Southwestern Region
Forest HealthFOREST HEALTH: Bark Beetle Outbreak
Frequently Asked QuestionsWe have compiled some of the most frequently asked questions about the bark beetle outbreak with their answers. If you do not see the answer to your question, please contact us for more information.
1. What is the overall pine bark beetle situation in the Southwest? Beginning in 2002, several species of pine bark beetles experienced a population explosion. The region-wide drought weakened trees’ normal way of resisting these insects . In 2003, more normal precipitation levels helped reduce tree mortality levels in many ponderosa pine forests, however, piñon pine mortality levels continued to increase. Consequently, millions of trees were killed in Arizona and New Mexico. Mortality in 2004 and 2005 was considerably reduced compared to the previous two years. In many areas, the highly susceptible trees have already been attacked and killed, while greater moisture has improved the health of many of the remaining trees. 2. When the drought ends, will bark beetle populations return to normal levels? Yes, but this may take some time, because trees depend on moisture to fight off beetle attacks. Because beetle populations are so high and geographically widespread, bark beetles have, in essence, a huge head start. In order for beetle populations to dwindle to normal levels across millions of acres, sufficient moisture over an extended period of time will be required. 3. Can insecticides be used to combat these insects? Applying an insecticide to the bark prior to beetle attack can protect individual trees. This treatment will protect trees for about a year. Once a tree is infested it is too late to consider the use of insecticides. Large-scale application of insecticides is not feasible from either an economic or practical standpoint. Aerial spraying is not viable as an alternative because the insecticide would not adequately cover the bark surface. 4. What happens once a tree dies? Within 3 to 6 months after a tree dies, its needles will drop to the ground. The snag (a standing dead tree) will stand for a while, usually between 2 and 6 years before falling to the ground. How long a snag remains standing depends on a number of factors, but especially on the rate of decay of the tree's root system. Dead trees could pose a hazard if the path of their fall threatens structures or areas frequented by people. 5. Where did these beetles come from? These native bark beetles are always present in our southwestern forest ecosystems, but usually at low population levels. 6. How do these beetles kill trees? Bark beetles chew their way through the outer bark of a tree and feed on the nutritious soft inner bark. After attack, they emit a chemical scent (called a pheromone) that attracts other beetles. The beetles then mate and lay eggs in galleries or chambers they construct between the bark and the wood. A “blue stain” fungus carried by the beetles contributes to the death of tree by clogging water-conducting tissues. 7. What is the Forest Service doing to address the bark beetle infestations on National Forests? The infestations developed so quickly and are so widespread that there is nothing the Forest Service or anyone can do to stop them. However, assessments of the situation are being conducted on affected National Forests and trends in tree mortality are being monitored. Thinning in and around recreation sites or adjacent to communities was accomplished in 2003. In 2003, a number of developed recreation sites were sprayed with insecticide to protect high value trees. The objective of these treatments is to protect the Forest Service investment in these facilities by maintaining aesthetic quality and minimizing the hazard dead trees pose to visitors. Evaluation of the 2003 treatments shows a very high success rate. The candidate areas include both previously treated and new sites. If we look at the bark beetle epidemic at the “Big Picture” scale, the recipe for future success requires thinning of unhealthy forests to restore their ability to naturally withstand these events, even in tough drought years. 8. What can an individual landowner do to protect trees on their property? That depends on a handful of variable factors. For example, if a landowner can afford to, one could treat individual trees with insecticides to prevent bark beetle attacks. Or, another strategy is to water trees to bolster their natural defenses. (Watering is no guarantee of protection, though, because a mass attack of bark beetles can overwhelm even a healthy, thriving tree and kill it.) Another way to protect a small stand of trees is to thin the smaller and less healthy trees in the stand so as to give the dominate trees that remain a better chance to regain enough vigor to fight off beetle attacks. Do not perform thinning unless slash can be removed, burned or chipped and dried (see following question). 9. What actions should be avoided when attempting to protect trees? Do not do anything that will introduce further stress to your trees. For instance, anytime a tree is damaged and must produce sap to cope with an injury, it has to expend precious moisture (in the form of sap). That weakens the tree and makes it that much more susceptible to beetle attack. Removing small or poorly competing trees from a stand can improve the vigor of the remaining trees. It is a mistake, however, to fail to deal with residual material from cutting trees (any parts of the tree that have a 3 inch or larger diameter, such as the boles and limbs). Untreated material left on the site is actually an attractant to additional beetles. If beetles breed in the residual material, they represent yet another source of new beetles to attack the remaining trees. Because feeding by the non-lethal bark moth or pitch nodule moth can resemble bark beetle attack, do not cut down trees before confirming bark beetle presence. 