The European wasp (Vespula germanica) is a social wasp that lives in large nest colonies. It’s native to Europe, North Africa and Asia, and has now spread throughout the world. In the US, these wasps are known as German yellowjackets.
Why Are European Wasps Considered Pests?
European wasps are a pest because they are an introduced species that does not have natural predators to keep their numbers low in the countries where they have spread to, such as in Australia.
In Europe, the cold winters destroy the whole colony, leaving only the queen wasp to survive and start a new colony in spring. In warmer climates with mild winters, the entire nest is able to survive throughout the year.
These European wasps have the potential to disrupt native ecosystems and succeed at the apparent expense of some native species through their aggressive foraging behavior, taking food sources away from the native species and disturbing the natural food chain.
Their environmental impact can be significant. European wasps require very large quantities of protein, such as insects, to feed and rear their brood.
The recorded maximum annual collection of prey by a single, overwintered nest in New Zealand was 99kg, which consisted mainly of flies, together with honey bees, moths, spiders and bird remains. This weight of prey is approximately equivalent to 3.5 million blowflies.
Where there is a high density of nests, European wasps can destroy virtually all insect life in a local area, which then leads to the disappearance of insectivorous birds. Researchers have observed in parts of Tasmania, Australia, where the wasps had cleared out all other insect life, they were preying cannibalistically on each other. In fragile ecosystem, the presence of European wasps can lead to the loss of insect pollinators of rare or endangered flora.
Since European wasps are far more aggressive than native wasps, lack natural predators, and don’t die off in winter in warmer climates, they are able to multiply in their numbers and become an increasing problem.
This introduced pest impacts the wine and fruit industries by feeding on fruit and damaging them, creating entry points for disease, leading to secondary fungal infections of produce.
European wasps are also troublesome to beekeepers. In late summer and autumn, when prey insect populations and nectar sources diminish, they often attack honey bee colonies, robbing honey from colonies and eating adult bees.
They like to live around humans, scavenging on the ready supply of food and drink available to them, particularly meat, sweet foods and beverages. This foraging behavior for human foods brings these wasps in frequent conflict with people, especially in the late summer and early autumn when their numbers peaks and other food sources begin to decline. As such, they can be a common nuisance at outdoor gatherings with food, such as picnics and barbecues.
European wasps are quite aggressive and will sting readily if disturbed. Unlike bees , which die after stinging once, wasps are able to sting repeatedly and survive, so their interaction with humans carries the potential for sting incidents.
They also have a tendency to build nests in or around human residences and buildings, and are known to be very territorial in defending their nests, creating a human health risk.
What Do European Wasps Eat?
European wasps are scavengers that are attracted to meat and sweet foods.
Unlike honey bees, which gather protein exclusively from flowers in the form of pollen, European wasps forage for protein from animal sources to feed the developing larvae, by scavenging meat from carcasses (carrion or dead animals), garbage bins, pet food and picnic tables; and predation of arthropod prey such as live spiders and other insects. They are also predatory on nestling birds.
They forage for carbohydrates to feed the adult wasps, obtaining sugars from various sources, such as fruit, nectar, tree sap, sweet beverages, beer, and ‘honeydew’, the sticky substance on plant leaves produced by sap-sucking pest insects such as aphids and scale insects. Sugars are also important to the new developing queen wasps in late summer.
What is incredible is that European wasps may travel up to half a kilometre (a third of a mile) from their nest to forage for food!
Where Do European Wasps Build Their Nests?
European wasps build large communal nests, which are usually built in sheltered locations, hidden away from view, with only a small entrance hole visible.
The nests are usually about the size of a basketball, round or football (oval) shaped, and are construct from chewed wood pulp and saliva, giving the outer surface a distinctive papery or paper mache appearance.
About 80% of European wasp nests are built underground, with the remainder usually found above ground. Only very rarely do they construct an exposed nest
When the nests are in the ground, they can be found in holes dug in the ground, abandoned burrows of rodents and rabbits, in garden rockeries, around the base of trees, along hedges, in rubbish heaps and junk piles, in uncovered compost heap or piles of grass clippings, within retaining walls or any concealed site.
When the nests are above the ground, they can be found in voids within buildings such as cavities in walls, ceilings, roof spaces, as well as outdoors in logs or tree trunks.
The walls of buildings are very attractive to European wasps because they provide many benefits, such as warmth during autumn and winter, shelter from moisture, protection from many predators, and close proximity to garbage and other food sources. This allows the colonies to remain active for more months of the year, enabling them to grow larger in numbers.
How to Locate Hidden Wasp Nests
To track European wasps back to their nest and locate where they reside, place food such as meat or pet food in a visible outdoor location. The wasp will fly virtually in a straight line from the food back to its nest. If necessary, keep relocating the food closer to the nest until it’s possible to see the wasp fly into its nest.
How to Identify European Wasps
(Image source: NSW Government, Department of Primary Industries)
It’s important to properly identify European wasps to ensure that non-threatening beneficial wasps or bees are not harmed in efforts to control them.
