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Are you familiar with the braconid wasp?
If you have ever seen a tomato hornworm struggling to carry what looks like a load of white rice on its back and sides late in the summertime – you have?
These small, white cylinders are actually tiny cocoons containing the larvae of the braconid wasp (Braconidae).
These beneficial wasps lay their eggs inside of hornworm caterpillars and a wide variety of other pest insects.
Depending upon the type of parasitic wasp and the type of host species, what follows is a gruesome and fascinating dance of death for the pest.
In this article, we will discuss the many merits of the braconid wasp and its close cousins read on to learn more.
What Are Braconid Wasps?
These small wasps belong to the Hymenoptera order which contains all wasps, bees, and ants.
Braconidae are especially desirable in the garden because, in addition to wreaking havoc upon tomato hornworms, they also help gardeners control thousands of other types of insect pests.
There are several common garden species of braconids. Just as with all types of parasitoid wasps, individual species among braconids tend to be specialized in specific hosts.
For example, Cotesia congregata (formerly Apanteles congregatus) is a tiny black wasp with clear wings and yellow legs. This sporty little number focuses on the tobacco hornworm and the tomato hornworm.
Female Cotesia congregata use the ovipositor (egg laying tube) to lay eggs just below the hornworm’s skin.
When the eggs hatch, the larvae gorge on the hornworm’s blood but do not eat its organs because they need to keep it alive.
When it’s time for them to pupate, the larvae chew through the caterpillar’s tough skin using a set of razor sharp teeth designed just for that purpose.
If you have problems with aphids you’ll want to attract Aphidius colemani and/or Aphidius ervi.
These two types of wasps specialize in parasitizing and help in getting rid of or killing aphids.
Aphidius matricariae has been introduced to the United States for the purpose of helping control green peach plant lice.
Another type of braconid, Diaeretiella rapae, specializes in doing away with the common cabbage worm.
There are also several different types of braconids. The most notable quality of all of the 15000 described species of braconids is that they are parasitoids. This is the term applied to parasites which kill their hosts. The various species of braconids attack a wide variety of garden pests including:
- Strawberry leafrollers
- Fall and Garden webworms
- Tomato hornworms
- Tent caterpillars
- Beetle larvae
- Leaf miners
- Squash bugs
- Stink bugs
If you have a healthy population of several varieties of these wasps in your yard and garden, they can provide you a great deal of assistance by parasitizing lots of different kinds of pests in great numbers.
For example, Aphidius colemani can really make a dent in your aphid problem. Although the lifespan of this insect is only four or five days, it can lay over 350 eggs in that time.
These parasitic wasps are not picky when it comes to caterpillars, and in addition to laying eggs in tomato hornworms, they also make use of the larvae of gypsy moths, cabbage butterflies, and sphinx moths.
One downside to having braconid wasps is they are not good for your butterfly garden. They cannot tell butterfly caterpillars apart from pest moth caterpillars, and they will just parasitize all of them.
If you have special caterpillars in your butterfly garden (e.g. Monarch caterpillars) try covering the plants where they live with mosquito netting. This will help keep them safe from parasitic wasps and birds.
What Do Braconid Wasp Look Like?
Adults vary in appearance depending upon the species. Braconid species range in size from 1/16th of an inch to 5/16ths of an inch. Generally speaking, they are less than half an inch long. Their bodies are long and stout.
They may be black, rust-colored, black and red, brown and yellow striped or a number of other color combinations. Some have a dark marking in the center of the forewing. Their antennae are quite long.
Although braconids have varying colored markings, because they are so tiny, they mostly look alike to the naked eye.
These wasps are generally dark colored and have four transparent wings.
Because they are quite small and not aggressive at all, you can have a thriving and varied population of them without ever being aware of their presence, other than by observing their handiwork.
When you notice tomato worms struggling about with a burden of tiny cocoons or mummified aphid carcasses where aphids once swarmed, you’ll know your tiny friends are doing their job!
It’s Good To Have More Than One Type Of Predatory Wasp
There are several wasp species that parasitize garden pests. In addition to braconid wasps, short and long tail Ichneumonid wasps and chalcid wasps can be very helpful.
From the Ichneumonidae family, we have Ichneumon wasps that make short work of a wide variety of caterpillars including:
- Corn earworms
- White grubs
These wasps are larger than braconids measuring as much as 1 1/2 inches long. The females have noticeably long ovipositors. Like braconids, they come in a variety of shades ranging from yellow to black.
Chalcid wasps are quite small with a maximum length of about 5/16ths of an inch.
