Rosemount braces for ash borer, residents should too

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The city of Rosemount is busy planning for a possible Emerald Ash Borer infestation. Readings of an ordinance that allows tree inspectors onto Rosemount properties to detect the invasive pest will be held during the next two council meetings, and the city has devised a plan for the 1,600 ash trees located on public property.

Residents also can plan for the destructive little insect, said parks supervisor Tom Schuster.

According to the Minnesota Department of Agriculture the Emerald Ash Borer, also known as EAB, is an insect that attacks and kills trees. The adults are small, iridescent-green beetles that live outside of trees. The larvae are wormlike and live underneath the bark of tree. The trees are killed by the tunneling of the larvae under bark.

All ash trees are susceptible to EAB and millions of ash trees have been killed in infested areas. According to department of agriculture, Minnesota has one of the highest volumes of ash on forestland in the United States.

While there have been no confirmed cases of EAB in Rosemount or Dakota County, Schuster said the insect spreads slowly, so it takes time to confirm cases. Cases have been confirmed in Hennepin and Ramsey counties.

“I couldn’t say with any certainty that it isn’t in Rosemount,” said Schuster.

The insect was first found in St. Paul in May 2009 and has spread. Most infestations have been traced back to the moving of wood, so the department of agriculture has quarantined the areas with confirmed infestations.

Schuster said when cases are confirmed the wood is chipped to 1 x 1 x 1 inch pieces. Removal of infected trees should be done during the fall, winter and early spring months to limit the risk of spreading the insect.

EAB can be treated with chemicals if caught early, before the larva does too much damage. The chemicals can either be applied at the base of the tree and taken up through the root system or injected into the tree. Schuster recommended working with a certified arborist to come up with a treatment plan.

Schuster said treatments have to keep going for the life of the tree and can be costly.

“You have to ask yourself, could you be happy with another tree,” said Schuster.

Going forward, Schuster said the city would like to see a more diverse tree population in Rosemount. The city will change out some of its ash trees with other species over the coming years. He encouraged residents to think about doing the same.

This past year city staff counted all the Ash trees on public property and created a plan to replace or treat trees. There are approximately 1,600 ash trees on city property: 1,100 on boulevards of city streets, 180 on parkways like Evermoor and Connemara Trail and 259 in parks and another 57 on city building and water tower sites. That number does not include trees in Carrol’s Woods, Schwarz Pond Park, the Wiklund Preserve or trees maintained by other entities.

“It behooves us to try and manage it to save on costs down the line,” Schuster said of the city’s actions on the issue.

Knowing what to look for can help residents identify an infested tree. Schuster said a tree under attack will have thinning of the crown of the tree and increased woodpecker activity. Look for small, D-shaped exit holes in trees. These are the result of borers exiting the tree once they have become adults. When larvae become numerous enough the bark will split and reveal tunneling.

Residents with specific questions about EAB or who suspect they might have a tree infested with EAB can contact the Arrest the Pest Hotline at arrest.the.pest@state.mn.us or call 651 201-6684 or 1-888 -545-6684 in Greater MN.

Other resources with information about Emerald Ash Borer include www.mda.state.mn.us/eab; www.extension.umn.edu/issues/eab; www.emeraldashborer.info; and www.dnr.state.mn.us/invasives/terrestrialanimals/ eab.

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