Carpenter Bees– Biology and Management

ALABAMA A&M AND AUBURN UNIVERSITIES Carpenter Bees– Biology and Management

ANR-1302

arpenter bees (Xylocopa it will not usually sting unless it is Cspp. ) are large and economi- handled or molested. cally important insects that are Identification active from early spring through Among the largest bees, car- summer. Like other bees, carpenter penter bees (Figure 1) resemble bees pollinate crops and home bumblebees, Bombus spp., (Figure 2) and giant resin bees, Megachile gardens. However, they tend to sculpturalis Smith, (Figure 3). All hover around houses and other three species of bees have yel- wooden structures when searching low hairs on a black-colored body. for mates and favorable sites to Carpenter bees and giant resin bees share more similarities than construct their nests. They almost Figure 2. A bumblebee visiting a flower (By courtesy of Takumasa Kondo) bumblebees. totally depend on man-made Homeowners are often fright- The giant resin bees are the structures for the wood used to ened about being attacked by the largest (1 to 1½ inch), followed by construct their nests. carpenter bees that hover erratically carpenter bees (½ to 1 inch), and around their homes. Homeowners bumblebees (¹⁄³ to ¾ inch). are also concerned about the holes carpenter bees make in wood, which often lead to more serious damage by woodpeckers when they try to feed on the carpenter larvae deep inside the holes. Carpenter bees are not stinging bees like honeybees and bumblebees. A male carpenter bee is aggressive when protect- ing its nesting site, but is harmless Figure 3. A female giant Figure 1. A carpenter bee visiting a because it does not have a stinger. resin bee (By courtesy of (By Xing Ping Hu) ARCHIVETakumasa Kondo) flower Although a female has a stinger,

Table 1. Identiﬁcation of Carpenter Bees, Giant Resin Bees, and Bumblebees Characters Carpenter bees and giant resin bees Bumblebees Biology Solitary Social Behavior Not a stinging hazard unless handled Aggressive - sting Nest Above ground in wood In the ground Body Thorax is covered with dense yellowish hairs but the Thorax and abdomen are covered dorsal surface of abdomen is bare and shiny black with hairs

www.aces.edu Carpenter bees and giant resin bees can be distinguished from each other using the following characteristics: • Carpenter bees excavate their own tunnels; giant resin bees locate and occupy tunnels and holes made by others. • A carpenter bee has a more robust and heavy body; a giant resin bee has a longer and Figure 4. A carpenter bee (right) and a giant resin bee (left) (By courtesy of cylindrical body (Figure 4). Takumasa Kondo) Male and female carpenter The second sign is the pile of be present beneath the entry bees look different from each coarse sawdust underneath freshly hole and burrowing sounds may other. A male carpenter bee has a drilled holes. The sawdust is cast be heard from within the wood. white- or cream-colored spot on out while carpenter bees excavate Normally, the gallery will extend the head between mandibles and tunnels. The third sign is the yel- about 4 to 6 inches, but with appears to have a white “nose” on low or brown excrement stains on repeated use, galleries may be the face. A female bee does not the sides of buildings underneath much longer. have the spot. Most of the congre- entrance holes. Females lay their eggs within gating bees in the early spring are Carpenter bees are usually a series of small cells. After com- males. They hover around wait- nuisance pests, but can cause pleting a tunnel, the female puts ing for the females and defending considerable structural damage a ball of pollen moistened with their territory. You can completely from repeated colonization of the nectar at the farthest point from ignore the males because they are same area. Woodpeckers often the entrance hole and lays an egg incapable of stinging, although peck through the wood surface on it. She seals off this cell with they will confront you whenever of carpenter bees’ tunnels to prey a thin wall of wood pulp and you enter their territory. on the larvae inside, thus causing repeats the process. Eventually, more severe damage. the tunnel is partitioned into as Carpenter Bee many as four to eight cells. The Infestation and Life Cycle of egg hatches and the larva feeds Economic Importance Carpenter Bees on the food ball. Interestingly, adult bees emerge from pupae Because carpenter bees nest Adult carpenter bees overwin- at nearly the same time within in wood, they can cause aesthetic ter in old nest tunnels in which a nest, regardless of age. Adults and structural damage. Common they have stored small amounts then chew through the wall of the nesting sites include house siding, of pollen. Overwintering adults cell and emerge in late summer. eaves, window trim, fascia boards, emerge and mate in spring. After shingles, decks, fences, and out- mating, fertilized females either Is Prevention Possible? door furniture. reinfest old tunnels or excavate The most distinguishing sign new ones. The female bores into Bare, unpainted, or weath- ARCHIVEered softwood is especially of carpenter bee infestation is the the wood perpendicular to the perfectly round ½-inch entrance grain for about the length of her attractive to carpenter bees. To holes bored into exposed exterior body, makes a sharp 90-degree prevent carpenter bee infesta- wooden surfaces (Figure 5). The turn, and tunnels parallel to the tion, paint or varnish all wood holes lead to tunnels deeper in grain of the wood. The entrance surfaces. Apply two coats of a the wood. hole and tunnels are perfectly good exterior primer and follow round and about ½ inch in diam- up with at least one coat of ﬁnish. eter. Coarse sawdust will often However, painting is not practical

2 Alabama Cooperative Extension System carpenter bees and to prevent recolonization by other nesting bees. This is challenging and labor-intensive. Do not use the foam insulation that comes out of pressurized cans and expands to fill cavities because carpenter bees go through it easily. Sealing holes can be done at any time of year. Refer to ANR-500-B, “Alabama Pest Management Handbook Volume 2”, for pesticide recom- mendations. ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY Figure 5. Entrance hole of a carpenter bee (By Xing Ping Hu) PESTICIDE! for the back of most fascia boards exposed saw cuts should be and many other wood surfaces. filled in with caulk or dowels Wood stains provide little repel- and painted. If practical, remove lent action. Carpenter bees do not severely damaged wood and occupy plywood, but no wood, replace with chemical pressure- even painted or pressure-treated treated wood to deter nest con- lumber, is safe from carpenter struction. Carpenter bees do not bees. The older type of pressure- damage nonwood surfaces, such treated lumber has been phased as vinyl siding. out and no current borate-treated product manufacturer currently How to Control? makes the claim that it prevents Spray or dust insecticide carpenter bee infestation. directly into the carpenter bees’ Sometimes standard window entrance holes or adjacent wood screening can be used to keep surface to reduce carpenter bee bees from getting into areas where activity. These control efforts there may be unpainted surfaces should be attempted in late after- or other places where it might noon or at night when the bees be difficult to paint. Cut strips of are inside the wood tunnels. metal window screening; don’t use Injecting a pesticide into the tun- the fabric or plastic type. Wedge nels can be effective, but a bar- or staple the screening into place rier lasts longer than a poison. where the bees are working. Therefore, 24 hours after inject- Paints that include an insec- ing insecticide, tunnel entrances ticide may repel bees attemptingARCHIVE should be sealed with caulking to nest. However, the insecticide compound to kill the trapped does not remain active for more than one season. Nail holes or

Carpenter Bees—Biology and Management 3 ARCHIVEXing Ping Hu, Associate Professor, Extension Entomologist, Auburn University For more information, call your county Extension ofﬁce. Look in your telephone directory under your county’s name to ﬁnd the number. Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability. 3M, New July 2006, ANR-1302 ANR-1302 © 2006 by the Alabama Cooperative Extension System. All rights reserved.