Ask The Expert - How To Control Wasps

The superfamily Vespoidea is one of the largest in Australia with over 5000 species ranging in size from 1-40mm.

Its colours are usually bright with many black, yellow and orange combinations to give a warning that they possess a powerful sting and you should avoid them. Interestingly, only the females have a sting and the wasps have no branched or plumose hairs on any part of their body.

The superfamily Vespidae contains 324 species of mostly social wasps and is the best known group as it includes most major stinging pest species.

Looking inside the nest

Wasps live in large colonies underground or cavities in trees and buildings. Nests consist of a paper comb and envelope built inside a sub soil chamber. Each nest can have one to many hundreds of individual wasps.

The nest structure varies by species but usually consists of layers or combs which are sometimes spiralling. It can be covered by a layer of paper-like material to help protect larval cells from weather exposure.

The nest will have one fertilised queen and a population of workers (many of these suppressed queens). Adults feed on nectar but hunt caterpillars to feed larvae. Food is masticated and fed progressively to larvae in the nest.

They give a very painful sting when defending the nest and recruit other nest mates to join the attack via pheromone secretions.

First aid for a wasp sting

Painful stings hurt for several days. Apply ice to the sting site to reduce pain and swelling. Some victims have a hypersensitive reaction and multiple stings can cause a massive allergic reaction. In extreme cases, the heart may stop beating. If a victim suffers a known wasp allergy, apply the same first aid procedure as a snake bite i.e. the pressure immobilisation technique and get them to hospital.

Types of common wasp

The Vespinae are a Northern Hemisphere sub-family with two introduced species in Australia:

- Vespula germanica the European Wasp is widespread throughout Southern Australia.
- Vespula vulgaris is found in Victoria only.

Treatment steps

Start with a thorough inspection during daylight and look for secondary colonies that may exist close by. Wasps guard the nest or its entrance but are generally not aggressive unless disturbed.

For subterranean nests, the best approach is to disturb as little as possible. Investigate how big the cavity is that they are using as you must get an idea of how big the nest will be for effective treatment.

Always plan a safe retreat if things do not go well. Let everyone know what you will be doing e.g. advise neighbours to stay inside, shut windows and keep the kids safe. Erect warning signs if there is any danger to persons in the area (especially on public access land - like a park).

Effective treatment types

Wasps navigate by the sun so are typically home after sunset. This is the best time to kill wasps.  Depending on the species and the conditions, there are a number of effective treatments:

Dust Blower

For underground European wasp nests, place an electric dust blower into the nest entrance. Ensure a light application to as large a surface area as possible. Take your time to guarantee a thorough coverage of all nest combs. Use the air setting to clear away any visible signs of dust at the injection point. Be careful. Many agitated European wasps can emerge; they will be really angry and looking for a victim.

Insecticide spray

To treat paper-nest wasps or other wasps in an open space use an extension spray wand, safely increasing the distance between this stinging pest and you.

Highly active insecticides such as Cislin^™ 25 kill wasps rapidly so they will drop to the ground and not sting you in the process. The paper nest should be brushed down once the insects have died to prevent the attraction of other wasps to the pheromones of the original colony.

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