10. What are the impacts of this epidemic? It is difficult to measure the social, environmental and economic impacts related to tree losses due to the beetle outbreak. The duration and extent of the epidemic cannot be predicted. Not all impacts will be negative. Potentially positive results will be the natural thinning of some stands, improved watershed yield, improved wildlife habitat, and enhanced biological diversity. Trees reproduce and die throughout the life of the forest; in this event, though, the process of trees dying is far more apparent. Even under the worst circumstances that can be envisioned, there will still be a forest; it just may not resemble the forest with which we are now familiar. 11. How bad was this outbreak compared to other outbreaks? While we know that bark beetles have been a part of the natural ecology of the Southwest for as long as our forests have existed, early reports don't provide many details. We know severe outbreaks occurred during the 1950's drought, but historic records do not detail locations, extent or severity. We cannot predict the duration of the current outbreak or how many trees will ultimately die. However, stand densities are believed to be well beyond the natural range of historic variability, so trees losses could potentially be greater than previously experienced. 12. How have past Forest Service management practices contributed to this problem? It is generally accepted by the scientific community that many forest management policies and practices contributed to the unnatural tree densities that now exist in our forests. Fire prevention and suppression activities appear to be the primary factors interrupting the natural fire return cycle. Fire suppression during the first three-quarters of the 20th century was supposed to protect forests from a perceived "enemy" but it only succeeded in programming our forests for more severe wildfires in the final quarter-century-not to mention these first few years of the 21st century. 13. Are federal funds available to help me thin trees on my property? No federal funds are directly available to private landowners for bark beetle prevention thinning. Some communities are participating with State forestry organizations in fuels reduction programs that could have a secondary benefit in reducing bark beetle susceptibility where thinning achieves improved vigor in the remaining trees. Community assistance grants of this type are generally announced in the local media and are posted on state and federal websites. 14. How much salvage logging will be used to remove dead trees? Salvage options are being considered by the individual National Forests on a case-by-case basis, but due to economic and administrative limitations, very little of the affected timber would likely be salvaged. Removal of dead trees vacated by beetles will have no impact on bark beetle populations. 15. How will this beetle outbreak contribute to our wildfire problems? Many people are concerned that numerous standing dead trees will contribute to our already ominous fire situation. However, the situation isn't as bad as it seems. Typically, beetle-killed trees shed their needles within a few months of dying, so they won't create as big a threat to massive fire spread as one might imagine. The millions of new snags do present a threat of spotting when a forest fire is burning around them, and that threat will have to be considered every time a fire is burning near beetle-killed trees. Once trees fall, a fire in these large fuels would burn longer and hotter, damaging soils and adversely affecting the site in the long-term. 16. Who should a private landowner contact for information
on protecting trees or reducing their susceptibility to pine bark
beetles? In Arizona, private landowners should contact the local county extension agent:
In New Mexico, they should contact Stephani Sandoval, Forest Health Specialist, NMSU/New Mexico Forestry Division at (505) 376-2204, or their local New Mexico Forestry District Office:
NM Forestry Districts 17. What will our future forests look like? People need to recognize that the pre-outbreak forests they once knew will not be the forests of the future. In the affected ponderosa pine type, woody shrubs and other understory vegetation will become predominant in the short-term. A ponderosa pine element will still exist where the impact of the beetles is less severe. Introduced exotic plants could also be at an increased advantage. In the piñon-juniper type, the loss of piñon will result in juniper becoming more dominant. In any case, forests will still exist, just not in the same condition, as we have previously known. 18. Who is responsible for addressing the potential hazard of dead trees falling onto roadways? Dead or dying trees, which have been attacked by bark beetles, can fall onto the roadway or shoulders, either striking vehicles directly or placing an obstacle on the travel way. The hazard from such trees is worst during windstorms, heavy rain, and snow events, but dead or dying trees can fall at any time. Public road authorities have the responsibility to remove trees and other vegetation that present a hazard to motorists. Public roads are defined as roads under the jurisdiction of and maintained by a pubic authority and open to public travel (23 U.S.C. 101). Public road authorities are those federal, state, county, town or township, Indian tribe, municipal or other local government or instrumentality thereof, with authority to finance, build, operate or maintain highway facilities (23 CFR 460.2(b)). An important maintenance objective of public road authorities is to provide safe highway travel to protect human lives and property. 19. Who is responsible for addressing the potential hazard of dead trees falling from national forest land onto private property? The approach to this concern varies by each National Forest Ranger District. Contact your local ranger district office for further information. |
![[Graphic]: New Mexico Forestry Districts](../images/nm_districts.gif)