About 45 of them are being treated on Wide Hollow Road and 96th Avenue in West Valley. Yakima County wants to make them disappear for good.
"They choke out anything that wants to grow, such as native vegetation," said Troy Ross-Havens, an engineer with Yakima County.
The crack willow tree is an invasive species. When they grow, they take over streams and can cause flooding. They kill other plants and fish are also at risk. The trees are a growing problem near creeks in West Valley.
"You can take a limb and jam it into the ground or mud or really anything with soil and water, and they'll start growing," said Ross-Havens.
Yakima County is trying to get rid of the trees. It started a pilot program to tackle the problem. Crews have been cutting strips of bark off their roots and using herbicide. The goal is to stop the nutrients from spreading so the trees die.
"It's hard to get rid of and the problem seems to be getting worse and worse."
Ross-Havens and his colleagues check these trees every week to see how they're doing. They hope all of them are dead by winter. The next move will be to clear them out and replant native trees in the spring. If this works, they'll go after the next set of crack willows downstream.
Yakima County is still determining the extent of the crack willow problem. Australia has had its own problem with the tree. Engineers are keeping tabs on the research coming from there to apply here.