Emerald ash borer threatens Minnesota trees
When the half-inch pests known as emerald ash borers arrived more than a year ago in St. Paul's St. Anthony Park neighborhood, on the border between Hennepin and Ramsey counties, forestry officials knew to take the matter seriously.
"Cities in other states have seen their ash populations decimated," says Brad Meyer, public information officer for the St. Paul Department of Parks and Recreation.
In Minnesota, the infestation is currently confined to fewer than 200 trees within two miles of the original find, all of which have been removed. But forestry experts say EABs will inevitably spread and threaten the state's 930 million ash trees.
"They can be in a tree for three or four years before someone actually sees the decline," says Greg Krogstad, owner of Rainbow Treecare in Minnetonka, the company that discovered the initial St. Paul infestation.
EABs were discovered in the United States in 2002, probably after hitching a ride on shipping crates. The beetle, which most likely spread from unsuspecting campers hauling infested firewood, has killed tens of millions of ash trees in 14 states. These trees have no defense against the beetles, which tunnel through bark, disrupt nutrient flow and eventually kill the trees. And the borers, native to Asia, have few natural predators.
St. Paul officials are removing ash trees from public spaces throughout the city, starting with the least healthy ones, which are most likely to be infested. They'll then replant more than 50 species, including Kentucky coffee and several varieties of elm and oak. "We'll have diversity instead of just one kind of tree on a block, so if another disease comes along, they won't all be wiped out," Meyer says.
Even experts have a tough time detecting an EAB infestation. Here are some things to look for:
• Dead branches in the upper canopy
• D-shaped exit holes
• S-shaped bark markings
• Increased woodpecker activity
Both Minneapolis and St. Paul also updated their nuisance ordinances to allow city officials to inspect ash trees on private properties and order property owners to remove or abate the problem. If they don't do so, the cities reserve the right to remove the tree and charge the owner for the work. Neither ordinance had been used against a homeowner as of July. Ramsey, Hennepin and Houston counties remain under quarantine, which stipulates that no firewood may be transported out of county. Violators may be fined $7,500 or charged with a misdemeanor.
Individual trees can be treated with great success if they aren't already too far gone, but treatment can be costly because it needs to be repeated annually or every other year, according to Krogstad. "This isn't something you do for any tree," he says. "This is for valuable legacy trees."
Angie's List member Cathie Anderson hired Rainbow Treecare to preventively treat four mature ash trees in her yard at a cost of $300, and plans to repeat the treatment each year. "I felt the cost of treating them would be a lot cheaper than trying to replace them down the road," she says. "They're beautiful, mature ash trees, so it's well worth it."
For the majority of ash trees in Minnesota, experts say it's a matter of when, not if, they'll be wiped out from the pest. "What we have now is time," says Jim Walsh, board-certified master arborist and owner of highly rated Vineland Tree Care in Minneapolis. "I think the money is best spent planting new trees.