How Wildfire Management makes Mountain Pine Beetle (and Other Pests) Worse

You may not think that tree pests and Colorado’s wildfires have anything to do with each other, but that’s not the case.

Tree pests, especially mountain pine beetles, can make our wildfires worse, and certain wildfire management practices can actually increase destructive beetle populations, draw beetles to properties, and/or make trees more appetizing for mountain pine beetles.

In this article, we will explain more about this strange relationship between wildfire suppression and tree pests, explore what can be done to change this pattern, and give you information on how to keep your Colorado property fire safe and your trees healthy.

Mountain pine beetle larvae under the bark of a ponderosa pine discovered by LAM Tree Service.

The First Problem: Modern Fire Suppression Practices

Our forests aren’t the same as they were before we lived here. Some of the changes we’ve made are small, and we’d like to think they are good for the little bit of forest under our watchful eye.

These are things like amending soil and supplementing water in the ornamental landscapes near our homes. They might also be things LAM Tree does at your property to improve the vigor of the landscape and prevent or control a pest or disease.

Then there are the big changes like clearing out places for our homes or digging inroads to get to them. The biggest change we’ve made to the forest is from the results of our fire suppression.

When you look at historical photos of the foothills of Colorado, and even the greater Front Range, the forest in the background is considerably thinner. Early photos of the Evergreen area from 100-120 years ago show forests that had fires in them fairly regularly.

This is evidenced by the open understory and abundance of shrubs. Those small, often regularly occurring fires kept the small tree and shrub population managed; in doing so, they preserved the larger trees, allowing them to grow into mature giants that had wide-reaching canopies.

The Second Problem: Mountain Pine Beetles

Nature had a way of maintaining the big trees as well, a native insect called the mountain pine beetle (MPB). This insect would attack the old, diseased, and weakened larger trees, killing them in a year’s time. Then those dead trees would be ripe for the next fire cycle that came through, finishing up the cycle.

MPB has a cycle that encourages the beetle populations to stop by Colorado’s Front Range about every 20-25 years. Some folks may remember the last few times it was here, during the 1970s and the 1990s. Anyone that was in the area for the last 50-60 years will tell you about the trees dying in patches, and sometimes whole hillsides of large, mature ponderosa died from the beetle during that 70s epidemic.

Neighbors helped each other to find and cut out the trees during the time the beetle was under the bark; many sprayed to keep their healthy trees from getting attacked.

In the 90s into the early 2000s, the MPB had a slight change of course. We saw it here around 1993, and it seemed to be similar to what occurred during the 70s epidemic.

After about 1998, we started to see the MPB on the other side of the divide in areas like the Frasier valley and Frisco. It never got as bad as those years in the 70s here on the front range, but it was much worse on the west side of the continental divide.

During the 1970s MPB outbreak, roughly 20% of the ponderosa of a certain size range were killed, almost all on the east side of the divide. In the 90s, that amount was fewer than 15% on the east side, but some areas like Grand County saw greater than 95% of their lodgepole pine (LP) killed. What was the difference?

The Third Problem: Drought

In the 1990s there was a horrible drought in Colorado, and the average temperatures were rising almost every year. Those lodgepole pine forests on the west side of the divide were very unhealthy and stressed.

Many of those LP stands had been mixed forests that were entirely clear-cut for fuel wood, mining, construction, and railroad use.

What grew back in was lodgepole pines, right around the time we began to suppress all forest fires.

Fast forward 100 years, and there was a totally dense, even-aged monoculture of lodgepole pines. This was a buffet for the mountain pine beetle; over a ten-year span, almost every LP larger than 15 feet tall was killed. The whole mountainsides were covered in dead, grey trees.

The common thought is that it was the stress that led to the unprecedented mortality rate. This is because MPB’s role is to cull the weak and stressed trees from the forest, leaving behind healthy trees.

Therefore, a whole forest of too dense, stressed trees turns into a whole forest of dead trees.

LAM Tree Service workers remove a tree in close proximity to other trees in the Colorado foothills.

