Beneficial parasitoids that can be an effective part of an organic integrated pest management (IPM) system are braconid wasps.
There is a great variety of Braconidae (a family of parasitoid wasps) that are parasitic to specific insect pests. These pests include tomato hornworms, caterpillars, aphids, and beetle larvae.
Below are some of the benefits of encouraging braconid wasps to the garden.
Firstly, it’s important of course to be sure of the correct identification. These predatory wasps are rather small with slim bodies, ant-like heads, narrow waists, and long antennae plus a dark spot possibly on the forewing.
The ovipositor of the female is long and black and protrudes from the rear. On first sighting, closer inspection reveals orange or reddish abdomens, very different from the familiar yellow/black buzzing nuisance at summer picnics.
Braconid wasps are more likely to be found around munching caterpillars or clouds of aphids.
Female braconid wasps lay eggs inside the host insect pests. As these parasitic wasps emerge into the larval stage, they begin to feed inside the host .
When ready to pupate, the larvae chew their way out of the host pest and make tiny silk cocoons on its exoskeleton.
These cocoons look very much like fluffy grains of white rice at this time. Additionally, they are often visible as tiny white clusters (that resemble insect eggs) along the back and side of the host insect.
Eventually, the host dies as the wasps break out of their cocoons and emerge as tiny adult wasps. Adult braconid wasps eat pollen and drink nectar, reproduce, and continue the cycle of parasitizing pests.
Braconid Wasps Benefits to the Garden
The vast variety of Braconidae allows for specific pests to be targeted and parasitized. They either live in or on their host from which the larvae feed and weaken.
Braconid wasps are beneficial because they are particularly useful in controlling aphids, cabbage worms, tomato hornworms, and other soft-bodied caterpillars.
Some attack cabbage butterflies, others target wood-boring insects. Adults will attack these creatures. However, their most beneficial purpose is in producing eggs and larvae to weaken or kill garden pests.
How Do They Kill Their Hosts?
In a season, a braconid female wasp can lay anything from 50-200 eggs. Moreover, the Aphidius colemani can produce even more eggs inside young aphids.
The wasps may deposit their eggs in the eggs of insect pests. These pest eggs are unlikely to hatch and if they do, will be too weakened to thrive. Other times and/or other types of braconids will deposit their eggs inside pests where the hatched larvae will feed off them.
The result is the same: the host will eventually die without causing too much damage to crops or reproducing.
Moreover, some Braconidae carry another weapon in their armory: a polydnavirus injected into the host pest . This type of virus has no negative effects on the host. However, it prevents its immune system from destroying the invading wasps’ offspring.
When the braconid larvae become adults they will make a hole in the cocoons, exit, and begin the life cycle. These natural predators are most prolific in warm and humid conditions in summers.
Do They Sting?
These very useful creatures do not sting humans, unlike the Hornets and Yellow Jackets that we are used to. However, they sting their prey to paralyze them for food to grow their offspring.
There are about 17,000 recognized species of braconids in the order Hymenoptera . However, many of them are found in North America, Australia, Europe, and other temperate climates.
They live in diverse habitats. You will also find different species throughout the world wherever there are suitable warm, humid, conditions.
They favor areas where there is dense vegetation and easy access to their food source. This includes forests, wetlands – (swamps and marshes), uplands, and meadows as well as gardens, crop fields, vineyards, and urban areas.
Other Beneficial Wasps
There are many other types of beneficial wasps, some of which are minuscule.
- Trichogramma are some of the most popular. These natural enemies control soft-bodied caterpillars like cabbage worms and cabbage loopers. They also deal with cutworms, armyworms, and corn earworms.
- Eulophids control caterpillars and are usually an iridescent green or blue color.
- Ichneumon are similar but larger than Braconids. They also have a different habit of spinning their cocoons under the skin of the host insect. Their prey includes white grubs, ants, corn earworms, Codling moths, and flies.
- Pteromalids are black and notable for their red eyes. The females mostly parasitize black scale and beetle larvae.
How to Attract Beneficial Predatory Wasps
As with all creatures, wasps need a supply of water. Therefore, a pool or birdbath will help attract these predators.
Additionally, they feed mostly on nectar and pollen. As a result, a flower-filled patch and herb garden will also help bring them in and other beneficial insects.
Recommended plants include:
- Sweet alyssum
- Dill (also attract their prey)
Small florets of flowers, carrot tops, and herbs also provide energy sources for the insects.
Additionally, Umbellifer plants attract them and other beneficial insects like ladybugs. These include fennel, sweet cicely, cow parsley, chervil, lovage, and angelica.
The new eco-conscious age is moving back to organic farming and gardening. Braconid wasps form part of the all-important biological control of pests and are of great benefit to the garden.