Asian Longhorned Beetle in September: What Homeowners Must Do Now

September 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) is currently in what is typically its final and most visible stretch of seasonal activity, and the damage it leaves behind can be devastating to maples, elms, willows, and other beloved hardwoods. Don't wait until your trees show advanced decline. Here's everything you need to know and do this month.

Check our seasonal forecast for a full picture of what pest pressures are building in your region right now.

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Why September Matters for This Threat

Based on typical activity patterns, the Asian Longhorned Beetle is active from May through September. That makes this month the tail end of the window — but don't mistake "tail end" for "safe." Adults that emerged over the summer have had months to mate and deposit eggs beneath tree bark. Larvae that hatched from those eggs are now tunneling deeper into the woody tissue of your trees, where they will overwinter and continue feeding.

This is also the time of year when signs of infestation become most visible. Round exit holes, sawdust-like material at the base of trees, and scarred bark are now easier to spot before autumn foliage obscures them. Acting in September — while you can still see clearly and while treatment windows remain open — gives your trees their best chance.

The USDA APHIS has identified the Asian Longhorned Beetle as a significant pest threat. View full details on this pest including its biology and management history.

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What to Look for Right Now

The Asian Longhorned Beetle earns its name — adults are large, striking insects with long antennae banded in black and white. But you're more likely to find the evidence of their presence than the insects themselves. Walk your property and inspect hardwood trees closely for:

• 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
• Shallow oval or round scars on the bark where females have chewed sites to deposit eggs
• Oozing sap or staining on the trunk or major branches
• Premature yellowing or wilting of branches that otherwise appear structurally sound
• Broken or dying branches that show no obvious weather-related cause

Not sure what you're seeing? Use our diagnosis tool to document your symptoms and get guidance.

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Where It's Active

This pest is currently tracked as active across all 50 U.S. states. Whether you're in the Northeast, the Deep South, the Pacific Coast, the Mountain West, or the Great Plains, this is a threat worth watching on your property this month. No region is categorically off the hook.

Severity is currently rated moderate, but moderate damage from a wood-boring beetle is still serious — internal tunneling weakens structural integrity and can make trees hazardous long before they look obviously sick from the outside.

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What to Do This Month

September gives you a narrow but meaningful window to act. Here are the recommended steps:

1. Targeted Insecticide Application If an infestation is confirmed or strongly suspected, apply an appropriate insecticide following all label directions carefully. Timing is critical — treatments are most effective when timed to the vulnerable larval or adult emergence stage. Consult a licensed professional to select the correct product and application method for your specific tree species and situation.

2. Consider Biological Controls Natural predators and parasitoids can play a supporting role in managing beetle populations. Encouraging or introducing beneficial insects — such as parasitic wasps — is an environmentally mindful complement to other strategies. Discuss options with a certified arborist to determine what's appropriate for your landscape.

3. Remove and Destroy Infested Material Prune out any branches showing confirmed signs of infestation. Remove fallen debris, limbs, and wood chips from the area around affected trees, as these can harbor eggs and larvae. Do not move infested wood to another location — dispose of it on-site or as directed by local guidelines to avoid spreading the pest.

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When to Call an Arborist

This is not a pest to manage casually. If you find any of the signs listed above, or if you're unsure whether what you're seeing is ALB damage, contact a certified arborist as soon as possible. Professional assessment is especially important because:

• Misidentification can lead to missed treatment windows
• Insecticide selection and application requires expertise to be safe and effective
• Structural damage from tunneling may make trees hazardous — a risk that only a trained eye can properly evaluate
• Early intervention dramatically improves the outcome for your trees

Find a certified arborist in your area through our professional directory and schedule an inspection before the season closes out.

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Your hardwood trees are long-term investments in your property and your community. September is the month to protect them. Don't let this activity window close without taking a closer look.