The dozen ash trees in Robert Delutri’s yard gave sweet relief from the sun during summer’s hottest days. And in the fall, the bright yellow leaves glowed with light about the time the first frost was setting in.

But Delutri’s beloved trees became stumps earlier this month — cut down in a hurry after experts confirmed they were being eaten alive by little green beetles that have gradually made their way west.

With an estimated 900 million ash trees in Minnesota — second only to Maine — many more homeowners face the certainty of losing treasured trees to the emerald ash borer, which has already killed millions of trees in 11 other states.

Seeing his trees get cut down was “kind of like attending a funeral,” Delutri said.

“It was hard to see them go,” he said, “but there’s not a lot you can do once it starts.”

Watching an entire tree species succumb to an insect is a familiar story for many in this St. Paul neighborhood. In the 1970s, many of Minnesota’s elm trees fell victim to Dutch elm disease, which is caused by a fungus spread by the elm bark beetle.

Like the emerald ash borer, one of the elm beetles that has spread the fungus isn’t native to the United States, and may have hitchhiked here on a ship. After arriving, it thrived in its new, less competitive environment, to the chagrin of tree lovers.

“Everyone remembers the elm trees going, and it was a huge loss,” said JoAnne Makela, a member of the neighborhood’s community council.

Linda Bryan is one of the neighborhood’s residents who remembers when Dutch elm disease moved through the state. She planted an ash tree in her side yard about the time time the elms were dying.

“It seemed like a safe tree,” said Bryan, who lives a street away from Delutri.

Bryan and her husband, Ray, also have an ash in their backyard — one that grew on its own. Neither trees have shown signs of ash borer, but Bryan says she’s accepted the fact that they might get it eventually.

Besides offering shade, ash trees grow relatively fast, aren’t as messy as some trees and adapt well to their surroundings. The tree is native to Minnnesota, so it grows well here.

Because there were no major threats to ash trees when the elms were dying off, many homeowners and cities planted them as replacements. Surveys of trees in Minnesota cities show that ash sometimes make up more than half of some cities’ trees, a lack of diversity that makes the insect’s threat all the more grave.

“When Dutch elm disease came, instead of putting a real concerted effort into having some diversity, people planted all these ash,” said Jeffrey Hahn, an extension professor of urban entomology at the University of Minnesota.

Hahn said city planners are learning from their mistakes, and urban forestry experts have tried to make tree nurseries aware of the benefits of offering a variety of species.

The mistake could be costly for local governments and homeowners alike. While federal and state money helped pay for an initial response to the ash borer infestation in St. Paul, those dollars have already been used. Lawmakers will have to decide whether to offer additional funds to take down any more sick trees that are identified in the future, said Mark Abrahamson, a Minnesota Department of Agriculture entomologist.

Pesticides are available for trees that have shown little or no sign of ash borer, but the treatments can cost $100 or more per year for bigger trees. Cutting down the trees is far from cheap, too: Delutri was told he likely would have paid $15,000 to have his 12 trees removed.

To lessen the blow, officials are trying to slow the spread. In states where it’s established, the ash borer can move about 20 miles a year on its own, Abrahamson said. So officials are trying to keep it in a concentrated area as long as possible by luring beetles to stressed ash trees rather than letting them go find healthy ones outside the infested area, he said. The state is also trying to prevent the borer’s artificial spread by telling people not to move firewood.

“Delaying the spread over time will make a huge difference,” Abrahamson said.

Delutri is already talking with neighbors about what to do to replace the ash trees. In the meantime, it could be a hot summer. “We’ll probably run the air conditioner more this year,” he said.