How to Save Your Douglas Firs: A Guide to MCH Pheromone Packs
If you live in our local service area, you’ve likely noticed the majestic Douglas Firs that define our landscape. Unfortunately, these icons are under a quiet but deadly threat: the Douglas-fir beetle.
At Trees & Co., we are seeing an uptick in beetle activity, but there is a proactive, eco-friendly solution that doesn’t involve heavy pesticides. It’s called MCH pheromone packs—and if you have large firs on your property, now is the time to act.
The Problem: How the Douglas-fir Beetle Kills
The Douglas-fir beetle (Dendroctonus pseudotsugae) is a small bark beetle that targets mature or stressed trees.
The Attack: Female beetles bore into the bark to lay eggs, creating "galleries" (tunnels).
The Damage: As they tunnel, they introduce a blue-stain fungus. Between the physical tunneling and the fungal growth, the tree’s vascular system—which moves water and nutrients—is completely blocked.
The Result: Within a year, a healthy tree can turn from green to yellow, then a brittle red. Once a tree is "red-topped," it is already dead, and the beetles have likely moved on to your neighboring trees.
The Solution: What are MCH Pheromone Packs?
Think of an MCH pack as a "No Vacancy" sign for your trees.
Naturally, when a tree is "full" of beetles, the male beetles release a pheromone called Methylcyclohexenone (MCH). This chemical signal tells other arriving beetles that there isn’t enough food left and they should keep flying.
By stapling a synthetic MCH "bubble cap" to your tree (like the one shown in our photo), we trick the beetles into thinking your healthy tree is already occupied. They fly right past it in search of a different home, leaving your Douglas Firs safe.
Installation: Where and How to Apply
For MCH packs to work, timing and placement are everything. Here is how our team handles the installation for local homeowners:
The Window: Packs must be installed before the spring beetle flight, typically by mid-April. Once beetles have already bored into the bark, the pheromones will not drive them out.
The Location: We staple the packs roughly 6 to 8 feet high on the North side of the tree. This protects the pack from direct sunlight, which can cause the pheromone to dissipate too quickly.
The Dosage: * Individual Trees: For high-value shade trees, we typically place 1–2 packs per tree.
Acreage: If you have a larger forested lot, we install them in a grid pattern (roughly 30–40 packs per acre) to create a "pheromone cloud" over the entire stand.
Which Trees Need Protection?
While the name suggests they only like Douglas Firs, these beetles (and their close cousins) can also impact Spruce trees. We recommend protection for:
Large, mature Douglas Firs (12" diameter or larger).
Trees near previous "beetle kill" sites.
Trees stressed by recent droughts or construction.
Protect Your Property Today
MCH packs are non-toxic to humans, pets, and even the beetles themselves—they simply act as a repellent. They are the most cost-effective way to prevent the loss of a 100-year-old tree that would cost thousands to remove once dead.
Is your property ready for the spring beetle flight? Don’t wait until your trees start turning red.