As you drive through Rocky Mountain National Park in Colorado it’s hard not to see the work of the mountain pine beetle. Whether you acknowledge the inevitable cycle of forests or just see it as the reason you had to cut down the once-beautiful pine tree in your front yard, the mountain pine beetle has always been a factor in the forest cycles of Colorado.
This last epidemic cycle caused wide-spread damage of lodge-pole pine forests. Real estate values suffered, and forest fires became more prevalent. erosion control was diminished as was bio-diversity.
Forestry experts and citizens are just now getting data on all the chemicals that were being sprayed to see if that was the right approach.
It seems clear that forest thinning and perhaps supporting healthy trees with deep root watering techniques may make pines more resistant to the beetle. Forest thinning does have a macro effect. To protect a tree in your backyard, careful cultivation and preventive tree spraying could protect high profile trees from being damaged by the infestation.
The mountain beetle is a native species, also referred to as the Rocky Mountain Pine Beetle. Biologists believe that a succession of mild winters from 1998 through 2010 allowed the beetle populations to explode. Typically, the beetle in its larval stage, can not survive the consistent 40 degree below zero temperatures that are typical in the Colorado high country. This allowed a substantial amount of larvae to survive and thrive during the summer months.
What are the seasonal patterns of MPB
Typically the beetle starts flying in late June or July and may continue into September. Although it seems that the beetle has been coming sooner in areas like the Estes Park Valley, according to local sources.
Pine beetles tend to pick large, weak or diseased trees in denser wooded areas. But in an epidemic, it will target healthy, green trees and smaller growth. There is not a consistent proximity pattern. The beetles won’t necessarily attack a tree nearby. Finally, once beetles infest a tree there is no practical way to save it.
Part of the power of this pest is the ability for a coordinated attack on a host tree. Once the beetle colony has finished with a tree it will move onto the next to lay eggs. Then the cycle repeats.
What’s worse is that a beetle colony will grow. If it affected one tree this year, it will be able to attack two or even three trees the next year.
How to protect trees from pine beetle
You can protect the pine trees on your property. Spraying unaffected pines for the mountain pine beetle in spring is the most effective treatment. Beetles will land on the tree and be disrupted by the protected bark.
While over-spraying in the Colorado high country has been an issue, part of the problem is tree spraying done by unlicensed individuals. Proper application requires knowledge of the short and long-term effects of pesticide application. Tips for a good experience include hiring a company that has a Qualified Pesticide Supervisor on staff. They also should be approved by the Colorado Dept. of Agriculture to apply pesticides. Cities such as Estes Park and Boulder have stricter ordinances.
Using different sets of chemicals will reduce the mountain pine beetle’s resistance to the treatment. Avoid spraying low value trees, such as trees which are very small, or trees which are already dead. In addition, spraying out of season will just kill natural predators and potentially contaminate water.
Promoting good tree health is important as well. Proper fertilization and watering will keep a tree healthy and make it more resistant to pine beetle attacked. finally, removing diseased and infested trees will prevent a colony from spreading. This should done in winter ideally when beetles are in their over-wintering state.
Pine Beetle FAQ
When does the mountain pine attack trees in Colorado?
Typically the mountain pine beetle is in flight from Mid-July through August. However, startling new data suggests their season is rapidly expanding according to ecologists at CU-Boulder. Beetles were caught as early as May 22nd and as late as September 20th in their wide-ranging study.
There are mountain pine beetles in my tree. Can you stop it?
The short answer is no. Preventive tree spraying is the best known way to prevent beetles from infesting a tree. Other tactics such as pheromones which attract and trap beetles is at best uncertain in its effectiveness. Tree health care cultural practices such as fertilization and watering help a pine tree make more pitch, giving it more ability to push out mountain pine beetles. But that solution is far from being uniformly effective.
When should you spray for mountain pine beetle?
The only time to effectively prevent beetle infestation is to spray before they attack the pine tree. There are no remedial treatments once the pine beetle has colonized the tree. We time our pine beetle spray between April and June before the adult beetles emerge.
If the application is done in early spring, there must be some sort of sticking agent (known as a surfactant) in the mix so that the active chemical stays on the bark long enough to provide control.
Are the insecticides dangerous?
We primarily use permethrin based products that are only available to commercial grade applicators. We take great care with pets, especially with fish and cats, when conducting our operations. The pesticides are toxic when wet so we always advise people to stay out of the way for about an hour or so, leaving more than enough time to dry in the Colorado climate. Also, following the label directions for personal protective equipment is required by law.
Some applications that contain carbaryl are available to the general public (and unlicensed tree sprayers). This is nasty stuff and we reiterate to follow label directions closely.
I thought mountain pine beetle wasn’t in the Denver area.
As of 2018 this latest cycle of the epidemic subsided, so if your pine looks like it’s been hit it might be an other type of beetle or some other factor. Mountain pine beetle go through long, multi-year cycles and once the majority of good targets are hit, it subsides. We have seen mountain pine beetle infestations from Boulder to Castle Rock.
David Merriman owns Arborscape and is a member of the American Society of Consulting Arborists. Contact us to get a free quote on protecting your pine trees.