Asian Longhorned Beetle Peak Activity: What to Do This August

If you have hardwood trees on your property, August is not the month to look the other way. The Asian Longhorned Beetle (ALB) — identified by USDA APHIS as a significant pest threat — is currently in the heart of its typical activity window, and your trees may be at risk. Here's what homeowners and land managers need to know this month.

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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 in its seasonal cycle. Adult beetles are mobile, capable of finding new host trees, and actively laying eggs during this period. At the same time, larvae from earlier in the season may already be tunneling deep into trunks and branches — causing structural damage that often isn't visible on the surface until it's too late.

The combination of active adults and developing larvae in August means the window for effective intervention is open right now. Acting this month — rather than waiting until fall — gives you the best chance of protecting your trees before damage becomes irreversible.

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 damages hardwood trees by tunneling deep into trunks and branches, and the signs of an infestation can be subtle at first. While symptoms vary, here are the key things to examine on your trees this month:

• Round exit holes in the bark, approximately the size of a dime, where adult beetles have emerged
• Sawdust-like frass (wood shavings mixed with excrement) accumulating at the base of the tree or in branch crotches
• Oozing sap or weeping wounds on the trunk or major branches
• Dying or dead branches in the upper canopy, sometimes called "flagging"
• Adult beetles — large, striking insects with long, banded antennae — visible on bark or nearby surfaces

If you're unsure what you're seeing, use our diagnosis tool to help identify the issue and get next steps.

For a complete breakdown of this pest's biology and identification, visit the full details page.

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Where It's Active

This is a nationwide concern. Based on current tracking data, the Asian Longhorned Beetle is active across all 50 states this season — from Alabama to Wyoming. Whether you're in a densely wooded rural area or a suburban neighborhood with street trees, hardwood trees in your landscape may be vulnerable.

Hardwood species are the primary targets, so if you have maples, elms, willows, birches, or similar trees, pay especially close attention during your August inspection.

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What to Do This Month

August is an action month. Here are three evidence-based approaches you can take right now:

1. Targeted Insecticide Application When treating for Asian Longhorned Beetle, timing is everything. August falls within the vulnerable adult emergence and larval stage window, making it one of the most effective times to apply an appropriate insecticide. Always follow label directions carefully, and consider the specific life stage present when selecting your product and application method.

2. Remove and Destroy Infested Material If you identify infested branches, prune and remove them promptly. Destroy the infested material rather than composting it, and dispose of it well away from healthy trees. Clear fallen debris from around the base of susceptible trees, as it can harbor eggs or developing larvae.

3. Encourage Biological Controls As a complementary strategy, you can support natural predators and parasitoids in your landscape. Encouraging a diversity of beneficial insects — including predatory beetles and parasitic wasps — contributes to a more balanced ecosystem that can help suppress pest populations over time.

> Important: Do not move firewood or wood debris from potentially infested trees to new locations. This is one of the primary ways wood-boring beetles spread to new areas.

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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 immediately if:

• You find multiple exit holes or widespread frass on a large or mature tree
• Canopy dieback is visible across multiple branches
• You're unsure whether what you're seeing is ALB or another pest
• The affected tree is large, near a structure, or poses a safety risk if branches fail
• You want professional guidance on insecticide selection and application for high-value trees

ALB infestations that go untreated can result in tree death and potential removal costs that far exceed the cost of early intervention. A certified arborist can assess the situation, confirm the identification, and recommend a treatment plan tailored to your specific trees and conditions.

Find a qualified arborist near you through our professional directory.

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Stay ahead of seasonal threats all year long with the TreeIssues seasonal forecast. Early detection is your most powerful tool.