How Do I Treat Emerald Ash Borer And Other Indiana Tree Pests

Emerald ash borer (EAB) is one of the most destructive invasive tree pests affecting Indiana and much of the United States. Managing EAB effectively requires a combination of early detection, the right treatment method for the tree and situation, and an integrated approach that includes cultural practices and monitoring. This article explains how to recognize and treat emerald ash borer, compares treatment options and timing, and summarizes practical approaches for several other important Indiana tree pests and diseases. Concrete recommendations and decision points are provided so you can protect high-value trees or plan removals when treatment is not realistic.

Recognizing emerald ash borer damage

Knowing the signs of EAB infestation is the first step in deciding whether to treat a tree and which treatment will be effective.

Canopy thinning and dieback, often starting in the upper crown.
D-shaped exit holes in the bark about 3/16 inch wide.
S-shaped galleries under the bark visible when bark is removed.
Epicormic sprouts or water sprouts on the trunk and main branches.
Increased woodpecker activity stripping bark to reach larvae.
Vertical splitting of bark revealing galleries.

If you see these signs on an ash (Fraxinus species), presume EAB is present and act quickly. Early-stage infestations (minor thinning and few exit holes) respond better to treatment than heavily infested trees.

Treatment objectives and decision framework

Before choosing a control method, determine your objective and constraints:

Is the tree high-value (shade tree in yard, historic specimen, street tree)? High-value trees are often worth treatment.
How large is the tree (diameter at breast height, DBH)? Some treatments have tree-size limits or different dosages.
How advanced is the infestation? Heavily infested trees may decline despite treatment and could become hazards.
Is the tree in a location that allows professional equipment access (for trunk injection, removal, or soil drench)?
Are you able to commit to follow-up treatments? Some methods need repeat applications.

Call a certified arborist or extension specialist if you are unsure; they can assess tree health and recommend a program.

Chemical treatment options: pros, cons, and practical guidance

The most reliable treatments for EAB are systemic insecticides that move through the tree to kill larvae feeding under the bark. The three main active ingredients used today are emamectin benzoate, dinotefuran, and imidacloprid. Application methods include trunk injection, soil drench/soil injection, and bark sprays for some products.

Emamectin benzoate (best long-term control for many trees)

Emamectin benzoate applied by trunk injection is widely regarded as the most effective option for protecting moderate- to high-value ash trees. Key points:

Mode: systemic injection into the trunk; moves in the xylem to foliage and branches.
Efficacy: Provides strong control and can significantly reduce larval survival; residual often 2 to 3 years with a single injection in healthy trees.
Timing: Best applied in late spring to early summer when sap flow is active, though many programs apply it any time when the tree is actively transpiring.
Tree size: Effective on a wide range of DBH sizes; professional applicators will determine dose by DBH.
Pros: Long residual, high efficacy even on moderate infestations.
Cons: Requires professional trunk injection equipment in many cases; more costly per treatment but less frequent.

Dinotefuran (fast knockdown, short residual)

Dinotefuran is a neonicotinoid that moves quickly in the tree and is used as a soil drench, soil injection, or trunk injection.

Mode: systemic, fast uptake to foliage and cambium; often used when rapid control is needed.
Efficacy: Fast-acting against adults and larvae but residual is relatively short (months to a year).
Timing: Useful in spring or early summer; can be used as an emergency rescue treatment when decline is rapid.
Pros: Quick reduction in larval activity; good when emamectin is not an option.
Cons: Shorter residual means annual treatments may be required.

Imidacloprid (common soil treatment, slower uptake)

Imidacloprid is another neonicotinoid used as a soil drench/injection or trunk injection.

Mode: systemic; typically applied as a spring or fall soil drench around the root zone or by trunk injection.
Efficacy: Effective for light infestations and smaller trees; slower translocation than dinotefuran and generally less effective than emamectin for heavy infestations.
Pros: Widely available, can be applied by homeowners for smaller trees following label directions.
Cons: May take weeks to move into the canopy; inconsistent control on heavily infested large trees.

Practical application guidance and safety

Always follow the product label for dosages and application methods; professional applicators use calibrated equipment and calculate dose by DBH.
Soil drenches require moist, uncompacted soil and adequate distance from impervious surfaces; do not apply when soils are frozen.
Trunk injections are precise and minimize non-target exposure; they cause small punctures in the bark but are generally safe when done correctly.
Avoid applying neonicotinoids as foliar sprays to flowering plants where pollinators may be exposed.
Consider hiring a certified arborist for trees over 6 inches DBH or when using trunk-injection formulations.

