Carpenter Bees in Boise: How to Identify the Drilling and Stop Deck and Eave Damage (2026)

Those Big Black Bees Buzzing Your Deck Are Probably Carpenter Bees

Carpenter Bee vs Bumblebee: The 30-Second ID

• The abdomen. Carpenter bee: shiny, hairless, and black. Looks polished, almost plastic. Bumblebee: fuzzy, with obvious yellow and black stripes. If the back end of the bee looks bald and glossy, you have a carpenter bee.
• Size. Both are about 3/4 to 1 inch long. Big and thick, not the little honeybee shape.
• Where you see them. Carpenter bees hover next to wood: deck rails, fascia boards, fence posts, patio cover beams, sheds. Bumblebees hover over flowers, clover, and the vegetable garden. Location is a huge tell.
• Behavior. Carpenter bee males patrol a small territory (5 to 10 feet of wood) and dive-bomb anything that flies through, including you. Bumblebees generally ignore you and stick to blooms.
• The male face. If you can look one dead-on (they hover close), the male carpenter bee has a big pale yellow or white patch on its face. Male bumblebees do not.
• Holes in the wood. Only carpenter bees drill perfect round entrance holes about 1/2 inch across. If you see the bee AND the hole in the same 3-foot section of wood, ID is done.

What Carpenter Bee Damage Actually Looks Like

• The 1/2-inch entrance hole. The female drills straight in about an inch. The hole is remarkably round and clean, like a drill bit. Fresh holes often have a small pile of sawdust (frass) directly below on the deck boards, the concrete pad, or the grass. That sawdust is the ID clincher.
• The 90-degree turn. Once inside, she pivots and starts tunneling with the grain of the wood. These galleries run 4 to 10 inches per season. On a 2x6 fascia board, a single tunnel can span most of the width.
• Chambers and stains. She partitions the tunnel into 6 to 8 cells, one per egg, with chewed wood pulp walls. You will often see yellow or brown streaks running down the wood below the entrance hole. That is a mix of frass, larval waste, and pollen. It stains cedar, redwood, and painted trim.
• The reuse problem. The next year, her daughters do not drill fresh holes. They enlarge the existing tunnel or branch off it. What was 6 inches of tunnel in year 1 becomes 3 feet of interlocking galleries by year 4. This is when boards start to feel spongy, fascia boards sag, and fence posts snap in a windstorm.
• Woodpecker damage. Woodpeckers hear the larvae inside the wood and chisel them out. If you see long jagged tears in a fascia board next to round bee holes, that is a woodpecker cashing in on carpenter bee larvae. This is often the biggest visible damage of all.

The Wood They Target on Boise Homes

• Unpainted and unstained softwood. Cedar, redwood, pine, fir, and Douglas fir. Painted or heavily sealed wood is a strong deterrent because they cannot get a grip to start drilling.
• Weathered wood. A 10-year-old deck rail that has gone silver-gray is a magnet. Fresh construction with a factory-smooth finish gets targeted less.
• Deck joists and undersides of rails. They love the underside of horizontal boards. Look under your deck, under the top rail, and along the bottom edge of your fascia. Not the top surface.
• Fascia boards under the eaves. This is where we see the most expensive damage on Boise homes. Two-story fascia is out of reach for most homeowners to treat and it is a favorite carpenter bee target.
• Fence posts and rails. Cedar fence panels around a Boise pool or backyard, especially the 4x4 posts and the horizontal top rail, take hits every summer.
• Patio covers, pergolas, and sheds. Any exposed dimensional lumber that is not painted is fair game. Old barn wood on foothill and rural properties is a favorite.
• Trim around windows and door frames. On homes with wood trim rather than composite or vinyl, we see entrance holes above windows and along the header trim.

When Carpenter Bees in Boise Are Active (and When They Go Away)

• April to early May. Adult carpenter bees that overwintered in old tunnels come back out. Males start patrolling. Females look for nesting sites. This is when you first see drilling on a fresh piece of wood.
• Mid-May through June. Peak drilling and egg-laying. Females excavate galleries and provision each cell with a pollen ball. If you catch them here, you cut off the whole generation.
• Late June through August. Larvae are developing inside the wood. Adult activity outside slows down a bit. Woodpecker damage often starts here because the larvae are big enough to hear.
• Late August through early September. New adults emerge from the tunnels. These are the biggest, most active bees you see all year. They feed on late-summer flowers, mate, and then start looking for a tunnel to overwinter in. This is the second treatment window.
• October through March. Adults tuck into old tunnels for winter. Very little visible activity, but they are still in the wood. This is the best time to plug empty holes because you know nothing is developing inside.