European wasps have smooth, shiny, stout bodies, workers are approximately 13 mm (1/2″) long, while the queens are 18 mm (3/4″) long.
They have bright black and yellow bands. The black bands have arrow-shaped black markings down the centre of the abdomen, and there are pairs of small black spots on the yellow bands.
Typically there is a small arrow-shaped black mark on the first abdominal segment, and a series of black spots down both sides from the second to the fifth segments.
The wings are long and transparent, and they actually have two pairs of clear wings, with the first pair larger than second pair that is not readily visible.
They have black antennae, their legs are mostly yellow, and they fly with their legs held close to the body.
They are a social species, with many living in a nest, and they build papery nests out of chewed up fibrous wood. If wasp nests are constructed of mud, they they are not European wasp nests.
Paper wasps are sometimes mistaken for European wasps, but they have certain distinguishing characteristics, namely yellow-orange antennae, longer, more slender bodies, they fly with their legs dangling, and aren’t attracted to meat.
(Image source: Government of Western Australia, Department of Primary Industries and Regional Development)
The image below compares a variety of Australian insects that are sometimes mistakenly identified as European wasps.
(Image source: Government of Western Australia, Department of Primary Industries and Regional Development)
How to Build a European Wasp Trap
European wasps can be controlled by reducing their numbers using a trap made from a clear plastic soft drink bottle (soda bottle).
To make a homemade European wasp soft drink bottle trap:
- Cut off the top of the bottle at the shoulders, turn it over and insert the top into the bottom to form a funnel.
- Punch or drill holes near the top, and add a wire for hanging the trap.
- Bait traps with 1/4 cup fruit juice, 2 or 2-1/4 cups water, 1/4 teaspoon of yeast, 1/4 teaspoon liquid dishwashing detergent, and mix.
- Place the fruit-juice baited traps around the yard and garden in mid and late summer. The traps can be placed approximately every 30 feet around the perimeter of fruit crops.
- Empty and refresh the bait every 2 weeks to maintain effectiveness, so be sure to put them in a readily accessible location.
The detergent is used to break the surface tension, so when the wasps touch the surface of the liquid, they can’t float on the surface but fall through and drown.
The level of the liquid should be a little below the end of the funnel so when the wasps fly in and land on the liquid, they fall into it and can’t crawl back out of the funnel.
Keep traps at least 6m (20 feet) away from bee hives so the European wasps don’t discover the location of the bee hives when they’re investigating the traps.
Traps are effective in the spring to catch the queens, and later in the season to catch the workers. Each colony can produce up to 5,000 workers at its peak, so eliminating the queens in spring can dramatically reduce their populations in late summer and autumn.
Using Different Attractants in European Wasp Traps
Many different attractant have been used in European wasp traps, such as heptyl butyrate, meat, pet food, fish, or rotting fruit.
Heptyl butyrate is a highly effective attractant that does not attract honey bees. It is a colourless liquid with a chamomile-like odor that is found abundantly in fresh apples and plums. When these fruit fall from the trees in late summer, they attract plenty of wasps. It is also found in babaco (champagne fruit), a subtropical Ecuadorean fruit related to papaya that grows in much colder climates.
Fresh meat or fish is also attractive to these wasps, but it may spoil within hours and become ineffective.
If building your own trap, it is important to avoid using sugary attractants that could inadvertently attract bees.
How to Discourage European Wasps
If experiencing a wasp problems:
- Do not leave fallen fruit or food scraps lying around the yard
- Avoid leaving uneaten pet food or dog bones outside
- Make sure rubbish bins have tight fitting lids
- Keep compost covered at all times
- Keep swimming pools covered when not in use
- Cover exposed food at picnics and barbeques
- Don’t drink out of cans or bottles, use clear containers or a straw
More articles on Garden Pests, Diseases and Problems
References
- NSW Government, Department of Primary Industries, European wasp, Vespula germanica, https://www.dpi.nsw.gov.au/biosecurity/plant/bees-and-wasps/european-wasp
- The Australian Museum, European wasp, Updated 07/12/20, Melissa Murray, https://australian.museum/learn/animals/insects/european-wasp/
- Oregon State University Extension, Yellowjacket, https://pubs.extension.oregonstate.edu/em9093/yellowjacket
- University of California, Riverside, Center of Invasive Species Research, German Yellowjacket, https://cisr.ucr.edu/invasive-species/german-yellowjacket
- Michigan State University, Plant & Pest Diagnostics, Yellowjackets, https://www.canr.msu.edu/resources/yellowjackets/
- Utah State University Extension, what-to-do-about-wasps, Diane Alston – Jul. 19, 2013, https://extension.usu.edu/archive/what-to-do-about-wasps
- Oregon State University Extension, Protecting Honey Bees from Yellowjacket Wasps, Carolyn Breece, Dan Wyns, and Ramesh Sagili, https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9211.pdf
- Victorian Government, Department of Health, European wasps – pest control, https://www.health.vic.gov.au/environmental-health/european-wasps-pest-control
- CABI, Invasive Species Compendium, Vespula germanica (German wasp) datasheet, https://www.cabi.org/isc/datasheet/56667
Great article! Very helpful.