Ground Bees Active But Pose No Threaten to People or Yards, by Steve Frank, NCSU Extension Entomologist

As I write this my front yard is abuzz with small bees. Many are flying around just above the ground while others fly back and forth to redbuds and camellias gathering pollen.

Although these bees do not generally sting, I watch as mothers nervously cross the street with strollers. Neighbors pass by and comment "Watch out for all those fire ants" referring to the small mounds that dot my sparsely vegetated lawn. Others offer suggestions on how to rid myself of these dangerous beasts that are "tearing up your lawn."

The bees I am watching are ground nesting bees in the family Andrenidae. All the species in this family are solitary and nest in the ground. Solitary means they do not maintain vast hives with hundreds of workers like honeybees or yellow jackets. A single female bee builds the nest by burrowing into the ground. She prepares larval cells where eggs will be laid. Mothers provision each brood cell with a mixture of pollen and nectar (called bee bread) that serves as food for young larvae. After laying an egg she closes the brood cell and starts another. After completing several brood cells the mother will seal the entrance and leave the nest to begin a new nest. After a few weeks she will die leaving the next generation safe in the ground.

Bee emerging from its mound (Photo: S.D. Frank).

In the spring, bees complete development and emerge as adults that dig their way out of the ground and forage for pollen and nectar to provision their own nests (see photo above). The visual spectacle of these bees is produced largely by males who swarm over nests trying to mate with newly emerged females. The other noticeable aspect of these bees is the small mounds of dirt excavated for each nest.

Hundreds of small mounds created by bees.

Hundreds of small mounds and swarms of bees often trigger calls to exterminators or landscape professionals (see photo at right). Homeowners fear that they will be attacked and stung as they bend over to pick up the paper and they believe that the bees are actively damaging their yard and want them gone. This is not the case.

An ovipositor is the organ female insects use to insert eggs into substrates such as leaves, wood, soil, other insects, or in our case brood cells. In social insects such as honeybees, most of the females are workers that do not mate or lay eggs and thus have no need for an ovipositor. However, they do need to protect the nest from invaders. Therefore, the ovipositor of these social species has evolved into a stinger to ward off threats.

With this in mind it is easy to understand why the threat of being stung by the ground nesting bees in my yard is so small. First, the bees swarming around are mostly males. Males don't lay eggs and thus do not have an ovipositor, modified or otherwise. The female bees are responsible for all aspects of nest construction and provisioning and are busy digging and foraging. Since the ovipositor of ground nesting bees is necessary for laying eggs, it is not well developed as a stinger, if at all. I won't say that you will never be stung because this would encourage some fool to torment bees until they proved me wrong. However, I have handled these bees quite a bit and have never been stung (see photo below).

Bee held safely for a portrait (Photo: S.D. Frank).

These bees prefer to nest in dry, sparsely vegetating areas. Therefore, if you have bees nesting in your lawn it is because the grass is thin and the soil is dry. The bees don't make it this way, they just take advantage of the conditions. If anything the bees are providing a valuable service by aerating the lawn!

The behavior and habitat preference of these bees leads us to the most promising ways to reduce their abundance in a particular yard. First they like dry soil they can dig nests in. Therefore, irrigation over the 3-4 weeks bees are active will encourage them to find other nest sites and reduce their abundance the following year. In addition, they like thin lawns with plenty of bare spots. Thus, you can take measures to improve the density of your grass to make it less appealing to bees. Native bees are an important part of ecosystems and food production. We should take steps to protect these bees or at least use non-lethal means to encourage them to nest somewhere else.

Paper Wasps Showing Up

Paper wasps (Polistes sp.) are long-legged, reddish brown to black insects with slender spindle-shaped abdomens. They may have differing degrees of yellowish or brown striping. Paper wasps can become a problem in the fall as the inseminated queens invade homes in search of overwintering sites. But paper wasps can also become a problem in the spring. As temperatures begin to climb, queens that spent the winter in structures become active and fly about. If they have been resting in an attic, wall void or crawlspace, the wasps may be attracted to light coming through a gap in the baseboard or a wall fixture, or around an AC vent and emerge inside the building. Since there are no nests or young to defend, the only real danger of being stung is from accidentally stepping on or pressing against one.

