Garden Detective

Garden Detective: Yellow jackets invaded his lawn

Yellow jackets have invaded my lawn. They hover over the grass and then drop down into it. I am afraid to even mow for fear of being stung. What can I do to get rid of them?

– John Benzon, Lincoln

According to UC master gardeners Carol Rogala and Mary Griggs, not all wasps are alike. In the Western states, there are two distinct types of social wasps – yellow jackets and paper wasps. Yellow jackets are by far the most troublesome.

If wasps have invaded your lawn, they are hunting for lawn insects, grubs and larvae.

Social wasps start their nests in the spring. From spring to summer, the workers are looking for protein and some sugars. By late summer, the colony requires more sugar.

Usually, scavenging wasps won’t become a problem if there is no food around to attract them. When nuisance wasps are present outdoors, keep foods, including pet food and drinks, covered or inside the house, and keep garbage in tightly sealed garbage cans. Once wasps discover food, they will continue to hunt around that location long after the source has been removed.

Trapping is one method that can be employed to try to reduce yellow jacket problems. Trapping isn’t suggested for other social wasp species. There are several types of traps:

• Lure traps: The easiest to use are lure traps, which are available for purchase at many retail stores that sell pest control supplies. Lure traps can help reduce the number of localized foraging workers but they don’t eliminate large populations.

• Water traps: These are generally homemade and consist of a 5-gallon bucket, string and protein bait such as turkey, ham, fish or liver. Fill the bucket with soapy water, and suspend the protein bait 1 to 2 inches above the water.

Additional information about using these traps can be found in Pest Note 7450 at www.ipm.ucdavis.edu.

If wasp nests must be eliminated, it is easiest and safest to call for professional help.

Instead of yellow jackets, your winged invaders may be European paper wasps. These wasps are particularly attracted to fresh-cut lawn, where they hunt for caterpillars and cutworms.

European paper wasps resemble yellow jackets ( Vespula), but have a longer, tapering abdomen. They also act differently.

UC Davis ecology professor Arthur Shapiro offered this observation in response to a Garden Detective last year: “Unlike yellow jackets, these paper wasps are not routinely attracted to sugary material such as soda cans or sweets, nor do they frequent roadkill. The standard yellow jacket trap doesn’t seem to attract them. They are very largely caterpillar-eaters, though they do visit flowers and eat pollen. They are not nearly so aggressive as yellow jackets. I have yet to be stung by one.

“They seem able to overwinter very well here most years and can become active earlier in late winter than other wasps,” he noted. “Their activity seems to diminish in very hot weather.”

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