Invasive beetle known to wipe out ash trees found in Oregon

PORTLAND, Ore. (AP) — Oregon forestry officials said Monday that an invasive beetle known to decimate ash trees in North America and Europe was recently discovered west of Portland.

The Oregon Forest Department said the iridescent emerald green ash borer is considered North America’s most destructive forest pest and was detected in 34 other states before being discovered in Forest Grove on June 30, KOIN-TV reported.

Officials said this was the first discovery of the insect on the West Coast. It is believed that the beetle came from Asia via Canada to the United States about 20 years ago.

Insects have killed up to 99% of ash trees in parts of North America. Years of attacks by invasive species of beetles have decimated Connecticut’s ash tree population, for example.

The emerald ash borer was discovered in Oregon by Dominic Maze, an invasive species biologist from the city of Portland. He was waiting outside a summer camp in Forest Grove to pick up his children when he noticed several ash trees with D-shaped exit holes in their bark, state officials said.

He recognized the holes as a sign of the emerald ash borer and then spotted the beetles. He called the Oregon Forest Department and an entomologist and two other invasive species specialists confirmed the invasion.

“It’s an ecologically vital tree because it shades the water, keeping it cooler for fish,” said Wyatt Williams, invasive species specialist with the Oregon Department of Forestry. “The roots stabilize the banks, reducing erosion. And many animals, birds and insects eat the seeds and leaves. Losing it will likely have a huge impact on these ecosystems.

Infested trees in Forest Grove were felled and chipped within 48 hours of discovery.

In 2021, the Oregon Invasive Species Council finalized the Emerald Ash Borer Preparedness and Response Plan for Oregon to guide the state in its response.

The Oregon Department of Forestry has previously collected seeds from Oregon ash trees across the state to try to preserve as much of the tree’s genetic diversity as possible. The researchers will test the seeds to see if any have resistance to the emerald ash borer, and if so, they may be able to reproduce the resistance in local strains and replant them.

Oregonians, cities, and towns should consider removing ash trees that are already in poor health or growing in spaces too small for them, and removing ash trees from approved street tree lists, officials said. Portland has already removed it from the trees it plants in the city.

“Beginning to regularly replace ash will distribute costs and impacts better than waiting for mass mortality,” said Scott Altenhoff, manager of the Oregon Department of Forestry’s Urban and Community Forestry Assistance Program. “Fortunately, there are many alternative tree species, including Oregon white oak, frankincense cedar, and Chinese pistachio, that may be more heat and drought tolerant than ash.”

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