Trees in the Front Range can present a lot of different signs and symptoms that’ll send chills up your spine.
D-shaped exit holes left by emerald ash borers, needle browning on your blue spruce, or mushrooms growing at the base of an old oak are often enough to send any homeowner searching for answers.
But there’s another warning sign homeowners across Colorado’s Front Range need to recognize: pitch tubes. Not all pitch tubes spell doom for a tree, but some certainly can.
We’ll explain everything you need to know about pitch tubes, the insects that create them, and the best ways to protect your pines below.
What Are Pitch Tubes?
Pitch tubes are small blobs of resin produced by pine trees (and some other conifers) in response to insect attacks. They form around tiny entry holes created by bark beetles and are often described as resembling pieces of popcorn stuck to the bark.
Pitch tubes are part of a pine tree’s natural defense system.
When a beetle bores into the bark, the tree responds by flooding the area with resin in an attempt to trap, drown, or physically push the insect back out of the tree.
In some cases, the strategy is quite effective, and healthy trees may successfully repel attacking beetles, allowing them to survive without suffering significant damage.
Not All Pitch Tubes Are Created Equally: The Usual Suspects
A number of different boring insects can trigger pines to produce pitch tubes. A few of the beetles in the Denver area that can cause pines to make pitch tubes include:
- Ips Engraver Beetles (Ips spp.)
- Red Turpentine Beetle (Dendroctonus valens)
- Western Pine Beetle (Dendroctonus brevicomis)
- Mountain Pine Beetle (Dendroctonus ponderosae)
The first three species tend to preferentially attack stressed pines. And even when this occurs, the pines can occasionally mount enough of a defense to survive.
But the last insect in the list — the mountain pine beetle — is a different foe altogether. This insect will attack even the healthiest pines on a property, and they often do so en masse. In some cases, thousands and thousands of beetles may descend on a single tree, overwhelming its defenses and eventually killing the tree.
Adding insult to injury, mountain pine beetles also live with a symbiotic fungus. This fungus causes further damage to the tree by disrupting water transport through the tree, making it harder for the tree to defend itself.
You may have already heard of the mountain pine beetle. It has been responsible for the death of millions of pine trees across the western portions of North America. The beetle is native to this region, but it’s become more problematic in recent decades thanks to climate change and shifting forest management practices.
Bugs Aren’t the Only Cause for Pitch Tubes
In addition to boring insects, you may see a pine produce pitch tubes in response to physical wounds. Everything from mower and string trimmer damage to nails driven into a tree can cause it to form pitch tubes.
Monitoring Your Trees for Pitch Tubes
Because pitch tubes can vary considerably in size, color, and abundance, they’re easy to overlook during routine yard work. That’s why it’s a good idea to periodically inspect your pines, particularly if you own mature specimens in a mountain pine beetle-prone area.
When examining your trees, be sure to inspect:
- The Trunk: Pitch tubes can appear anywhere on a tree’s trunk, so don’t limit your inspection to eye level.
- The Base of the Tree: Some bark beetles preferentially attack the lower portions of a pine’s trunk, making the base of the tree a great place to start looking.
- Bark Crevices: Small pitch tubes and boring dust can sometimes hide in the bark’s natural fissures.
- Signs of Wildlife Activity: Heavy woodpecker activity may indicate that insects are present beneath the bark.
- Needle Discoloration: Browning or reddening needles can indicate that an infestation has progressed, although this often occurs well after the initial attack.
Just remember that pitch tubes aren’t always a cause for alarm.
Some trees successfully repel attacking insects and recover completely. However, because mountain pine beetles can kill otherwise healthy pines, it’s always worth taking a closer look when you spot resin masses on your trees.
What Should You Do If You Find Pitch Tubes?
Unfortunately, it is usually difficult for homeowners to distinguish pitch tubes made by mountain pine beetles — which are very concerning — from those stemming from other, less alarming causes.
So, it is always wise to contact an ISA-certified arborist for an evaluation anytime you notice pitch tubes. This is especially true in the following circumstances:
- You’re located near a current mountain pine beetle outbreak
- The affected pines are high-value trees
- There are a significant number of pitch tubes present
- More than one of your trees is producing pitch tubes
- You see boring dust or woodpecker activity on your trees
How Can You Protect Front Range Trees from Mountain Pine Beetles?
Part of the problem with mountain pine beetles is that they’re difficult-to-impossible to eradicate once they’ve invaded your tree. At this point, your tree is either going to be able to mount a robust enough defense to thwart the insects or it’s not.
However, there are preventative treatments that are quite effective at protecting your trees from mountain pine beetles. Typically applied as a bark spray, these treatments help kill the beetles before they can cause serious damage to your tree.
