Ichneumon Wasp – How To Control Garden Pests Naturally [USE GUIDE]

No need to search for Ichneumon Wasps in the garden. When you spend quiet time simply observing your garden, you will notice lots of different insects going about their business harmlessly.

What you may not realize that many of these insects like the Ichneumon wasp are actually beneficial and can help keep insect pests under control naturally.

Ichneumon wasp - Megarhyssa macrurusPin
Megarhyssa macrurus (Ichneumon)- image via Bruce Marlin | Wikimedia Commons – | CC2.5

There are a couple of types of beneficial garden insects, parasitoids and predators.

Given the right setting, these natural helpers are abundant in most gardens.

In fact, for every species of pest insect, you can usually find several species of beneficial garden insects standing ready to “make contact” with them.

In this article, we discuss one of the most plentiful and parasitoids, the Ichneumonid wasp.

Although we often refer to these types of wasps as parasites, the fact is they are actually parasitoids.

Parasitoids feed off a host only so long as is necessary to mature into adult wasps.

Once achieved, they kill the host. True parasites thrive within or on their hosts indefinitely without killing the host.

Can Ichneumon Wasp Sting?

These types of wasps are nothing but beneficial to people. In fact, the Ichneumon wasp is just the kind of good bugs you want to keep in your garden.

Very few of them even have the ability to sting and find themselves so absorbed in their valuable work they take no notice of humans.

You really have to mishandle the few stinging Ichneumon varieties to force them to sting.

Although the ovipositor of the female is similar to the structure used by stinging wasps to deflect threats.

The conspicuous, long, sturdy ovipositor of the female Ichneumon wasp is not at all dangerous. It is only used for laying eggs and as a tool for drilling holes.

Are These Wasps Harmful To People In Any Way?

Far from it. These wasps are beneficial in every way. They help keep insect pest numbers under control by eliminating the larvae before they become adults and produce more pests.

Even though they look like wasps, these insects are harmless to humans.

Ichneumon wasps do have some enemies of their own and find themselves eaten by some types of beneficial insect predators like the praying mantis (Mantodea).

Additionally, the larvae of these wasps are surely consumed by predatory insects targeting the larvae of the very same insect pests ichneumons target. [source]

How Many Known Species In The World And In The US?

You might think of wasps only as scary, stinging critters, such as hornets and yellow jackets.

However, entomologists apply this term to a much larger group of insects. The largest part of this group are stingless wasps, which are natural enemies of pest insects.

There are over 5000 species of family Ichneumonidae in North America, alone. They are members of the order, Hymenoptera, which included other wasps, bees and ants.

The super-family, Ichneumonoidae, is made up of two families:

  • Stephanidae can be mostly found in the tropics. This group is made up of several hundred species.
  • Braconidae can be found in both tropical and temperate regions and is very generously distributed worldwide.

These two families contain more than 80,000 species.

Sometimes you might hear Ichneumonid wasps referred to as ichneumon flies; however, this is incorrect.

You will find this large, extended family of stingless wasps throughout the spring and summer in all areas of North America.

The wasps are solitary insects but are numerous. They busily seek out a wide variety of insect pest hosts in all sorts of garden, grassland and woodland settings.

What Does A Ichneumon Wasp Look Like?

These parasitic wasps (aka Braconid wasps) look similar to stinging wasps in appearance but differentiated by their longer, slimmer bodies and very long antennae, which may be as much as half the length of the wasp’s body.

The ovipositor (egg-layer) of female parasitic wasps is usually much longer than the body and may be five or six inches long.

It is a filament or needle-like appendage with the same placement as a stinger in a stinging wasp.

Ichneumon wasp feedingPin
Ichneumon wasp on flower feeding – via Wikimedia Commons | Charles J Sharp | CC4.0

With so many different species, Ichneumon wasps vary greatly in size, markings, and color.

They may also vary in form because they tend to evolve in a way which best enables them to prey upon their chosen hosts.

In general, these wasps are slender and elongated.

In fact, some are so long and slender, and strongly segmented, with yellow striped abdomens they are called “scorpion wasps”.

The sizes of the various species ranges from smaller than an eighth of an inch long to over six inches (if you include ovipositors of the female).

Some are very brightly colored, but others may be drab shades of tan, brown or black.

Some are banded like stinging wasps but differentiated by their long, slim body shape and non-aggressive behavior.

Ichneumon wasps’ wings may range in color from brown to blue.

Some species have dark markings on their fore-wings. All species have very long legs and long antennae.

In fact, the antennae may be made up of more than sixteen segments.

The Ichneumon wasp uses the antennae to locate items of interest by tapping them as they move about over grass stems, tree trunks or logs.

The males use their antennae to locate recently hatched females for mating. Females use their antennae to locate host larvae for egg-laying purposes.

Why Does The Ichneumon Wasps Drill Holes?

These wasps are opportunists!

They do not build nests or care for their eggs or their young. Instead, they lay their eggs directly into or onto their hosts and go their merry way.

