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Stand Visualization for Southern Pine Beetle
Management and Decision Making

A Visual Guide for Managing Existing Pine Stands

This guide will assist landowners, foresters and land managers to visually evaluate
stands for risk to SPB and facilitate management decisions.

David J. Moorhead, Charles T. Bargeron, G. Keith Douce
University of Georgia

Funding provided by USDA Forest Service Forest Health Protection - Southern Region

Recognizing susceptible stands

Across the South, pine stands which are susceptible to southern pine beetle (SPB) infestations are usually dense, older, slower-growing stands on poorly drained sites or those growing on severely eroded sites of poor quality. However, younger stands also may be at risk. Generally SPB susceptible stands have one or more of these characteristics:
Annosus root rot
Fusiform rust
Littleleaf disease
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Survey and Detection

For many owners, on-site inspections for determinations of SPB hazard may be most practical. Evaluating stands of similar ages, stocking levels, and on similar sites can help pinpoint potential outbreaks. Information from management plans and inventory or timber cruises also is valuable. Pay particular attention to well-stocked and over-stocked stands nearing thinning age or those which are past optimum thinning age and are beginning to experience reduced growth. Other hazard sites are stands on poorly-drained or eroded clay soils and those on steep slopes. Factors leading to tree stress and to possible outbreaks include:
  • Prolonged moisture or drought stress in trees or prolonged flooding.
  • Slow tree growth common to overstocked and over-mature stands.
  • Sites having poor internal drainage or low soil fertility.
  • Diseased and storm-damaged stands.
  • Excessive damage to residual stand when cutting or doing other work (more likely to lead to black turpentine beetle or Ips beetle attacks.
During outbreak conditions, rapid assessment can be made from aerial surveys and by ground checking previously identified hazard stands.

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Silvicultural treatments to reduce losses in existing stands

Good stand management offers the cheapest, most practical, and longest lasting means of preventing SPB infestations, especially where the beetle epidemics occur frequently. Recommended practices are:

  • To reduce stand susceptibility and damage from southern pine beetle, periodically reduce stand density to increase or maintain tree vigor.

  • Southern pine beetle infestations are often associated with poor tree vigor. Tree vigor is related to site, tree, stand, and environmental conditions.

  • Poor tree vigor is usually associated with densely stocked stands and declining or slow radial growth.

  • Other factors that affect vigor include age, species composition, soil texture, and type, drainage patterns, and stand disturbances associated with cultural practices.

  • Thinning, especially of weak, less vigorous trees in lower crown classes, that are susceptible to southern pine beetle attack, reduces competition and enhances the vigor of residual trees.

  • Thinning to reduce southern pine beetle hazard is recommended when stand basal area approaches 120 square feet/acre or when live crown ratios of dominant and co-dominant trees drop to about 40 percent.

  • Thinning stands back to 60 to 90 square feet/acre basal area reduces the risk of attacks and may also help to slow infestation expansion (spot growth) if an attack does occur.

  • For greater effectiveness, thinning should be conducted in winter when the beetle is least active.

  • Any thinning strategy to reduce the risk of southern pine beetle attack should be compatible with management goals and consider such things as site and stand factors, equipment, seasonality, market price for small diameter trees, and product objective. Management of other potential hazard (e.g., fusiform rust, annosus root rot, Ips spp., and black turpentine beetle) that might conflict with recommendations for southern pine beetle must also enter into the decision-making process.

Timing of the First Thinning

Precommercial thinning

  • Precommercial thinning is probably justified in dense, natural stands and in plantations established by direct seeding or supplemented with natural regeneration from surrounding stands if there are 1,500 or more well-spaced seedlings per acre

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  • The first thinning often is performed as soon as the seedlings are well established, usually between ages 2 and 5 before they have experienced severe intraspecific competition and while they still are small enough to permit thinning with relatively light equipment such as a rotary mower or light chopper.

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  • If stocking is fairly uniform, seedlings can be removed in strips. Where stocking is extremely high, cross stripping can be used to further reduce seedling numbers. The best response appears to be obtained with a residual stocking of 500 to 750 trees/acre.

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Commercial thinning

  • First commercial thinnings should be made just prior to overcrowding, reduced diameter growth, and heavy mortality and before the live crown ratio is reduced to below 35 percent of total height.

  • The beginning of suppression-caused mortality in 4- to 5-inch-diameter trees serves as a good signal for a first thinning in most stands. Generally this occurs at 13 to 18 years.

  • Thinning guidelines for southern pines frequently suggest removing 30 to 45 percent of the stand basal area.
  • The percentage of the basal area to be left tends to increase with increasing site quality because of greater productive capacity. Residual basal areas range from 60 to 90 square feet/acre and tend to be lower on poor than on good sites.

