Welcome Back, Wasps! The Return of a Garden Friend

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If I were a wasp, I would be stinging mad! Those honeybees get all of the credit in the garden!

Yesterday, I was delighted to find that paper wasps we’re out scouting for this year’s nest sites under the eaves of our home. A well-protected corner near my kitchen door has been a popular construction site over the past three years, and the wasps have returned to use it again. It’s a rather high-traffic area, but we’ve been coexisting rather peacefully and without incident, although there have been some close calls.

Not from the wasps… from humans.

Like the time my mother-in-law almost took out the nest with hornet spray while I was gone to work; thankfully we don’t keep spray on-hand.

And just earlier this week, a nice gentleman conducting our annual termite inspection was about to “do me a favor” and rid us of the nest, but I stepped out of the house just in time.

Last year's wasp nest, and two new queen wasps flying in to check out the site.

Last year’s wasp nest, and two new queen wasps flying in to check out the site.

Those poor wasps are flying Rodney Dangerfields… they get no respect. That’s a shame, because they deserve a lot of it, especially if you grow a garden.

Paper Wasps as Garden Beneficials?

Paper wasps aren’t usually considered important pollinators, as they don’t have pollen baskets or body hair that helps transport much pollen from plant to plant. For plants that require cross-pollination, like squash or melons, wasps aren’t helpful. But for the many garden crops that largely self-pollinate, such as beans and tomatoes, wasps are a big help. The flowers of these plants still require “tripping,” a process that occurs when the stigma and anthers of a self-fertile flower make contact with each other due to a physical force from vibration (like wind) or, more efficiently, when an insect visits the flower. The tripping of bean flowers by visiting insects like wasps can increase bean yields by about a third.

But why would wasps visit flowers if they are carnivorous? True, they are not heavily dependent on nectar like the honeybee, but that doesn’t mean that they don’t enjoy a sweet drink like the rest of us. In fact, sophisticated “extrafloral nectaries” have evolved in some plants that encourage wasp visitation. These nectaries, commonly located on leaf petioles or near where they attach to plant stems, produce nectar and organic acids that attract wasps, which in turn protect the plant from pests. Considering that wasps are one of the most efficient predators of caterpillars in the garden, I can understand how some plants have evolved to keep them around.


A paper wasp queen gets a sweet energy drink from the extrafloral nectaries of my over-wintered fava beans.

A paper wasp queen gets a sweet energy drink from the extrafloral nectaries of my over-wintered fava beans.


There are MANY types of wasps, as well… not just the paper wasps you find nesting under the eaves of your home. Many of these wasps are specialists in the types of insect pests that they target, such as caterpillars or beetles. So if you want balance in your garden ecosystem and natural pest control, don’t forget that wasps factor into Mother Nature’s equations as well.

Attracting wasps to your garden

This is the time of the year that wasps are re-emerging from winter hibernation and scouting for new nest sites. Unlike honeybees which produce stores of honey that sees the entire colony through winter, it’s only fertilized paper wasp queens that live until the next year. Wasp queens seek winter shelter in protected sites (such as your home), and then emerge in spring to find nest sites. When you find a wasp crawling inside your home this time of year, it is most likely a confused queen trying to find a proper exit. Rather than squashing her, help her find her way out, as they rarely sting without a nest to defend. Placing a cup over her and sliding a stiff piece of paper under her body is a quick and easy wasy to return her outdoors.

This is also the time of year that you can help wasps choose appropriate nesting sites. Their favorite nest sites will be under the eaves of your home, and so consider leaving them there if it isn’t a high traffic area. Paper wasps usually only sting to guard their nest(or if they feel threatened by a human that is swatting madly at them), so give them several feet of room to feel safe. If you do not like the location that a wasp queen has chosen to begin building her nest, simply knock it down while the nest is small and new, without any defenders to protect it… she’ll likely find another building site.

Finally, include in your garden plans those plants that produce extrafloral nectaries: fava beans and cowpeas! These plants attract not only wasps, but other beneficials as well, such as lady beetles and honeybees. Studies have shown that intercropping cowpeas with other crops reduces insect damage and is an effective integrated pest management (IPM) strategy. Although it is too late to plant fava beans this season, make sure that you get some cowpeas in the ground this year. You’ll see reduced pest pressure, and get some great nitrogen fixation and delicious cowpeas to boot.






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