The female wasp locates the host by finding its food source and then tapping about the area with her antennae to pinpoint the sound of the host feeding.

When the female wasp finds a host larva, she lays an egg in or on its body.

This can be quite an arduous task as some hosts are located deep within the trunks of trees.

In this case, the female wasp must use her ovipositor to drill a hole in the wood, locate the host larvae and lay her egg.

What Happens After The Female Wasp Lays Her Egg?

After laying eggs the Ichneumon female flies away and does not care for or guard her egg.

The egg hatches on its own, and the wasp larva feeds on the host for a period ranging from ten days to a number of weeks (depending on the species of wasp).

Most of the time the adult Ichneumon female wasp only lays one egg per host organism, so a single wasp larva feeds on a single host.

However, some members of this species lay multiple eggs in or on a single host.

If you notice a big, juicy hornworm scrabbling about with white “rice grains” (wasp larvae) on its back, you know a parasitoid wasp has been at work.

tomato hornworm with wasp larvae on its backPin
Ichneumon wasps larvae on back of tomato hornworm

How Does The Wasp Larvae Kill The Pest Larvae?

The vast majority of Ichneumon wasps lay an egg inside the larvae of the host organism.

Some lay an egg externally on the “skin” of the host organism.

Either way, when the egg hatches, the wasp larva feeds on the host larva either internally or externally.

This naturally kills the host larva before it can grow up to become an adult pest insect.

As the ichneumon larva grows inside or on its host, it lives by feeding on the body fluids and fats of the host.

When it’s ready to metamorphose into a full-grown wasp, the wasp larva may spin its own cocoon or may simply take advantage of the cocoon spun by its host.

Sometimes the host insect survives until the wasp larva is fully developed and simply emerges from the host’s body like an outer-space monster.

Other times, the wasp larva opportunistically makes use of the cocoon the host spins for its own development.

The Ichneumon wasp larva continues to consume and suck the life out of the host inside the cocoon. The wasp then emerges from the cocoon instead of the expected moth or butterfly.

When the parasitoid wasp larva “finishes” with the host larva, it leaves behind a mere husk or “mummy” of the host.

If you see mummified pests, such as aphids killed, scattered about beneath your plant, you know the husk of an insect fell victim of a parasitoid wasp larva.

How Many Offspring Does A Single Female Wasp Produce?

Some species of Ichneumon wasps produce only one generation of offspring annually.

Others produce as many as three or more generations per year.

Even though the female wasp usually only lays one egg per host organism, keep in mind she does this hundreds of times in her short lifetime.

For this reason, a single parasitoid wasp female can potentially wipe out hundreds of pest insects.

These non-aggressive, non-stinging, non-poisonous wasps are easily used to control pests in the garden.

They have tremendous potential for use in large-scale biocontrol projects. For this reason, these wasps can be of great economic importance. [source]

What Is The Giant Ichneumon Wasp?

The largest species of parasitoid wasp is the giant ichneumon wasp, a member of the genus Megarhyssa macrurus.

These North American wasps can grow to be a couple of inches long (not counting the ovipositor, which may be 4” or 5” inches long).

The wasp uses the ovipositor to bore into dead wood and lay eggs on the larvae of its chosen host insect, the pigeon horntail (Tremex columba, Symphyta).

Because of this behavior, this type of parasitoid wasp is sometimes called a “stump stabber”.

  • Is this giant dangerous? These beneficial insects are harmless to everyone except horntail larvae.
  • Where do giant ichneumon wasps live? These wasps live mostly in the eastern US and southeastern Canada. Look for them around the Great Lakes regions.

What Kinds Of Pests Do Most Parasitoid Wasps Target?

There are several species of parasitoid wasps. The wasps known as Ichneumon are most common, followed by braconid wasps and chalcid wasps.

All of these types of wasps make hosts of such scoundrels as tomato hornworms, caterpillars, the sawfly and beetle larvae.

Natural prey of the ichneumon wasp include:

Braconid wasps typically prey upon:

Chalcid wasps are very tiny and include the popular and readily available trichogramma wasp. This type of wasp targets:

All of these wasps will eat other types of wasps, bees, and ants. They also go after the larvae of crop-damaging beetles, moths and butterflies and some spiders.

Although some parasitoid wasps do target beneficial insect species (e.g. butterfly caterpillars) for the most part, their target hosts are insect pests and occasionally spiders.

For this reason, this group of insects is incredibly beneficial to gardeners and to people in general.

Why Are There So Many Different Species Of Parasitoid Wasps?

It is reasonable to speculate as to why we find so many species and different kinds of wasps from the family ichneumonidae is that there are so many different types of insect pests.

Parasitoid organisms tend to evolve in a way very closely linked to the traits and lives of their hosts.

A very tight association between host and parasite typically results in the parasite feeding only on a single type of host or on a group of very closely related hosts.

A looser association based more on the behavior of the host than its physical traits may result in a species of parasite targeting a more diverse range of hosts.

