Asian Longhorned Beetle in August: Protect Your Hardwoods Now

August is here, and if you have hardwood trees on your property, this is one of the most important months of the year to pay attention. The Asian Longhorned Beetle (ALB) — identified by USDA APHIS as a significant pest threat — is entering what is typically the heart of its active season. Knowing what to look for right now, and acting quickly, can make a real difference for the trees in your yard.

For a broader picture of what's threatening trees across the country this season, visit our seasonal forecast.

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Why August Matters for This Threat

The Asian Longhorned Beetle follows a typical activity window running from May through September, and August falls squarely in the middle of that peak window. This is the time of year when adult beetles are most likely to be visible, actively feeding, and laying eggs beneath the bark of host trees. Larvae — the primary drivers of structural damage — burrow deep into trunks and branches, creating tunnels that disrupt the tree's ability to move water and nutrients.

Because the most destructive work happens inside the tree, damage can be well underway before outward signs become obvious. That's exactly why vigilance this month is so critical. The sooner a problem is caught, the more management options are available to you.

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What to Look for Right Now

ALB attacks hardwood trees by tunneling deep into trunks and branches. While the data on specific visible symptoms is still being compiled for your region, there are several general signs associated with wood-boring beetle activity that warrant a closer look:

• Round exit holes in the bark, roughly the size of a dime, where adult beetles have emerged
• Sawdust-like frass (a mixture of wood shavings and insect waste) accumulating at the base of the tree or in bark crevices
• Weeping sap or staining on the bark surface near entry or exit points
• Dying or dead branches in the upper canopy despite adequate water and soil conditions
• Adult beetles — large, glossy black insects with white spots and very long antennae — spotted on or near your trees

Not sure what you're seeing? Use our diagnosis tool to walk through your observations and get guidance on next steps.

For the complete description of this pest and its biology, see our full details page.

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Where It's Active

This pest is currently tracked as moderately active across all 50 U.S. states, meaning no region should consider itself off the hook. Whether you're in the Northeast, the Deep South, the Mountain West, or the Pacific Coast, hardwood trees in your landscape may be at risk. Urban and suburban landscapes with ornamental hardwoods — maples, elms, willows, birches, and others — can be particularly vulnerable.

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What to Do This Month

August is a key window for intervention. Here's what homeowners and land managers should prioritize right now:

1. Inspect Your Hardwoods Walk your property and examine hardwood trees carefully — trunk, major limbs, and the ground beneath the canopy. Look for the signs described above. Take photos of anything suspicious.

2. Targeted Insecticide Application If ALB activity is confirmed or strongly suspected, timing is everything. Insecticide treatments are most effective when applied during the vulnerable larval or adult emergence stage — which aligns closely with this month. Always follow label directions precisely, and consider whether a professional application is appropriate for the size and number of trees involved.

3. Biological Control Options In some situations, natural predators and parasitoids — including parasitic wasps and predatory beetles — can play a supporting role in managing beetle populations. Discuss with a certified professional whether biological control agents are appropriate for your specific situation.

4. Remove Infested Material If you identify infested branches, prune and destroy them promptly. Remove fallen debris and any material that may harbor eggs or larvae. Dispose of infested wood away from healthy trees — do not chip or compost it on-site if active infestation is suspected. Do not transport infested wood to new locations.

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When to Call an Arborist

Some situations go beyond what a homeowner can safely or effectively manage alone. Contact a certified arborist if:

• You suspect active infestation in large or mature trees
• You're unsure whether what you're seeing is actually ALB versus another issue
• Affected branches are large, high up, or close to structures
• You want a professional assessment before investing in treatment

A qualified arborist can confirm identification, assess the extent of damage, and recommend a treatment plan tailored to your trees and local conditions. Use our find an arborist directory to locate ISA Certified Arborists in your area.

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Don't wait for obvious decline to set in. August is the month to act — inspect your trees this week, document what you find, and take the steps that give your hardwoods the best chance of staying healthy through the season and beyond.