Asian Longhorned Beetle: What to Do in August 2025

If you have maples, elms, willows, or other hardwoods on your property, August is the month to pay close 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. This is not a pest to ignore. Its damage is structural, progressive, and in many cases, fatal to the trees it infects.

Check our seasonal forecast for a full picture of what threats are peaking in your area right now.

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Why August Matters for This Threat

Based on typical activity patterns, the Asian Longhorned Beetle is active from May through September, making August one of the most critical months for monitoring and action. During this window, adult beetles are most likely to be actively emerging from trees, feeding, mating, and laying eggs in new host trees. The damage they cause — tunneling deep into trunks and branches — is done largely from the inside out, meaning by the time visible symptoms appear on the surface, significant internal destruction may already be underway.

Acting in August, while the pest is active and detectable, gives you the best chance of catching an infestation before it becomes irreversible. For full details on this pest's biology and life cycle, visit our dedicated ailment page.

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What to Look for Right Now

The Asian Longhorned Beetle is a moderate-severity insect pest that targets hardwood trees. When inspecting your trees this month, walk the perimeter of each hardwood and look up into the canopy as well as along the trunk and main branches. Key signs to watch for include:

• Round exit holes in the bark, roughly 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 bark crevices
• Weeping sap or discolored patches on the bark surface
• Broken or dying branches in the upper canopy, sometimes called "flagging"
• The beetles themselves — large, glossy black insects with white spots, and long banded antennae that may exceed their body length

Not sure what you're seeing? Use our diagnosis tool to help identify symptoms on your specific trees.

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Where It's Active

This pest is currently being tracked across all 50 states, meaning no region of the country is without some level of risk this season. Whether you're in the Northeast, the Pacific Northwest, the Gulf Coast, or anywhere in between, hardwood trees on your property may be vulnerable. Landowners and homeowners nationwide should treat August as a high-alert month for this pest.

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What to Do This Month

If you suspect or confirm Asian Longhorned Beetle activity on your property, there are three primary approaches to consider:

1. Targeted Insecticide Application Timing is everything with insecticide treatments. August — when adult beetles are active and larvae may be in vulnerable early stages — is a critical treatment window. Apply an appropriate insecticide following all label directions carefully. Products must be selected and applied correctly to reach the right life stage. Improper application wastes resources and can harm beneficial insects.

2. Infested Material Removal If you identify infested branches, prune and destroy that material promptly. Do not leave cuttings, fallen limbs, or debris near healthy trees — eggs and larvae can survive in cut wood and spread the infestation. Dispose of material well away from your tree line, and check local regulations regarding the movement of potentially infested wood.

3. Biological Control Agents For a longer-term integrated approach, encouraging or introducing natural predators and parasitoids can help reduce populations. Options include predatory beetles, parasitic wasps, or applications of Bacillus thuringiensis (Bt) where appropriate. This approach works best as part of a broader pest management plan rather than as a standalone emergency measure.

Start monitoring now, document what you find, and don't wait for damage to worsen before taking action.

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When to Call an Arborist

While homeowners can do a great deal — inspecting trees, removing debris, applying labeled treatments — Asian Longhorned Beetle infestations often require professional intervention, especially when:

• You've found exit holes or confirmed beetle presence
• A tree shows significant canopy dieback or structural damage
• You're unsure which treatment is appropriate for your tree species or situation
• The affected trees are large, near structures, or difficult to safely access

A certified arborist can assess the full extent of an infestation, recommend the most effective treatment timing, and help you decide whether a tree can be saved or needs to be removed before it becomes a hazard. Find a qualified arborist in your area through our directory.

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August is your window. Inspect your hardwoods now, know what to look for, and take action before this pest does more damage than necessary. A few hours of attention this month could save a tree that's been growing for decades.