AN INTEGRATED PEST MANAGEMENT PROGRAM FOR THE SOUTHERN PINE BEETLE

 

Whatís new!

(topics in red are in development or under investigation)

 

This integrated pest management (IPM) program for the southern pine beetle (SPB) (Dendroctonus frontalis) serves as a simple, concise guide for strategies to reduce losses.  It is designed to:

1.     List proven methods of control and prevention,

2.     Describe recent and upcoming developments in SPB detection and suppression,

3.     Discuss novel approaches for SPB management,

4.     Link to more detailed information on SPB management.

 

To properly implement an integrated pest management program for the southern pine beetle, the land manager must first understand the biology and population dynamics of the beetle.  An IPM program will not eradicate the beetle or prevent all infestations, but should significantly reduce the economic and ecological impacts caused by periodic SPB outbreaks.

 

There are six components of an IPM program for the southern pine beetle (click on each title for more information):

 

PREVENTION.   Silvicultural treatments designed to prevent or minimize impacts of future SPB infestations in a stand.  Also includes chemical or other treatments to individual, high-value trees to prevent attack by beetles from nearby infested trees.

 

PREDICTION.  Forecast of the likelihood that SPB infestations (spots) will occur in an area or stand.  Predicting the potential of individual SPB spots to increase.

 

DETECTION.  The process of locating SPB infestations in a timely manner.

 

EVALUATION.  Evaluate the potential of continued growth of an infestation and assess the need for suppression.  

 

INFESTATION SUPPRESSION.  Methods of direct control implemented to stop the expansion of existing, active SPB infestations.

 

AREA-WIDE SUPPRESSION.  Methods, that combined with direct controls, are employed to reduce the impacts of existing SPB outbreaks over a large area.

 

 




PREVENTION

 

Preventative measures are important for reducing losses to SPB in pine forests, and for protecting individual pines in urban or other special areas.  In forest stands, prevention is designed to minimize the impacts of future SPB outbreaks.  The first step in a prevention program is to hazard rate the stands.  There are numerous hazard rating systems for SPB, and one designed for your area should be selected.  In general, dense, older stands of pure pine are considered as high hazard for SPB infestation.  If a stand is rated as high or medium hazard to SPB, the following silvicultural treatments may be applied to lower the hazard:

 

Thinning.  Reduce the pine basal area to less than 100 sq. ft/acre.  Precommercial thinning of young, dense stands also is recommended.  Remove all lightning-struck and heavily damaged or stressed pines that are highly susceptible to attack by SPB.  Avoid damage to residual trees during thinning operations.

 

Maintain a pine-hardwood mix when possible and where appropriate.  A healthy hardwood component can slow the expansion of SPB infestations. Maintain total basal area below 120 sq. ft/acre if possible.

 

Plant the appropriate species for the site.  Silvicultural guidelines should be followed when selecting a pine species for planting. Slash, longleaf, and eastern white pines generally are more resistant to SPB.  Loblolly, shortleaf, Virginia, and pitch pines usually are more susceptible to SPB attack, and should be planted only when conditions dictate that these species are appropriate for the site. 

 

Prescribed burning, when applied appropriately, can reduce competition and increase stand vigor, resulting in decreased losses to pests such as SPB.

 

Plant or promote resistant seedlings.  Though this is not currently an option, research is underway to try to improve the resistance of pines to SPB, and more resistant seedlings may be available in the future.  Escapes, pines that are avoided or missed by SPB within infestations, have been found to have higher than average resin production.  These trees could be utilized as seed trees to regenerate an area following SPB infestations.  It is also important to maintain genetic diversity to prevent possible devastating losses to other pests or adverse environmental conditions.

 

For more detailed information on prevention, see ìSilviculture can reduce losses from the southern pine beetleî.

 

 


PROTECTION OF INDIVIDUAL PINES.

 

In urban settings, recreation areas, endangered species habitat, or other special areas, it is often necessary to protect high-value pines from SPB infestation.  The following steps can help protect these high-value trees:

 

Maintain tree vigor.  Stressed pines are more susceptible to SPB and other bark beetles, so it is important to maintain vigorous tree health.    Watering and fertilization may be necessary during periods of adverse environmental conditions.  Avoid soil compaction and disturbance within the rot zone of the tree.

 

Remove lightning-struck or other heavily damaged pines, as these are highly susceptible to SPB and other bark beetles.  Avoid damaging the residual trees.

