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Blue-Winged Wasps and Deadly Yellowjackets


You Bet Your Garden
Question of the Week © 2019 Mike McGrath

Note: Hundreds of Mike's informative articles are available (in alphabetical order!) right here at the Gardens Alive website. To find Mike's answers to your specific garden problem, Click here and find your topic (like Weeds, Worms, Rhododendrons...) in our complete alphabetical archive of Questions of the Week.

Blue-Winged Wasps and Deadly Yellowjackets

Q. Diane in Western Washington State writes: "We used a weedeater in the backyard and what I thought were honeybees came flying out and hovering over the ground. No obvious opening or nest apparent. We have had yellowjackets before, but these look like honeybees. Dog was curious but they didn't attack him. They were out buzzing around late last night...after midnight...and more are out there today. Look less like bees now; maybe small hornets? Definitely not yellow jackets. Can't get close enough to look for a hole in the ground; Sprayed the area with wasp/hornet spray last night to no effect. They just kept flying around. What are they & how do I get rid of them safely?"

A. First, honeybees do not nest in the ground. Escaped 'feral' colonies will sometimes nest in the walls of a house or in a rotting tree, but never in the ground.

There are many types of NATIVE ground-nesting bees, aka "digger bees". There are also ground-nesting wasps. Ground nesting insects that look like bees are never a problem in the Spring, as the vast majority of these native bees have no stingers, and none are aggressive. But late summer and early fall are when yellowjacket nests become apparent, and these must be taken seriously. Like honeybees and ants, yellowjackets are social insects with large colonies; and a typical yellowjacket nest can contain five thousand or more of the highly aggressive hornets by the end of summer.

Yellowjackets LIKE to sting. Each wasp can sting repeatedly. When they sting, they inject you with a pheromone that encourages other yellowjackets to come and pile on. And they bite. As with your story, many nests are discovered by someone weed whacking or lawnmowing. I once stepped on a nest opening while pushing a wheelbarrow full of compost and was saved only because the compost covered the hole when I dropped the wheelbarrow in a panic. (You See? Compost really IS good for everything!)

But there are also a few beneficial ground nesting bees active in the late summer/early fall; and the kind of swarming you describe sounds like the Blue Winged Wasp, which can sting (all wasps and hornets have the ability to sting), but generally don't because they're non-aggressive. I walked through a swarm of several hundred at a community garden some years back and got the willies but I didn't get stung.

If blue winged wasps you have, let them be--the females are digging into the earth to locate the grubs of Japanese and other scarab beetles, which they will lay their eggs inside of. Now that's natural grub control!

Q. Jim in Coopersburg, PA writes: "We have a yellowjacket nest by the side of the house. Bug spray didn't kill them. We're going to try hot soapy water tonight..."

A. "Hot soapy water?" Yikes! I hope that Jim is still with us. "Bug spray" is useless against these pests because of the design of their nests. Same thing with water; all it does is make them mad. If you try something like this or equally foolish, have some fresh papaya or a meat tenderizer made with papain handy to rub on the stings to denature the venom. (Yes; it really works.)

Q. Henry in Ambler, PA writes: "Nasty yellowjackets have made a nest in my raised potato bed. They stung me three times last night when I was tending to it. Of course, I can't work there again unless I can eliminate the problem. Can I flood them with water? Is there any other remedy you have in your arsenal? I don't want to use toxic material because we'd like to eat the potatoes."

A. I can't stress it enough--water and insecticides don't work! (And 'toxic material' is NEVER the answer; there's an organic response to every issue.). Anyway, the nest should be destroyed; yellowjackets are responsible for dozens of so-called 'bee sting' deaths every year.

First, go out on a cool evening and see if you can locate the hole they're going in and out of. There should be a few guards around the entrance but they'll be sluggish at night. If you can locate the hole, get a big glass bowl and a helper with an aerosol can of non-stick cooking spray. Again, on a cool evening, slowly approach the nest and put the bowl over the opening while your helper Pams any attackers. That's it; problem solved. They can't dig their way out. And to answer the obvious question, they don't reuse old nests. So yellowjackets may trouble you again, but they won't be using that nest.

If the area is complicated by multiple entrances or a crush of plants, get an old canister vacuum cleaner (thrift shops are a great place to start looking if you don't already have one), install a fresh bag, make sure its switched on but not plugged in, and with the aid of your Paming protector gently drop the hose nozzle near one of the holes in the bed and then run like hell. In the morning, plug the machine into an outdoor outlet with a ground fault interrupter. The vacuum will roar to life and the yellowjackets will all fly to a sucking death. Fun to watch. Drag out a lawn chair and make a day of it.

After a couple hours, things should slow down. After 20 minutes goes by without a sighting, carefully approach the hose end--again with your Pam protector ready to spray--and seal the hose end with duct tape. Only then should you pull the plug on the machine. Apply more duct tape and let the machine sit in the sun for a few days before you empty it out.

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