The Solution: Forest Thinning, Plant Diversity, and Stress Reduction

We know that fire thinned the forest, and we know that this thinning led to trees that vary in age, variety, and density. We’ve seen what MPB is capable of in a forest that isn’t varied in age, variety, and density. We’ve also seen what fire does in our too-dense forests with houses mixed in.

The answer seems to point to keeping a thin forest that is varied in age, variety, and density as the best option to prevent MPB and fire.

But, sometimes, in the effort to thin the forest, we cause stress on the trees that remain after work. This can be because of the following:

  • the soil being disrupted,
  • roots getting damaged from equipment,
  • too many trees getting cut out at once,
  • debris piles and chips left behind,
  • or not leaving the right trees to remain as our “healthy” trees.

These stressors can all be a draw for MPB. Often after a fire, there is an increase in MPB on the edges of the burn.

These stressors can be managed the most with a good plan and cautious implementation.

How Tree Debris Plays a Role

Areas that have seen the worst MPB activity and have recently had a fire mitigation job have some common traits. The most common of them are leaving behind debris.

Debris can be:

  • logs,
  • chipped material
  • stumps
  • piled limbs and other tree parts

All this debris smells like a stressed forest to a bug that is looking for stressed trees, especially when there’s a lot of it.

Often there’s another insect that will be drawn in, build in population and then move to the healthy trees. Their activity can also lead to more MPB, just like when we’re tired or worn down, it’s more likely for us to get a cold.

LAM Tree Service employees use tree care equipment during a tree removal in the Colorado foothills.

What You Can Do

Now that we know the problem, what can we do to change the relationship between our trees and mountain pine beetle in the future? Below are some suggestions.

Prioritize plant and tree diversity on your Colorado property

Aim for a property that has a variety of native trees and shrubs that vary by size, age, type, and density as a means to prevent fire damage and pest destruction.

Diverse tree and plant species will also provide more options for food and shelter for local birds and wildlife.

Plus, your property will be more visually interesting with a variety of plants, trees, shrubs, and flowers.

Check out these recommended Colorado trees >>

Learn about firewise plants for your landscape >>

Thin your trees rather than removing them all

Thinning, or removing select trees, can make your property more fire-wise. We recommend this method rather than removing or clear-cutting all trees from a property.

LAM Tree can help you decide which trees to remove to thin the trees on your property. We talk more in this blog post about why removing all the trees isn’t the best idea.

Schedule a tree removal with LAM Tree Service >>

Ensure your property is free of tree debris

Keep your property clear of cut wood and other tree debris, which can attract mountain pine beetles.

Removing pine needles and other flammable items from the ground can help with fire mitigation.

Prevent or minimize stress on your existing trees

Stressed trees attract pests and diseases and are more likely to succumb when they infest your trees. Keep your property healthy with proper tree maintenance, which includes:

Water trees to prevent drought stress

Trees benefit from slow and deep watering at the drip line. Young and recently planted trees need more supplemental water than mature trees, but all benefit from regular watering.

Winter watering is helpful for many Colorado trees, especially during times of drought.

Learn more about our winter watering programs >>

Watch for and Treat Mountain Pine Beetle Infestations

Check out our article on mountain pine beetle (and watch the video) to learn how to spot mountain pine beetle infestations on your property.

If mountain pine beetle is confirmed on your trees, treat the infestation as soon as possible.

Mountain pine beetle treatments are generally applied from May through July. Contact LAM Tree for more information. 

Use Fire Mitigation Methods to Protect Your Property

The fire suppression methods used in the past (and even recently) aren’t the only option for preventing fires on your property.

LAM Tree Service provides fire mitigation services to help keep your property and family safe.

Learn more about fire mitigation >>

Contact LAM Tree Service

Now that you know and understand the unique relationship between Colorado wildfires and tree pests such as mountain pine beetles, you are better informed on how to best protect your property.

Contact LAM Tree Service to discuss individualized plans for your unique Colorado property. We can help you create and maintain a beautiful property that is healthy, beneficial for the environment, and fire wise.

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