Wood-Boring Insects in Atlanta Trees: Identification & Management

What Are Wood-Boring Insects?

Wood-boring insects, also called borers, are beetles, wasps, and other insects whose larvae tunnel inside wood, consuming the tissue and creating galleries that weaken branch and trunk structure. While many borer species are relatively benign and infest only dead wood or stressed branches, some are serious pests that attack healthy trees and can cause significant damage or mortality. In Atlanta, several borer species threaten landscape trees, with particular concern around recently planted or stressed specimens.

Understanding which borer species are present in your area, recognizing that most borers attack stressed trees (and thus prevention focuses on tree health), and implementing appropriate management strategies when borers do attack are essential for protecting Atlanta's landscape trees.

Types of Wood Borers in Atlanta

Flatheaded borers

Flatheaded borers (family Buprestidae) are beetles whose metallic, flattened larvae create winding, ribbon-like galleries in wood:

• Appearance: Adult beetles are small, colorful, and metallic-looking. Larvae are flattened and cream-colored.
• Damage pattern: Galleries are flattened and ribbon-like, following the grain of the wood.
• Tree susceptibility: Flatheaded borers attack recently transplanted trees, drought-stressed specimens, and trees with bark injury. Stress is the primary risk factor.
• Atlanta species: Several species attack fruit trees and ornamentals in the Atlanta area.

Roundheaded borers

Roundheaded borers (longhorn beetles, family Cerambycidae) create round exit holes and cylindrical galleries:

• Appearance: Adult beetles are elongate with long antennae. Larvae are cream-colored and cylindrical.
• Damage pattern: Round exit holes (1/8 to 1/2 inch diameter depending on species) are characteristic. Gallery patterns are cylindrical and often quite large.
• Severity: Some species cause minor damage; others (particularly Asian longhorn beetle) can kill trees. Most roundheaded borers attack stressed or declining trees.
• Atlanta species: The carpenterworm (a cossid moth, not technically a beetle but functionally similar) is common, as are several native longhorn beetle species.

Wood wasps

Wood wasps (family Siricidae) are wasps whose larvae tunnel in wood, creating cylindrical galleries:

• Appearance: Adults are wasp-like with a blunt posterior and long ovipositor. Larvae are cream-colored and cylindrical.
• Damage pattern: Galleries are cylindrical and fairly large. Wood wasp infestations often coincide with fungal associations that may be more damaging than the insect itself.
• Risk: Wood wasps primarily attack stressed or recently dead wood, though they can infest declining trees.

Bark beetles

Bark beetles (family Scolytidae) bore under bark, creating characteristic gallery patterns:

• Appearance: Adult beetles are tiny (2-8 mm) and cylindrical. Galleries are visible when bark is removed.
• Damage pattern: "Shotgun holes" in bark (1-2 mm exit holes) are characteristic. Galleries often have distinctive patterns (adult gallery with larval galleries branching from it) when bark is removed.
• Severity: Most bark beetles attack stressed, dying, or dead trees. However, some species (particularly pine bark beetles) can attack healthy trees under certain conditions and cause serious damage.

Species Affected in Atlanta

Yoshino Cherry (Prunus yedoensis): These ornamental cherries are attractive to several borer species, including flatheaded borers and roundheaded borers. Recently transplanted or drought-stressed cherry trees frequently experience borer attacks. The damage is particularly concerning because it occurs in a prominent landscape specimen that was likely expensive and represents significant long-term investment.

Dogwood (Cornus florida): Dogwoods, particularly stressed specimens, can be attacked by borers. Dogwoods weakened by anthracnose, drought, or other stresses become vulnerable to borer colonization, which further weakens the tree.

Recognizing Borer Damage

Early detection of borer infestation allows intervention before serious tree damage occurs:

• Exit holes: The most obvious sign is small holes in bark where adult borers have emerged. Hole size and shape vary by species—flatheaded borers create irregular holes; roundheaded borers create round holes; bark beetles create tiny "shotgun" holes.
• Sawdust or frass: Boring insects produce sawdust and frass (droppings) that accumulate near entrance holes or fall to the ground below infested branches. Fresh, wet, light-colored sawdust indicates recent activity.
• Bark or cambium damage: Bark may be rough, partially removed, or show tunnel entrances. Where bark is damaged, wood beneath may be visible.
• Gum or sap ooze: Some trees respond to borer activity by producing protective sap or gum. Sticky accumulation on bark, particularly around entrance holes, may indicate borer activity.
• Branch dieback: Infested branches often wilt and die as galleries disrupt water movement. Dieback in otherwise healthy-appearing trees may indicate borer activity.
• Canopy thinning: Heavy borer infestations cause progressive branch dieback and canopy loss as more branches become infested and fail.

Why Trees Become Vulnerable to Borers

Understanding borer vulnerability helps with prevention:

• Stress from transplanting: Recently transplanted trees are particularly vulnerable. The stress of transplanting, combined with root loss and reduced water uptake capacity, weakens trees and attracts borers.
• Drought stress: Trees weakened by drought cannot defend against borer attacks. In Atlanta's dry summers, drought-stressed trees become susceptible.
• Sunscald and bark damage: Trees with sun-exposed bark damage or winter sunscald develop weak points that borers exploit.
• Disease or pest pressure: Trees weakened by disease, other pests, or environmental stress attract borers. Borers are typically secondary pests that attack already-compromised trees.
• Construction or mechanical injury: Trees damaged by construction activity, mowers, string trimmers, or other mechanical injury develop weak points vulnerable to borers.
• Poor site conditions: Trees planted in inappropriate sites or in compacted soils are chronically stressed and borer-vulnerable.

