The Asian paper wasp (*Polistes chinensis*) is an invasive species in New Zealand, characterized by its slender body, long legs, and distinct umbrella-shaped honeycomb nests often found on eaves and fences. To control them effectively, homeowners must locate the nest, apply a targeted insecticide dust or spray during low-activity periods (dusk or dawn), and physically remove the structure to prevent recolonization.
Understanding the Asian Paper Wasp in NZ
In the pest control landscape of New Zealand, and specifically within the humid, temperate climate of Auckland, the Asian paper wasp has become a formidable nuisance. First recorded in Auckland in 1979, this species has spread rapidly across the North Island and parts of the South Island. Unlike the bulky, aggressive German or Common wasps that often nest underground or in wall cavities, the Asian paper wasp prefers the open air, building its home in places that bring it into direct conflict with human activity.
While they are generally less aggressive than their Vespula (yellowjacket) counterparts, they are far from harmless. Their sting is painful and can trigger allergic reactions. Furthermore, their sheer numbers in urban environments can make outdoor living spaces unusable during the peak of summer. Understanding their behavior is the first step in reclaiming your property.
Identification: Spotting Umbrella-Shaped Nests
Correct identification is critical before attempting any form of pest control. Mistaking a paper wasp for a honey bee or a German wasp can lead to ineffective treatment methods or unnecessary harm to beneficial pollinators.
Physical Characteristics
The Asian paper wasp is relatively easy to distinguish if you know what to look for:
- Body Shape: They are more slender and longer than Common or German wasps. When flying, their long back legs trail noticeably behind their body.
- Coloration: They feature black and yellow bands, similar to other wasps, but often have a more brownish or reddish hue on the antennae and wings.
- Flight Pattern: Their flight is often described as “lazy” or hovering, with legs dangling, unlike the frantic, direct flight of Vespula wasps.
The Tell-Tale Nest
The most definitive sign of an infestation is the nest itself. Unlike the football-sized, paper-mache enveloped nests of German wasps, the Asian paper wasp builds a single-comb nest that resembles an inverted umbrella.
- Structure: The nest consists of a single layer of hexagonal cells opening downwards. There is no outer protective envelope; you can see the white larvae capped in the cells directly.
- Attachment: The nest hangs from a single stalk (petiole), usually attached to a solid surface.
- Size: These nests are generally small, ranging from the size of a golf ball to a saucer (up to 10-15cm in diameter), though multiple nests can be found in close proximity.
Why They Build on Eaves, Fences, and Shrubs
Homeowners in Auckland often wonder why their property has been selected as a breeding ground. The location of these nests is not random; it is driven by the wasp’s biological needs for warmth, shelter, and building materials.
The Search for Warmth and Shelter
Paper wasps are heat-loving insects. Eaves, soffits, and north-facing fence lines absorb and radiate heat, acting as incubators for the developing larvae. The overhang of a roof eave provides the perfect shield against New Zealand’s unpredictable rain, keeping the paper nest dry. If the nest gets wet, the paper pulp (made from chewed wood fibers and saliva) can disintegrate, destroying the colony.
Access to Building Materials
The term “paper wasp” is literal. These insects scrape wood fibers from weathered fences, deck posts, and unpainted outdoor furniture to create the pulp for their nests. If you have an older wooden fence or a timber deck, you are providing a convenient quarry for the queen and her workers. This is why nests are frequently found attached directly to the very fences they are harvesting from.
The Impact on Auckland’s Ecosystem
While the primary concern for most homeowners is the risk of being stung, the Asian paper wasp poses a significant threat to New Zealand’s biodiversity. According to Manaaki Whenua – Landcare Research, these wasps are voracious predators of invertebrates.
They feed their larvae a diet rich in protein, which they source by hunting caterpillars. While this might sound beneficial for pest control in a vegetable patch, they do not discriminate. They are a major predator of the Monarch butterfly caterpillar and other native species. A high density of paper wasps in a garden can result in a “silent spring” effect, where native butterflies and moths are decimated.
Effective Treatment for High-Up Nests
Treating Asian paper wasp nests requires precision. Because they often nest high up on second-story eaves or deep within dense hedges, simply spraying a can of fly spray is often ineffective and dangerous.
Timing is Everything
Never attempt to treat a wasp nest during the heat of the day. During the day, the workers are out foraging. If you destroy the nest while they are away, returning wasps will hover around the area in an agitated state for days. The best time to treat a nest is at dusk or early dawn. At these times, the entire colony is on the nest, and their activity levels are low due to the cooler temperatures.
