Asian Longhorned Beetle August Alert: Protect Your Hardwoods Now

If you have hardwood trees on your property, August is the month to pay close attention. The Asian Longhorned Beetle (ALB) is entering what is typically its peak period of activity, and the damage it causes can be devastating — often going undetected until it's too late. Here's what you need to know right now to protect your trees. Check our seasonal forecast for the latest updates on this and other active threats.

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Why August Matters for This Threat

The Asian Longhorned Beetle follows a typical activity window that runs from May through September, with summer months representing the height of adult beetle emergence and egg-laying. August sits squarely in this critical window. Adult beetles are actively chewing their way out of infested trees, mating, and depositing eggs beneath the bark of host trees — setting the stage for the next generation of larvae to begin tunneling through the wood.

This tunneling is what makes ALB so destructive. Unlike surface-feeding insects, the larvae bore deep into the heartwood of trunks and branches, disrupting the tree's ability to transport water and nutrients. By the time visible symptoms appear, significant structural damage has often already occurred. Acting in August — while adults are active and detectable — gives you your best opportunity for early intervention.

For the complete background on this pest, visit the full details page.

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What to Look for Right Now

The Asian Longhorned Beetle is identified by USDA APHIS as a significant pest threat to hardwood trees. When inspecting your trees this month, walk the perimeter of each tree and look carefully at the trunk and major branches. Key warning signs to watch for include:

• Round exit holes in the bark, approximately the size of a dime, where adult beetles have emerged
• Sawdust-like frass (wood shavings and excrement) accumulating at the base of the tree or in branch crevices
• Egg-laying sites — shallow, oval depressions chewed into the bark where females deposit eggs
• Adult beetles themselves, which are distinctive: large, black insects with white spots and very long, banded antennae
• Weeping sap or staining on the bark near entry and exit points
• Premature yellowing or dropping of leaves on otherwise healthy-looking hardwood trees

If anything looks suspicious, use our diagnosis tool to document and identify what you're seeing before the damage progresses.

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Where It's Active

This threat is currently tracked as active across all 50 U.S. states, making vigilance important for homeowners and land managers nationwide. Hardwood trees — including maple, elm, willow, birch, ash, and others — are potential hosts wherever they grow. No region should consider itself immune during this typical activity period.

Severity is currently rated Moderate, but moderate damage from a wood-boring beetle can still mean significant structural decline or tree loss if left unaddressed.

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What to Do This Month

August is an actionable month. Here are the three primary approaches recommended for managing Asian Longhorned Beetle:

1. Targeted Insecticide Application If you have confirmed or suspected activity, timing is everything. Apply an appropriate insecticide following all label directions precisely. Treating during the active adult emergence and larval stage — which aligns with right now — maximizes effectiveness. Consult a licensed professional to select the right product for your tree species and situation.

2. Biological Control Agents For a more ecologically integrated approach, consider encouraging or introducing natural predators and parasitoids. Options include predatory beetles, parasitic wasps, or applications of Bacillus thuringiensis (Bt). These approaches work best as part of a broader integrated pest management plan.

3. Infested Material Removal If you identify infested branches, prune and destroy that material promptly. Remove any fallen debris from around the base of the tree, as it may harbor eggs or larvae. Critically — do not move infested wood off your property without following proper disposal guidelines, as this can spread the beetle to new areas. Chip, burn (where permitted), or arrange for appropriate disposal well away from healthy trees.

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When to Call an Arborist

Some situations call for professional eyes. Contact a certified arborist promptly if:

• You find exit holes, frass, or adult beetles on any hardwood tree
• A tree shows unexplained leaf loss or dieback during the growing season
• You're unsure whether what you're seeing is ALB or another issue
• You want to apply insecticides but aren't comfortable with product selection or timing
• An infested tree is large, near a structure, or poses a safety concern

An ISA Certified Arborist can assess the extent of damage, recommend the most effective treatment timeline, and help you make informed decisions about tree retention or removal. Use our find an arborist directory to locate a qualified professional in your area.

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Don't wait for obvious decline to take action. August's window of beetle activity is also your window of opportunity. A proactive inspection this month could be the difference between saving a mature hardwood and losing it entirely.