Exotic and Invasive Species

Though there are multitudes of invasive plants within the forest’s nearly two million acres, there are several distinct invasive species to be aware of.  

The following is a list of invasive plants commonly found here on the Coconino National Forest.

• Dalmation Toadflax
• Diffuse Knapweed
• Giant Reed
• Leafy Spurge
• Russian Olive
• Saltcedar
• Tree of Heaven
• True Thistles (Scotch and Bull)
• Yellow Bluestem

A large number of the dead trees located on the Coconino National Flagstaff have fallen victim to bark beetles. Bark beetle infestations occur often in drought-stricken areas.

Information:

• Much of Arizona is currently experiencing a large upswing in pinon and ponderosa pine mortality due to outbreaks of several species of Ips beetles and the western pine beetle.  Low tree vigor caused by several years of drought and excessively dense stands of trees have combined to allow beetle populations to reach outbreak levels.
• These insects are native to ponderosa pine forests and pinon-juniper woodlands of the Southwest, and normally only attack a small number of diseased or weakened trees.  Healthy trees are usually not susceptible to these beetles.
• The beetles are tiny, roughly 1/8 inch long, or about the size of a matchhead.
• These beetles have multiple generations per year, and they have a tremendous capacity to increase their populations.
• The beetles attack trees by boring through the bark and laying eggs.  When the eggs hatch, the larvae feed on the soft inner bark.  Also, the beetles introduce a "blue-stain" fungus that spreads and clogs the water and nutrient conducting tissues and hastens tree death.  Once the insects mature, they leave the infested tree and travel to a new host.  Usually, they travel only a short distance, but they are capable of moving up to ½ mile or more.
• Millions of ponderosa pine and pinon trees have been killed.  Overall, this equates to a loss of less than 2-3% of forests, although tree losses may be as high at 90% on some localized sites.  This is the largest bark beetle epidemic ever recorded in Arizona.  Many more trees are expected to die, especially if the drought persists.
• Currently, most tree mortality is centered in "stress-zones" such as drier south-facing slopes, transition areas between ponderosa pine and pinon-juniper areas, recent construction sites, and areas heavily infected with dwarf mistletoe.
• Infested trees will start to turn reddish-brown within a month of attack.  Evidence of infestation can include sawdust at the trees base or in bark crevices, small pop-corn like masses of sap ("pitch tubes"), small boring holes, and a "fading" of the needles.
• Once beetles have left a tree, it no longer poses a threat to other trees as a source of beetle infestation.

Treatment:

• There is nothing that can be done to save a tree after it has been successfully attacked by bark beetles and infected with the blue-stain fungus.  If the goal is to kill the beetles under the bark, then infested trees must be cut down and treated by one of the following means:
  • Cover logs with clear plastic in a sunny site (this produces high temperatures by a greenhouse effect), ensure that the plastic remains intact, wind and ultraviolet damage can easily cause tears in the plastic and allow the beetles to escape.  Burry the edges of the plastic creating a tight seal around the infested wood.  Logs can be left uncovered in a sunny site but must be rolled weekly for even drying.
  • Peel the bark from logs, or
  • Burn, chip, or bury the logs.  (It must be noted that fresh pine chips can attract bark beetles and should not be left adjacent to standing green pines.)
• Fresh pine debris over 4-inches in diameter, created during tree thinning operations, must be removed from the forest or treated, because it can serve as a breeding site for Ips beetles.
• There is no effective insecticide treatment for infested trees.  Injecting trees with insecticides is not an effective method of control or prevention.
• Due to the large extent of the outbreaks and the tremendous capacity of bark beetles to increase their numbers, there is no possibility of implementing effective control actions to prevent further tree losses on a landscape level.

Prevention:

• Trees not yet infested can be protected by annual applications of a preventive insecticide. Carbaryl and permetherin-based insecticides are specifically labeled for this purpose, but carbaryl is the preferred material because it provides longer protection. Typical home and garden insecticides should not be used. The entire surface of the trunk and large limbs must be sprayed all the way to within a few feet of the top.
• Watering individual trees can help increase a trees natural defense of pitching out attacking beetles.
• Over the long run, selective removal of designated trees, coupled with brush disposal and appropriate use of prescribed fire, will not only improve forest and tree health, but also greatly reduce the probability of bark beetle outbreaks and catastrophic wildfire.

Frequently Asked Questions:

• What is the overall pine bark beetle situation in the Southwest?
  • Several species of pine bark beetles have experienced population explosions over the last few years. In 2002 conditions were especially favorable for these insects because the region-wide drought weakened trees' normal way of resisting these insects. Consequently, millions of trees were killed in Arizona and New Mexico.
• 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.
• 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.
• What happens once a tree dies?
  • Within three to six months of a tree dying, its needles will drop to the ground. The snag (a standing dead tree) will stand for anywhere between two and six 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.
• Where did these beetles come from?
  • These native bark beetles are always present in our southwestern forest ecosystems, but usually at low population levels.
• 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.
• What is the FS 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 recreations sites is already taking place, helping insure the enhanced vigor of healthy stands, as well as continued treatment of National Forest lands adjacent to communities. Hundreds of dead and infested trees have been cut in Coconino National Forest campgrounds and other developed sites to minimize the likelihood for beetles to spread to nearby trees, and to minimize hazards to the public. Some developed recreation sites are being evaluated for insecticide application to protect high value trees. The objective of these treatments is to protect the FS investment in these facilities by maintaining aesthetic quality and minimizing the hazard dead trees pose to visitors. 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.
• 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 initiate thinning unless slash can be removed, burned or chipped and dried (see #9).
• What actions should be avoided when attempting to 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, but it is a mistake to fail to deal with the slash (tree tops and limbs generated by cutting). Untreated slash left on the site is actually an attractant to additional beetles. If they breed in the slash, 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.
• 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.
• How bad is this PBB 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 1950s 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.
• 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 fiercer wildfires in the final quarter-centuryÑnot to mention these first few years of the 21st century.
• 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.
• How much salvage logging is the FS going to do to address this problem?
  • Salvage options are being considered by the Forests on a case-by-case basis, but due to economic and administrative limitations, very little of the affected timber would likely be salvaged. Because bark beetles require living inner bark for successful colonization, removal of dead trees has no impact on bark beetle populations.
• 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.
• 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 their local county extension agent, tree services, nurseries.
• 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 under story 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 pinyon-juniper type, the loss of pinyon 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.
• 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 public 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.