Wasps of All Sizes Perform Great Acts of Pest Control!

July 10, 2026

In this week’s edition of ‘Ask Mike’, the You Bet Your Garden man explains why you should welcome wasps—yes, wasps, into your garden. Really—especially if you grow tomatoes! Plus lots more topics when you tune into the entire show audio at the You Bet Your Garden page at the Gardens Alive/Gurney’s website

Courtesy of Penn State Extension

“Hey Mike! It's your loyal listener Sean from Boston back to ask you another question! I recently got a TikTok video telling me I should keep wasps in the garden as a way to control pests. Now I'm a lifelong wasp hater, but I hate aphids and other plant munchers even more. Now, I know the Internet would NEVER lie to me, but I wanna hear your opinion!”

A. Well, my first opinion was 100% positive. Even without watching the video, I knew that they were talking about parasitic mini-wasps. Here’s a nice introductory explanation of them from the Minnesota State Extension service:

{quote}: “Tiny parasitic wasps (also called parasitoid wasps) are minuscule, harmless insects that act as natural pest controllers. Most measure just 0.18 to 5 millimeters long. Instead of stinging, females use a needle-like appendage to lay eggs inside or on host insects (like aphids, caterpillars, and whiteflies). They are completely harmless to humans. [1, 2, 3]”

Many tomato growers have seen these helpful insects in action but didn’t realize what they were seeing. The tomato hornworm—an extremely large caterpillar with a ravenous appetite whose color blends in perfectly with its target plants—has a smooth green body. But even people who’ve been growing tomatoes for years only notice them when their green back is covered with white spikes. (And/or they notice the massive amounts of frass (bug poop) under the plants, which strangely resembles miniature deer scat.)

The Hyannis County Garden site continues the conversation:{quote} “The most formidable enemy of the tomato hornworm is the braconid wasp (Cotesia congregates). These non-stinging, beneficial insects lay their eggs under the skin of the hornworm. Once the eggs hatch, the wasp larvae feed on the inside of the caterpillar before bursting through its skin to spin tiny, white cocoons that look like grains of puffed rice on the worm's back.” [1, 2, 3]”

It is a gruesome death for the caterpillar, but doubly beneficial for the grower, as the massive caterpillar stops eating shortly after being parasitized; and then baby wasps emerge from the cocoons to devour more pest caterpillars, essentially creating a passive breeding ground in your garden.

You can buy starter wasps online, but they seem to be ubiquitous across the United States. You can deliberately attract them by planting nectar-rich plants like dill, chamomile, fennel and sweet alyssum. The microscopic wasps come for the nutritious nectar and pollen and then go to work on the {quote} “worms”. And of course, use no pesticides or you’ll kill your natural helpers.

Note: Any destructive farm or garden pest of this type was long ago tagged with a common name that included ‘worm’ (the corn earworm for example). They are all caterpillars, but that ‘worm’ name will live on forever.

If you see caterpillars with white spikes on their back, do not harm them. The caterpillar has already stopped eating and will wither away within a week.

The OSU Extension website also names Trichogramma (which target pest eggs), and Aphelinid wasps (which control whiteflies and aphids) as other beneficial mini wasps. (And no, they don’t sting—they don’t have stingers.

A great natural strategy would be to plant dill around your tomatoes and cabbages (to combat the cabbage worm). Why dill? You also get a great pickling ingredient; if you pickle, you can’t have too much dill!

OK. Mr. Smarty Pants then actually watched the video that Sean forwarded, and it showed a gardener who was using paper wasps to eat the offending pest. The video shows several paper wasp nests around his garden up in the air with soffit-like surroundings. He has a whole bunch of them, but as we who cleaned their gutters by hand know all too well, they have stingers and use them IF THEY ARE DISTURBED. Leave them alone and they won’t bother you.

If your garden is near a structure, they will naturally build there—and their nests are relatively small, typically containing a maximum of 20 or 30 wasps. Again, no danger to you and they eat a LOT of pests. Same goes with big hornets nests up in trees; there are a lot of hungry wasps in there and they ignore humans who don’t go all Elmer Fudd on them.

Underground yellowjacket nests are another story; there are thousands of the highly aggressive wasps, which like to sting people, can sting repeatedly and will chase you down to sting you over and over when disturbed. It is my strong opinion that the vast percentage of {quote} ‘bee sting deaths’ in the United States are actually caused by yellowjackets. Any nest you find near your house must be vacuumed out by a beekeeper or professional exterminator. It is not a DIY project, you can’t leave them there, and the structure of the nest renders insecticides useless.