Polar Vortex may have slowed Emerald Ash Borer infestation

By MARGIE O’LOUGHLIN

If you’ve struggled to stay positive through this year’s long winter, take heart.

“The Polar Vortex of February may have killed up to 75% of the Emerald Ash Borer (EAB) population in the Twin Cities, and up to 95% in northern parts of the state,” said Jonathan Osthus, an Emerald Ash Borer Biocontrol Coordinator for the Minnesota Department of Agriculture.

Osthus was one of three featured speakers at a Longfellow Community Council (LCC) event held on Mar. 12 at St. Peder’s Lutheran Church. The event was sponsored by LCC’s Environment and River Gorge Committee.

The Emerald Ash Borer is a green jewel beetle native to Northern China that feeds on ash species. It made its way to North America in 2002, arriving in the Detroit, MI area in wood palettes used for shipping. It has since spread to every part of the country that has ash trees. Minnesota has approximately one billion ash trees—more than any other state in the country.

EAB was first discovered in Minneapolis in Prospect Park in 2010 and has since spread to every part of the city and 17 Minnesota counties.

Photo right: Recent record-breaking cold temperatures may have helped to slow the spread of the Emerald Ash Borer, an insect that feeds on all species of ash trees. The Mississippi National River Recreation Area (viewed here from the River Gorge) has an estimated half million ash trees. (Photo by Margie O’Loughlin)

Philip Potyondy, Sustainable Forestry Coordinator with the Minneapolis Park & Recreation Board, was the event’s second speaker. “The city’s Ash Canopy Replacement Plan began in 2014, and will run through 2021,” he said. “We’ve had an aggressive plan to remove boulevard ash trees since the beginning, at the rate of 5,000 per year. There are approximately 40,000 boulevard Ash trees in Minneapolis, and we are replacing every ash tree we remove with a different species of tree. For homeowners with ash trees on their property (not their boulevard), the options are to treat or remove the tree at their own expense.” Mountain Ash is not a true ash and therefore is not susceptible.

Starting in 2019, the focus shifted toward maintenance of the ash population in woodland settings, such as along the Mississippi River. Here and there, infected ash trees that could pose a hazard if they fell are marked with a green dot and slated for removal.

“We’re trying to mitigate potential hazards by taking out trees near paths, benches, or parking areas—but for the majority of woodland trees in unpopulated areas, we’re using a different approach,” Potyondy said.

“At the woodland level, biological control is the only option,” Osthus said. “We can’t remove all the ash trees because they grow in precarious places. We can’t inoculate them all because the cost would be too high. What we’re doing is introducing three different parasitoids (insects that penetrate the egg or larvae of the EAB) to try and reduce the number of beetles that hatch each year. These three parasitoids were rigorously tested by the USDA to make sure they won’t have negative effects on other native species of insects. We hope to be able to maintain at least some of the ash trees in the forest landscape by doing this.”

Mary Hammes is the Environmental Stewardship and Volunteer Manager for Mississippi Park Connection, a non-profit partner of the Mississippi National River Recreation Area, and was the event’s final speaker. The Mississippi Park Connection engages with more than 6,000 volunteers annually.

“We have about half a million ash trees in our 54,000-acre park along the river from Dayton and Ramsey down to Hastings,” Hammes said. “The loss of those trees, and the break in the canopy that will occur, will increase the pressure of invasive species on native ones. We have to decide how we want to fill that canopy gap with new species of trees that can do well as the climate continues to change.”

LCC’s Environment and River Gorge Committee will be sponsoring their Annual Earth Day Clean-Up at 36th and 44th streets along West River Pkwy. on Sat., Apr. 20.

Sat., May 4 is the scheduled Neighborhood Bird Walk at the Prairie Oak Savannah; sign up on the LCC website.

The Environment and River Gorge Committee meets the first Wednesday of each month at 7pm at the Longfellow Recreation Center, 3435 36th Ave. S. New members are always welcome.