Chemical Control Options
There are two primary methods for chemical control:
- Insecticide Dust (Carbaryl or Permethrin based): This is often the most effective method for nests in cavities or dense vegetation. The worker wasps walk through the dust and carry it into the nest, contaminating the larvae and the queen.
- High-Velocity Aerosol Sprays: For hanging nests under eaves, a specialized wasp killer spray that shoots a jet of up to 4-6 meters is ideal. This allows you to maintain a safe distance. The spray kills on contact and often leaves a residual that discourages returning wasps.
Handling High-Up Nests
Nests located on second-story eaves pose a fall risk. Do not use a ladder to treat a wasp nest if you can avoid it. If the wasps attack while you are on a ladder, the panic can lead to a serious fall. Instead, use an extension pole with a duster attachment or a spray can actuator. If the nest is unreachable from the ground, it is strongly recommended to hire a professional pest control service.
Safety Protocols for DIY Control
If you decide to tackle the infestation yourself, strict adherence to safety protocols is non-negotiable. Wasps release an alarm pheromone when threatened, which signals the rest of the colony to attack.
- Protective Clothing: Cover as much skin as possible. Wear thick, long-sleeved shirts, long trousers tucked into socks, gloves, and a hat. A bee veil is highly recommended to protect the face and neck.
- Escape Route: Before you begin, plan your escape. Ensure the path is clear of tripping hazards like garden hoses or children’s toys.
- Lighting: If treating at night, use a red filter on your torch. Wasps cannot see red light well, whereas a bright white beam will attract them directly to you.
- Do Not Crush: Never swat or crush a wasp near the nest. Crushing them releases pheromones that trigger an immediate attack from the colony.
Preventing Nest Rebuilding and Future Infestations
Eliminating the current nest is only half the battle. Asian paper wasps are notorious for returning to the same favorable sites year after year. Prevention requires a multi-faceted approach.
Remove the Pheromone Trail
After a nest has been successfully treated and all activity has ceased (usually 24-48 hours later), knock the nest down. Dispose of it in a sealed bag. Importantly, you must scrub the area where the stalk was attached with soap and water or a mild bleach solution. Wasps leave chemical markers at the nest site; if these are not removed, new queens will identify the spot as a prime location next spring.
Physical Barriers and Maintenance
Seal cracks and crevices in eaves and soffits where wasps might anchor their nests. Regular maintenance of fences—painting, staining, or oiling—can also deter them. Wasps prefer weathered, raw wood for pulp gathering. By sealing the wood, you make it difficult for them to harvest building materials, forcing them to move elsewhere.
Trapping Queens in Spring
The most effective long-term control is catching the overwintering queens when they emerge in early spring (September/October in NZ). Placing wasp traps early in the season can capture the foundress queens before they have a chance to establish a colony. Every queen caught in spring represents one less nest in summer.
When to Call an Auckland Pest Control Expert
While many homeowners handle small, accessible nests, there are scenarios where professional intervention is required. If you are allergic to stings, the risk is simply too high. Furthermore, if the infestation is extensive (multiple nests), or if the nests are located in confined spaces like roof voids or wall cavities, professional equipment is necessary.
Professionals have access to potent, industrial-grade dusts and motorized application equipment that can penetrate deep into cavities, ensuring the destruction of the entire colony. For reliable information on pest management standards, resources like the Department of Conservation (DOC) provide guidelines on invasive species management.
People Also Ask
Are Asian paper wasps aggressive?
Generally, Asian paper wasps are less aggressive than German or Common wasps and will not usually attack unless their nest is disturbed. However, if they feel threatened, they can deliver a painful sting which may cause allergic reactions in some people.
What is the best time of day to spray a wasp nest?
The best time to spray a wasp nest is at dusk or early dawn. At these times, the wasps are less active, their vision is poor, and the majority of the colony is inside the nest, ensuring the treatment is most effective.
Do paper wasps return to old nests?
No, paper wasps do not reuse old nests. However, they will often build a new nest in the exact same location if the area provides good shelter and the scent (pheromones) of the previous nest remains.
How do I stop wasps from building nests on my house?
To prevent rebuilding, remove old nests and scrub the attachment site with soapy water to remove pheromones. Painting or staining wooden fences and furniture also reduces the availability of wood pulp, which they use for construction.
What do Asian paper wasps eat?
Asian paper wasps feed on nectar and honeydew for energy, but they feed their larvae protein in the form of invertebrates. They are major predators of caterpillars, including those of the Monarch butterfly.
Can I use water to remove a wasp nest?
Using water (like a hose) is not recommended. It often fails to kill the wasps and instead makes them extremely aggressive. It can also damage the building materials of your home. Chemical control or professional removal is safer.