MCH (Methyl Cyclo-Hexanol) Douglas-Fir Beetle Protection
Douglas fir Beetles – What Trees Are at Risk
Douglas fir trees (Rocky Mountain Douglas-fir Pseudotsuga menziesii var.glauca) is the most common conifer tree species found in the forests of Montana and Idaho. This tree displays an ability to grow across a wide variety of environments. It spreads easily due to its relatively light seed that can catch wind currents and disperse up to 2 miles. Douglas-fir is a hearty and resilient tree that is moderately fire-resistant and can withstand snow, wind, drought, and mild insect infestation. Despite being a highly resilient tree, Douglas fir trees are susceptible to various insects and pests. The most well-known enemy of Douglas-fir is the Douglas-fir beetles.
Douglas-fir beetles (Dendroctonus pseudotsugae) prefer to first bore into host trees that are large, old, and already stressed or have recently died. The stress can be from other pests such as defoliating Tussock Moths, or Western Spruce Budworms. Trees also may be experiencing stress from different environmental factors such as fire, drought, or disease. While Douglas-fir beetles outbreaks tend to start in large, old, and stressed trees, beetles are opportunistic and during outbreaks will also attack healthy trees within a stand.
How Douglas-Fir Beetles Damage Trees
Adult Douglas-fir beetles bore through the bark of Douglas-fir trees into the cambium and then lay eggs. When the eggs hatch the larvae continue to spread throughout the cambium damaging tree tissue that is vital to the survival of the tree. While a single Douglas-fir beetle is unable to kill a host tree on its own, once a beetle has infected a tree other beetles will quickly follow.
How Douglas Fir Beetles Spread
Many Douglas-fir beetles simultaneously attacking a tree can quickly overwhelm a Douglas-fir Tree’s natural defenses and kill it. Douglas-fir beetles coordinate attacks on trees by following chemical signals called pheromones. The pheromone signals can be emitted from the host tree or by beetles that have found a susceptible host tree. Other Douglas-fir beetles follow the aggregation pheromones (vacancy signal) or an anti-aggregation pheromone (NO vacancy signal) and soon the host tree is overwhelmed and an outbreak has begun within a stand of trees. Peak flights for Douglas-fir beetles generally are April to May dependent upon weather conditions.
How to Protect Trees from Douglas Fir Beetles
Management of Douglas-fir beetles can take many forms within an Integrated Pest Management (IPM) system. Sometimes the best option might be tree removal and thinning, spraying, or preventative synthetic pheromone patches that are attached to trees. Preventative pheromone patches called Methyl Cyclo-Hexanol (MCH) is the synthetic version of the Douglas-fir beetles natural anti-aggregation pheromone. This pheromone essentially sends out a “NO VACANCY” signal which tells beetles this tree cannot support additional beetles, effectively stopping an infestation and outbreak before it can begin. Preventative application measures must be taken before peak flight and are most effective when applied in early April.
MCH Bubble Caps: Safeguarding Trees from Bark Beetle Trouble
What Are MCH Bubble Caps:
MCH Bubble Caps contain anti-aggregation pheromones and are highly effective in repelling Douglas fir beetles and preventing infestation. MCH Bubble caps are currently registered as a bio-pesticide by the EPA. Unlike conventional pesticides that kill insects, MCH is a biological agent that only affects Douglas-fir beetles’ behavior.
When to Use MCH Bubble Caps:
Spring Beetle Season: When spring arrives, so do the beetles.
Preventative application measures must be taken before flight and are most effective when applied in early to mid-April. However, if it is applied early in the flight season but after beetles have initiated attacks on some trees, it may still reduce the number of trees that are killed within the treated area as compared to doing nothing.
MCH Bubble Cap Application Rate:
Always use MCH in accordance with the product label.
To protect individual trees in an area 1 acre or less apply 1-4 MCH bubble caps per tree. With trees over 24″ in diameter, add 1 unit of MCH for each additional 8 inches in diameter.
For areas 1 acre or larger, apply a minimum of 40 MCH bubble caps per acre. For low to moderate beetle activity, place 1 unit of MCH per tree in a 32′ by 32′ grid pattern.
For high to extreme beetle activity, an application rate of 60-80 units/acre is recommended. Not to exceed 80 units/acre.
Where to Put Them:
Attach MCH bubble caps to trees, snags (dead trees), shrubs, or even fence posts.
Caps should be applied to the North side of the tree at a height that applicators can easily reach (i.e., 6-12 feet). However, caps can also be placed in higher areas such as campgrounds or residential sites where it is likely that they may be disturbed. Ladders or a special long-handled hammer, known as a Hundle hammer, can be used to attach bubble capsules at a height where they are beyond reach.
Spacing Matters:
Even Distribution: For 1 acre or more, spread the MCH bubble caps evenly around the perimeter, creating a buffer zone, similar to making a grid on a piece of paper, while maintaining a spacing of approximately 32′ between each bubble cap.
Key Takeaways:
Apply MCH in early-to mid-April.
Apply 1-4 unites to individual trees. For 1 acre or more apply in a grid layout (minimum 40 caps/acre maximum 80/acre).
Staple bubble caps 6-12′ on the north side of the trunk, bubble facing outward. Do not puncture the bubble reservoir.
Always apply according to label.