LANSING – The Michigan Department of Natural Resources has released its 2014 Forest Health Highlights report.

The report is an overview of Michigan’s forests, the insects and diseases that have threatened them over the past year, and details about what DNR staff is doing to improve forest resources.

Michigan’s approximately 20 million acres of forest land play a key role in the state’s recreation, forest products and other industries.

The report breaks down forest health threats by examining insects and diseases, forest decline, invasive plant control and other health concerns. Accompanying photos and maps illustrate the pests and show the effects they have had on Michigan’s forest system.

“The key to slowing the onslaught of exotic invasive organisms in Michigan’s forests is public awareness,” said Bob Heyd, manager for the DNR forest pest management program. “The Forest Health Highlights report provides timely information about the condition of our forests and what’s being done to protect this important resource.”

Among the highlights in the report are DNR’s efforts to control oak wilt, a serious disease that threatens Michigan’s extensive red oak resource.

Established widely in the Lower Peninsula, oak wilt has been confirmed in Dickinson, Iron, and Menominee counties, the only three counties in the Upper Peninsula with confirmed reports in 2014.

According to the report, oak wilt is one of the most serious tree diseases in the eastern United States, killing thousands of oaks each year.

The oak wilt fungus is carried from tree to tree through root connections, and is also spread above ground by sap beetles. New oak wilt areas occur when the fungus is carried by sap beetles from infected wood to a fresh wound on a healthy oak.

To prevent further spread, the DNR recommends that Michigan residents do not transport firewood and refrain from pruning oak trees between April 15 and July 15, when sap beetles are most active.

With funds provided by the U.S. Forest Service, the Michigan DNR and Michigan State University Extension worked together in 2014 to treat oak wilt on state forest land and in state parks and recreations areas.

This year’s project focus was the Shakey Lakes Area of Menominee County and a small area of eastern Iron County. Oak wilt pockets totaling 100 acres were isolated with over 36,000 feet of root graft barriers to prevent the disease from moving to healthy trees through infected root systems.

“Treated areas in Menominee and Dickinson counties remain free of oak wilt with few exceptions,” the report reads. “Although much has been achieved, untreated oak wilt pockets remain. Diligence will be needed as the DNR strives to remove the threat of oak wilt to the Upper Peninsula’s oak resources.”

Dickinson County is listed as an advancing front for another ailment, beech bark disease. White scale insects that initiate the disease by feeding on sap and allowing fungi to invade the tree have been found within the county.

The fungus, which eventually kills tree by inhibiting the flow of sap through infested portions, has been confirmed in Menominee County, which is listed as a killing front.

An infested tree is “painted” white by the tiny scale insects. The canopy of a scale-infested tree may appear healthy even though its main stem is weakened by the fungus.

According to the report, controlling the natural spread of the disease is not feasible because both the scale and fungus are moved by the wind, and scale insects can also be transported by animals.

Since 2002, the Michigan DNR has worked with the U.S. Forest Service to select and breed American beech trees for resistance to beech bark disease.

Techniques to propagate resistant trees through grafting have been developed, and genetic tests have demonstrated that resistance is heritable. When two parent trees are resistant, approximately 50 percent of the progeny can be expected to be resistant, according to the report.

Other pests and diseases in Michigan covered in the report include Diplodia shoot blight, eastern spruce dwarf mistletoe, the eastern larch beetle, the emerald ash borer, and forest defoliators both exotic, such as the gypsy moth, and native, such as the large aspen tortrix.

The report also touches on the record-breaking string of extreme cold weather that affected the entire state last year.

It states that the cold did not appear to seriously affect native trees and shrubs, but exotic species growing near the limits of their temperature zones were often damaged. Animals browsing for supplemental food and winter burn and salt injuries also caused some damage.

In addition, “Forest Health Cooperator Reports” from the Michigan Department of Agriculture and Rural Development and Michigan State University, which detail research and programs dedicated to forest health, are included within the 2014 Forest Health Highlights.

To learn more about the health of state forests, download the 2014 Forest Health Highlights report at www.michigan.gov/foresthealth.