Several native bark beetles attack pine trees in Tennessee, but most only become a problem after trees are weakened by drought, construction damage, lightning, or other stressors. Healthy pines typically withstand their attacks and continue growing for many years.
But one beetle is an important outlier that will make any pine tree owner nervous. Called the southern pine beetle (SPB), this bark beetle readily attacks even the healthiest and most established pines, often causing them to die in a matter of weeks or months.
Fortunately, there are things homeowners in the Nashville area can do to protect their pines. We’ll explain everything you need to know about the southern pine beetle and outline the steps you’ll want to take to defend your trees from this pest below.
The Southern Pine Beetle in Tennessee: Basic Information
As when dealing with any tree pest, the first thing homeowners and property owners should do is familiarize themselves with the basics.
Description & Range
Known to biologists as Dendroctonus frontalis, the southern pine beetle is a tiny black to brown insect, measuring about 3 millimeters in length — about half as long as a grain of rice. Its eggs, pupae, and larval stages are even smaller and white to cream in color.
Unlike many other problematic tree pests in the U.S., which are invasive and hail from distant shores, the southern pine beetle is native to the southern and eastern portions of the country, as well as parts of Mexico. Unfortunately, the insect also appears to be spreading farther into New England.
Life Cycle
The insect’s life cycle begins when an adult female locates a pine tree, tunnels through the bark, and begins feeding. The adult females then construct winding, S-shaped galleries in which they’ll deposit eggs before tunneling back out of the bark and seeking out a new tree.
The newly hatched larvae feed beneath the bark before pupating into adults and eventually emerging to attack new trees and begin the cycle anew.
Feeding Habits & Tree Damage
Both the larvae and adults feed on the inner bark (phloem) of trees. As they tunnel, southern pine beetles also introduce blue-stain fungi into the tree. Together, the beetles and these fungi disrupt the movement of water and nutrients, eventually killing the tree.
And unfortunately, because of the nature of southern pine beetle attacks, they often cause large areas of pine forests to die during outbreaks, leading to serious problems for foresters, tree farmers, and government agencies.
In fact, the southern pine beetle is so problematic that the USDA Forest Service characterizes it as the “most destructive insect for pines in the Southeastern U.S.”
Southern Pine Beetle vs. Other Pine Beetles
In addition to the southern pine beetle, several other native bark beetles attack pine trees in Tennessee, including:
- Southern pine beetle (Dendroctonus frontalis)
- Black turpentine beetle (Dendroctonus terebrans)
- Six-spined Ips engraver (Ips calligraphus)
- Eastern five-spined Ips engraver (Ips grandicollis)
- Small southern pine engraver (Ips avulsus)
- Pine engraver (Ips pini)
All of these species tunnel beneath the bark and feed on the tree’s inner tissues, but they don’t pose the same level of risk the southern pine beetle does. It regularly attacks healthy, vigorous pines, and it does so in great numbers.
A single female begins the attack by boring into the bark and releasing pheromones that attract hundreds or even thousands of additional beetles. This coordinated “mass attack” overwhelms the tree’s natural resin defenses, allowing the beetles to establish themselves beneath the bark and eventually kill the tree.
Trees Susceptible to Southern Pine Beetles
While southern pine beetles attack nearly all native pines found in Tennessee, some species are more susceptible than others. A few of the species at greatest risk include:
- Shortleaf pine (Pinus echinata): One of Tennessee’s most widespread native pines, shortleaf pines are a frequent victim of southern pine beetle attacks.
- Virginia pine (Pinus virginiana): Virginia pines are highly susceptible to southern pine beetle attacks, particularly when growing in dense stands or on dry sites.
- Loblolly pine (Pinus taeda): Frequently planted for timber production and landscaping, loblolly pines are readily attacked throughout the Southeast.
- Pitch pine (Pinus rigida): Found primarily in eastern Tennessee, pitch pines are susceptible where they occur.
- Table Mountain pine (Pinus pungens): Most common in the mountains, table mountain pines can experience significant mortality during outbreaks.
Other southern pines, including eastern white pine (Pinus strobus), slash pine (Pinus elliottii), and longleaf pine (Pinus palustris), may also be attacked under the right conditions. Longleaf pine is generally considered one of the more resistant southern pines because of its exceptional resin production, though it is not immune.
Fortunately, southern pine beetles rarely attack ornamental conifers such as spruces, firs, cedars, arborvitae, junipers, or cypress trees. Their hosts are almost exclusively pines.
Signs of a Southern Pine Beetle Infestation
While pines may remain green during the initial stages of infestation, they often exhibit several telltale signs before the canopy begins to decline.
- Pitch Tubes: Small, popcorn-sized masses of resin form where beetles have bored through the bark. These pitch tubes may be white, cream-colored, pink, or reddish-brown and can appear from the base of the trunk to the lower branches.
