LANSING - Unseasonably warm weather this spring sparked the spread of oak wilt disease earlier then expected, environmentalists say.
The Michigan Department of Natural Resources has asked state and private landowners not to prune or "injure" oak trees between April and July, when they are more susceptible to the disease.
It hits mainly red, black and pine oaks, with red oaks usually the most vulnerable.
Oak leaves infected with wilt disease are seen in this file photo. (Courtesy photo)
Robert Heyd, the forest pest management program manager at DNR, said the disease spreads when beetles move spores from last year's diseased trees to fresh wounds in healthy oaks.
"Because of the warm weather, the beetles that move oak wilt disease are present everywhere. Prevention efforts such as not cutting and pruning the trees really need to start now," he said.
In addition, Heyd said major contributors to the spread are people who cut oaks for firewood in the spring and move the logs to vacation properties.
"Moving wood from diseased trees to new areas, mostly as firewood and logs, can spread the disease up to three years after the tree dies," he said.
When an oak is infected, the fungus moves to neighboring red oaks through root grafts. Oaks within 100 feet of each other, depending on the size of the tree, have connected root systems. If oak wilt is left untreated, it continues to move from tree to tree, progressively killing them in a large area.
Matthew Sands, a silviculturist for the Huron-Manistee National Forest, said wounds on trees usually occur due to construction projects, use of machinery that bump into trees, workers using spikes on their shoes and storms that break branches.
"Sometimes, people think they help the tree by cutting dead branches, but they don't know it can actually kill it," he said.
According to Sands, over the last few years the national forests removed dozens of red oak trees from the roots. His agency couldn't identify the exact source of the infections but started close collaborations with nearby private landowners and state agencies.
"It is a major problem for us. Once the tree is infected, you can't really save it. We need to educate arborists, private landowners and people in general save how to identify and protect oaks," Sands said.
DNR reported that the disease has been found in more then 40 counties including Alpena, Cheboygan, Kent, Lenawee, Ottawa, Crawford, Wexford, St. Joseph, Antrim, Manistee, Grand Traverse, Gladwin, Oakland, Macomb and Montcalm.
In 2011, the department identified the disease spread to 3,026 acres of state forest land in Crawford, Missaukee, Benzie and Grand Traverse counties.
Dennis Fulbright, a professor of plant pathology at Michigan State University, said it is important to develop strategies to increase knowledge on how to identify and prevent the disease.
"We have a huge epidemic of oak wilt because citizens don't know how to determine oak wilt and the timing, when oak trees should be cut," he said.
General symptoms can be recognized by leaves turning dark brown or dropping around July.
According to Fulbright, it is necessary to set regulations for utility and timber companies and put signs in the parks reminding people that oak trees shouldn't be cut or wounded in warm weather.
"Nature doesn't take rules from us, it gives us rules. You want that oaks, you better do it nature's way," he said.
Meanwhile, the dead oaks are a big loss for timber companies and individual landowners.
Brenda Owen, director for policy and programming the Michigan Association of Timbermen in Newberry, said any disease that affects natural timber resources is a strong concern for the industry.
"Oak is one of the highest-quality lumber production species. Oak disease is fast-acting and that doesn't give landowners much time to harvest the trees before rendering the value of the timber nearly useless," she said.
According to Owen, the loss of oak lumber puts a big financial strain on mills, loggers and landowners that produce lumber products.
"If they are unable to meet those orders, then revenue is lost to the business," Owen said.