St. Paul's ash borer invasion has spread to trees near historic Summit Avenue.
Minnesota Department of Agriculture entomologist Mark Abrahamson said the ash trees near the intersection of Dale Street and Summit Avenue may have been infected by emerald ash borers spreading from a nearby neighborhood.
"We've got six trees that we know were infested and the city, I think at this point, has removed those," he said. "We will find more as we go along but it takes time for those to show up."
Summit Avenue in St. Paul is lined with mansions and mature trees including ash. Abrahamson estimates about 20 percent of Twin Cities trees are ash, and are susceptible to emerald ash borer infestation.
He said it will be several years before entomologists can judge the effectiveness of introducing a wasp to attack and control the spread of the beetles.
Abrahamson said there's no way to stop the spread of the ash borer. He said the infestation slows during colder weather as the beetles go dormant and then picks up again with warmer weather.
Abrahamson said control of the beetle includes cutting down infested trees and use of chemicals to kill the insect. The emerald ash borer infestation in the United States is traced to a starting point in Detroit, Michigan and is slowly spreading outward from there.