If you live in Evergreen, you’ve probably driven past pines that didn’t make it through last year—their rust-red needles a reminder of mountain pine beetle damage. In hard-hit areas like Soda Creek, Hidden Valley, and Ruby Ranch, July is your last opportunity to protect healthy trees before beetles begin flying in August.
Once mountain pine beetles are searching for a host, the window for preventive treatment has largely closed. Protecting high-value pines now with sprays, pheromone packets, and proper watering gives them the best chance of surviving the season.
Key Takeaways
- Mountain pine beetles fly from mid-July through August and attack healthy pines you can still protect now.
- July is your final window for preventive sprays; applications once August flight begins are often too late.
- Three proven strategies that work together are protective bark sprays, anti-aggregation pheromone packets, and maintaining tree health through deep watering.
- Avoid non-emergency pruning during July and August, since fresh wounds release signals that draw beetles in.
- A well-watered pine defends itself far better than a drought-stressed one, making watering as important as any treatment.
Healthy pines are most vulnerable when adult mountain pine beetles emerge and begin flying in mid-July through August. Preventive treatments must be in place before beetles attack.
Why Should You Treat Pine Trees Before Mountain Pine Beetles Fly?
Preventive treatments are only effective before mountain pine beetles begin attacking healthy trees. That’s why July is your last opportunity to protect susceptible pines before peak flight in August. Here’s the cycle that makes timing so important:
- Adults emerge from last year’s killed trees and fly off to find healthy hosts.
- Within a day or two of landing, females bore through the bark and lay eggs.
- Larvae feed under the bark all winter, creating a fresh wave of adults that emerge next spring.
An attacked pine often stays green through winter and only fades to red the next season. By the time you see red needles, the tree is gone, and the beetles have moved to a neighboring tree. Prevention only works if it’s in place before the beetles fly—so waiting for visible damage means waiting a year too long. LAM’s complete guide to mountain pine beetles covers the full lifecycle and identification signs.
Prevention Strategy 1: Protective Bark Sprays
Protective bark sprays are the most effective way to defend a healthy, high-value pine. A spray coats the bark with an insecticide that kills beetles on contact as they try to bore in, and done right, they protect roughly 98 to 99 percent of treated trees.
When Bark Sprays Make Sense
Sprays are your best option if you have trees you want to keep, especially high-value pines in prominent locations. You need to act now, though. Treatments must be completed before mountain pine beetles begin flying in mid-to-late July. If you’re reading this in July, the prevention window is closing quickly. One spray protects for a single season, so trees in outbreak areas need treating every year the threat persists.
What Bark Sprays Won’t Do
A spray only protects healthy, uninfested trees. If a beetle is already inside, the spray seals it in rather than killing it. Sprays also kill other insects living on the bark, which is worth knowing if that’s a concern on your property. A Certified Arborist can determine which trees are worth protecting and recommend the right treatment.
LAM’s certified arborists can help you prioritize which trees to treat and handle the application through their Plant Health Care program.
What About Soil and Trunk Injections?
Injections are a supplemental option for protecting individual high-value trees, but for mountain pine beetle specifically, results are less consistent than bark sprays. Rather than coating the bark, an injection delivers a systemic insecticide through the tree’s vascular system. They can make sense in specific situations:
- Where spraying isn’t practical, such as near water, structures, or where drift is a concern.
- As an added layer of protection on a prized specimen tree.
Because efficacy varies against this beetle, LAM treats injections as a case-by-case option to complement spraying, not replace it. An arborist can tell you whether a given tree is a good candidate.
Prevention Strategy 2: Pheromone Packets
Pheromone packets release a synthetic anti-aggregation pheromone (verbenone) that mimics the “no vacancy” signal a fully colonized tree gives off. Incoming beetles read that signal and move on to find a different host. Unlike sprays, packets don’t kill anything. Instead, they redirect the threat.
When Pheromone Packets Make Sense
Packets are most useful for clusters of trees or when spraying isn’t the best option because of nearby water, structures, or concerns about spray drift. They’re also a good starting point if beetle populations in your area are still low. Some Colorado communities offer discounted verbenone pouches through partnerships with the Colorado State Forest Service. They’re more affordable than sprays if you’re protecting multiple trees.
Because pheromone packets work by discouraging beetles before they arrive, they must be installed before beetle flight begins and replaced annually.
What Pheromone Packets Won’t Do
Pheromone packets are about 80 percent effective when beetle populations are low, but that effectiveness drops sharply as numbers climb into epidemic territory—the situation in the worst Evergreen pockets right now. They work best as a complement to other strategies, not as a standalone defense during an active outbreak.
If you’re in a high-infestation area and need help deciding whether packets make sense for your trees, request an estimate and an arborist can map out a strategy with you.
Deep, infrequent watering helps pines produce the resin they use to defend against mountain pine beetle attacks, making proper irrigation a critical part of summer prevention.
Prevention Strategy 3: Tree Health and Watering
A healthy pine’s best defense is its own resin. When a beetle bores in, a healthy pine floods the wound with thick, pressurized resin that pushes the attacker out—what arborists call “pitching out” an attacker. But resin takes water and energy to produce, and a drought-stressed tree can’t build enough pressure to fight back.
