How Do You Treat Common Bark Pests In North Carolina Trees?

Bark pests are a serious and recurring threat to the health and longevity of North Carolina trees. They include insects that attack the bark surface, burrow under the bark, or feed on bark-associated tissues. Effective treatment requires accurate identification, timely intervention, and integrated tactics that combine cultural, biological, and chemical methods. This article describes the most common bark pests in North Carolina, the signs to watch for, and practical, step-by-step treatment plans for homeowners and land managers.

Common bark pests in North Carolina

Southern pine beetle and other bark beetles

Southern pine beetle (Dendroctonus frontalis) is the most destructive bark beetle for pines in the Southeast. Other bark beetles include Ips spp. and black turpentine beetle. These beetles colonize living pines, tunneling under the bark and disrupting the tree’s nutrient and water transport.
Signs and biology:

• Pitch tubes or small masses of resin on the trunk.
• Fading or yellowing of the crown, progressing to brown.
• Fine sawdust-like frass in bark crevices or at the base.
• S-shaped galleries under removed bark.

Typical hosts and areas: loblolly, shortleaf, and longleaf pines across the coastal plain and Piedmont; outbreaks often follow drought or storm damage.

Ambrosia beetles and shot hole borers

Ambrosia beetles (e.g., Xylosandrus crassiusculus) and invasive shot hole borers attack a wide range of hardwoods and ornamentals. Females bore into stressed hosts and cultivate symbiotic fungi that cause wood staining and can kill small stems.
Signs and biology:

• Tiny round entry holes (1.5 to 3 mm) in stems and trunks.
• Dark staining of sapwood from fungal growth.
• Wilting branches, branch dieback, or sudden collapse in small-diameter stems.

Typical hosts and areas: container and landscape trees, young orchards, and stressed trees in urban and suburban settings.

Emerald ash borer (EAB)

Emerald ash borer (Agrilus planipennis) is an invasive wood-borer that kills ash trees by larval feeding in the cambial region, producing serpentine galleries.
Signs and biology:

• D-shaped exit holes (about 3-4 mm) on the bark.
• Vertical splits in bark and S-shaped galleries under the bark.
• Thinning crown, epicormic sprouts on trunk, and branch dieback.

Typical hosts and areas: all native ash species. EAB has established in parts of North Carolina; check local extension for current distribution.

Hemlock woolly adelgid (HWA)

Hemlock woolly adelgid (Adelges tsugae) is a tiny, sap-sucking insect that attacks eastern and Carolina hemlocks and is widespread in NC mountain ranges.
Signs and biology:

• White, woolly ovisacs at the base of needles.
• Needle yellowing and progressive crown thinning.
• Rapid tree decline within a few years on untreated trees.

Typical hosts and areas: high-elevation hemlocks in the mountains and riparian stands.

Bark and scale insects

Various scales and sucking insects live on bark surfaces and in crevices. Examples include lecanium, oystershell, and beech scale (associated with beech bark disease).
Signs and biology:

• Scales appearing as bumps or crusty patches on branches and trunks.
• Honeydew, sooty mold, and branch dieback with heavy infestations.
• For beech: scale feeding followed by fungal cankers that create beech bark disease.

Typical hosts and areas: a wide range of hardwoods and ornamentals statewide.

General approach to treatment

Early detection and monitoring

• Learn the signs of attack described above and inspect high-value trees regularly, especially after drought, storms, or construction.
• Use traps and visual inspections. Ethanol-baited traps can monitor ambrosia beetles; sticky cards or bark examination can reveal beetle presence.
• Record location, symptoms, and progression to track spread.

Prevention and cultural controls

• Maintain tree vigor: proper mulching, deep watering during drought, and avoiding trunk injury help trees resist pests.
• Plant species and cultivars appropriate for site conditions and diversify species to limit outbreak spread.
• Avoid overfertilizing nitrogen-sensitive species; excessive growth can attract borers.
• Do not move firewood or untreated logs between properties; many bark pests spread on infested wood.

Sanitation and removal

• Promptly remove and destroy heavily infested trees or logs. Chip material to small pieces, burn if allowed, or debark and solarize logs.
• Sanitize pruning tools between trees to reduce disease or pest transfer.
• When removing infested material, act quickly to prevent beetle emergence and further spread.

Biological control

• Promote natural enemies: woodpeckers, predatory beetles, parasitoid wasps, and specific biocontrol agents (for example, Laricobius nigrinus for HWA).
• Consider releasing approved biological control agents for specific pests where local programs are active; coordinate with extension or forestry agencies.

Chemical control — principles and commonly used options

Note: Always follow pesticide label directions. Many active ingredients are restricted-use and require licensed applicators for trunk injections or professional application.