 

Remove infested trees.  When individual pines are infested, the emerging beetles may attack an adjacent pine, so infested trees should be removed prior to beetle emergence.  Avoid damage to residual trees.  If the trees cannot be safely or promptly removed, remove as much of the infested bark as possible.  Bark removal should occur during the late larval and pupal stages of the beetle, when the brood is in the outer bark and the bark is easier to remove.  The infested bark should be burned, buried, chipped, or otherwise destroyed so the brood is killed, or deposited in an area far removed from pines.

 

Treat susceptible or threatened pines with insecticide.  When nearby SPB infestations threaten high-value pines, the threatened trees may be sprayed with approved insecticides to prevent SPB attack.  Currently the only insecticide registered for this use is Onyx.   It may be difficult to find this insecticide in a formulation labeled for this purpose, so check with your local agricultural or forestry supply center.  The entire bole must be treated, so it may be wise to hire a tree service to handle the spraying.  Do not spray standing infested or vacated trees.  New insecticides are currently under evaluation for individual tree protection from SPB, so more options may be available in the future.

 

Treat threatened trees with repellent semiochemicals.  There are currently no registered semiochemicals for individual tree protection, and none of the compounds rigorously tested have proven effective.  Research continues in this area.

 

 




PREDICTION

 

Prediction involves forecasting the likelihood that outbreaks will occur in an area.  Generally, SPB is in outbreak status somewhere in the southeast U.S. every year, and accurate prediction helps forest managers plan detection flights and allocate funding and resources for suppressing SPB appropriately.  Models may also be used to predict the rate of expansion of existing SPB infestations.

 

 

South-wide SPB pheromone trap survey.  Each spring, pheromone traps (see photo) for SPB are deployed throughout the range of SPB, and the trap catches of SPB and its main predator, Thanasimus dubius, are used to predict SPB population levels during that year.  Predicted population levels are ranked as low, medium, or high, and their expected trend listed as decreasing, static, or increasing.   For this yearís prediction, click here.

 

Long-term prediction.  Unfortunately, there are no proven methods for long-range prediction of SPB activity in a given area.  SPB outbreaks are cyclic, so in areas with large acreages of susceptible host type, expect outbreaks every 7-10 years.  Outbreaks generally last 2-4 years, so the best long-term prediction may be to base estimates of future SPB levels on the current yearís activity.  If populations are increasing and numerous infestations are present in the fall, expect continued activity in the coming year.  Numerous publications have attempted to link SPB outbreak with climatic conditions, with varying results.  But until accurate, long-range weather forecasts are available, the usefulness of using weather as a predictor of future SPB population levels remains low.

 

Predictions of individual infestation growth.   In the summer and early fall, during the period when SPB dispersal is limited and activity is concentrated in expanding spots, an infestation is usually considered a good candidate for continued growth if freshly- attacked trees are present and susceptible host type is available in front of the spot head (the expanding edge of the infestation).  For a more in-depth analysis on the predicted rate of spot expansion, the University of Arkansas has developed a SPB spot growth model.  The model will estimate daily and cumulative numbers of currently-infested and total infested trees.  The model has been validated for summer and fall infestations, and work is ongoing to expand its use year-round. 

 

Expert systems.  SPB expert systems, which visually incorporate spot growth model results with stand type data, can be used to predict infestation impacts within stands or forests and help manage SPB on a landscape scale.  Though several expert systems have been developed or are in development, none are currently operational or available on-line.

 


DETECTION

 

Early and accurate detection of SPB infestations is vital for implementing timely suppression measures and reducing adverse impacts.  Aerial detection of dead and dying trees is the primary method of infestation detection. 

 

AERIAL DETECTION.  Procedures for conducting SPB aerial detection surveys are described in ìHow to conduct a southern pine beetle aerial detection surveyî and ìAn observerís guide to recognizing and reporting southern pine beetle spotsî. 

 

The scheduling of detection flights should be based on predicted and observed levels of SPB activity. Flights may begin in early spring, but fading of foliage of infested trees is influenced by environmental conditions, so new spots often cannot be detected until later in the season.  From May-October, the following schedule of flights is recommended, based on current or expected levels of SPB activity:

            Outbreak:        Flight every 2-3 weeks

            Moderate:        One flight per month

            Endemic:         One or two flights per year

Detection flights in late fall and winter are occasionally necessary.

