Asian Longhorned Beetle Peak Activity: What to Do in August

If you have hardwood trees on your property, August is the month to pay close attention. The Asian Longhorned Beetle (ALB) — identified by USDA APHIS as a serious pest threat — is currently in the heart of its typical activity window, and the damage it causes can be severe and lasting. Here's what every homeowner and land manager needs to know right now.

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Why August Matters for This Threat

Based on typical timing, the Asian Longhorned Beetle is active from May through September, making August one of the most critical months for monitoring and action. Adult beetles are mobile, capable of flying to new host trees, and actively laying eggs during this period. Meanwhile, larvae that hatched earlier in the season are tunneling deeper into the wood of your trees, making the internal damage increasingly difficult to reverse.

The combination of active adults and established larvae means that August presents a dual threat — new infestations can begin while existing ones are intensifying. Waiting until fall to investigate means giving the beetle another full month to expand its foothold. Check our seasonal forecast for updated activity outlooks in your region.

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What to Look for Right Now

The Asian Longhorned Beetle is a wood-boring insect that does its most destructive work inside the trunks and branches of hardwood trees. Because much of the damage is internal, you need to know the external signs that something is wrong. Walk around your hardwood trees this month and look for:

• Round exit holes in the bark, approximately the diameter of a pencil, where adult beetles have emerged
• Sawdust-like frass (a mix of wood shavings and excrement) collecting at the base of the tree or in branch crotches
• Weeping sap or discolored patches on the bark where eggs have been deposited
• Dying or dead branches in the upper canopy, sometimes called "flagging," that appear out of season
• The beetles themselves — adults are large, glossy black with white spots and have very long, banded antennae

Not sure what you're seeing? Use our diagnosis tool to document symptoms and get guidance, or visit the full details page for a comprehensive look at this pest.

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Where It's Active

This pest is currently being tracked as active across all 50 states, meaning no region should consider itself exempt from risk this August. Whether you're in the Northeast, the Southeast, the Midwest, the Mountain West, or the Pacific Coast, hardwood trees in your landscape could be vulnerable. High-risk host trees include maple, elm, willow, birch, poplar, ash, and several other common hardwood species.

If you live in an area with a known ALB infestation, be especially vigilant — and be aware that moving firewood from infested areas can spread the beetle to new locations.

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What to Do This Month

August is not a month for a wait-and-see approach. Here are the three primary management actions to consider right now:

1. Targeted Insecticide Application If you have confirmed or strongly suspected activity, timing is critical. Applying an appropriate insecticide during the adult emergence and egg-laying stage — which aligns with August's typical activity peak — can help protect trees from new infestations. Always follow label directions precisely, and consider a licensed applicator for large or valuable trees.

2. Infested Material Removal If you find infested branches, prune and destroy them promptly. Remove fallen debris and dead wood from around the base of your trees, as this material can harbor eggs and larvae. Dispose of infested material well away from healthy trees — do not chip or compost it on-site if infestation is suspected.

3. Biological Control Agents For a supplementary, environmentally conscious approach, natural predators and parasitoids can play a supporting role. Encouraging or introducing beneficial insects, including parasitic wasps, can help manage populations over time. This is generally most effective as part of an integrated pest management strategy rather than a standalone solution.

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When to Call an Arborist

Some situations go beyond DIY management. Contact a certified arborist immediately if:

• You find multiple exit holes or widespread frass across one or more trees
• Canopy dieback is visible and progressing quickly
• You're uncertain whether what you're seeing is ALB or another pest
• You have large, mature, or high-value trees at risk
• You're considering the removal of a potentially infested tree

A certified arborist can assess the extent of damage, recommend a targeted treatment plan, and help you determine whether a tree can be saved or needs to be safely removed before the beetle spreads further. Find a qualified arborist near you through our professional directory.

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Don't let August pass without a thorough inspection of your hardwood trees. Early detection and prompt action are your best tools against this destructive pest. Visit the full details page to learn more, and stay informed with our seasonal forecast throughout the rest of the activity window.