Emerald ash borer effects now cover 77% of St. Paul

30,000 ash trees remain in boulevards and parks, with unknown numbers on private property

By JANE MCCLURE

The emerald ash borer continues its wave of destruction in St. Paul, now covering almost 80 percent of the city. In February the St. Paul Parks and Recreation Commission heard the grim update. It’s anticipated that the pests will someday destroy all of the public and private ash trees in St. Paul, and throughout North America.

Photo right: The red dots indicate actual infestations of the ash borer. When you account for one-mile radius around each infestation, you get the pink areas that indicate the infected areas of St. Paul. (Map courtesy of the City of St. Paul)

The emerald ash borer was discovered in St. Paul first in the St. Anthony Park neighborhood in May 2009. Since then, infestations have been found in Hamline-Midway, Como Park, Frogtown, Desnoyer Park, Highland Park, Lexington-Hamline, West End, Summit Hill and Summit-University neighborhoods, as well as in East and West Side neighborhoods. Measuring one mile around each infestation allows city forestry staff to determine the one-mile buffer around every infestation. “Seventy-seven percent of the city is covered,” said Rachel Coyle of the St. Paul Department of Parks and Recreation Forestry staff.

Another infestation was found in February, said Coyle.

One challenge in trying to eradicate the pests is that emerald ash borers can be present for a few years before they are detected. The insects, which look like small grasshoppers, have larvae that bore under ash bark and feed on nutrients there. That feeding behavior eventually kills trees by cutting off circulation beneath the bark.

The city has removed about 7,580 ash trees from boulevards and parks, with about 20,000 remaining on boulevards and 10,000 in parks. It’s not clear how many ash trees are on private property.

Coyle said the city would continue to treat some public ash trees. But she, and Parks and Recreation Director Mike Hahm, said that while the city’s past efforts have slowed the spread of emerald ash borer, there is no way to stop the insects.

“Treatment was meant as a containment measure, not as a way to preserve trees,” said Hahm. But with the spread of the insects, “the benefit of containment is gone.”

Another challenge for the city is that cost of replacement trees has risen. During the recession, tree sales fell, and nurseries planted fewer trees, Coyle said. Now that trees are needed by cities and private property owners, prices are higher.

One change in 2016 is that the city no longer proactively inspects ash trees on private property. Nor will it condemn private trees. Property owners will continue to be responsible for tree removal on their property. The city will continue to provide information about the spread of the infestation to property owners as requested and on the city website.

The city will also continue surveying street boulevards and parks for infested ash trees, and will be marking trees until April. Parks and Recreation hasn’t yet announced which neighborhoods will be the focus of future structured removal programs. In the programs, where there are many declining or dying ash trees in an area, crews come in and remove every ash tree. The areas are then replanted with a variety of trees. One factor in the spread of emerald ash borer is that on many streets, ash trees were the only trees planted along the boulevard. Many were planted to replace the elms lost in the 1970s when Dutch Elm Disease swept the region.

Area residents affected by structured removal will receive postcards from the city. After trees are removed, residents will receive door hangers saying what type of trees will be planted as replacements. Residents can have some say in what type of replacement tree is planted, using the city’s species list. The city is planting different species of replacement trees, to promote diversity and avoid the widespread loss of trees happening now.

The intent is to plant replacement trees in the spring or fall, depending on the species. Residents can ask the city for water bags to help the young trees.

Winter is the best time to transport ash logs and debris for disposal. September to May is the “low risk” period for spreading emerald ash borer. But Ramsey County and much of the metropolitan area has long been under a quarantine that prohibits moving of ash wood outside of the counties.

For more information about emerald ash borer and city programs, go to www.stpaul.gov/eab.