Yellowjacket Calls increase in the Fall

The calls have started.

While mowing the grass, someone gets stung several times by a 'bee'.  What can they do to deal with the problem.

Although it is impossible for me to identify the culprit with 100% confidence, unless I can see a sample of the offending insect (or at least, a photo), I suspect that the assailant is not a bee, but is instead, a yellowjacket.

Yellowjackets forage for sugar and carrion.  You'll find them attracted to your soda-pop, as well as your tuna sandwich.

Here's why.

1. Yellowjackets nest in the ground.  
2. Of the bees that nest in the ground, most do not sting ~ or else their sting is painless.  In our study of bees in Westchester County, NY gardens, Calliopsis, Agopostemon and Andrena bees are solitary, soil nesters.  Solitary bees tend to be very docile, as they don't have a colony to defend.  Lasioglossum and Halitctus bees are eusocial, soil nesters.  These are the 'sweat bees' ~ so called because they have been seen drinking sweat from humans (probably to get some salts).  Although they sometimes (rarely) sting humans, their sting is rated a very low 1.0 on the Schmidt Sting Pain Index, making it almost painless.
3. Yellowjacket colonies build in size over the gardening season.  Right about now is when they reach their maximum size, and when they're most noticeable and problematic to gardeners.
4. Multiple stings suggest yellowjackets.  Honey bees can only sting once.  Bumblebees can sting more than once (and may also nest in abandoned rodent burrows in the ground).  But, most people would be able to recognize a large bumblebee, rather than be left wondering what stung them.

So ~ you have yellowjackets.  What can you do?

In my experience and from my reading of the literature, you have two practical options.

1. Leave the nest alone.  The fall is the time of the year when new males and queens will emerge and mate.  The males, with their 'live fast, die young' approach to life will soon bite the dust after mating.  The newly-mated queens fly away to a protected site, where they will spend the winter.  The nest will be abandoned, and will start to break down over the winter.  Nests are almost never used again.  You will not have the same yellowjacket problem, in the same nest, next season.  If you do decide to leave the nest alone, make sure  you mark off the area ~ so that you don't forget where the nest is, and so that visitors to your yard know to avoid that area.  If you have young children (who would not abide by a 'keep out' directive), if you have large pets (who might trigger an aggressive response by the yellowjackets) or if you simply can not stay out of the area, leaving the nest alone may not be an option.
2. Use a commercial wasp or hornet pesticide, during the coolest part of the day.  Wasp sprays tend to be highly pressurized, so that you can spray them at a distance from the nest entrance.  Spraying during the coolest part of the day means that the yellowjackets will be less able to mount a defense against you.  It will be simply too cold for them to move with gusto.  Still, by spraying the nest, you do risk getting stung.  Make sure to spray the entrance of the nest.  This will get the yellowjackets as they fly in and out of the hive.  It will also do the best job of dousing all that reside within.  Don't light your way using one flashlight, which you aim at the entrance of the nest.  This could create a beacon that tells the aggressors exactly where to fly, to protect the nest.  I would wear two layers of thick clothing (jeans with leggings underneath, a tee shirt, with thick sweatshirt or jean jacket over top).  I would tuck my pants into my socks and my shirt into my pants.  This will prevent a yellowjacket from getting under your clothing, where you could be repeatedly stung. Cover your neck, hands, head and eyes, as well.  Yes, you may look like Ralphie from 'A Christmas Story', but better safe then sorry ~ right? [I stand corrected.  It was Randy, and not Ralphie, who was bundled up in winter wear.  Edited September 20, 2013.]

When I'm asked to treat a yellowjacket or bald-faced hornet nest, this is a pretty fair representation of how I dress for battle.

Other options I've seen, but don't particularly like for dealing with a fall fest of yellowjackets include:

1. Trapping the yellowjackets.  At this point in the year, when the nests have built up to a large number of residents, I don't think that trapping will solve the problem.  It may, however, help keep yellowjacket numbers down, early in the gardening season ~ next year.  Use them earlier in the season, if you decide to employ a trap.  Waiting until the fall is likely too late to do any good.
2. Vacuuming them up, in the evening, at the site of the nest.  Hmmm.  I just can't see this one working very well.  I'll let the author of that idea try it out, and let me know how it goes. [Edited September 20, 2013: the one reference I read about vacuuming up the yellowjackets suggested that it could take two or more hours to treat the large nests that are characteristic of the fall season.  Standing on top of a yellowjackets' nest for two hours, to hold a vacuum at the nest entrance and try and suck up all that come out?  It still doesn't sound like a practical idea to me.]
3. Pouring soapy water down the entrance of the nest, also at night (when temperatures are cool).  Soapy water helps to break down the waxy cuticle of an insect's exoskeleton ~ but I just can't see this being an efficient way to deal with yellowjackets.  Once again, I'll let someone else try this one out, and let me know how it goes. [Edited September 20, 2013:  I've had several people tell me that soapy water, followed by boiling water poured down into the nest, has worked for them.  They note that when performed during the day, they did get stung.  Soapy water, alone, is not likely to work ~ as soap works best against small, soft-bodied insects.  The soap literally degrades the waxy cuticle of an insect's exoskeleton, the same way it helps wash away grease on your dishes.  Thick-bodied insects aren't as prone to soapy water as are things like aphids or thrips.  But, followed by boiling water ~ it likely does the trick.  The soap, acting as a surfactant, will help the boiling water spread thoroughly throughout the nest.  Because you'll have to get up close to the nest to pour in the soapy water, and then the boiling water, prepare for a high probability of agitated yellowjackets.]

To prevent future infestations, consider whether or not you have a rodent problem in your yard.  Often, abandoned rodent burrows are used as nests.  Fill the burrows, or focus on the rodent issue, and the yellowjacket problem will likely subside.

Some great references on yellowjackets include:

• Washington State University publication on yellowjackets and paper wasps. 
• University of California Statewide IPM Progrma publication on yellowjackets