Ask a Master Gardener

photo of cicada killer wasp

Wasps Are Our Friends

8/6/24

Today let’s talk about wasps but not in the way you are likely thinking. I’ll admit that I am a little leery of wasps, but I am working on it. I mean, they do look rather like a heavily armed, attack insect with that giant stinger end, but I am working to get over my kind of knee-jerk reaction to seeing a wasp. Now when I see a wasp nearby, my first reaction is no longer to run or swat them away. I tend to say hello now and embrace the attitude that they mean me no harm. We can coexist and all I can say is so far, so good.

So, let’s talk about wasps and the role they play in our ecosystem so maybe, you too can learn to look at wasps as our partners rather than dangerous adversaries. Since there are literally thousands of different types of wasps in North America let’s talk about some of the more common ones in our area.

First up is the Braconid wasp. You may have seen these and perhaps thought they were a fly of some sort because braconid wasps only grow to be about 1/2 inch in length. They are dark in color and have 4 transparent wings. The braconid wasp is what we call a parasitic wasp, meaning that the braconid wasp uses other insects to serve as hosts for their young. One of their favorites is the tomato hornworm.

Many a tomato grower has gone out to visit their garden one day, only to find a branch or several branches of their tomato plant missing their leaves. This work is oftentimes the result of a tomato hornworm feeding on your plant. Here’s where the braconid wasp comes in.

Female braconid wasps inject their eggs under the skin of the hornworm. At the same time, they also inject a virus called polydnavirus. This virus works against the natural defense system of the hornworm to keep the hornworm’s immune system from attacking the newly laid eggs. In addition, the eggs release a hormone that inhibits development of the hornworm (because they want to turn into a moth) so that it can remain a host for up to 60 braconid wasp eggs.

Then, once these eggs hatch inside the hornworm, they begin to feed. I admit that’s kind of creepy. Once these feeding larvae are ready, they chew their way out of the hornworm and spin a small cocoon so they can begin the pupation process. Once the adult braconid wasps emerge, the tomato hornworm dies.

Some of you may have one of these tomato hornworms on your plant that is playing host to a bunch of tiny braconid wasp cocoons and thought this was something that immediately needed to be removed from your garden. However, it’s best to just leave them alone. The hornworm’s days are numbered, and they are serving to launch a small army of braconid wasps that will continue to protect your tomato plant from future hornworm damage. This places the braconid wasp squarely in the category of the good guys.

While you may not have seen a braconid wasp before, you have likely seen one of the more common wasps known as the paper wasp. These are the ones that like to build those umbrella shaped nests under the eaves of our house or under the deck etc. These wasps can sting if provoked, but for the most part they are minding their own business looking for food to feed their young.

Paper wasps can be brown, yellow, black, or red depending on the variety but all of them are typical about 3/4 of an inch in length. Those interestingly shaped nests are constructed out of chewed up plants and wood mixed with wasp saliva.

We tend to first notice paper wasps in the spring when the females emerge from their overwintering site to build nests. Over the season, these paper wasp colonies can number somewhere between 20 to 75 wasps and their nests can vary in size from between 3 to 10 inches in diameter depending on the size of the colony. In the fall, female wasps seek out a mating partner who dies shortly thereafter, leaving the female to find an overwintering site.

We consider these wasps to be beneficial in that they not only serve as pollinators as they feed on nectar from our flowers, but they also because capture a sizable quantity of caterpillars to take back to the nest to feed their young. Favorite feeding targets include hornworms, loopers, armyworms and corn earworms. So, having a few paper wasps in the neighborhood is a good way for a little natural pest control.

There is one wasp that I am happy has a taste for cicadas rather than humans and this is the Cicada Killer wasp. Cicada killer wasps are one of the largest wasps in North American in that they grow up to 2 inches in length.

Cicada killer wasps live underground in burrows with these burrows usually being located near a tree that is hosting cicadas. They get the name cicada killer because after finding a cicada, they paralyze the cicada with their sting (oftentimes in mid-flight) and take the cicada back to its burrow.

After the cicada is relocated to the burrow, the female will deposit their eggs on the cicada and place them in a cell of their burrow. Then in about 2 to 3 days, the egg hatches and begins to feed on the captive, paralyzed cicada. The circle of life at work. No humans were harmed in this process.

All this to say, while wasps are oftentimes an irrational object of fear, many of them are either good partners in our ecosystem or relatively harmless fellow earth-dwellers just trying to live their lives and take care of their kids. Just give them some space and you should be fine. If you have an allergy to insect bites, you might want to give them a little more space. Of course, you probably already knew that. See you in the garden. I’ll be the one saying hello to the nearby flying wasps.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Gerald J. Lenhard, Louisiana State University, Bugwood.org