Which Trees Need Extra Water
After one of the warmest, driest stretches on record across the Front Range, many Evergreen pines are entering beetle season already running on empty. For already-stressed trees, this isn’t just nice-to-have maintenance—it’s a rescue measure. If you have pines that look thin, pale, or drought-stressed, deep watering is one of the most important steps you can take to strengthen their natural defenses.
Deep watering around the drip line helps the roots absorb the moisture needed to produce defensive resin. During dry periods, water slowly and deeply rather than lightly every few days. Continue watering through dry winter spells, since pines need moisture year-round.
What Watering Won’t Do Alone
Watering keeps a tree healthy and able to defend itself, but it isn’t a complete substitute for prevention sprays or pheromones if you’re in an active outbreak area. The best protection combines healthy, well-watered trees with professional preventive treatments selected for your property and the current level of beetle activity.
LAM’s Plant Health Care program brings these pieces together into an integrated plan.
Should You Prune Pine Trees During Beetle Season?
Even the best prevention plan can be undermined if healthy pines are unnecessarily stressed during flight season. Hold off on non-emergency pruning during July and August, because fresh wounds release the very signals that help beetles find your trees.
Why Cutting Attracts Beetles
A fresh cut on a live pine releases terpenes—the same volatile compounds beetles use to sniff out stressed, vulnerable hosts. During peak flight, that’s like ringing the dinner bell, and wounded trees become easier targets than untouched ones.
What to Defer and What to Do Now
Wait until beetle season ends to:
- Shape or thin the canopy.
- Prune for a better view.
- Remove dead branches for appearance only.
Don’t wait to:
- Remove trees that are already infested.
- Remove trees that pose an immediate safety hazard.
Can an Infested Pine Tree Be Saved?
Once a pine is infested it can’t be saved, so the goal shifts to removing it before the beetles inside emerge and spread to healthy neighbors.
How Can You Tell If a Tree Is Infested with Mountain Pine Beetles?
A tree likely needs removal if you spot:
- Pitch tubes—popcorn-like blobs of resin—on the trunk.
- Reddish boring dust in the bark crevices.
- Fading or discoloring needles.
The longer an infested tree stands, the more beetles it releases into nearby pines.
When Should an Infested Pine Tree Be Removed?
Infested trees must come down before the adults emerge and fly, ideally by July. Once the beetles have exited, you’ve missed the window—the next generation is already spreading. Don’t wait until August to make the call.
What Should You Do with Wood from an Infested Tree?
How you handle the wood decides whether you’ve stopped the beetles or just relocated them:
- Chipping: Most effective; destroys the larvae under the bark.
- Debarking: Strips away the layer where larvae live.
- Solar Treatment: Cover cut logs with clear plastic for four to six weeks in hot months.
- Burning: Where safe and permitted, best with snow on the ground.
Never haul infested wood off-site unless it’s going straight to a secure processing facility, since moving it is a top way beetles spread. Spot pitch tubes or suspect infestation? LAM’s tree removal team can evaluate and remove the tree before August flight.
When to Call a Professional Arborist
Call a Certified Arborist if you:
- Aren’t sure which trees are most at risk.
- Need help prioritizing treatment.
- Suspect a tree is already infested.
LAM’s Plant Health Care program helps homeowners identify vulnerable trees, build a property-specific prevention plan, and protect the pines that matter most. Acting now costs far less than removing beetle-killed trees later.
Frequently Asked Questions About Preventing Mountain Pine Beetle
What’s the difference between preventive sprays and pheromone packets?
Sprays kill beetles on contact and are the most effective option, while pheromones redirect beetles elsewhere without killing them. Sprays suit individual high-value pines and pheromones suit clusters, so an arborist will often recommend both as part of a plan tailored to your property.
Is it too late to treat trees in July, or should I wait until next spring?
July is your final window, and the earlier in the month the better, because applications once August flight begins are usually too late for the current year. Waiting until spring leaves this season’s pines unprotected through the whole flight period.
If I didn’t treat my trees this year, what happens to them in August?
Untreated pines face a high risk of attack during flight season, and many will be infested, killed within a year, and become a source of beetles for next season. If you see signs of infestation, removing the tree before August flight is critical to protect your neighbors’ pines.
Do pheromone packets really work?
Yes. Pheromone packets can help protect healthy pines, especially when beetle populations are low. They work best alongside protective bark sprays and other prevention strategies rather than as a standalone treatment during heavy outbreaks.
Can I do some pruning in July, or should I avoid all cutting until September?
Avoid non-emergency pruning during the July–August flight season, since fresh cuts release signals that attract beetles. Safety-critical removals and the removal of already-infested trees are the exceptions; routine pruning, thinning, and view work should wait until September.
How much does professional beetle prevention treatment cost?
Costs depend on tree size, property access, and treatment type, since sprays are priced per tree and pheromone packets per pouch. A property-specific estimate is the best way to understand your investment and which trees to protect.
Preventive bark sprays create a protective barrier that kills mountain pine beetles before they bore into healthy pines. Applications are most effective when completed before the August flight season.
Protect Your Pines Before the August Flight
Mountain pine beetle prevention comes down to timing. Once beetles begin flying, it’s too late to protect trees for this season. If you have valuable pines in Evergreen or the surrounding foothills, don’t wait.
Call LAM Tree Service at 303-502-2188 or request an estimate online to schedule a property evaluation. Our certified arborists can identify your highest-priority trees and put the right prevention plan in place before beetle flight begins.