 

Get accurate spot coordinates.  Marking spots on up-to-date maps or aerial photos of the survey area, utilization of the planeís Geographic Positioning System (GPS) system to log spot coordinates, and taking pictures of the infestations can facilitate the ground-checking phase of spot detection.

 

Record spot activity and size.  Estimates of spot size, current activity, and growth potential should also be recorded.

 

Electronic sketch-mapping.  A new sketch-mapping system has been developed.  Selected backdrops of the survey area are loaded into a lap-top computer. The computer is also linked with an on-board GPS system and a touch-sensitive screen.  During the survey flight, the computer uses the GPS to display the proper backdrop and indicate the plane location.  The surveyor plots observed spots by touching their location on the display screen.  The data is downloaded into a GIS program, and maps with spot coordinates can be produced.

 

Pre-visual detection.  SPB detection relies on visually identifying color changes of foliage, and spots may become quite large before trees begin to fade.  Methods of pre-visually detecting infestations are under investigation.  Possibilities include using acoustical equipment to recognize sounds of beetle infestation, and special camera filters or satellite imagery to pick up pre-visual changes in foliage.




 

EVALUATION

 

Suspected infestations are ground-checked to verify the cause of tree mortality, mark boundaries, calculate current and expected tree loss, and assign treatment priorities and methods.

 

Prioritize infestations for ground-checking.  The estimates of spot size, current activity, and growth potential should be used to prioritize infestations for efficient ground-checking, enabling swift treatment implementation for spots in areas of particular concern.

 

GROUND-CHECKING.  Detailed information on ground-checking suspected SPB spot is given in ìA field guide for checking southern pine beetle spotsî. 

 

Use GPS units to navigate to spot coordinates obtained from aerial survey flights when available.  Update or collect the coordinates once the spot is reached to provide accurate locations for subsequent visits and for mapping. 

 

Verify causal agent.  Look for signs of bark beetle infestation and check under bark to determine if SPB or other bark beetles are responsible (Ips or SPB).

 

Determine if spot is active.   Check if SPB brood is still present.

 

Check for fresh attacks.  Look for and count all freshly attacked (stage 1) trees, identify the leading edge, and check if susceptible host type is available in front of the leading edge.

 

Record pertinent information.  Estimate or count all currently infested trees, note stand data (BA, avg. dbh, host sp., etc.), and determine direction of spot movement.  A standardized data sheet should be used (view example).  SPBIS data can now be entered on portable data loggers for direct download to the database.

 

Assign control priority and method, based on spot activity, location, access, available resources, landowner concerns, and other factors.  If necessary, notify landowners who have active infestations that require control.

 

Mark the spot.  If the spot is still active, the spot boundary should be flagged.  The spot may be marked for treatment, but marking should be done close to the date of control to ensure effective treatment application.

 

Flag a route from the spot to a point of easy access.

 

Record data into a SPB database, such as SPBIS (Southern Pine Beetle Information System).

 

Run the SPB spot growth model. If necessary, enter the data into the SPB spot growth model to receive a prediction of future infestation growth.

 

 

 

DIRECT CONTROL

 

There are currently four proven control methods for SPB infestations: cut-and-remove, cut-and-leave, cut-and-hand-spray, and pile-and-burn.  Cut-and-remove is usually the method of choice when conditions allow, as infested material is moved off-site and the landowner receives some return for affected timber.  A south-wide evaluation of treatment efficacy on USDA Forest Service lands gave the following success rates based on a single application:

 

                                                 Treatment                               Success                       Percentage of detected

                                                                                                   rate                                 spots treated

 

                                                Cut-and-remove                        97%                                       53%               

                                                Cut-and-leave                            90%                                       12%

                                                Cut-and-hand-spray                  99%                                        3%

 

 

Only active SPB infestations should be treated.  Infestations with no fresh attacks or with 10 or fewer currently-infested trees may die out and should be monitored unless other concerns dictate immediate control. During periods of very high SPB activity, direct control should be targeted at infestations with 30 or more currently-infested trees.  If direct control is deemed necessary, treatment should be applied as soon as possible to limit tree loss and increase the chance of success.

 

Below is a brief description of each technique.  For more information, see ìDirect control methods for the southern pine beetleî.

 

Cut-and-remove. 

 

All currently-infested trees, plus a horseshoe-shaped buffer strip of uninfested pines around the spot head, are marked, felled, and then removed (see figure). 

