Invasive Tree Pests Identification

Why this matters

Several non-native pests have devastated specific tree species across the US in recent decades. Emerald Ash Borer alone has killed hundreds of millions of ash trees. A tree service company that can identify these pests at the inspection visit becomes the trusted advisor for what's often a homeowner's most valuable landscape feature. Early identification means treatment is possible; late identification means removal is the only option.

Emerald Ash Borer (Agrilus planipennis)

Introduced from Asia, first US detection 2002 (Michigan). Now in 35+ states.

Host trees: all North American ash species (Fraxinus). Green ash, white ash, black ash all severely affected.

Lifecycle:

• Adult beetles emerge May-August
• Lay eggs on ash bark
• Larvae bore into the cambium under bark
• Larvae spend 1-2 years feeding under bark
• Adults emerge through D-shaped exit holes

Visual signs:

Trees in mid-stages: thinning crown, some bark damage, exit holes increasing. Detection at this stage allows treatment.

Trees in late stages: significant crown death, heavy bark damage, structural integrity declining. Removal typically the answer.

Treatment:

• Systemic insecticides (emamectin benzoate, imidacloprid, others)
• Trunk injection most effective
• Soil drench (less effective for large trees)
• Treatment effective for healthy trees with <30-50% crown dieback
• Annual / biannual treatments required for ongoing protection

Customer education:

1. "EAB is established in [region]; all your ash trees are at risk"
2. "Healthy ash can be protected with annual treatment"
3. "Trees showing more than 30% crown decline are usually beyond saving"
4. "Treatment is more expensive than removal; the choice depends on the tree's value"

Asian Longhorned Beetle (Anoplophora glabripennis)

Introduced from Asia, first US detection 1996 (New York). Currently localized infestations.

Host trees: maple primarily; also willow, elm, sycamore, horse chestnut, poplar, birch, mountain ash, ash. Hardwoods generally.

Lifecycle:

• Adults large (1-1.5 inch); shiny black with white spots; long antennae
• Adults emerge May-October
• Lay eggs in chewed pits in the bark
• Larvae bore deep into the wood (not just under bark)
• Pupate inside the tree
• Emerge through round holes

Visual signs:

Treatment:

• Systemic insecticides used with limited success
• Federally regulated quarantine areas
• Removal of infected trees often mandated
• Replacement with non-host species

This is a more severe quarantine pest than EAB. USDA APHIS coordinates response.

Reporting: any suspected ALB sighting should be reported to USDA APHIS or state department of agriculture. Field samples preserved for verification.

Hemlock Woolly Adelgid (Adelges tsugae)

Introduced from Japan, first US detection 1924 (Virginia). Now established in eastern hemlock range.

Host trees: eastern hemlock (Tsuga canadensis); Carolina hemlock (Tsuga caroliniana). Western hemlocks much less affected.

Visual signs:

Treatment:

• Horticultural oil (dormant season)
• Soil drench with imidacloprid (provides multi-year protection)
• Soil injection
• Trunk injection
• Predatory beetles (biological control)

Hemlocks can typically be saved with treatment IF infestation is caught early.

Spotted Lanternfly (Lycorma delicatula)

Introduced from Asia, first US detection 2014 (Pennsylvania). Spreading rapidly through northeast.

Host plants: tree of heaven (preferred); also fruit trees, hops, grape, maple, walnut, willow, more

Lifecycle:

• Adults active July-November
• Lay egg masses (gray, mud-like) on bark, stones, equipment
• Eggs overwinter; hatch April-June
• Nymphs feed on plants
• Multiple instar stages with changing color (black with white spots → red with white spots and stripes)
• Adults bright red and black with spotted wings

Visual signs:

Treatment:

• Egg mass scraping (any time)
• Adult-stage insecticides (specific products)
• Tree of heaven removal (preferred host)
• Reporting to state agriculture for tracking

This is a recent introduction; treatment protocols evolving.

Oak Wilt (Bretziella fagacearum)

Fungal disease, not insect. Native pathogen but heavily damaging in some regions (Texas, Midwest).

Host trees: red oak group (rapid kill); white oak group (slow decline)

Visual signs:

Spread:

• Bark beetles carry spores
• Root grafts spread between trees (oaks within 50 feet of each other)
• New oak wounds during the warm season are entry points

Prevention:

• DO NOT prune oaks April-July (vector active season)
• Paint cuts immediately if cutting in growing season is unavoidable
• Sterilize tools between trees
• Sever root grafts between infected and healthy oaks (specialty service)

Treatment:

• Trunk injection with propiconazole (preventive AND treatment)
• Removal of severely infected trees
• Investigation of nearby oaks

Dutch Elm Disease (Ophiostoma novo-ulmi)

References

• USDA APHIS (Animal and Plant Health Inspection Service) pest information
• USDA Forest Service pest documentation
• ISA (International Society of Arboriculture) treatment guidelines
• State Cooperative Extension pest publications
• ANSI A300 (Part 8) - Lightning Protection (related; for high-value trees)
• Manuall internal: Declining Tree Diagnosis, Tree Risk Assessment, Tree Species Guide