• Systemic insecticides (for cambial feeders and sap-suckers):
• Emamectin benzoate: trunk injection or basal drench; highly effective for emerald ash borer and some borers; residual often 1-2 years.
• Imidacloprid: soil drench/soak or trunk injection; slower acting, used for HWA and some scale but may take weeks to translocate.
• Dinotefuran: fast-acting systemic (soil drench or trunk injection); useful for HWA and foliar-feeding beetles where rapid control is needed.
• Contact insecticides (preventive bark sprays):
• Pyrethroids (bifenthrin, permethrin): effective as a protective bark spray to repel or kill attacking bark beetles on high-value pines when applied correctly and timed before flight periods.
• Horticultural oils and soaps:
• Effective against soft scales, young crawlers, and HWA when applied thoroughly; best used during dormant season or low-temperature windows depending on product.
• Biological insecticides:
• Beauveria bassiana and Metarhizium formulations may help suppress ambrosia beetles and wood-boring adults; efficacy varies and often requires multiple applications.

Step-by-step treatment plans for common pests

1. Southern pine beetle — immediate response for high-value pines

1. Confirm the pest: look for pitch tubes, crown discoloration, and galleries under bark.
2. Remove and destroy infested trees quickly (within days to weeks) by chipping, debarking, or burning where permitted.
3. For adjacent high-value pines, apply preventive sprays of a labeled pyrethroid to the lower trunk before beetle flight (timing depends on local monitoring; contact extension for local phenology).
4. Maintain tree vigor with proper thinning, watering, and reducing stressors; avoid fresh wounds during beetle season.
5. For large forested properties, work with a forester or NC Forest Service to coordinate landscape-level response.

2. Emerald ash borer — long-term management

1. Confirm EAB by D-shaped exit holes, galleries, and canopy thinning.
2. Decide on treatment vs. removal based on tree value, size, and infestation level. Heavily infested large trees may not be salvageable.
3. For treatment, use emamectin benzoate trunk injection (recommended for multi-year protection) or dinotefuran for rapid knockdown. Imidacloprid can be effective but is slower.
4. Treat annually or biannually as recommended on the product label and by extension guidance; emamectin injections may provide two years of control per treatment.
5. Dispose of removed ash wood responsibly; do not move untreated firewood.

3. Hemlock woolly adelgid — integrated approach

1. Inspect trees for woolly dots at the base of needles.
2. For small infestations or individual landscape trees, apply horticultural oil sprays during dormancy to suffocate overwintering immatures.
3. For longer-term control, apply systemic dinotefuran for rapid reduction or imidacloprid for longer residual control — consider trunk injection for targeted application and reduced non-target effects.
4. Release or encourage biological control agents where available and appropriate.
5. For heavily infested and declining trees, plan removal and replacement with non-host species to reduce local pest pressure.

4. Ambrosia beetles and shot hole borers — prevention and monitoring

1. Reduce stress on trees; avoid overwatering, poor drainage, and mechanical injury.
2. Use ethanol-baited traps to monitor beetle presence; traps do not usually control populations but indicate activity.
3. For attack prevention on high-value nursery stock, consider systemic insecticide dips or early-season trunk sprays; timing and product choice depend on crop and label.
4. Remove and destroy infested small trees and branches promptly.

5. Scale insects — targeted timing and contact control

1. Monitor for scale crawlers in spring and apply contact insecticides or horticultural oil timed to crawler emergence.
2. For heavy infestations on large trees, use systemic insecticides (imidacloprid or dinotefuran) applied per label instructions.
3. Prune heavily infested branches and dispose of them.

When to call a professional and legal considerations

• Call a certified arborist, licensed pesticide applicator, or your county Cooperative Extension office when the pest is difficult to identify, the infestation is extensive, or when using restricted-use pesticides or trunk injection equipment.
• Many systemic trunk injections and high-volume pesticide treatments are restricted-use or require training. Follow North Carolina pesticide laws and label requirements.
• Consider engaging a certified arborist for large trees to avoid injury to people and property during removal.

Practical takeaways and short checklist

• Early detection matters: inspect high-value and vulnerable trees twice a year and after stress events.
• Maintain tree vigor through proper watering, mulching, and avoiding wounds.
• Sanitation is essential: remove and destroy infested material quickly to reduce spread.
• Use integrated methods: combine cultural, biological, and chemical tactics tailored to the pest and tree value.
• Select appropriate chemistry and application method: emamectin benzoate for EAB and some borers, dinotefuran for rapid systemic control, imidacloprid for longer residual control, pyrethroids for preventive bark sprays on pines, and horticultural oil for scales and HWA.
• Do not move firewood or infested logs; coordinate with local extension for reporting and management recommendations.
• When in doubt, call a professional and follow labels and local regulations.

North Carolina has a diverse mix of trees and pests; matching timely identification with the right combination of sanitation, cultural care, biological support, and properly applied treatments gives the best chance of saving individual trees and limiting landscape or forest-level outbreaks.