When to remove rather than treat

Treatment is most cost-effective for trees with good structure and less than about 30-50 percent crown decline. Consider removal when:

Crown dieback is extensive and the tree poses a hazard to people or property.
Multiple years of treatment would be required but canopy recovery is unlikely.
The tree is nearing the end of its useful life or is low-value relative to treatment cost.
Nearby public safety concerns require removal (fallen branch hazard over street or sidewalk).

If you remove ash trees, do not leave infested wood in place where it can support larval development. Follow local guidance for disposal — chipping, burning where allowed, or processing to prevent spread.

Monitoring and cultural practices

Regular monitoring reduces surprise failure. Practical steps:

Inspect ash trees annually for thinning, exit holes, or woodpecker damage.
Look for epicormic shoots and bark splits.
Maintain tree vigor: mulch appropriately, avoid root compaction, water during droughts, and prune dead wood properly.
Avoid injuring trunks and roots during construction; stressed trees are more vulnerable.

Biological control programs (release of parasitoids) have been used in some places, but these are not a substitute for individual tree protection.

Other common Indiana tree pests and how to address them

EAB is not the only threat. A broad, practical overview of other pests and diseases follows, with treatment ideas.

Gypsy moth (defoliator)

Signs: Irregular defoliation in late spring and summer, caterpillars with hair tufts and blue/red spots.
Treatment: For small trees, hand-pick egg masses or caterpillars; biological insecticides containing Bacillus thuringiensis kurstaki (Btk) are effective when applied early in the larval stage. Maintain tree vigor to tolerate defoliation.

Oak wilt and other fungal vascular diseases

Signs: Rapid wilting and discoloration of leaves on oaks; lower branches die back.
Treatment: Prevention is key — avoid pruning oaks in spring and early summer when beetles that spread the fungus are active. Trenches and fungicide injections (propiconazole) can be used in some cases; consult a specialist for oak wilt response.

Hemlock woolly adelgid

Signs: White woolly egg sacs at branch bases, twig dieback on hemlocks.
Treatment: Apply systemic insecticides (imidacloprid or dinotefuran) and/or insecticidal soaps and oils for small specimens. Biological controls and annual monitoring are recommended.

Bronze birch borer and other borers

Signs: Thinning crown, D-shaped exit holes, bark discoloration.
Treatment: Keep trees healthy; trunk injections or soil-applied systemic insecticides can protect valuable birch. Remove and replace heavily infested trees.

Scale, aphids, and minor sap feeders

Signs: Honeydew deposits, sooty mold, yellowing foliage.
Treatment: Horticultural oils, systemic insecticides for severe outbreaks, and beneficial insects (lady beetles, lacewings) for long-term control.

Dutch elm disease

Signs: Rapid wilting of one branch then whole crown, vascular discoloration under the bark.
Treatment: Sanitation (remove infected wood promptly), fungicide injection in high-value elm trees, and pruning to maintain tree health. Quarantine rules may apply to movement of elm wood.

Integrated pest management (IPM) checklist for Indiana property owners

Identify: Know the species and symptoms before treating.
Monitor: Inspect trees annually and after storms.
Prioritize: Decide which trees are worth protecting based on value, location, and health.
Choose treatment: Match method (emamectin, dinotefuran, imidacloprid, pruning, removal) to tree size and infestation level.
Implement cultural controls: Mulch, water, minimize root damage, prune correctly.
Use professionals for large trees, injections, or when removal is required.
Reassess: Monitor treated trees and retreat as needed based on residual efficacy and label guidance.

Costs, permits, and finding help in Indiana

Costs vary widely. Expect professional trunk injections with emamectin to be higher per application but last multiple years; soil drenches are less expensive per treatment but often require annual application. Tree removal costs depend on DBH, location, and difficulty. Obtain multiple quotes from licensed arborists.
Check local city or county regulations for tree removal permits, especially for street trees or protected species. Contact your county extension office or state forestry agency for up-to-date quarantine zones, reporting procedures, and recommendations.

Final practical takeaways

Act early. Early detection and treatment dramatically improve chances of saving an ash tree.
Match product to situation. Emamectin via trunk injection offers multi-year protection and is usually best for large or heavily used landscape ash. Dinotefuran gives quick knockdown. Imidacloprid can protect smaller trees when applied correctly.
Use professional services for large trees or trunk injections; homeowners can apply certain soil treatments for small trees but must follow labels.
Maintain tree health. Good cultural care increases resistance to pests and improves response to treatments.
Prepare for replacement. Plan to diversify species in the landscape; do not replant only ash or another single species to avoid future widespread losses.
When in doubt, consult an ISA-certified arborist or your local extension service for a site-specific plan.

Effective management of emerald ash borer and other Indiana tree pests is both science-based and site-specific. By combining careful monitoring, appropriate systemic treatments, sound cultural practices, and professional assistance when needed, you can significantly reduce risk and preserve valuable trees in your landscape.