- Boring Dust: Fine reddish-brown sawdust, known as frass, may collect in bark crevices, around the base of the tree, or in spider webs nearby. This material is produced as adult beetles tunnel through the bark.
- S-Shaped Galleries Beneath the Bark: If you carefully remove loose bark from a recently infested tree, you may notice winding S-shaped galleries etched into the inner bark. These galleries are created by the adult females as they lay eggs.
- Woodpecker Activity: Increased woodpecker feeding on the trunk may indicate that birds are searching for beetle larvae beneath the bark. While woodpecker damage alone doesn’t confirm an infestation, it can be an important clue.
- Discolored Needles: As the insects disrupt the tree’s vascular system, the needles will gradually fade from green to yellow before turning reddish-brown. By the time the entire canopy has changed color, the tree has usually been fatally damaged.
- Exit Holes: Small, round holes in the bark appear after a new generation of adult beetles emerges. Unfortunately, by this point the infestation has already completed its life cycle, and the beetles may have spread to neighboring pines.
How to Tell Southern Pine Beetles from Other Pine Beetles
Southern pine beetle pitch tubes can resemble those produced by black turpentine beetles and Ips engraver beetles. However, black turpentine beetle pitch tubes are typically much larger and concentrated on the lower few feet of the trunk, while Ips beetles often leave little or no resin at all. Because these pests require different management approaches, it’s a good idea to have a suspected infestation evaluated by an ISA-certified arborist before deciding on treatment or removal.
Southern Pine Beetle Treatment Options
Unfortunately, southern pine beetles are difficult to control once they’ve established themselves beneath the bark. By the time obvious symptoms develop, trees are often beyond saving.
But that doesn’t mean there’s nothing homeowners and property managers can do to protect their trees. The following strategies can help prevent infestations in some cases and reduce the risk that an outbreak will spread in others:
- Professional Evaluation: If you suspect southern pine beetles are attacking one of your pines or there is an active outbreak in your area, contact an ISA-certified arborist as soon as possible. Early diagnosis will help provide the best chance of limiting the damage.
- Monitor Nearby Pines: Southern pine beetles often spread from one tree to another. If a pine on your property — or a neighboring property — has been confirmed with southern pine beetles, inspect nearby pines regularly for new pitch tubes, boring dust, or needle discoloration.
- Preventative Insecticide Treatments: High-value pines that have not yet been attacked may be protected with preventative trunk sprays. These treatments are designed to prevent beetles from successfully colonizing the tree in the first place.
- Prompt Tree Removal: Once southern pine beetles have successfully infested a tree, removal is usually the most effective course of action. Removing the tree before a new generation of adults emerges may help reduce the likelihood of nearby pines being attacked.
- Improve Tree Health: While healthy trees can still be attacked during outbreaks, maintaining vigorous pines may improve their ability to defend themselves. Water trees during prolonged drought, reduce soil compaction, and mulch the root zone to help minimize stress.
Protect Your Pines Before the Next Southern Pine Beetle Outbreak
Because southern pine beetles can kill healthy pine trees quickly, prompt action is essential. With more than 10 ISA-certified arborists on staff, AKA Tree Service is ready to provide the expert guidance you need to protect your landscape.
Contact us today to schedule an inspection and protect your pines before an infestation spreads.
Sources and References
- USDA Forest Service, Southern Research Station – “Southern Pine Beetle Withheld Timber Volume – State Data”
Index page linking to state-level southern pine beetle withheld-timber-volume data across the affected region, including the Tennessee dataset already in your list.
https://www.srs.fs.usda.gov/econ/data/spb-withheld/ - USDA Forest Service – “Southern Pine Beetle” (Forest Insect & Disease Leaflet 49)
Federal leaflet covering the biology, identification, host damage, and management of Dendroctonus frontalis across its southern range.
https://www.fs.usda.gov/foresthealth/docs/fidls/FIDL-49-SouthernPineBeetle.pdf - USDA Forest Service – “Use of Chemicals for Prevention and Control of Southern Pine Beetle Infestations”
Treesearch-hosted research document; the numeric filename gives no indication of title or subject beyond the repository itself.
https://research.fs.usda.gov/download/treesearch/39086.pdf - USDA Forest Service – “Integrated Pest Management of the Southern Pine Beetle”
Treesearch-hosted research document; the numeric filename gives no indication of title or subject beyond the repository itself.
https://research.fs.usda.gov/download/treesearch/39091.pdf - University of Tennessee Extension – “The Southern Pine Beetle”
UT Institute of Agriculture Extension publication (SP482); the code-style filename doesn’t reveal the title or specific topic.
https://utia.tennessee.edu/publications/wp-content/uploads/sites/269/2023/10/SP482.pdf - National Park Service – “The Southern Pine Beetle: The Tree Killer”
NPS interpretive article on southern pine beetle outbreaks and their ecological impact on pine forests in park units.
https://www.nps.gov/articles/000/the-southern-pine-beetle-the-tree-killer.htm
