Colorado State University Extension services estimates that one infested tree will kill at least two and possibly more trees. Thus the exponential devastation occurs.
Methods of controlling the beetles have been tested for the past several years by the Canadian Forestry Service, United States Forestry Service, United States National Parks Service and many other arboreal organizations, Universities, and private research facilities.
While there is certainly not space enough to discuss all here, we will try to give you a synopsis of several well-respected studies.
IGR's (Insect Growth Regulators): Unfortunately, our research has not produced any studies confirming that IGR's (birth control for insects) can affect the Mountain Pine Beetle. Despite our best efforts, the beetles' ability to propagate under the bark makes it impossible to contact the larvae during their metamorphosis and thus impossible to affect or mutate their development. This is certainly a pity, as IGR's are the safest bulwark against many species of insects that plague man and beast.
Systemic Insecticides: Delivered through the root system, there was much hope that the trees would take up the chemicals from root to top and kill the beetle larvae in their dens. Unfortunately, these delivery systems have not proven effective against the Mountain Pine Beetles either. As of 4/07, there were no commercially labelled insecticides specifically for Mountain Pine Beetles.
Carbaryl: Certain formulations are currently being used by Rocky Mountain National Park and other Park services to help prevent devastation to the important, old, and landmark trees in the national parks. While Carbaryl (Sevin) has been shown to be very effective in preventing beetle attacks (through one MPB flight - one year) by killing the beetles before they can successfully bore into the tree, it has many drawbacks. It is a cholenesterase-inhibiting chemical. That means that its affects are worked on the nervous system of mammals. National Park personnel who spray the trees must wear heavy protective clothing, and must have blood tests frequently to monitor their exposure.
Additionally the run-off is very damaging to the environment.
Both the U. S. Forest Service (USFS) and Rocky Mountain National Park (RMNP) are spraying thousands of trees in Colorado. What risk does this pose to downstream water users? Who will monitor streams, ditches, and wells for carbaryl? Forty percent of Boulder,Colorado's water is from Barker Reservoir, so it is of great concern that the Silverthorne/Dillon Joint Sewer Authority declared they found carbaryl in the Silverthorne plant effluent (i.e., treated water) in 2007.
And it is highly toxic to bees, stoneflies, and some fish. In 2005, twelve groups representing farmworkers, beekeepers, and environmentalists called on the Environmental Protection Agency (EPA) to cancel carbaryl due to the unreasonable risks associated with it. In 2007, the EPA restricted many pet and home uses of carbaryl.
This is not a treatment we recommend for home application, and feel it should be banned altogether.
Permethrins: (Astro) A synthetic approximation of a naturally-occurring chrysanthemum flower chemical. Wikipedia states that, "According to the Connecticut Department of Public Health, it 'has low mammalian toxicity, is poorly absorbed through the skin and is rapidly inactivated by the body. Skin reactions have been uncommon.' However, it is still a substance that is not without its side effects. It is toxic to honey bees and other beneficial insects as well as the Mountain Pine Beetle. It can produce changes in the number of oxygen-carrying cells in the blood of birds. It is extremely toxic to fish, and great care should be taken not to let it get into any water source. This is a kinder, gentler solution but not without some risks. Additionally, it comes in hard-to-manage, large volume containers not readily suited to home application.
Esfenvalorate: A synthetic pyrethroid like Permethrin .
Formulations of Esfenvalorate have been shown to be effective through one flight season of the MPB. In a study by the Arboriculture & Urban Forestry 2006. 32(5):247-252, testing the effectiveness of Permethrin Plus-C (Masterline) and Carbaryl (Sevin SL) for protecting Individual, High-Value Pines from Bark Beetle Attack, the results showed that esfenvalorate applied at a rate of 0.025% and 0.05% provided protection of P. ponderosa for a full summer in more than one study in more than one forest. However, Masterline is no longer manufactured, and we know of no substitute that can be used in a home-delivery system.
Self-application of poisons is very difficult. Delivery to large trees is difficult because application requires drenching the entire trunk to a height where the trunk diminishes to about 6" diameter until run-off. Most individual-use spray containers don't have enough power to reach that high. Any more powerful sprayer has the danger of blow-back onto the applicator.
It is best to spray trees in early summer, before the beetles have left their winter trees in search of new habitat. Trees sprayed after July 4 may already have been attacked, and reaching the egg-laying adult will already be impossible.
Spray the tree from the very ground up the trunk to where the trunk tapers to approximately 6" diameter. Spray the entire circumference.
Due to the nature of pine bark surface, application rates are more concentrated for tree application than for other lawn or garden use. However each product is different. Consult the manufacturer for recommendations.
Windy weather can be a hazard to the environment as well as to the applicator and can prevent the insecticide from sticking to the tree. Usually morning spraying is best. Significant rain within 2-4 hours of spraying can dilute or wash the chemical off the tree.
During epidemic conditions, the pressure from beetle populations who must go SOMEWHERE (even if conditions are not optimum for them) may reduce the effectiveness of all treatments. see: "The Future of Forests of North America".
Disclaimer: Please read the pesticide label prior to use. The information contained at this web site is not a substitute for a pesticide label. Trade names used herein are for convenience only; no endorsement of products is intended, nor is criticism of unnamed products implied.
Always carefully read and follow all label precautions before applying insecticides for MPB prevention.