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Density Management Targets

Click on each picture to view stand images and iPIX Immersive 360-degree images. More information of iPIX technology.

Thinning younger stands is an important tool in long term prevention of southern pine beetle.

Characterized by trees with reduced radial growth, due to overstocking Using thinning to reduce the basal area of stands to 70 to 90 ft2/acre can maintain vigorous growth of trees and minimize the risk of southern pine beetle-caused mortality. Dense stands can be especially vulnerable to southern pine beetle attack. Trees which are currently infested by southern pine beetle should be removed as soon as possible, together with adjacent "buffer" trees.

Thinning older stands is an important tool in long term prevention of southern pine beetle.

Characterized by trees with reduced radial growth, due to overstocking and older age. Using thinning to reduce the basal area of stands to 60 to 80 ft2/acre can maintain tree vigor and increase tree spacing thereby minimize the risk of southern pine beetle-caused mortality Older, dense stands are extremely vulnerable to southern pine beetle attack. Trees which are currently infested by southern pine beetle should be removed as soon as possible, together with adjacent "buffer" trees.
Above images and information developed by: USDA Forest Service - Kier Klepzig (Southern Research Station); Jeanine Paschke (INTECS International Inc., Forest Health Technology Enterprise Team), Wes Nettleton and Robert Anderson (Forest Health Protection).

Other factors

Annosus root rot
Littleleaf Disease
Fusiform Rust
Mechanical (harvest)
Black Turpentine Beetle
Ips Beetles

Setting Control Priorities for the Southern Pine Beetle

All southern pine beetle spots (groups of infested trees) do not have the same control priority. The following guidelines should help you set priorities for controlling individual spots.

A. Classify the infested trees according to the stage of attack shown below.

Stage of Attack
Symptom Stage 1
Fresh attacks
Stage 2
Developing broods
Stage 3
Vacated trees
Foliage Green Green; fade to yellow before beetles emerge Red; needles falling
Pitch tubes Soft; white to light pink Hardened; white Hard; yellow; crumble easily
Checkered beetles Adults crawling on the bark Larvae in SPB galleries; pink or red; 1/2 inch long Larvae and pupae are purple; occur in pockets in the outer bark
Bark Tight; hard to remove Loose; peels easily Very loose; easily removed
Color of wood surface white, except close to new adult galleries Light brown with blue or black sections Dark brown to black; may have sawyer galleries
Exit holes ---- May appear where parent beetles left the tree Numerous; associated with brood adult emergence
Ambrosia beetle dust ---- White; begins to appear around the base of trees Abundant at the base of trees

B. Collect spot expansion data:

  1. Walk completely around the spot and look for stage 1 trees, which indicate the area of most recent beetle activity. Areas with stage 1 pines are called "Active Heads." Check to see if the spot is expanding in more than one direction. Large spots can have more than one "active head."
  2. Determine the number of stage 1 and 2 trees. For large spots that have more than 50 trees, it is not necessary to examine each tree. Just walk the boundaries and estimate the number of these trees in the spot.
  3. From a location about 20 feet (6 m) in front of the active head(s), determine the pine basal area (a measure of stand density) in square feet per acre. A 10-factor prism is useful for this purpose.
  4. Note whether most trees in the spot are pulpwood (less than 9 inches in diameter) (23 cm) or sawtimber size (more than 9 inches in diameter).
  5. If only stage 3 trees are present, control is not necessary.
  6. Determine the control priority for the spot. See C, below.

C. Guide to southern pine beetle control priorities (May through October):

  Key to spot growth Your spot's classification Risk-rating points
A. Stage 1 trees (fresh attacks) absent


B. Stage 1 (fresh attacks) and Stage 2 trees (developing brood) 1 to 10

11 to 10

21 to 50

more that 50



C. Pine basal area (ft2/acre) or stand density at active head or heads less than 80 (low density)

80 to 120 (medium density)

more than 120 (high density)


D. Stand class by average d.b.h. (in inches) pulpwood (9 inches or less)

sawtimber (more than 9 inches)


Add up the risk rating points that apply to your spot:

Score Control priority
70 to 100 High
40 to 60 Medium
0 to 30 Low

Related Publications and References:

More Information

University of GeorgiaThe Bugwood Network Forestry Images The Bugwood Network and Forestry Images Image Archive and Database Systems
The University of Georgia - Warnell School of Forestry and Natural Resources and
College of Agricultural and Environmental Sciences - Dept. of Entomology
Last updated on Wednesday, October 21, 2015 at 09:26 AM
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