How to Stop Carpenter Bees From Drilling (The Fix That Actually Works)

1. Find every hole. Walk the deck, patio cover, eaves, fascia, sheds, fence, and any other exposed wood. Look for the round 1/2-inch entrance and the sawdust pile below. On two-story fascia, use binoculars. Mark each hole with a pencil dot or a bit of blue tape so you do not miss one at treatment time.
2. Puff insecticidal dust into every hole. After dusk, when the females are inside for the night, puff a light shot of a labeled insecticidal dust (pyrethrin-based or similar, look for a wood-boring bee label at D&B Supply or a farm supply store) deep into each hole with a hand duster or a bulb duster. Do not spray a liquid, it does not carry into the tunnel. The dust coats the tunnel walls so every bee walking in or out picks it up.
3. Wait 7 to 10 days. This is the step everybody wants to skip. You have to give the adults time to work in and out of the tunnels and let the larvae emerge into treated galleries. Do not plug the holes yet. Sealing an active tunnel forces bees to chew a fresh hole.
4. Plug the holes. After 10 days with no fresh sawdust, plug each hole. Dab wood glue on a 1/2-inch dowel, tap it in, and cut it flush. Or fill the hole with paintable exterior wood filler. This step is critical. Unplugged holes are a homing beacon for next year's bees. They can smell the pheromones left from last year's tunnel.
5. Paint or seal the raw wood. The permanent fix. Prime and paint any unpainted deck rails, fascia, or exposed trim within reach of ladders. Painted wood is 90% less attractive to carpenter bees. On a cedar deck you want to keep natural, a heavy solid stain works better than a thin translucent one.

When to Call Green Guard for Carpenter Bees

• The holes are in your fascia, roofline, or two-story eaves. Ladder work on a 20-foot wall to puff dust into a soffit is not a DIY job. This is where we see the worst damage on Boise homes and it needs a technician with proper ladder gear.
• You count more than 10 active holes. This means you have 2 or 3 generations of tunneling and the galleries are branching. Getting product into every branch takes a professional-grade duster with an extension wand. See our related wasp nest removal guide for a similar high-access approach.
• Woodpecker damage is already happening. Jagged tears in the fascia mean the larvae are large enough that birds are chiseling them out. You need to treat, plug, and often repair damaged boards before the next spring.
• You have wasps or hornets in the same area. We often find paper wasps or bald-faced hornets nested near carpenter bee holes because the wood is already compromised. See our bald-faced hornet guide if you spot large gray paper nests up under the eaves. Treating both at once is safer than a homeowner mixing product types.
• You are not sure what you have. If the ID is off, the treatment is wrong. Bumblebees, honeybees, and carpenter bees look similar to a lot of people. Killing a honeybee nest is not what anyone wants. Our full bee and wasp ID guide covers the differences, and a technician on-site can confirm in 2 minutes.
• The holes are near a pool, sandbox, or where kids play. Even though carpenter bees rarely sting, no one wants dive-bombing bees over a birthday party. A pro treatment before the party is the calm option.

What a Green Guard Carpenter Bee Visit Includes

• Full property walk. Every deck, patio cover, fence line, shed, garage trim, and fascia board gets inspected. Homeowners usually find 4 or 5 holes. We usually find 10 or 15.
• Species confirmation. Carpenter bee, bumblebee, or honeybee. If we find honeybees, we do not treat. Idaho honeybees are protected and we refer you to a local beekeeper for removal.
• Targeted dust application in every hole. We use a professional bulb duster with an extension wand to reach eave and fascia holes safely from a ladder. Organic-based product, hospital-grade, safe for kids and pets once dry.
• Exterior perimeter treatment. The standard barrier spray around the foundation catches any bees exiting and reduces overall pest pressure on the property.
• Follow-up plugging (or your DIY). After 7 to 10 days, we can come back to plug and seal, or we walk you through doing it yourself with dowels and wood filler.
• Quarterly protection. Our 90-day cycle keeps a fresh barrier in place through spring emergence next April. If bees drill fresh holes between visits, we come back free.

How to Never Deal With Carpenter Bees Again

• Paint or heavily stain every unpainted wood surface. This is the single biggest deterrent. Cedar fence tops, deck rails, fascia, patio cover beams. Solid stain works. Thin transparent stains do not.
• Plug every old hole. Even holes from years ago that look empty. Pheromones left in old galleries call new females back. Dowels or wood filler, painted over.
• Swap old wood for composite where you can. If you are already replacing a rotted fascia board or a deck rail, use composite or PVC trim instead of cedar. Carpenter bees ignore both.
• Inspect every April. Walk the property in the first warm week of the year. Look for last year's holes, listen for the buzz, and treat any fresh drilling immediately. Catching it in April prevents the whole summer's generation.
• Do not leave scrap lumber against the house. Old fence boards, deck offcuts, and rough pine leaning against a shed are the first thing they colonize. Break it down or store it in a sealed shed.
• Consider a year-round pest control plan. Our quarterly service keeps a spring-emergence barrier in place at the exact window carpenter bees come out. The math is easy: $119 per quarter costs less than one summer of woodpecker fascia damage.

Big Black Bee, Big Round Hole, Big Headache. We Can Fix It.