Buggin’ Downriver: Pine beetle infestation prompts tree removal at historic city golf course

A persistent pest killing parched pines in Spokane’s oldest municipal golf course prompted park officials to take the extraordinary step of cutting down dozens of trees this winter.

Earlier this month, a crew from Spirit Pruners began felling ponderosa pines in Downriver Golf Course in the effort to stem an infestation. The trees had shown the signs of two types of pine beetles, both native to the Inland Northwest, that state entomologists say are attacking more of Washington’s conifers as the climate gets hotter and drier.

Park officials quickly put a $302,000 contract before the city’s park board earlier this month to catch the bugs while they’re dormant in tree bark.

“We wanted to be able to attack this now,” said Garrett Jones, Spokane’s park director.

Toppled ponderosa pines crisscrossed the fairways of Downriver, originally opened in 1916 and later expanded to 18 holes, on a foggy Friday morning two weeks ago as the crew from Spirit Pruners discussed the work that needed to be done that day. The trees had been chopped into chunks to facilitate carrying them out on smaller equipment to limit disturbance of the playing surface.

When Downriver opened, The Spokesman-Review gushed about its ties to surrounding nature.

“The engineers placed a severe penalty on the slice and the pull,” J. Newton Colver wrote for The Spokesman-Review on April 2, 1916, just a month before the course opened to the public. “The fairways are fairly narrow and, in one or two instances, deflected from a straight line from hole to tee. Unless you drive straight you are in the trees.”

Felling those infested trees in the winter is the surest way to keep the beetles, which burrow into bark to lay several generations of eggs beginning in the spring, from reappearing, said Glenn Kohler, a forest entomologist with the Washington Department of Natural Resources. An entomologist working with urban forestry and park officials in Spokane walked the course in the summer and fall, detecting what they believed was damage from two types of native beetles common in Washington: the Ips beetle, and the Western pine beetle, both of which go dormant in the winter.

Kohler, who was not on the ground in Spokane but has seen bark beetle activity throughout the state, said when they emerge varies by year. “But usually, by mid-April, is when the new flights start happening, or the ‘attack flights,’ as we call them,” he said.

The Ips beetle attacks the upper layer of the tree, while Western pine beetles usually infect areas near the trunk, Kohler said. Both types of beetle burrow into a tree creating what are known as “galleries,” serpentine tunnels that wind through the part of a tree rich in sugars that hatched larva eat, according to research by the U.S. Forest Service.

Healthy trees are able to create pitch, a sticky substance that can trap the burrowing insects in the bark layer before they reach the food within, Kohler said.

“Now, if a tree is drought-stripped, or diseased, or the roots aren’t as healthy, the pitch response isn’t as good,” Kohler said. “So the beetles are kind of able to take advantage of that opportunity.”

The infestation, found in roughly 200 trees living and dead on the golf course, was identified in areas where there wasn’t as much watering, Jones said.

“It’s not concentrated in one area. There’s pockets throughout the course,” Jones said.

Removing the trees now, when the beetles are dormant and the ground is firmer due to colder temperatures, will cause the least disruption to those using the course, Jones said. It also will limit the infestation by eradicating trees that could be sources of food in the spring, and destroying the bugs that are dormant in the trees cut down.

“We’re trying to take this proactive approach,” Jones said. “We’re trying to tackle these 200 trees, rather than thousands of trees.”

Any beetles that survive will wake in the spring and look for food, Kohler said. That could include branches left on the ground after cutting that are at least 3 inches in diameter, which is why it’s important for crews to remove any dead wood, or slash, from a treated area, he said.

“The Ips beetles, their tendency is that they would prefer to attack something that’s already dead,” Kohler said. “It’s still green, has good sugar for their babies, but it’s not defended.”

Both types of beetle communicate to others with pheromones, Kohler said. When a new source of food is found, one beetle will signal others to follow. That leads to a kind of cluster, “group kill,” that’s being seen on the Downriver course, he said.

Just across the Spokane River to the west lies the southern edge of Riverside State Park, the 9,000-plus-acre destination full of ponderosa pine. Kohler said it’s “certainly possible” beetles could travel from Downriver to trees in the state park, but also noted that both insects were “everywhere” in the environment.

“If you put up a trap, with these pheromones, you’ll catch them, almost certainly, no matter where you are,” he said.

Western pine beetle activity, specifically, has been on the rise in Washington for the past decade, Kohler said. In 2022, an estimated 44,000 acres of pine trees were infested with the insect, based on aerial surveys conducted by the Department of Natural Resources. That’s up from 37,800 acres surveyed in 2021, and 29,400 acres in 2019 (2020 trend data is unavailable due to changes in survey methods, according to DNR).

The bill for the work on Downriver will be covered by fees paid by city golfers, not taxpayers. The park board elected to tap the dedicated fund for course tree removal, which could delay some other tree work in 2023, Jones said.

“It fits within our budget,” Jones said.

The removal is expected to be completed by early February. The city hopes to replenish the account with revenue from the upcoming golf season.

Spokane Parks is required to replace two trees for every one tree removed within 150 feet of the Spokane River based on shoreline regulations in city law. Park officials plan to replant replacement trees this year.

Stumps will remain on the course until they can be removed as time and money permit. Park staff said stump removal isn’t necessary to end the fight the infestation. Golf season is set to begin around March 1.