The city's tree-removal crews received refresher training in March, learning how to spot signs of the emerald ash borer.
The S-shaped tunneling in the wood. The D-shaped exit holes through the bark.
So when they spotted the scars in a tree they removed last week on the 3700 block of F Street, they knew what they were looking at.
“They said, ‘Oh, this is suspicious,’” Lorri Grueber, the city’s community outreach forester, said Tuesday. “And I said, ‘Don’t chip it; bring it back to the shop.’”
Monday, state entomologist Julie Van Meter examined the tree and found live ash borer larva — marking the first time the tree-killing insect was confirmed inside the city limits. But by the looks of the tunneling marks on the tree, the bugs have been here, undetected, for more than a year.
“Some are older and some are fresh,” Grueber said. “So it’s here.”
City officials have been expecting it — and planning for it — for more than a decade. The Asian insect has killed tens of millions of trees since it started its march west in the early 2000s, when it was confirmed in North America.
It was discovered in Nebraska in June 2016, in an infested tree in Douglas County. The Nebraska Department of Agriculture has since confirmed infestations in Cass, Dodge and now Lancaster counties. Its quarantine zone includes all of those counties and nearby Otoe, Sarpy, Saunders and Washington counties.
The ash borer was first detected in Lancaster County last summer, when the state trapped one northwest of Pioneers Park.
Monday’s confirmation of an infestation won’t change the city’s response, Grueber said, because it was already following its plan — removing and replacing the estimated 14,000 city-owned ash trees at a rate of about 1,000 trees a year.
But it could spur the public into action. The city has estimated Lincoln is home to nearly 50,000 private ash trees, all of them vulnerable.
“It will likely trigger a high response from people with private ash trees,” she said. “I’d anticipate our phones being very busy from people calling in and wanting us to take a look.”
Early infestations aren’t easy to detect. The tree on F Street, for instance, looked like a “run-of-the-mill healthy tree,” Grueber said, with few outward signs of what was happening beneath its bark. She and Van Meter both credit the city staffers with knowing what to look for.
“It was an excellent find on their part,” Grueber said. "It’s a very wily little insect."