a severe ice storm in northern Michigan, the Department of Natural Resources is assessing damage and conducting cleanup at several state parks, state park campgrounds, state forest campgrounds, boating access sites and state-managed trails. Find up-to-date information about closures, volunteer opportunities and more" "on the DNR storm recovery page [ [link removed] ]."

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