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The City’s forest management approach has generally been to encourage and allow natural ecological processes to take place in our natural areas. We are only taking this action because the scale of this Douglas-fir beetle outbreak could significantly impact a sizeable portion of the forest, including large, older, and healthy trees, and because of the unique value of Hendricks Park to our community.
The MCH pheromone is contained within a capsule that slowly releases the chemical over a period of three months (April – June). Each capsule is housed within a plastic strip that is stapled to the tree at a height of 6-8 feet, usually on the north side of the tree.
In the forest and picnic area, tabs will be placed on a rough grid, so they will appear scattered around. In the Rhododendron Garden and Native Plant Garden, tabs will be placed at borders or on individual, high value trees that may be quite close to one another.
The tabs will be installed in late March and be up through the end of June, which encompasses the main beetle flight period in April-May as well as a smaller second flight in June. After that, the tabs run out of pheromone and will be removed gradually over time.
We only plan to take this action in 2020, to respond to the high proportion of downed wood from the 2019 storm coupled with the confirmed presence of a concentrated Douglas-fir beetle population.
The MCH pheromone was isolated from the beetles themselves, and is known only to transmit signals to Douglas-fir beetles. There should be no impact to humans or wildlife from the installation of this product.
A pheromone is a chemical produced by an animal that sends signals to another animal of the same species. While the MCH tabs we will be using are synthetic, this technique came about from biologists who studied the beetles and isolated the pheromones back in the 1970s.
The tabs are a registered pesticide with the Oregon Department of Agriculture. If someone removed the tabs from the trees, inhaled the contents in a confined space, ingested the contents of the tabs, or otherwise interacted with the tabs in a way other than their intended use, that person should seek medical help.
Douglas-fir beetles have minimal energy reserves, typically searching for the next closest suitable tree to the one they emerge from. They typically do not disperse over long distances, so beetles within most areas of the park are anticipated to be contained within the park. Use of MCH in other areas has not shown evidence of beetles traveling off-site in response to the pheromone.
The City is not able to provide pheromone tabs to private citizens, but tabs are quite affordable at approximately $2.00 per tab. Two tabs per tree on individual trees is the recommended application rate.
Dead trees can stand for many years, providing valuable wildlife habitat as snags. When they are within the core of the woods, they become part of the natural forest regeneration process when they fall.
All visitors to a forested area should be aware of their surroundings, and understand that forests are dynamic places and that even seemingly healthy trees can fall without notice. Please use common sense when recreating in the forest, stay on trails, and do not enter the forest under high winds.
In areas close to a trail, trailhead, or bench, the City conducts annual trail inspections to search for hazardous trees. If a tree is deemed an imminent or high risk, then it will be removed. If you are concerned about a particular tree that is actively failing or severely leaning near one of these locations, please contact Parks and Open Space at 541-682-4800.
Parks and Open Space does not have plans to install MCH in any other City-owned forestland at this time. Douglas-fir beetles are present in some of our natural area parks, but we do not have confirmation that they are causing this same scale of tree die-off as we are seeing at Hendricks Park. The decision to use the pheromone at Hendricks also factored in the high value of this specific park due to its proximity to the urban core and the historic value of the park.
However, if in the future we were to learn of a Douglas-fir beetle infestation in another forested park, we would assess the likelihood that the infestation would have on the forest or parkland immediately surrounding the infestation. If such an impact were to be deemed serious, we would then begin a process to evaluate the use of the pheromone in that location.