 

The buffer strip is generally 40-70 feet at its widest point, and should not exceed the average tree height. 

 

Vacated trees should not be included, as these trees may harbor SPB natural enemies.  

 

Trees should be felled toward the center of the infestation, away from uninfested trees. 

 

From May-October, felling and removal should proceed inward from the buffer strip to the currently-infested trees.  The remainder of the year the direction should be reversed.  

 

Treatment should occur as quickly after marking as possible. 

 

Logging decks should not be adjacent to uninfested pines.

 

Cut-and-remove is recommended year-round when conditions are favorable for logging.

 

Monitor for breakouts and re-treat as needed.




 

Cut-and-leave.

 

All currently-infested trees, plus a horseshoe-shaped buffer strip of uninfested trees around the spot head, are marked, felled toward the center of the spot, and then left on site (see figure). 

 

The buffer strip is generally 40-70 feet at its widest point, and should not exceed average tree height. 

 

Vacated trees should not be included, as these trees may harbor SPB natural enemies.  

 

Felling should proceed inward from the buffer strip to the currently-infested trees. 

 

Trees should be felled toward the center of the infestation, away from uninfested trees.  If an infested tree, particularly one recently or currently under attack, must be felled into uninfested trees, it should be bucked into sections and hauled back into the center of the spot.

 

Treatment should occur as quickly after marking as possible.

 

Recommended May-October.  May be used the remainder of year upon recommendation of forest entomologist.

 

Monitor for breakouts and re-treat as needed.

 

 

Cut-and-hand-spray.

 

All currently-infested trees are marked and felled.

 

A buffer strip is generally not required, though a one-tree buffer around the most recently-attacked trees is advisable to ensure all infested trees are included.

 

Vacated trees should not be included, as these trees may harbor SPB natural enemies.  

 

Trees should be felled toward the center of the infestation, away from uninfested trees. 

 

Felled trees are limbed and bucked into workable sections. 

 

Spray entire bark surface of all infested material, turning large logs as necessary to ensure complete coverage.  Do not spray stumps (see figure).

 

Use only approved insecticides from containers with labels stating the insecticide may be used against pine bark beetles.

 

Recommended for small infestations, and can be used year-round when other treatments are not practical or available.

 

Monitor for breakouts and re-treat as needed.




Pile-and-burn.  Pile-and-burn is rarely used.  It may be applied to infestations in pulpwood or young plantations, where the infested trees may be easily bulldozed and piled for burning.  No buffer strip is required, and vacated trees should not be included.  This treatment should only be applied when fire danger is low.

 

 

ALTERNATIVE TREATMENTS. 

 

The treatments described above all require tree-felling, which is not always allowed or desirable, so new tactics are in development. 

 

Semiochemicals.    Semiochemicals are compounds that organisms use in communication.  They include pheromones, allomones, kairomones, and host compounds.  Investigators are testing control strategies using various semiochemicals.

 

A.  Verbenone.  Verbenone is an anti-aggregation pheromone produced by male SPB.  Two tactics, verbenone-only and verbenone-plus-felling, have been developed and tested extensively.  These methods work well when used within given parameters and with an effective elution device.  Verbenone has been registered by the U.S. Environmental Protection Agency, but the elution device registered has not had sufficient field-testing. Training in application procedures is necessary before using these tactics.

 

 

B.  Frontalin.  Frontalin is an aggregation pheromone of SPB.  It is used in the pheromone trapping survey.  There are two potential uses of frontalin in SPB control. 

1.     Redirection.  Frontalin is applied to vacated trees at the back of a spot or in adjacent non-host type, often in combination with anti-aggregation semiochemicals placed at the spot head, to try to redirect the beetles and cause the spot to collapse.  This tactic has had mixed success, and appears to work best when SPB populations are at endemic levels.  More work is needed to determine when this tactic might be used efficaciously.

2.     Trap-out.  Pheromone traps placed within the spot in an attempt to ìtrap-outî the beetles as they emerge.  This tactic has not been successful in most instances.

 

C.  4-aa.  4-aa is a host compound that has demonstrated repellency to SPB in lab studies.  Field trials of spot disruption, alone and in combination with verbenone, have had limited success.  4-aa has also been studied for individual tree protection, but it was unable to prevent infestation of susceptible pines under rigorous testing.

