Facing Mountain Pine Beetles


Identify and treat this major tree pest

The mountain pine beetle (MPB) is wreaking havoc across the western United States, and identification and treatment, either by landscapers or in partnership with specialists, should be a profitable sideline this year.

Done correctly, spray application of trees in towns can be remarkably successful.

Signs of infested trees

For landscapers driving through developments or on back roads, trees infested by MPB will be easy to spot. According to Matthew Jedra, forester of the Boulder district of the Colorado State Forest Service, the symptoms of MPB infestation include popcorn-shaped masses of resin called “pitch tubes” on the trunk where beetle tunneling begins. About nine to 10 months after being attacked, the needles of infested pines will turn reddish-brown. A white paper by the Colorado State University (CSU) Extension explains that during the early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease or old age.

In Vail, Colo., lodgepole pines surround many of the golf course developments on the south side of town. Jamie Gunion, special projects manager with the town of Vail, says homeowners who have been consistently spraying their trees over the past few years have been successful at saving their trees. Gunion says MPB is very aggressive and it can’t be stopped, so the town is just trying to keep up with it.

According to Gunion, 73 percent of the trees in that area are standing dead. Over 90 percent will die because of the beetles. Areas on the south side are difficult to work on because they are steep. Vail Public Works has been working on removing infested trees and spraying the trees surrounding the golf courses that can be saved. Gunion says that the town is now focusing on new regulations that require removal of hazardous or infested trees within 30 days of notification.


When Paul Payne, owner of St. Vrain Arbor Care in Boulder County, visits a site, he determines how many trees the homeowner has, where they are sited on the property and if he can reach the trees. He focuses on a 1-acre plot around the house that the homeowner wants to save. He determines, based on size, preferring the larger trees, which trees are worth spraying.

Kevin Marks, consulting certified arborist with Davey Tree out of Boulder, Colo., says there are several courses of action that a homeowner can take to prevent MPB infestation on their land. He suggests that homeowners start with a healthy forest stand, which means thinning out the trees by getting rid of any standing dead trees, or trees that are in marginal health or stressed. He recommends that the homeowner set a perimeter of trees around the house, which they refuse to lose. Those healthy trees will then be sprayed to be sure that they will survive if an infestation occurs.

Marks says that the MPB problem is so bad at this point that if a homeowner wants to preserve their trees they need to be sprayed. “We have a lot of tools in our bag, and we always bring out the pesticides last,” he says.

What to spray

Jedra says that there are no labeled pesticides for use on MPB once they attack a tree. Certain formulas of carbaryl (common name Sevin), permethrin (Astro, Dragnet and others) and bifenthrin (Onyx) are registered for use to prevent attacks on individual trees.

Davey Tree and St. Vrain Arbor Care spray Astro, a synthetic pyrethrin insecticide. According to Marks, it is one of the safest pesticides available. In addition, the pesticide doesn’t smell longer than it is wet and doesn’t leave a residue, with the exception of a grey, dusky coat on the bark that is noticeable with heavy applications, adds Payne.

One downside to Astro is that it is toxic to fish. Technicians need to be aware of where drainages are and where they go.

The mountain pine beetle

The mountain pine beetle is native to the forests of western North America and has a one-year life cycle in Colorado. According to the CSU Cooperative Extension, MPB are the most important insect pest of Colorado’s pines, and they often kill large numbers of trees annually during outbreaks.

The MPB develops in lodgepole, ponderosa, Scotch and limber pines. Their place in nature is generally above 7,000 feet. At these higher elevations, there is massive destruction of trees. In the process, there are more and more beetles building up, and they need somewhere to go, which is why people are finding their trees being infested at lower elevations. The CSU says outbreaks develop irrespective of property lines, being equally evident in wilderness areas, mountain subdivisions and backyards.

At the current rates of spread and intensification of tree mortality, the MPB will likely kill the majority of Colorado’s large-diameter lodgepole pine forests within the next three to five years, according to the U.S. Department of Agriculture.

These red trees near Evergreen, Colo., need to be removed, not sprayed.

Partners in spraying

There has been an increase in the last couple of years with MPB problems on the Front Range. Payne says that with all of the media coverage surrounding the problem, homeowners are calling companies “reflexively.” From an operator’s standpoint, Payne stresses several points. The home or landowner should always choose a sprayer that is properly certified. Not all landscape companies are equipped to deal with tree insects. If they want to treat trees affected by the MPB, they need to have the proper certifications and equipment.

To a company that does not have the proper equipment or certification, it would be advantageous to develop a relationship with a tree care company they trust, says Payne. It could be a company they have worked with in the past or one that’s been referred to by others in the field.

