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Frequently Asked Questions About Southern Pine Beetle

University of Tennessee Extension Specialist,  Dr.Wayne Clatterbuck sits down and answers some of the most often asked questions concerning the Southern Pine Beetle.       


1. Why the outbreak of pine beetles in 1999 and 2000?

Southern pine beetle populations are cyclic and tend to build to elevated levels in Tennessee every 10 to 12 years. Other population outbreaks were in 1975 and 1988. The late season summer droughts of 1998 and 1999 and the snow/ice storms damaging many trees during the winter of 1998-1999 stressed many pine trees allowing them to become more susceptible to pine beetle infestations. The mild winters also contributed to the buildup in pine beetle populations. Overwintering beetles are killed when temperatures stay below freezing (32 degrees F) for 5 to 7 consecutive days or can be killed in 2 consecutive days when night time temperatures are below 5 degrees and daytime temperatures do not reach freezing. The past two winters in Tennessee did not have these freezing temperatures.


2. What are the factors that lead to tree stress and southern pine beetle attack?

Pine trees under stress are more susceptible to pine beetle attack. Factors such as prolonged moisture or drought stress, slow tree growth that is common in overstocked or overmature stands, diseased or storm-damaged trees and excessive damage to residual trees after a harvesting operation are common factors leading to tree stress and pine beetle outbreaks. During the current outbreak, the buildup of pine beetle populations in damaged, stressed, overstocked and overmature natural pine stands has spread to younger, more vigorous stands including some plantations because of the high population levels.

3. How do you control southern pine beetle?

The most effective and economical control method is to remove infested trees, including a buffer strip of uninfested pines about 100 to 160 yards in width. The salvaged pines should be sent to the wood-processing mills as soon as possible. When markets are oversupplied with pine and trees cannot be sold, the "cut and leave" technique where infested trees and a buffer strip are cut down and left to decompose is recommended.  Timing is important for pine beetle control. The life cycle of pine beetle is about 6 weeks and 4 to 6 generations of beetle can be produced each year. Control must take place within a few weeks once beetles are found or the spot will continue to spread. Once the pine trees become red-topped, beetles have already attacked and left the tree. The tree is dead. Freshly infested trees have pitch tubes formed from resin where beetles have bored into the tree. No exit holes are apparent. The beetle larvae are in the tree. The brood develops in the innerbark of the trees and exits through pencil lead-sized holes in the bark. Once the exit holes are found, the beetles have left the tree.


4. What are the best ways to avoid southern pine beetle?

Keep trees healthy and actively growing. Thin trees to keep the stand vigorous.  Do not allow tree or stand growth to decline. Salvage promptly all lightning-struck, logging-damaged, diseased or overmature pines when there are few beetles. These trees can become centers for building beetle populations. Salvage larger actively spreading infestations first when there is a general outbreak. Exercise care not to damage residual trees during harvesting operations. Harvest all mature trees before they begin to decline.  Consider planting pine at wider spacings (400 trees per acre) to encourage larger trees that can be utilized during a thinning operation.


5. Can chemicals (insecticides) be used to control southern pine beetle, especially in yard trees?

The only chemical registered for pine beetle is Dursban. The chemical is sprayed on the surface of the tree at weekly intervals to deter the attack of pine beetle. However, once the pine beetle is inside the tree, the chemical is ineffective. Some chemical salesmen are suggesting that tree injections will control the beetle. First and foremost is that the chemical suggested for injection is not registered for control of southern pine beetle. Second, research has not shown whether tree injection is effective or not. Most injections will put the chemical in the xylem of the tree where the chemical is spread by water transport. However, the larvae develop in the innerbark of the tree where the chemical does not reside. Tree injected chemicals are not recommended at this time.


6. Why is the beetle attacking white pines?

Generally, white pine is able to repel beetle attacks. The mechanism that all pine trees use to repel beetle attacks is resin flow when the beetle first bores into the tree.  White pine usually has more resin flow to repel the beetle when compared to yellow pines such as Virginia, loblolly and shortleafpines. However, the high beetle population densities and the late season droughts that have reduced resin flow have made white pine more susceptible to southern pine beetle. Pine beetle has also been found in hemlock this year.

7. Why are pine prices reduced during pine beetle epidemics?

More wood is on the market creating more supply than demand. Thus, prices are reduced. Also, pine beetle-infested timber reduces the quality of timber products. For example, pine beetle wood is of a lower moisture content than harvested green timber.  The lower moisture content affects the chip size and the digester time for papermaking.  These additional variances can alter the quality of paper being made, thus increasing costs. The blue stain in wood also alters the appearance of many wood products making, them undesirable for consumers. Most of the time, the stain is only a visual blemish, not affecting structural integrity. However, consumers will avoid stained timber, whether for lumber, oriented strandboard, or preservative timbers based on appearance. Consistency, appearance and quality are what consumers look for from a manufacturer. Blue-stain from beetle infested pine does not meet consumer's specifications, thus creating a lower demand for this timber.

8. Should I continue to plant pine considering the damage from pine beetle?

Pine beetles have been part of the ecosystem for years. Beetle populations crash and build based on climate and disturbances over time. With increased marketing opportunities and higher prices, growing pine continues to be a good investment for forest landowners in the long term.  Most of the stands affected by pine beetle are those that are not managed, i.e., those stands that are over-mature, over-crowded and slow-growing. Good forest management is the only way to resist pine beetle attacks through maintaining vigorously growing trees. Thinning overcrowded stands, and regenerating slow growing, overmature or diseased trees will promote vigorous trees and improve resistance to southern pine beetle.



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