Parasitoid wasps are members of a large group of insects that includes thousands of parasitic insect species in over 40 families. These small, flying wasp parasites are so tiny that they are hardly ever noticed. Most are tiny, with many species smaller than a millimeter. However, they make up for their small size by their sheer numbers and efficiency. As a group, these tiny parasitic predators are an important biological agricultural pest control method.
We all know the impact that harmful insects can have on your crops. Many organic producers, or those looking to reduce their use of pesticides, partner with beneficial insects to help eliminate harmful insects. Parasitoid wasps are an important non-pesticide control method to manage or reduce certain agricultural pests.
In this article we’ll cover details on parasitoid wasps, their benefits to your farm or garden and how to attract them.
What are parasitoid wasps?
Parasitoid wasps are a part of a larger group of flying wasps. The difference is that parasitoid wasps lay their eggs inside other insects in order to complete their lifecycle. These tiny wasp are very diverse in appearance and can range in size from 0.005 inches to over 3 inches long. The smallest known adult insect is actually called Dicopomorpha echmepterygis. These tiny wasps are sometime called fairy-flies and have bodies smaller than a single-celled paramecium. Parasitoid wasps are helpful in controlling native and invasive species of agricultural pests.
Parasitoid wasps are typically so small and are very diverse in appearance, that they can only be reliably identified by an expert.
Like other parasitoids insects, they lay their eggs in or on the bodies of other arthropods. As you can imagine this results in a very bad day for the effected insect, which sooner than later will die and become a host for a new generation of wasps. Different species of parasitoid wasps lay their eggs in different insects, including aphids, beetles, leafhoppers, caterpillars, and flies, who are among the unfortunate.
The good news is that these tiny beneficial wasps don’t sting or bite people or have a nest or hive that needs protection.
Parasitoid wasp lifecycle
Each species of parasitoid wasp has a species of insects it needs to complete its lifecycle. The adult wasps seek out these other insects and then lay their eggs on it or inside it. The wasp eggs hatch inside or on the body of the parasitized victim and then provide a ready-made meal for the larvae. The larvae will typically continue to feed on the hosts until they enter their pupae stage. The pupae can sometimes be seen on the outside of the host insect. Eventually the adult parasitoid wasp will fully emerge and fly away, leaving the host insect dead.
- Eggs: The eggs of the parasitoid wasp are hardly ever seen as they are often laid inside the bodies of the host insect.
- Larvae: Also rarely seen, they may sometimes been noticeable as a small dark shape within the body of the parasitoid wasp’s victim.
- Pupae & Cocoons: Each wasp larvae will spin its own cocoon once they break free from inside the host’s body. These tough cocoon of parasitoid wasps can be identified as small lightly colored (white or yellow) oblong (rice shaped) cocoons often in clusters. These cocoons can sometimes be spotted on or near parasitized host insects.
- Adults: Once parasitoid wasps become an adult they can vary in size from very tiny (0.005 inches) to a few inches long. The adults are solitary insects and typically feed on the pollen and nectar of flowers.
This image was ,originally posted to Flickr by Alex Popovkin, Bahia, Brazil.
Benefits of parasitoid wasps
The parasitoid wasps main benefit to farmers and gardeners is to provide a pesticide free way to help reduce, control and manage harmful agricultural pests. The wasps lay eggs inside or on the body of their hosts, which will later emerge, feed upon and kill the host insect. There are a huge variety of parasitoid wasps, each with their own evolutionary preference for host insects.
These tiny killers are known to seek out zombie hosts from various other insects including:
- Caterpillars (including armyworms, cabbage looper, fall webworm, tent caterpillars, tomato fruitworm, redhumped caterpillar, etc)
- Some spiders
- and others
Because of their efficiency in reducing populations of harmful pests, parasitoids wasps are one of the most widely used biological (non-pesticide) based insect control method in North America and are especially beneficially for organic producers.
Parasitoids wasps do not bite or sting humans and pose no risk to people.
How to attract parasitoid wasps in farms and gardens
While parasitoid wasps are one of the most beneficial groups of predatory insects. Due to their small size they often go unnoticed. Here are a few simple ways to help attract and promote parasitoid wasps in your farm or garden
- Reduce the use of insecticides – Because parasitoid wasps are very sensitive to pesticides you should reduce the use of chemical insecticides in order to create a safe and friendly ecosystem for beneficial insects, like parasitoid wasps, lady bugs, green lacewings, bees and others
- Plant consistently flowering plants – Adult parasitoid wasps feed on nectar and pollen so keeping flowering plants that provide a reliable nectar source will help attract parasitoid wasps and other helpful insects.
- Keep some bad garden pests around – While no farmer or gardener wants to leave potentially destructive bugs on their crops, keeping a low level of pests around will provide a valuable food source and encourage beneficial bugs to take up residence.
- Use sugary sprays – Because adult parasitoid wasps feed on sweet nectar and pollen, you can apply a mixture of sugar and water to plants where you’d to attract them.
- Buy parasitoid wasps – If all else fails or you need a jump start to reduce the population of harmful garden pest, you can purchase parasitoid wasps to control a variety of pests. You can often find them for sale online or at a local garden center.
These tiny killers often go unnoticed, but they are one of a variety of beneficial insects that you should try to attract and protect in your garden. While the lifecycle of parasitoid wasps may seem like something out of a science fiction horror movie, these tiny wasps are an excellent ally in the fight against harmful crop destroying insects and they can be a valuable tool that every farmer and gardener should consider using.
To learn more, check out some of these other resources:
- Aphid wasp parasitoid
- Braconid and ichneumonid wasps
- Parasitic wasp of whitefly
- Scoliid wasp
- Parasitoid wasp biology