Bee on the Lookout for Carpenter Bees

— Written By and last updated by

“I’m bringing home my baby bumble bee,
won’t my Mommy be so proud of me!
I’m bringing home my baby bumble bee —
OUCH! It stung me!!”

No, they are not bumble bees, but they sure do look like them! Carpenter bees are out, and they are back to their destructive activities. You know what I am talking about, those small, round holes under the eaves of your porch, porch handrails, or front porch swing. If you have not seen the holes, you may have seen the small sawdust piles underneath the round holes. Your wooden structures may have some immunity to their attack IF they are painted or treated but beware, immunity does not last forever.

A Carpenter Bee on a pink flower

Carpenter bees are yellow and black bees that look like bumble bees, but they have a black shiny abdomen or tail section. The male carpenter bees do not have stingers but can act aggressive. The females can sting but usually do not unless they feel threatened. They are somewhat larger in size than the bumble bee. Carpenter bees do not live in colonies like other bees. The mated female bees feed on plant nectar and then begins constructing new tunnels or what you see as perfectly circular holes in your wood. One hole is usually used by one carpenter bee, but it could be shared in a pinch. The tunnels are relatively long (6 inches up to 1 foot) and may branch off if several bees use the same entrance. The same hole can be used for several years.The female places food into the tunnel along with an egg. She can place up to seven eggs in cells throughout the tunnel. These females will die in a couple of weeks and the eggs will hatch in a matter of days. Five to seven weeks later (usually late summer), the offspring emerge. They spend their days foraging for pollen and cleaning out old tunnels to use as overwintering sites when the weather turns cold.

Most homeowners are annoyed by these flying critters. They do not pose serious structural damage to the wood unless there are a lot of them and are present over several years. But who wants holes in their wooden house? They also make a mess. They poop before entering the tunnel. I mean, who wants a dirty house? So, they leave yellowish-brown staining from voided fecal matter. There is also the issue about the tunnels attracting woodpeckers looking for bee larvae. This damage can be sever. Holes on exposed surfaces can allow rainwater to enter the wood which could lead to damage by wood-decaying fungi or other insect attacks, such as their cousins, the carpenter ants.

Holes in a porch caused by carpenter bees.

Holes in porch railing and fecal matter on a porch post caused by carpenter bees.

Preventative measures are tricky and difficult. Protective insecticide sprays applied to wood surfaces are effective for only a short period of time even when repeated every couple of weeks. The carpenter bee may not be exposed to lethal doses of the pesticide since they are not actually eating the wood. It is almost impossible, maybe impractical and sometimes unsafe to try applying a pesticide to all possible sites where the bees may tunnel. Spraying visible bees is not particularly safe. It would be more practical if you would purchase a tennis racquet and start swatting at the bees. And, on the bright side, this method may have added health benefits.

Besides practicing your tennis moves, the best method may be to treat the entrance holes with an insecticidal spray or dust to reduce future nesting activity. A list of chemicals for use against carpenter bees can be found in the North Carolina Agricultural Chemicals Manual. Avoid inhaling the insecticide or contaminating your clothing with the spray and always stand upwind from the surface you are treating. After the insecticide application is complete, seal the hold with a small ball of aluminum foil and caulk after 24-36 hours. Sealing the holes is important to deter other carpenter bees from using them as an overwintering site. This treatment will kill adult bees and offspring as they emerge later. Try to resist plugging up the holes with wire mesh or something similar because the trapped bee can be resourceful and may chew another exit hole.

Bee on the lookout for the carpenter bee, and don’t forget your racquet!