2009 is a good year for wasps

An article in the Merced Sun-Star today declares that wasps are in full force this summer. Reporter Carol Reiter set out to determine why and what to do.

UCCE farm advisor Maxwell Norton told her he suspects the high number of local homes abandoned due to foreclosure has boosted the wasp population.

"So many abandoned homes means that they are multiplying unabated," Norton was quoted. "Garage eaves and home eaves give them a lot of places to build their nests and be undisturbed."

Reiter also spoke to Mary Louise Flint of the UC Integrated Pest Management Program. She said yellow jackets are aggressive and can pose problems for humans; paper wasps, on the other hand, won't usually sting unless they get trapped. Unfortunately, it's hard to tell the difference.

The UC IPM online guideline for "Yellowjackets and other social wasps" says some social wasps provide a great benefit by killing large numbers of plant-feeding insects and nuisance flies; others are exclusively scavengers. Wasps are only a problem when they threaten to sting.

The guideline provides information on preventing and trapping wasps, but the advice for spraying will probably discourage all but the most fearless homeowners from doing it themselves.

"Wasps will attack applicators when sensing a poison applied to their nests, and even the freeze-type products are not guaranteed to stop all wasps that come flying out," the guideline says.

UC Master Gardener wasp identification illustration.

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