Figure 1. Use an aerosol insecticide 

to destroy a paper wasp nest

(Photo: Patty Alder)

Control. Queens that are found indoors may simply be swatted or vacuumed. If a queen does manage to get outdoors and start a nest, a broom may be all that is needed to knock it down. If a wasp nest has had some time to grow and is considered to be a hazard, they are most easily destroyed in the evening with an aerosol insecticide that is labeled for "hornets or wasps" (see Figure 1). This type of treatment may be considered an emergency (especially if the nest is located in place likely to be encountered) which means application to the nest can be made as long as notification occurs within 72 hours of application.

Ground Nesting Bees, by Mike Waldvogel

You may start getting complaints from folks at some of your schools where people see either small mounds of soil in the ground or report "swarms" of bees showing up. People often panic because they think these are swarms that pose a health risk to the children. However, they are most likely the solitary bees, such as the "colletids" and "andrenids," that often emerge at this time of year.

The bees begin foraging for food and seeking out new nesting sites. This activity will continue for about the next two months depending on the area of the state and the species of bees. They dig vertical tunnels in the soil on which they make small side chambers where they provision pollen for their offspring. These bees are "solitary," which means there is not a true colony. A lot of the "swarming" that you see are males and females attempting to pair up and mate. The bees frequently make small mounds in the soil, often where the soil is loose and vegetation may be sparse. It is not uncommon to see clusters of these nests but each mound is made by an individual queen which does the work without the help of workers as occurs in a honey bee nest.

Although the damage can be unsightly with large numbers of mounds in the ground, it is mostly a cosmetic issue. The bigger problem is usually that people walking by panic because they assume that these are swarms of honey bees (or a similar bee) that will likely attack them if they venture too close to "the nest." Turf-nesting bees can sting but rarely do so, since they are not "social" and there is no nest that a large number of worker bees are trying to protect. There is no "mass attack" as might occasionally occur with a close encounter of the yellowjacket kind (and it's still early in the year for us to see any yellowjacket colonies out there).

These bees are beneficial and should be left alone if possible. If one of your schools wants something done, you can apply almost anything that you typically use outdoors for perimeter treatments (be sure to follow proper notification procedures). One problem is that the bees often try to dig into the sand in play areas at schools. Of course, parents and teachers are concerned about stinging incidents particularly if a child (or teacher) is hypersensitive to bee stings. In those instances, I still strongly discourage any chemical treatment, particularly in sandy play areas where kids come into direct contact with the soil (and which they might get in their mouths as well). However, facility managers have to weigh the safety of children (and staff) and the misinterpretation by the public of ignoring the problem as meaning they lack concern about the children.

If the bees try to nest in a sandbox, a simple solution is to cover it during the day, but it will take a few weeks for you to deter most of the bees that show up over time. While the tarping approach isn't
always successful, wider areas can be saturated with plain or soapy water which will bring the bees out. Since soap will work as an insecticide to some extent, it may kill some of the bees in the process but I still consider this preferable over the use of conventional insecticides IF people are unwilling to simply ignore the problem. The water-logged soils will hopefully deter the bees but again we're looking at activity that can take place over a few weeks.

Information, including pictures, of these bees and the "damage" that they cause can be found at:

http://www.ces.ncsu.edu/Insects/O&T/lawn/note100/note100.html

Ground-nesting wasp, Scolia dubia - by Mike Waldvogel

(Photo:  Sheryl Pollock, 2011) 

Now that cicada killer activity is finally winding down, we've had a few sightings of scoliid wasps, Scolia dubia, hovering over yards. This solitary wasp is bluish-black with bluish-colored wings. The end segments of the abdomen may be more brown in color and hairy. A key feature are two yellowish spots on the abdomen, which may appear more as a yellowish band.

The object of their attention is the grub stage of the green June beetle which spends most of this time of year near the soil surface. Activity will should stop in a few weeks (peak activity should be in about 10-14 days depending on where you are). As with the other ground-nesting solitary bees and wasps, pesticide broadcast sprays are rarely needed or very effective.

For more information on this wasp, see the web page:

http://insects.ncsu.edu//O&T/lawn/note12/note12.html