I had such a fascinating day with the pest control guy, learning more than I ever thought possible about cicadas and the Eastern Cicada Killer Wasps who trap and kill them.
This ground-burrowing wasp may be found in well-drained, sandy soils to loose clay in bare or grass-covered banks, berms and hills as well as next to raised sidewalks, driveways and patio slabs. Females may share a burrow, digging their own nest cells off the main tunnel. A typical burrow is 25–50 centimetres (10–20 in) deep and about 1.5 cm (0.59 in) wide. In digging a burrow, the female dislodges the soil with her jaws and, using her hind legs, pushes loose soil behind her as she backs out of the burrow. Her hind legs are equipped with special spines that help her push the dirt behind her. The excess soil pushed out of the burrow forms a mound with a trench through it at the burrow entrance. Cicada killers may nest in planters, window boxes, flower beds or under shrubs, ground cover, etc. Nests often are made in the full sun where vegetation is sparse.
After digging a nest chamber in the burrow, female cicada killers capture cicadas, paralyzing them with a sting. After paralyzing a cicada, the female wasp holds it upside down beneath her and takes off toward her burrow; this return flight to the burrow is difficult for the wasp because the cicada is often more than twice her weight. A wasp will often lug its prey up into the nearest tree, to gain altitude for the flight to the burrow. After putting one or more cicadas in her nest cell, the female deposits an egg on a cicada and closes the cell with dirt. Male eggs are laid on a single cicada but female eggs are given two or sometimes three cicadas; this is because the female wasp is twice as large as the male and must have more food.
What’s so fascinating is that because cicadas are cyclical, the pest guy said that the killer wasps die off when there aren’t any cicadas but their DNA knows when to propagate again when cicadas are back out.
My question was – are the wasps then doing the trees a favor by killing off cicadas? Cicadas can and do eat tree leaves and have been known to cause harm to a tree. Yes, was his answer, that the wasps don’t harm people – their goal is to get the cicada.
This photo and paragraph (from Wiki) describes Periodic Cicada Flagging:
Grooves made by a cicada during ovipositing: The weakest limbs of a tree are often temporarily damaged or killed off, the result of which is called flagging, as the leaves of the branch will turn brown and look like a hanging flag.
Okay, if the cicadas are doing some flagging to the trees and the wasps are designed to kill the cicadas and don’t harm humans, then should I kill them? Hmmmmm.
I opted to kill them. It was a two-step process. First, an insecticide dust, heavily concentrated, goes into the grooves of the patio where the wasps have burrowed. The long snout of the dust sprayer went deep. The dust he used is called Delta Dust, Deltamethrin.
It was explained to me that the dust disables the wasps, breaks down their bodies. It doesn’t kill them immediately like spraying Raid, but it kills them s-l-o-w-l-y!
Then the pest control man sprayed the areas where the nests were burrowed, no more than that specific area. He used Cyzmic insecticide.
He added that I should leave the mounds of stone and dirt, NOT to sweep it back in the hole because if new wasps fly in, they will be hit with the Delta Dust and also become disabled and eventually die.
He will come back in a week or two to see if new mounds have cropped up and treat them similarly, if so. By nature, the wasps will disappear when the cicadas do, come autumn but that they LOVE the heat and humidity. As a matter of fact, the wasps will not burrow in the shade so my patio, with sun all afternoon, is prime location for them. He said I could put a sprinkler on the patio if I think I’m seeing more wasps – the water confuses them and keeps them from burrowing.
As a total aside, in talking about bugs and the pest control biz, we chatted about stink bugs and how there weren’t nearly as many this year as in previous years. He said some birds are starting to eat them and that has caused many of them to die off before they appear in the house. Good for that!!!!!!!!
I trust your lesson is bugs and chemicals wasn’t too boring today boys and girls. I loved what I learned.
UPDATE: Sunday afternoon. I watched two or three wasps hover over their former burrows but not crawl in. As a matter of fact, they flew away pretty quickly. Says the combination dust and spray is working.