Why you should plant a garden that’s wasp-friendly

A smoky-winged beetle bandit wasp, on a Virginia mountain mint (Pycnanthemum virginianum). This wasp helps scientists track the emerald ash borer, a devastating invasive beetle that is killing native ash trees. (Photo: NYTimes)
Attention, spheksophobes: Wasps just want to help.

And Heather Holm wants to help them make their case to gardeners and others.

Holm, a biologist and pollinator conservationist, knows it’s not an easy sell. But in her recent book, “Wasps: Their Biology, Diversity, and Role as Beneficial Insects and Pollinators of Native Plants,” she asks that we consider wasps — and not just their cousins, the bees — in the plant choices we make and the pollinator-friendly gardens we create.اضافة اعلان

“If we took wasps out of the equation,” she said, “many of the leaf- and seed-eating insects they prey on would just go unchecked.”

Troubled by cabbage loopers chewing on your brassicas? There’s a wasp for that.

There are also wasps that target tarnished plant bugs (a pest with a taste for a wide range of vegetables and small fruits) and ones that prey on brown marmorated stink bugs and fall webworms. All such sustenance is brought back by adult female wasps to provision their nests, as food for their larvae.

The list of the organic pest control services offered by wasps goes on, and yet it is the wasps that we humans reflexively regard as pests. That reputation is the result of just 1.5 percent of the total wasp species in North America — the ones that build social nests above or below ground, forming colonies and cooperatively living in multigenerational nests during the breeding season to rear the next generation.

The irony: It is the social wasps toward whom we feel anti-social. They have inadvertently tainted our view of the other 98.5 percent (although, to be fair, the social ones provide ecosystem services, too).

The trigger is typically a run-in with ground-nesting yellowjackets (Vespula). Or a too-close encounter with a nest of paper wasps (Polistes) or perhaps with a larger, more complex nest of bald-faced hornets (Dolichovespula maculata), its many layers of combs enclosed in an envelope. The result is a sting — always delivered by a female — that we just cannot forget.

If the wasps had been nectaring on flowers they would have paid us no mind, Holm is quick to point out. But when we threaten their nests — the home to the next generation — their best defense is a good, and painful, offense.

“The flower garden is the restaurant, not their home — they don’t defend it,” Holm said. “But social wasps are very inclined to defend their home.”

Flowers a wasp could love

Wasps need habitats similar to those preferred by bees. But bees eat a plant-based diet. Their prey-seeking cousins, the wasps, need something more: to be around the specific plants that attract the insects they hunt to feed their young.

Wasps make up 15 percent of the total number of flower-visiting insects worldwide. But they are regarded as incidental or secondary pollinators, not the pollination machines that bees are designed to be, with their hairy bodies that pollen granules cling to.

Another anatomical difference: The range of flowers that adult wasps can drink nectar from is limited because their tongues are typically shorter than those of bees. While choosing native plants is important when you’re creating a habitat that supports beneficial insects, the wasps have an additional request: simple, shallow flowers, please.

Oh, and lots of wasps love the color white, as many of those examples underscore.

Remember the restaurant-versus-home analogy, she said, and go ahead: Start planting with wasps in mind. Enhancing the garden with their preferred flowers will not increase your chances of being stung — and it might make your vegetable garden a more resilient place.

Limiting the risk of getting stung

But what’s the best way to discourage them from stinging — and to avert the near-inevitable human impulse to spray some chemical from a distance to eradicate an established nest, killing all of the individuals in it?

Intervene early, Holm advised, to dissuade nest-building in high-risk spots, sparing risk to yourself and to whole colonies, above or underground. “Don’t even think of trying to intervene in August,” she said.

One insight toward that end: Yellowjacket females, probably the wasp most often responsible for stinging humans, search out preexisting cavities, like rodent holes in the ground, when they are emerging from winter hibernation in early spring. Try closing up those holes proactively.

And if you had a ground-nesting colony in the yard last year, look there first, Holm recommended, because wasps will often search for and initiate a nest near the site of their natal one.

Similarly, check eaves, overhangs, and birdhouses early and regularly for any sign of the construction of a nest comb, she said, “when maybe there is only an occupant or two involved.”

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