Keep in mind that homeowners are worried; they probably realize the risk of losing trees to MPB. If they call a company that is not familiar with the MPB and its effects on trees, a misdiagnosis could increase tree loss. However, a reputable landscaper, or one who has a contract with a sprayer, is more likely to get the homeowner the results they desire. This creates a win-win situation for the homeowner, sprayer and landscape company.

Growing problem

A 2007 aerial survey by the U.S. Department of Agriculture and the Colorado State Forest Service showed that there were approximately 500,000 new acres infested by the MPB epidemic. These organizations are calling the epidemic a catastrophic event that has affected more than 1.5 million acres from the first signs of outbreak in 1996. The infested trees were isolated to the dense forests of northern Colorado last year. Today, infested trees can be seen in the Front Range areas. The situation has gotten so dire that experts are no longer concentrating on prevention; they are now focusing on mitigation.

Mechanics of application

There is a science to spraying healthy trees to prevent MPB infestation. St. Vrain Arbor Care tries to group all of their applications to save time and keep costs low. Trees that are being sprayed to prevent MPB infestation are sprayed once a year. There is a state law that prohibits more than 5 quarts of insecticide per 100 gallons of water to be sprayed on any one site per year.

Almost all arborists agree that mixing 3 to 4 quarts of insecticide per 100 gallons of water is a good rule of thumb.

Payne suggests that his clients don’t skimp on the spray to save costs, but do not overdo it, either.

“A mixture of 2 quarts per 100 gallons will do the job, but the insecticide tends to photodegrade. The light and air oxidize the product on the bark and make it ineffective. Using a concentration of 5 quarts per 100 gallons is excessive,” says Payne.

The insecticide is applied with a hydraulic sprayer from the top of the tree, around all sides and all the way to the ground. St. Vrain’s crews can get 300 feet from the vehicle to any point with their hoses.

Normally, they run with #3 tips on everyday activities. For larger trees, they use a #5 tip on an FMC gun, with a 5/8-inch diameter hose. The #5 tip allows them to get more volume and apply more pressure to hit the higher elevations in the tree. Payne says that the insecticide should be applied to the trunk up to 35 feet high, or 6 inches in diameter, whichever comes first, and all sides must be covered thoroughly.

Typically, homeowners will want a landscaper to spray anywhere from 20 to 200 trees. Payne tells people to be prepared to spray for five years. “If they are careful and aware of their surroundings—what’s going on within a 5 or 10-mile radius of where they are—and they start to see groups of yellowing trees, they shouldn’t risk it,” says Payne. They should spray their trees on a preventative basis.

When to apply pesticides

The forest service and certified arborists recommend applications should be no later than July 15. The Colorado State Forest Service says that trees infested with MPB can be mechanically treated to kill developing beetles before they emerge as adults, which begins in mid-July and continues through the middle of September.  

Payne says that pesticides can remain active on the bark for three months. Spraying before July 15 allows the pesticide to be active prior to the MPB flights and continues to be active throughout flight, so when they hit the tree it stops their process for the year. Davey Tree recommends to their customers to have a preventative spray application completed by the July 4 weekend so that homeowners can get the spray down in time and enjoy their land.


When a homeowner sees pitch tubes in a tree, they need to seek expert help.

“The biggest confusion I see is that homeowners don’t understand that once a tree has been hit, it needs to be cut down. That tree is a lost cause and should never be sprayed,” says Marks. The tree needs to be pruned at the base, cut to the ground and removed from the property, he adds.

Payne says it is important to explain the aspects of the MPB. He is looking at a tree that may have been hit multiple times some distance up the trunk, which will be yellowish within six months and dead within the year.

St. Vrain Arbor Care services homeowners along the Front Range with .5-acre or larger sites. If Payne sees live trees that are still green with pitch tubes, he advocates removing the trees immediately.

The Colorado State Forest Service has several other recommendations for control. Logs may be burned, debarked, buried under 8 inches of soil or chipped.

Solar treatments that raise the temperature under the bark to 110 degrees will kill beetles and their larvae. This is done by spraying the logs with water, covering them in clear plastic and placing them in an area that receives several hours of direct sunlight for approximately two months. The logs must be laid in a single layer on the ground.

The future

The more media attention and education we can get to the public, the better we will be able to prevent and control the MPB epidemic. Lawn and tree care experts are a big part of that process. They can educate landowners on the proper course of action to save their trees.

Marks says the biggest problem he sees is people who bring infected pinewood down from the forest to use as firewood in the towns in lower elevations. “They stack it up on the side of their house without realizing they have a burrow site for beetles to come out in July to attack the forest,” says Marks.

Curt Harler is a freelance writer and a frequent contributor to Turf. He resides in Strongsville, Ohio. Rebecca Roach is a Boulder, Colo.-based freelance writer who specializes in turfgrass and business reporting.