Direct answer: Round, clean-looking holes about the size of your fingertip in a pergola post are usually carpenter bee entry holes, especially on bare or weathered softwood. Start by checking whether the holes are active and whether the post is still solid before you fill anything.
Most likely: The usual problem is active carpenter bees boring into a dry, exposed wood face, often under a beam or on the sunnier side of the post. The next concern is hidden tunneling that has started to soften a localized area.
Look at the hole shape first. Carpenter bee holes are typically very round and neat, not ragged. Then press around the area with a screwdriver or awl. If the wood is still firm, this is often a localized repair and prevention job. If the post feels punky, split, or loose where it carries weight, treat it as a structural problem first. Reality check: a few old holes can look ugly without meaning the whole pergola is failing. Common wrong move: filling active holes before checking for fresh sawdust, bee traffic, or soft wood behind the face.
Don’t start with: Do not start by smearing filler over every hole. If bees are still using the tunnel, they will often reopen it, and filler over soft or rotten wood does not restore strength.
You see smooth round openings and light sawdust or yellowish droppings on the ground, beam, or post base below.
Start here: Start by watching the hole area for a few minutes in warm daylight and checking whether the wood around the opening is still hard.
The holes look weathered, darkened, or partly sealed by dirt, and you do not see fresh dust or bee traffic.
Start here: Start by probing around the holes to see whether the damage is only surface tunneling or the post has softened deeper inside.
The post has round holes, but it also shows splits, flaking fibers, or spots that give way under a screwdriver.
Start here: Start with a structural check before any filler or paint. Bee damage may not be the only problem.
The openings are irregular, or you find coarse wood shavings and ant-like activity instead of neat round entry holes.
Start here: Start by separating carpenter bee damage from carpenter ant damage or rot, because the repair path changes.
Carpenter bees usually make a clean round entry hole, then tunnel with the grain behind the face. Pergola posts and beam undersides are common targets when the wood is unfinished or weathered.
Quick check: Look for fresh sawdust, yellow-brown spotting below the hole, or bees hovering near the same area during warm daylight.
Old holes often stay visible for years. They may look inactive but still weaken a small area if there are several close together.
Quick check: If the hole edges are dark, dusty, or weathered and there is no fresh debris or bee traffic, the tunnel may be old rather than active.
Bee holes in otherwise sound wood are one thing. Bee holes in damp, softened wood are different because the post can lose strength much faster.
Quick check: Press an awl or screwdriver into the wood around and below the holes. If it sinks in easily or pulls out damp fibers, moisture damage is part of the problem.
Carpenter ants do not drill the same neat round entry hole. They usually leave more ragged openings and coarse frass, often where wood is already damp or decayed.
Quick check: If the hole edges are rough, the debris looks shredded instead of fine, or you see ants using the area, do not assume bees are the only issue.
You want to separate neat bee entry holes from ant damage, rot pockets, or random weathering before you repair the wrong thing.
Next move: If the holes are round and you confirm fresh activity, treat this as active carpenter bee damage and move to the wood condition check. If the holes are irregular or you see ant activity, the problem may be carpenter ants or decay instead of bees alone.
What to conclude: Neat round holes point toward carpenter bees. Ragged openings or shredded frass point away from that diagnosis.
A few tunnels in sound wood can often be repaired. A post that is soft, split, or loose needs a different level of response.
Next move: If the wood stays firm and the post does not move, the damage is likely localized and you can plan a repair after activity is dealt with. If the tool sinks in easily, the wood crumbles, or the post shifts under load, stop cosmetic repair and treat the post as compromised.
What to conclude: Firm wood means the tunnels are probably limited enough for localized repair. Softness, splitting, or looseness means the post may need reinforcement or replacement, not just filling.
If you patch an active tunnel too soon, the bees often reopen it or move a few inches over and start again.
Next move: If activity stops and no fresh dust appears, you can move on to repairing the holes and protecting the wood surface. If bees keep returning to the same post or the infestation is widespread across multiple members, it is time for a pest-control approach before finish repair.
This is the point where a simple repair makes sense: inactive tunnels, firm surrounding wood, and no structural looseness.
Next move: If the patch stays firm and the post surface is solid, you have handled the localized damage and improved the post's resistance to repeat attack. If filler will not hold, the void is larger than expected, or the wood keeps breaking away, the damage is too deep for a simple surface repair.
Once a pergola post is soft, split, or loose, the job is no longer about insect holes. It is about restoring support safely.
A good result: If the post is stabilized, connections are tight, and the wood is sound, the pergola can be returned to service with ongoing monitoring and surface protection.
If not: If you cannot get the post solid without shoring or you are unsure how load is being carried, stop and bring in a pro.
What to conclude: At this stage the real fix is structural, not cosmetic. Replacing the weak connection hardware or post base only makes sense when inspection supports it.
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Only after you are reasonably sure the holes are inactive and the surrounding wood is still solid. Filling active tunnels usually leads to reopened holes or new holes nearby.
Carpenter bee holes are usually very round and clean. Carpenter ant damage tends to look rougher, with shredded frass and openings that are less uniform, often in damp or already damaged wood.
Yes, sometimes. A few old holes in otherwise hard wood are often more of a maintenance issue than a structural failure. The concern rises when the holes are clustered, the wood is soft, or the post moves at its connections.
That usually means the damage goes beyond a simple surface patch. If the surrounding wood is still hard, a localized repair may still work. If the area feels hollow, crumbly, or split, treat the post as potentially compromised.
They can. Weathered, unfinished, and repeatedly exposed wood is more likely to be reused. Surface protection and early repair of old holes help, but you also need to watch for fresh activity each season.
Not automatically. Replace or structurally repair the pergola post when probing shows deep softness, major splitting, looseness, or damage at a load-bearing connection. Cosmetic holes alone do not always justify full replacement.