Often maligned, wasps and hornets benefit gardens by eating pests

Territorial as humans are, we resent having our garden strolls and twilight picnics interrupted by wasps. There is something about seeing one or two insistent German yellow jackets dance around on a piece of chicken or barbecued salmon that causes humans to lose all patience for sharing their space.

But the several common wasp relatives that inhabit gardens in Western Washington throughout the summer are definitely beneficial predators. They hunt insects such as white flies and aphids. They kill caterpillars; a nest of fall webworms can provide ample meat. A friend of mine who grows roses reports that his aphid problems nearly vanished when a nest of paper wasps settled in his garden.

The ones you're most likely to see buzzing nearby here are the Northern paper wasp (Polistes fuscatus pallipes) which makes a large paperlike hanging nest; the bald-faced hornet (Vespula maculata) with a smaller hanging nest; and the German yellowjacket (Vespula germanica), a ground nester.

These are fascinating creatures — just ask local expert Doug Cheney, whose keen interest in landscape wasps and hornets has only increased in the nearly 20 years he's collected and studied them.

"I'm a sentient being, a naturalist by inclination," says Cheney, who visits nests needing removal and gathers insects for shipment to a processing center where their venom is used to create medication. "There's no instruction book for doing what I do," he adds.

Cheney wears heavy protective gear and collects the insects using a vacuum equipped with a collecting tube. "These rascals will teach you a lesson if you don't know how to handle them."

To coexist with wasps, start by observing your landscape. Watch their flight paths to locate hidden nests in trees, shrubs, on buildings or in the ground.

Cheney notes that wasps don't generally chase humans around, but if they're disturbed by vibrations or by jolting of their nests, they will.

(I can testify from experience about the inadvisability of running a hedge-trimmer through a bald-faced-hornet nest.)

Before using equipment, take time to carefully survey the area for nests. "A two-minute scan of the garden can save lots of anguish," Cheney points out.

If you find a nest, avoid the area until winter, when they die out and do not reoccupy the same nest again.

Despite their garden benefits, sometimes it is necessary to remove wasps. Cheney will respond to calls for nest removal if someone suffers from allergies, or if the nest is on a house wall, in a parking strip, or otherwise located right where the human territory gets the most traffic.

(Cheney may be reached in Snohomish County at 425-485-0103; several professional removal services are listed under "pest control" in the Seattle area Yellow Pages.)

It is possible to kill out a nest yourself, but proceed with great care. Commercial products sold for clearing out nests instruct users to work after dark, but Cheney notes "even at 2 a.m. they are moving, crawling over the nest."

Yellow jackets that dally over your chicken are just "a few curiosity seekers," says Cheney. He explains that the insects typically survive by gathering insects, and will hunt human food or pet food only in unusual circumstances, such as the situation in the San Juan Islands, where the hornet population has, over time, outgrown the natural food supply by the end of summer, making them worse pests to humans. Typically adult hornet-workers collect insects, returning with them to the nest, where they feed the developing larvae and are rewarded by a drop of sweet fluid — an intriguing natural process that keeps them motivated to return with their insect instead of consuming it when they catch it.

Cheney's not a believer in setting baited traps, which he says are largely ineffective.

But, still, setting a trap may provide a grumpy picnic host the small satisfaction of taking some action — and distract the buzzing visitors long enough for the human interlopers to enjoy a piece of chicken in peace.

Mary Robson is area horticulture agent for Washington State University/King County Cooperative Extension. She shares gardening tips every Wednesday. Her e-mail is gardeningtips@seattletimes.com.