My yard has been invaded with yellow jackets. They have built 50 -60 ground...

Asked September 11, 2013, 8:55 AM EDT

My yard has been invaded with yellow jackets. They have built 50 -60 ground nests. In our attempt stop this invasion we sprayed the inset with spray and we able to kill several. We also covered each nest with Sevn powder. This seem to stop them from returning to that nest some of the time. The yellow jackets have now left the yard. My question is will these nest have yellow jackets larva which will become problem next year when the warm weather returns? Can I safety destroy these nests by tilling up the yard? I would appreciate any assistance you can provide. Regards, Richard

Miami County Ohio bees yellow jackets

3 Responses

Are you certain that they are yellow jackets? Yellow jackets typically nest in a single large colony, similar in that regard to honeybees. If you found a nest and sprayed it, killing most but not all of the yellow jackets, the survivors might move to a new spot and form a new nest, but 50-60 nests at the same time in the same yard would be very unusual. This sounds more like one of the other types of ground nesting bees, perhaps ground bees, or miner bees. Miner bees look fairly similar to yellow jackets. These bees form solitary nests (not truly solitary, there may be up to 4-5 bees per nest), but they will make their nests fairly close together so it may seem initially like they are all coming from the same nest. In reality though, it is usually several small ones, and 50-60 could easily exist within a relatively small area.

This distinction is important for a couple of reasons. First, yellow jackets are quite aggressive and will string with little provocation, whereas miner bees are not aggressive at all and aren't likely to sting unless you attempt to actually handle one. Second, miner bees are helpful pollinators while yellow jackets mostly scavenge other insects and food scraps. Third, their nesting habit effects control options.

Since yellow jackets colonize a single nest, the best treatment is to spray directly into the nest when all (or nearly all) of the yellow jackets are present (typically at night). A second spray may be necessary, but typically the majority of a colony can be killed with a single 10-20 second spray from a can of hornet and wasp spray.

Miner bees are much harder to eliminate because of their multiple nests, but truth be told, because of their importance as pollinators and their lack of aggression, we don't typically recommend trying to kill them. There may be some exceptions, such as if they are in a high traffic area, as they can certainly be a nuisance, but if they are tolerable, they should be left alone. If you want to get rid of them, a better option than spraying would be to manipulate the environment in order to encourage them to move to another location. Tilling might help somewhat, but the best option is to keep the area where they have been observed very wet while they are active. They are generally drawn to dry areas and don't like to nest where it is wet. It won't help much to do this now, but when they are active next year, run some sprinklers over the area they are found in for several days and this will likely push them somewhere else to lay eggs.

Here are a couple additional publications that might be helpful:
http://www.oardc.ohio-state.edu/ale/images/Bee_ID_guide.pdf
http://www.uri.edu/ce/factsheets/sheets/miningbees.html
http://www.ces.ncsu.edu/depts/ent/notes/Other/note114.html

Thanks for your help. I have attached a picture of their nests. The ground has been very dry. When I would mow the grass they would circle the mower (riding) until I was away fro their nest. They would become aggressive if I walked close to their nest. The second picture is of a cicada which was killed by these bees which were almost as large as the cicada.

Glad you sent these pictures and additional info. There is, believe it or not a ground nesting bee called a cicada killer. These bees are predators of cicadas, and they kill them by a paralyzing sting. They are considered beneficial due to their predation of cicadas, but they can damage lawns through their nesting and can otherwise be a nuisance to humans. The best control would be spraying or broadcasting a pyrethroid insecticde over their nesting area. Look closely on the label of insecticide products for the active ingredient, if it ends in -thin it is a pyrethroid. If using a spray, target the entrance to the nest as much as possible.

Here is a publication that may be of further help.

http://www2.ca.uky.edu/entomology/entfacts/ef004.asp