Question: I just saw a huge wasp drag something into a hole in the ground near my patio. I am freaked out a bit. I want wildlife in my yard, especially butterflies, but I don't want to use pesticides to kill the wasp. Do you have any idea what it is and what to do about it?
Answer: You most likely saw a cicada killer wasp. There are five species native to the Americas. They are an inch or 2 long, and they are black and yellow like you would expect a wasp to be colored. They hatch as adults in the summer, when cicadas are also maturing as adults.
The female has a big stinger that she uses to sting cicadas and inject venom that paralyzes them. She then flies the cicadas to her burrow and lays eggs on them. The larvae hatch, eat the cicadas and then pupate until next summer.
If a cicada is too heavy to fly back to the burrow, the female will drag it up to the highest object she can find and fly as far as she can. She will repeat this until she makes it back to the burrow. I have let one crawl up my leg and up to the top of my head so it could fly. I realize that would terrorize some people, but they are not interested in people as long as they don't try to pick them up or step on them barefoot. They lack the guarding instinct of other wasps, but a sting is very painful.
The male will defend his territory by flying toward anyone or anything that enters. It has no stinger, but when a 2-inch wasp repeatedly flies at your head, it can be hard to remember that it is harmless.
The females create a burrow that can be an inch around, a foot deep and several feet long. A dozen cicadas may be buried in one burrow. Even though they are solitary, several wasps may nest near one another. They prefer dry, sandy soil. That soil is often found under sidewalks and patios. Loose soil in flowerbeds and gardens is also used. The volume of soil excavated can cause settling problems. Skunks and other mammals may dig up the burrows.
If possible, you can leave the wasps alone. But over a few years, the population could increase to becoming intolerable. If they are nesting near a playground or golf course sand trap, they may need to be controlled. For your single burrow, a pot of boiling water poured in the hole may be enough to kill them. Sticking the garden hose in the hole and letting it run until the burrow is full may be enough to drive them away. But they may just move a short distance away and nest in a different burrow, making those controls not entirely helpful.
If necessary, pyrethroid insecticides can be used to kill them. The insecticide should be limited to the burrows and not sprayed on the whole lawn. Do a search for a glue board trap that could catch them.
Even if the wasps are killed this summer, they may be back next year if the soil conditions are good for making burrows.
Email questions to Jeff Rugg at email@example.com.
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