Prevention Strategies

Since most borers attack stressed trees, prevention focuses on maintaining tree health:

Proper establishment care

Newly planted trees are borer-vulnerable. Ensuring successful establishment reduces borer risk dramatically:

• Water thoroughly and regularly during establishment (first 1-2 growing seasons). Consistent moisture reduces transplant stress.
• Mulch properly (2-4 inches, keeping mulch away from trunk) to moderate soil temperature and retain moisture.
• Avoid pruning except to remove dead branches. Pruning creates stress and wound sites that attract borers.
• Protect bark from sun damage (particularly in winter) through shade or tree wrap if appropriate.
• Provide structural support without wounding if needed, using proper staking techniques.

Ongoing tree care

Mature trees remain borer-resistant if they're healthy:

• Maintain consistent soil moisture through proper irrigation, particularly during dry periods.
• Mulch to moderate soil conditions and reduce stress.
• Avoid wounding bark through mower damage, pruning injuries, or other trauma.
• Prune only to remove dead, diseased, or crossed branches—avoid unnecessary pruning.
• Address disease and pest problems promptly, as these weaken trees and increase borer risk.
• Maintain appropriate nutrition through plant health care programs.

Site selection and preparation

For new plantings, choosing appropriate sites and preparing soil reduces stress and borer risk:

• Plant in sites matching the tree's needs (sunlight, soil type, moisture, etc.).
• Amend soil with organic matter to improve structure and water retention.
• Ensure proper drainage to avoid saturation.
• Provide adequate space for root expansion and canopy development.

Management of Existing Infestations

If borers are already infesting your trees, several options are available:

Remove infested branches

For branch infestations, removing infested branches is often the most practical approach:

• Prune branches showing borer damage back to healthy tissue, removing all infested portions.
• Dispose of infested wood promptly by chipping, burning, or burying (never leave on ground where emerging adults can escape).
• This approach works best for branch infestations; trunk infestations are more problematic.

Improve tree health

For trees with minor borer infestations, supporting tree health often allows the tree to compartmentalize damage and outgrow the problem:

• Implement intensive irrigation, mulching, and plant health care to maximize tree vigor.
• Healthy, vigorous trees often overcome minor borer populations as the tree's defensive chemistry kills emerging larvae or compartmentalizes galleries.
• This approach requires patience but avoids chemical treatment and allows the tree to heal naturally.

Targeted chemical treatment

For serious infestations, particularly on valuable trees, professional pest management may be warranted:

• Preventive trunk sprays: Insecticide sprays applied to bark can prevent borer egg-laying. These are applied preventively and are most effective for species that attack healthy trees.
• Trunk injections: Systematic insecticides injected into trees can kill boring larvae within the tree. These are reserved for valuable trees with serious infestations.
• Timing: Treatment timing is critical—applications must coincide with borer life stages. Professional application ensures proper timing and technique.
• Cost-benefit: For expensive, valuable specimens like flowering cherries, professional pest management may justify the cost. For less valuable trees, acceptance or removal may be more practical.

Removal

For heavily infested trees that cannot be saved or that pose safety risks, removal is sometimes the most practical option:

• Infested wood should be chipped or destroyed rather than left on-site, as emerging adult borers can spread to nearby trees.
• After removal, ensure proper site remediation and consider replanting with stress-resistant species or varieties.

Species-Specific Management

Yoshino Cherry: These beautiful trees are vulnerable to borer attack when stressed. Ensuring proper establishment (ample water, appropriate site, protection from mechanical injury) prevents most borer problems. If borers do appear, removing infested branches and improving tree health often allows the tree to recover. Heavy infestations may require removal.

Dogwood: Borers often attack dogwoods weakened by anthracnose or other stresses. Managing primary disease/stress issues (anthracnose prevention, proper site selection, adequate moisture) prevents secondary borer problems. For infested dogwoods, supporting tree health and removing infested branches allows recovery if the tree's primary stress is addressed.

When to Call an Arborist

Contact an ISA-certified arborist if you suspect borer activity:

• Professional assessment identifies which borer species is present (critical for determining appropriate management).
• An arborist evaluates tree health and determines whether the tree can recover with improved care or whether serious intervention is needed.
• Professional management of serious infestations ensures proper treatment timing and technique.
• Arborists can recommend preventive care for valuable specimens to reduce future borer risk.

Atlanta-Specific Borer Considerations

Atlanta's warm climate supports year-round borer activity, though spring and early summer are peak periods. The region's severe summer droughts stress trees and increase borer vulnerability. Additionally, the popularity of flowering cherry and ornamental specimens in Atlanta landscapes means there's continuous borer pressure on these preferred hosts. Proper establishment care and health maintenance are particularly important in Atlanta to prevent borer-related losses of expensive landscape specimens.

Protect Trees From Borer Damage

Borer damage is preventable through proper tree care. The best defense is maintaining healthy, vigorous trees through proper watering, appropriate site selection, and consistent care. For trees that do become infested, early detection and professional management can often save the tree. EastLake Tree Services provides borer assessment, preventive care, and management services for Atlanta trees. Call 404-850-1174 or request a consultation.