Examples of adaptation of parasite to host include the fact that parasitoid wasps focus on hosts whose larvae are buried.

They also tend to have a stouter body shape than those which must drill into tree stumps to locate and access hosts. [source]

Where Do Giant Ichneumon Live?

These wasps are numerous and found in all sorts of habitats around the world.

Since these wasps prey upon a wide range of pests, it makes them very important members of any ecosystem and should be carefully cultivated.

How To Use Ichneumon Wasps In Your Garden

We understand how detrimental pesticides are to wildlife, the environment and us, more and more people look to biological pest control measures these days.

Ichneumon wasps are especially valuable in this pursuit. They are effective at pest control in almost any setting.

These wasps are often host specific. This makes selecting the right type of parasitoid wasp to assist with a specific type of pest control easy for gardeners, farmers, woodland managers.

Environmentalists, home gardeners, foresters and farmers find the use of these wasps valuable, sustainable and preferable to chemical pest control or genetic modification of crops.

How To Encourage Ichneumon Wasps In Your Garden

We encroach upon nature more and more every day. This encroachment brings challenges for the environment and for us.

How can we maintain a healthy environment and encourage a positive balance between prey and predators in nature when we constantly disrupt nature?

One good way is to pay close attention to the health and well being of beneficial insects.

In North America, there are over 3000 species of Ichneumonid wasps, and all-told, they parasitize a wide variety of insect pests.

However, most individual species are host-specific and only attack a certain type of pest. For this reason, it’s a good practice to encourage a wide variety of these stingless wasps to dwell in your garden.

Luckily, parasitoid insects are able to thrive in urban settings and small gardens when provided a diversity in plantings, shelter, and food.

Establishing a native plant garden using species indigenous to your setting is a good way to attain this goal.

Beneficial insects are just as subject to poisoning as pests. When poisoned, you only harm yourself and ultimately make your pest problem worse.

You must protect beneficial insects against pesticides and other toxins.

6 Things To Consider In Attracting Beneficial, Parasitoid Insects To Your Yard And Garden

  1. If you must use an insecticide, do so selectively. Insect pests tend to be target specific and only attack a limited selection of plants. Don’t blanket your garden with pesticide. Only treat plants being attacked by pests.
  2. Choose pesticides carefully. Look for natural pesticides that break down rapidly after application. Choose those that specifically target the pest you wish to eliminate.
  3. Don’t spray during the daytime. This is especially true when treating flowering plants. The vast majority of beneficial insects are active during daylight hours. Wait until dusk to spray, using a product that breaks down quickly. When you do this, you avoid targeting beneficial insects, and you reduce the chance of negatively impacting them with residual chemicals when the sun rises.
  4. Learn to recognize parasitoid wasps. They are ubiquitous in most settings, yet we often overlook them. Watch for them and identify the areas they frequent. Take care not to do anything that would harm them or reduce their numbers.
  5. Provide safe watering stations. Be sure that any deep water in your yard has stepping stones included so the wasps (and other beneficial insects) can drink without drowning.
  6. Plant lots of different types of flowers (especially native flowers) to provide the adult insects with pollen and nectar. They like asters, daisies, members of the dill family and members of the carrot family. [source]

What Does An Ichneumon Wasp Eat? What Plants Attract Them?

Mature wasps feed on the nectar and pollen of flowers and may especially be seen around plant members of the carrot family, such as:

  • Hogweed (H. mantegazzianum and H. sphondylium)
  • Carrot (Daucus carota, subspecies sativus)
  • Celeriac (A. graveolens, variety rapaceum)
  • Coriander/cilantro (Coriandrum sativum)
  • Poison hemlock (Conium maculatum)
  • Queen Anne’s lace (Daucus carota)
  • Cow parsnip (genus Heracleum)
  • Parsley (Petroselinum crispum)
  • Asafetida (Ferula assa-foetida)
  • Chervil (Anthriscus cerefolium)
  • Earthnut (Conopodium majus)
  • Water hemlock (genus Cicuta)
  • Lovage (Levisticum officinale)
  • Smallage (Apium graveolens)
  • Cumin (Cuminum cyminum)
  • Fennel (Foeniculum vulgare)
  • Water parsnip (genus Sium)
  • Cowbane (genus Oxypolis)
  • Celery (Apium graveolens)
  • Angelica (genus Angelica)
  • Parsnip (Pastinaca sativa)
  • Dill (Anethum graveolens)
  • Cicely (Myrrhis odorata)
  • Caraway (Carum carvi)

Where To Buy Ichneumon Wasps

You can purchase Ichneumon wasps from garden supply stores or online (Amazon). However, it may be hard to find any other than the trichogramma wasp available for purchase.

Remember, with a little patience, your garden can attract parasitoid wasps perfect for your environment and eagerly seeking exactly the types of pest insects you have on offer.

If you do purchase trichogramma wasps, take care to establish a welcoming environment for them before you receive them.

Wait until pest insects start to emerge before releasing any wasps. This will help ensure they stay in residence.

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