 

D.  Green-leaf volatiles.  Green-leaf volatiles are produced by non-host trees of SPB.  They have demonstrated repellency to SPB in trapping studies, but field trials of spot disruption have yet to be conducted.

 

 

Biological Control.  The SPB has a suite of parasitoids, predators, and competitors that can impact populations.  While supplemental biological controls may be applied to infestations and aid in direct control, they are discussed under area-wide suppression.

 




AREA-WIDE SUPPRESSION

 

Area-wide suppression involves strategies designed to reduce the impacts of SPB outbreaks on a landscape scale.  The goal is to limit the duration, frequency, and/or intensity of SPB outbreaks.  While some of these tactics may be applied within infestations by themselves or in concert with direct control measures to enhance efficacy, they are generally utilized to provide long-term or long-range suppression of SPB.  The techniques listed below have not received testing sufficient to recommend their implementation, but ongoing studies are in place to evaluate their potential inclusion in a SPB management program.

 

Maintenance of natural enemies.   Leave all trees vacated by SPB standing when implementing direct controls.  Vacated trees harbor natural enemies, many of which may emerge after southern pine beetles.  Vacated trees may also provide nesting sites for woodpeckers, which can prey on SPB.  Use chemical insecticides only as a last resort.

 

Natural Enemy Augmentation.  A current theory states that SPB outbreaks are controlled by a delayed density-dependent response from natural enemies, so augmenting natural populations of predators, parasitoids, and competitors may accelerate the decline of SPB epidemics.   Mass-rearing techniques have been developed for the predator Thanasimus dubius and the parasitoid Roptrocerus xylophagorum.  Mass release must be evaluated.

 

Supplemental Feeding of Parasitoids.  Research has discovered that supplemental feeding of SPB parasitoids increases their egg-production and longevity.  Studies are underway to determine if providing food for parasitoids can increase parasitism of SPB to levels that reduce short- or long-term impacts.

 

Trap Trees.  During endemic periods of SPB activity, infested trees are difficult to locate, and populations may rapidly increase to outbreak levels.  Baiting pines with aggregation pheromone in the fall and in the spring, periods of SPB dispersal, then removing the infested trees prior to brood emergence, may help concentrate beetles to known locations and reduce the potential for outbreak initiation.  A study has been implemented.

 

Pathogens.  SPB inoculate the wood with fungi carried on their bodies.  As the relationships between SPB and the various fungal species are discovered, it may be possible to use fungi limit SPB success.  Viruses of SPB are also under investigation as potential control agents.

 

 

Selected References


Belanger, R.P. and Malac, B.F. (1980). Silviculture can reduce losses from the southern pine beetle. Agriculture Handbook No. 576, Washington, D.C.: USDA Forest Service.


Billings, R.F. and Doggett, C. (1980). An aerial observerís guide to recognizing and reporting southern pine beetle spots. Agriculture Handbook No. 560, Washington, D.C.: USDA Forest Service.


Billings, R.F. and Pase III, H.A. (1979). A field guide for ground checking southern pine beetle spots. Agriculture Handbook No. 558, Washington, D.C.: USDA Forest Service.


Billings, R.F. and Ward, J.D. (1984). How to conduct a southern pine beetle aerial detection survey. Texas Forest Service Circular 267. Lufkin, TX.


Branham, S.J. and Thatcher, R.C. (1985). Integrated pest management research symposium: The proceedings. USDA Forest Service General Technical Report SO-56, New Orleans, LA.


Mason, G.N., Lorio, P.L., Belanger, R.P., and Nettleton, W.A. (1985). Rating the susceptibility of stands to southern pine beetle attack. Agriculture Handbook No. 645, Washington, D.C.: USDA Forest Service.


Nebeker, T.E and Hodges, J.D. (1983). Influence of forestry practices on host-susceptibility to bark beetles. Zeitschrift f¸r angewandte Entomologie 96, 194-208.


Swain, K.M. and Remion, M.C. (1981). Direct control methods for the southern pine beetle. Agriculture Handbook No. 575, Washington, D.C.: USDA Forest Service.


Thatcher, R.C., J.L. Searcy, J.E. Coster, and G.D. Hertel (eds.). (1980). The Southern pine beetle. USDA Forest Service Technical Bulletin 1631.


Waters, W.E., Stark, R.W. and Wood, D.L. (eds.). (1985). Integrated Pest Management in Pine-bark Beetle Ecosystems. New York: John Wiley & Sons.