Ideally, you’d speak with a certified arborist about protecting your trees before you notice any pitch tubes. However, while it may not be possible to save a tree already producing pitch tubes, you may still be able to protect other vulnerable pines on your property if you act quickly.
Mountain Pine Beetle Pitch Tubes: FAQ
Pitch tubes are one of the most visible signs that something may be happening beneath your pine’s bark. Here are a few of the questions Front Range homeowners ask most often about pitch tubes and mountain pine beetles.
Do pitch tubes always mean my tree is dying?
No. Pitch tubes are actually a sign that your tree is actively defending itself. Some pines successfully repel attacking insects and recover completely. However, because mountain pine beetles can kill otherwise healthy pines, pitch tubes should never be ignored.
Can healthy pine trees survive mountain pine beetle attacks?
Sometimes. Healthy trees are better equipped to defend themselves than stressed trees, but mountain pine beetles are certainly capable of killing even healthy, mature pines — and they often do so in large numbers.
What time of year should I inspect my pines for pitch tubes?
It’s a good idea to inspect your pines periodically throughout the year, particularly if mountain pine beetle activity has been reported in your area. Regular inspections can help you identify potential problems before they become more severe.
Can I treat a pine tree after I find pitch tubes?
It depends on the insect involved and the extent of the attack. Some infestations may be manageable, while others may already be too advanced for treatment. A certified arborist can help determine whether the affected tree can be saved and whether neighboring pines should receive preventative treatments.
Are mountain pine beetles a problem throughout the Denver metro area?
Mountain pine beetles are generally a greater concern in the foothill and mountain communities of Colorado’s Front Range, where mature pines are more common.
Can mountain pine beetles spread from one pine tree to another?
Yes. Adult beetles fly in search of suitable host trees and may attack multiple pines on a property or throughout a neighborhood. This is one reason preventative treatments are often recommended for high-value pines in mountain pine beetle-prone areas.
What’s the best way to protect my pine trees from mountain pine beetles?
Preventative treatments are typically the most effective strategy for protecting valuable pines. Monitoring your trees regularly, maintaining their health, and consulting an arborist when mountain pine beetle activity is present can help safeguard your investment.
Protect Your Pines with Knothead Tree & Lawn Care
Mountain pine beetles and other bark-boring insects don’t wait for trees to become unhealthy before attacking.
By the time obvious symptoms appear, your management options may already be limited. Fortunately, preventative treatments and early intervention can go a long way toward protecting valuable pines throughout Colorado’s Front Range.
If you’ve noticed pitch tubes on your trees — or simply want to protect the mature pines that define your property — the ISA Certified Arborists at Knothead Tree & Lawn Care can help. We’ll evaluate your trees, identify potential threats, and recommend the right treatment or preventative strategy for your landscape.
Contact us today to schedule a professional tree health evaluation and keep your pines thriving for years to come.
Sources and References
- Colorado State Forest Service – “Mountain Pine Beetle”
State forestry agency hub on mountain pine beetle (Dendroctonus ponderosae) covering its ecology, susceptible pines, outbreak history, identification, and management on Colorado’s Front Range.
https://csfs.colostate.edu/forest-management/common-forest-insects-diseases/mountain-pine-beetle/ - Journal of Forestry (USDA Forest Service) – “Mountain Pine Beetle in Colorado: A Story of Changing Forests”
Peer-reviewed synthesis by Negrón and Cain documenting Colorado’s 1996–2013 outbreak, the roughly 3.4 million affected acres, and the epidemic’s effects on forest ecosystem services.
https://research.fs.usda.gov/treesearch/57417 - Gilpin County, Colorado – “Mountain Pine Beetle FAQs”
Detailed county extension–informed Q&A on beetle biology, pitch-tube identification, cold-temperature survival, and prevention through thinning, verbenone, insecticides, and infested-wood disposal.
https://gilpincounty.colorado.gov/mountain-pine-beetle-faqs - CU Boulder Today – “The Pine Beetles Are Back. Here’s Why—and What You Can Do About It”
Q&A with a CU Boulder entomologist explaining the 2026 Front Range resurgence, the role of warm winters and drought, wildfire risk, and homeowner actions.
https://www.colorado.edu/today/2026/01/28/pine-beetles-are-back-heres-why-and-what-you-can-do-about-it - USDA Forest Service – “Western Pine Beetle: Forest Insect & Disease Leaflet 1”
Federal leaflet on the western pine beetle (Dendroctonus brevicomis), covering its biology, host pines, outbreak behavior, and management, including the 2013–2017 Sierra Nevada epidemic.
https://research.fs.usda.gov/download/treesearch/66205.pdf
