Cicada Killing Wasps are Harmless (unless you're a Cicada)
Q. I have a "Cicada Killer" wasp problem in the summer time. The wasps always emerge from the same general area in the lawn, which happens to be adjacent to my pool, so the situation is quite problematic. (Although I must admit that no one has been stung by them and they aren't aggressive.) I'm turning to you for help before they emerge this season. Thanks,
- ---Will in Jessup, MD
- ---Amy in Delaware County, PA.
I realize that I'm more stridently against garden chemicals than most, but emails like Amy's make my heart sink. She'll let her kids and pets play on a toxic and dangerous lawn rather than try and educate people that although, yes, they do look kind of fearsome, these wondrous wasps are 100% harmless and even a little beneficial.
Rather than move the risk of future cancers up a notch for everyone in the area, I suggest installing nice big signs that say something like: "These wasps do not sting." Although I'd prefer something more along the lines of "Just leave them alone"; or "Hey! They live here too!"
I'm no orthodox Buddhist; if you click on our previous questions of the week about yellowjackets, fleas, ticks and mosquitoes, you will be presented with control options that are deadly to the dangerous creature named (just not deadly to humans, pets and the environment). Pests that spread disease or sting aggressively should not be tolerated, and I have no touchy-feely attitudes towards them. But—like the ground nesting native bees that many of you are frightened of right now—these big wasps are harmless. The males have no stingers. Females do, but don't want to waste a sting on you—those paralyzing punches are reserved for unlucky cicadas.
The female wasp is a real wonder of nature; one of the hardest working women in the show business of the natural world. She will find a cicada in a tree and sting it into paralysis. If she is lucky, the cicada will stay put. If she is not and the cicada drops to the ground, she flies down, takes ahold of it and drags it back up the tree. (This is HARD work; the females are one of the largest wasps in North America, but cicadas are much bigger.)
She makes this arduous climb because she needs height to be able to clumsily fly her heavy prey to a previously prepared (and highly intricate) burrow she has dug out of the soil, drop the cicada in and deposit an egg or three on the unlucky creature. The wasp babies hatch and consume the cicada; then spin cocoons and pass the fall, winter and Spring underground, emerging the next summer, so that the females can once again do all the heavy lifting while the smaller males eat pollen and have sex with the females. (Not the worst species for a guy to be.)
They are beneficial insects: the females protect young fruit trees by keeping the cicada population down and the males pollinate flowers. And a review of ten years' worth of frightened emails about them from listeners and every research article I could find says the same thing: Everybody gets scared, but nobody ever gets stung (except cicadas).
Oh, there's one other common thread in those emails: whether it's a homeowner or a pest control company applying the poisons, when poisons are applied, the wasps are unaffected. (Told you those burrows were intricately designed!)
To try and get them to nest elsewhere, allow this season's brood to emerge and then put a heavy mulch over the area if it's bare ground, or spray a garlic oil-based insect repellant heavily on the turf if they're in a lawn. (Sold for protection of crops and as non-toxic backyard mosquito foggers, these garlic sprays are felt to be the most effective overall insect repellant.)
And if they are nesting in your lawn, build up the lawn! Female wasps look for bare ground, bare spots, or really thin and ratty lawns—like female Japanese beetles, they don't want to have to dig through three inches of tough turf.
If you have a cool-season grass (bluegrass, rye or fescue), that means never cutting it below three inches, never cutting it during a dry summer heat wave and never ever feeding it in the summer. (But DO feed it with corn gluten meal in the Spring; and feed it again in the Fall with compost, corn gluten or a bagged organic lawn fertilizer.) If the lawn needs reseeding or over-seeding, wait for the 'magic window' of August 15th to September 15th, give it a big compost feeding, spread the new seed into the compost and water gently every day until the grass comes up, which will be fast in late summer, the only sensible time of year to sow cool season seed.
As with weeds, the best cure for bugs burrowing in a lawn is indirect. Build up the lawn, mulch any bare soil, and these hard working wonders of nature will simply dig elsewhere.