This group of wasp includes the commercially valuable Trichogramma wasp, which effectively controls a wide variety of butterfly and moth caterpillars including:
- Tomato hornworms
- Cabbage loopers
- Cabbage worms
- Corn earworms
- Corn borers
Some other chalcid species specialize in parasitizing strawberry leaf rollers.
How Do You Attract Predatory Wasps To Your Garden?
You probably already have them in your yard and garden without knowing it. In North America, there are more than 1700 recognized species.
Around the world, there are over 100,000 species. It is very likely that many species have not yet been discovered and documented by humans.
In addition to being great at pest control, parasitic wasps are also good pollinators, and the mature wasps need nectar and pollen for nourishment.
Plant lots of different kinds of herbs and flowers with small, nectar-producing florets. Some good examples are:
- Sweet alyssum
- Roman and German Chamomile plant
In addition to ornamental flowers, these wasps enjoy flowering herbs, such as cilantro.
To be sure of universal appeal, plant lots of different kinds of flowers to attract a wide variety of beneficial insects. [source]
Water is essential to all life, so it is always a good idea to provide drinking stations for beneficial wildlife in your yard.
To attract parasitic wasps, bees and pollinators, set up shallow bird baths and trays of water around your yard and garden.
Remember to include a stone that breaks the surface of the water so that wasps, bees, and butterflies can land and drink without falling in and drowning.
Can You Buy Parasitic Wasps?
There are some parasitic wasps that can be ordered from garden supply houses. They do tend to be a bit pricey.
However, if you set up your garden to attract and support local wildlife, you should have plenty of braconids and other beneficial insects to suit your purposes.
How Long Does The Braconid Life Cycle Take?
Braconids have a holometabolous life cycle. This means they undergo a complete metamorphosis from egg to larva to pupa to adult.
The life cycle of each type of braconid wasp varies, so it is not possible to say exactly how long it takes.
The smallest ones have very brief lives but several generations are produced annually.
The larger varieties live a bit longer but only reproduce once a year.
Each individual species grows and moves from one phase of its life to another in concert with the life cycle of the host insect.
Generally speaking, The life cycle of a braconid starts when the parent wasp inserts its eggs into the host.
The larvae hatch and grow inside the body of the insect host.
When they are set to pupate, they might stay inside the host insect (which is quite ill or dead by this time) or, they might spin cocoons on the exterior of the host.
Although it may sound as if this process takes a long time, it really is just a matter of a few days.
Without parasites, hornworm caterpillars live two or three weeks, eating the whole time.
When a parasitic wasp lays eggs in a hornworm caterpillar, its life is shortened to about one week, and during much of that time, it is too ill to eat.
Then it dies without ever reaching maturity or reproducing, so it’s easy to see that parasitic wasps have a tremendous impact on the potential damage done by hornworms and other pests. [source]
Why Does Parasitic Wasp Infestation Kill The Host Insect?
In addition to simply invading the body of the host, these wasps also use a secret weapon to block the hosts’ defenses.
When the female wasp injects eggs into the host, she also injects a polyDNAvirus.
As soon as the virus is introduced it begins working to disable the host insect’s defense systems which would normally fight off intruders, such as the wasp eggs, larvae, and pupae.
If it were not for this virus, the host’s immune system would quickly destroy the eggs.
Here is a rather horrifying video that shows the entire, fascinating process in tremendous detail and explains exactly how the coevolution of the wasps and the virus work to make the very existence of these wasps possible.
Do Predatory Wasps Sting People?
Although it is possible for these helpful wasps to sting humans, it is very rare and you really have to try to get them to sting you.
Only the females can sting, using their ovipositor. They have no venom, and their sting is medically harmless.
Generally, they are the non-stinging wasps and will only sting if mishandled or trapped. Of course, you should not handle or trap them at all.
Parasitic wasps are focused on finding food and finding hosts to lay their eggs.
They are not territorial. They don’t build nests. They don’t care about people. If you leave them alone, they will leave you alone.
Parasitic Wasps Greatly Reduce Or Eliminate Pesticide Use
It’s easy to see that welcoming barely noticeable braconids and other parasitic wasps into your garden is an excellent, carefree alternative to use of costly and dangerous toxic pest control methods.
Be aware that these little wasps are also quite sensitive to pesticides, so if you want to engage them, it’s best to take a holistic approach to garden pest management.
The best biological control uses a wide variety of natural pest management methods and avoids any use of broad-spectrum insecticides, which will kill off your beneficial insect population and may have little or no effect on garden pests. [source]