Unfortunately, many rumors and misinformation exists about the mountain pine beetle. Hopefully, these questions will help clear up the confusion.
Questions and Concerns
Question: Where did the infestation in Colorado start?
Answer: Mountain pine beetles are always present somewhere in Colorado. During low periods of their cycle, called “endemics”, the mountain pine beetles are normally found in stressed trees, such as those infested with mistletoe, mechanically damaged by construction or soil compaction, or weather impacted (mainly by drought). High periods of infestation are called “epidemics.” There is no epicenter from which the state’s current epidemic started, although many in the industry consider ground zero to be Grand County, Colorado.
Question: What types of trees are likely to be attacked by the mountain pine beetle?
Answer: In Colorado, the mountain pine beetle normally attacks Ponderosa, Lodgepole and Limber Pines.
Question: How long is it between epidemic cycles?
Answer: There is no regular cycle to epidemics, but on average a given area of Ponderosa or Lodgepole Pines can be expected to experience mountain pine beetle infestations every 10 to 50 years.
Question: Does cold weather kill the mountain pine beetle and end an epidemic?
Answer: Sometimes. The mountain pine beetle produces its own “anti-freeze” compounds, which protect it from all but the coldest weather. If the below-the-bark temperature reaches -4 degrees Fahrenheit for a several consecutive days, the beetles may be killed. To achieve this, however, the outside-the-bark air temperatures must be at or below -30 degrees Fahrenheit.
Question: If mountain pine beetles are attracted to fresh-cutting activity, when should this be suspended to avoid drawing them to an area?
Answer: The usual recommendation is to suspend all cutting immediately prior to and during the expected flight of the beetles, if you are within one mile of infected trees. The mountain pine beetle usually flies around mid-July, so it is generally a good idea to allow a minimum of one month prior to that time for any cuts to dry. Cutting after mid-June would most likely attract the beetles, so to be safe, stop cutting in mid-May, if possible. Of course, cutting should not be done during the actual flight period, which usually runs from around mid-July through mid-September.
Question: When does the mountain pine beetle fly?
Answer: The normal flight period (the time when mountain pine beetles leave infested trees and fly to attack new ones) in Ponderosa Pine forests is usually July 20th through September 10th. For Lodgepole Pine forests, the flight time runs approximately July 10th through September 1st. Exceptions do occur, but the flight times rarely vary.
Question: How far and in which direction does the mountain pine beetle fly?
Answer: Usually, mountain pine beetles will only fly as far as required to find another suitable tree to attack. The new tree may be right next to the infested one, or it may be up to a mile away. While flights in excess of five miles have been documented, they probably involved strong winds or some sort of human assistance (for example, introducing infested firewood into a new area). Mountain pine beetles normally fly upwind toward a source of attractant pheromones. Wind speeds vary greatly and are therefore quite unpredictable. As such, the direction of flight often cannot be determined.
Question: Are pitch tubes reliable indicators of a successful attack?
Answer: To the inexperienced eye, pitch tubes merely convey the fact that beetles have visited a tree. Other signs need to be considered in order to determine whether or not a tree was able to fend off an attack. If a tree is healthy enough, it may be able to “spit out” the beetles, but the pitch tubes will remain.
Question: Do all trees need to be preventatively sprayed?
Answer: First, there should be a threat of a local beetle attack before spraying any tree. Second, the trees should be big enough for the beetles to want to attack it. (Around 8″ in diameter at eye level.) Third, the trees to be sprayed should also be “signature” trees, that is, trees of high-value to the homeowner and the property. Finally, the decision will also depend on how much money the property owner wishes to spend.
Question: How safe is preventative spraying for the environment?
Answer: The primary chemical we use, Permethrin, is considered environmentally friendly to animals, birds and groundwater. Our preventative spray dries fairly fast, after which time normal activity may be resumed.
Question: Can a layperson apply preventative spray?
Answer: While a layperson can legally spray their own trees, to do it correctly and achieve the desired results can be extremely difficult. Not only is it is necessary to get high enough on the tree (up to 45 feet) to be effective, but all sides of the tree need to be sprayed. In addition, you must wear protective clothing and the proper chemical formula is also a consideration.
Question: Do the mountain pine beetles have any natural enemies?
Answer:Woodpeckers are one of the beetles’ primary enemies. There are other insects and beetles that also prey on the mountain pine beetle.
Question: Do solar treatments work?
Answer:Solar treatment of infected trees can be effective but it is extremely important that it is done properly…which is very difficult. If plastic is used, it needs to be clear plastic with thickness of at least 6-mil. The wood should be stacked no more than one log high and receive at least two, preferably three, months of warm weather prior to the beetles’ flight time. There must be NO holes or rips in the plastic. Beetles that emerge from plastic covered logs sometimes die, but usually just chew through the plastic and fly away. A further difficulty with solar treatment occurs at higher altitudes where the plastic has a tendency to break down rapidly under exposure to ultraviolet light. In short, solar treatment with plastic is not a recommended method.
Question: Does carrying infested wood on a truck spread it along the route?
Answer:Research shows that beetles do not emerge and infest trees along a haul route.
Question: Is the mountain pine beetle harmful to people?