Emerald ash borer could kill thousands of trees, change look of city
Lakeville is preparing for a deadly invasion.
City crews have been counting and mapping trees on city property in preparation for the arrival of the emerald ash borer, a green Asian beetle capable of mass destruction.
“It’s like a plague,” Lakeville Parks and Recreation Director Brett Altergott said, noting no ash is safe from the beetles.
Emerald ash borer larvae tunnel under ash tree bark, destroying the tree’s ability to transport water and nutrients, typically killing infested trees within three to five years.
“The death rate is 100 percent,” Altergott said.
The loss of ash trees in Lakeville would be significant,” said Mac Cafferty, Lakeville environmental resources manager. “It could have some pretty significant impacts in the city and on our park system.”
Ipava Avenue is lined with ash trees and many were planted in city parks. Cafferty said 30 percent of the trees in Antlers Park are ash.
There are also many ash trees in wild areas of the city that are not being individually marked but will be included in estimates.
A 2010 Minnesota Department of Natural Resources survey states that 17.8 percent of the city’s tree population is ash, second only to maple, which it said makes up 21.2 percent.
Emerald ash borer travels slowly, and infestations spread primarily by the transport of wood products. The bug is thought to have arrived in the United States through a shipping container that arrived in Michigan in 2002.
The beetle has killed millions of trees around the country, and has been found in Minneapolis and St. Paul.
Altergott said although there have been no signs the ash borer has made it to Lakeville, it is only a matter of time. The beetles may be here already because the problem can take a few years for symptoms to appear – dying upper branches, woodpecker feeding, thinning and discolored leaves and splits in a tree’s bark.
Lakeville has installed purple bags on some ash trees to attract and trap ash borer bugs.
Management options for containing damage done by the emerald ash borer are expensive, and include treating or removing ash trees and replanting with different species.
Altergott said treatment methods have improved since emerald ash borer was first found and the course of action was to cut, grind, chip and destroy ash trees.
He said infested cities and counties still quarantine the transportation of firewood to outside areas, but there are also treatment and reforestation options that may be employed to help ash trees potentially survive an infestation.
Cafferty said they have talked to Burnsville and Twin Cities-based Rainbow Treecare officials as Lakeville develops management options for the City Council to consider.
Burnsville has implemented a $3.5 million, 10-year plan to protect public trees from emerald ash borer. It is the first city in the state to use TreeAzin, a natural insecticide injected every two years, that aims to save a selection of the city’s most important, large and healthy ash trees.
Cafferty said Lakeville may replicate parts of Burnsville’s plan.
He said the city is using the tree inventory to help determine what it would cost to manage ash borer on a smaller scale; the price for treatment or removal usually depends on tree size.
“There’s a fair amount of ash trees that were planted 15, 20, 30 years ago and to lose all those trees out there, this is definitely something we’re concerned about,” Cafferty said.