Description of Common 

Wasp & German Wasp

(Vespula vulgaris, Vespula

germanica)

Habitat
Temperate species forming nests in soil banks, roof spaces, wall cavities and trees. Nests formed of paper (chewed wood) and may become very large. Colonies only survive one season in UK, new ones started each spring by overwintered queens. Forage on wide range of foods including insects, spiders and sweet substances. May be aggressive if threatened.

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Biology
Egg – larva – pupa – adult.
Eggs – many 1,000’s laid by queen in hexagonal cells throughout spring and
summer.
Larvae – legless grubs within cells fed by workers on chewed insects, spiders. Develop in 4 weeks.
Pupae – develop in about 2 weeks within cell.
Adults – workers winged, 10-20mm long, distinctive black and yellow colouration. Queen winged, similar colouration but larger.

Importance
Nuisance, potentially more serious if nest in close proximity or within buildings. Widely feared for ability to sting which is painful and, very rarely, lethal. Potential disease transmission from feeding on rotting food materials. Also beneficial in killing many other garden insect pests.

Control
Consider whether necessary if nest well away from dwellings and sensitive
areas.
Control is easy if access to nest is good. Care necessary to avoid being stung ( PPE required - Bee veil, full face respirator, sting proof gloves ) .
Residual sprays or dusts on alighting areas or into nests. Bendiocarb very effective but also many organophosphates, pyrethroids.
Pyrethroid fast acting wasp destroyer aerosols (professional use only).

Distribution and Habitat

An indoor insect common throughout Britain and most of the world, with the exception of the tropics. Reasonably cold-hardy and associated with many natural products of animal origin, especially woven fibres, fur and feather products and fertilisers. Despite these food preferences, this species is not a frequent inhabitant of birds' nests.

Biology

The overwintering and fertilised queen wasp emerges from hibernation around mid-April and searches for a suitable site for her colony. From chewed bark and dried timber mixed with saliva she makes the initial "cell", which is smaller than a golf ball. Within individual chambers inside this cell she lays between 10 and 20 eggs feeding the resultant larvae on insects and other invertebrates. The emergent first brood of adult workers (sterile females) takes over the task of enlarging the nest and providing food for the subsequent eggs laid by the queen. By late summer, the normal wasps’ nest will contain from 3,000 to 5,000 individuals and be up to 30cm across. During the latter part of the summer males and young queens emerge, mating occurs, and the fertilised queens fly away to select suitable overwintering sites. With the onset of cooler weather the workers and few remaining males become sluggish, and their feeding on ripe and over-ripe fruit can produce a "tipsy" behaviour, leading to aggression towards anyone interfering with them. The onset of the cold winter weather kills off all the workers and the males, with only fertilised queens surviving individually in hibernation, to start new colonies in the following spring.

Old nests are not re-used although in favourable sites a new nest may be built in close proximity to an old one.

Importance

Although wasps visit dustbins, waste depots and dead animal bodies (carrion) and may possibly spread disease, they are mainly known for their nuisance value in late summer. Wasps in the earlier part of the year are too busy collecting insects to be a nuisance. Insects are caught in flight and have their wings chopped off by the strong mandibles of the worker wasps. Later in the season, as larval rearing is reduced, the workers search for sweet substances and can become a significant nuisance in homes, bakeries, fruiterers and especially jam and sweet factories.

Wasps can inflict a painful sting, a habit which increases as the insects become more irritable with the onset of cooler weather, and the ingestion of fermenting, over-ripe fruit juices.

In most cases the sting is no more than unpleasant although multiple stings and those in sensitive places such as the head region or inside the mouth may be more serious. In rare cases even a single sting may induce a condition known as anaphylactic shock (an extreme reaction to the toxins in the wasp’s venom) which, without rapid medical attention, can result in death within a short time. This only occurs in a very few hypersensitive individuals after sensitisation by a previous sting or stings. It is important to avoid being stung if at all possible and to be aware if the reaction to stings becomes more acute. Medical advice should be sought if increasing sensitisation occurs.


Control

In many instances the real or potential risk of stings and the annoyance caused by wasps will result in requests for nest destruction. Where they are located well away from buildings or sensitive areas it must be questioned whether "automatic" destruction of nests is necessary. Wasps also destroy many insect pests in gardens.

Wasps are generally easy to control using a number of commercial products if access to the nest, or near to the nest area, can be gained. Control of adults in flight alone is unlikely to exert significant control on an active social colony. The main aim should be to disable the nest by applying a residual insecticide to the nest entrance or nearby alighting area. Wasps entering the area should contact a dose of insecticide that will eventually prove lethal, allowing the inside of the nest to be contaminated. Faster acting treatment involving soaking the nest may also be possible using a liquid formulation.
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Locating Nests
Nests are frequently located in loft spaces, in cavity walls, behind structural cladding and in flowerbeds. Some nests are inaccessible and only fairly remote entrances can be treated. Treatment of a general loft space containing a nest is unlikely to be as effective as treating the nest direct. In addition, such treatments may present an unnecessary threat to bats which are protected under the Wildlife and Countryside Act.

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Dusts
In general, dust formulations applied to alighting areas or nest entrances are likely to be even more effective than liquid sprays. Again, they should be applied to entrance sites preferably using injection tubes.
Bendiocarb is the most effective chemical to use for wasps’ nests. Organophosphorus products will work but pyrethroids tend to overexcite wasps.

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Residual Insecticides

High-volume emulsifiable concentrate or wettable powder sprays may be applied to entrance sites.
Injector nozzles or specific crack and crevice nozzles can be used to improve penetration. Most residual sprays cleared for use against wasps if applied close to the nest entrance or in the nest itself. Care must be taken not to over soak the nest leading to dripping of pesticide onto the surfaces below and causing staining.

 

Aerosols

Directional jet spray aerosols containing both knockdown and residual pyrethroids are available for professional use. Most domestic type aerosol sprays based on pyrethrins / pyrethroids are not suitable for wasp control in view of their tendency to cause hyper-activity in their target.

 

Control of non-harmful Wasps and Bee species

Every effort should be made to avoid carrying out control treatments against non-pest wasp species and bees, because of their strongly beneficial role as pollinators and predators of garden pests.
Mason bees may need to be controlled on occasion but the real answer to the problems they cause is to re-point with good hard mortar.
 

 

Other Species

 

Hornet (Vespa crabro)

This insect is larger than the common wasp, at 19–35mm in length, and is banded in yellow and brown. It is in the same order (Hymenoptera) , and occurs locally in the southern half of England, and throughout Europe. The biology and life history of the hornet is similar to the preceding species, with only the young, fertilised females surviving the winter in hibernation to emerge in the spring and form new colonies. Despite its large size it is not particularly aggressive and because it is relatively uncommon should not be destroyed unless absolutely necessary .

 

Tree Wasp (Dolichovespula sylvestris), Norwegian Wasp (Dolichovespula norwegica)

These are two very similar wasp species occurring quite locally in Britain, with the Norwegian wasp being the dominant species in northern Scotland. They are slightly smaller than the common and German wasps but both are aggressive species. Fortunately, they nest in trees and bushes, seldom enter buildings, and only rarely come into conflict with humans despite their aggressive natures.

 

Giant Wood Wasp (Urocerus gigas)

This sub-order Symphyta of the order Hymenoptera includes the sawflies and the wood wasps. They are distinguished from the rest of the bees, wasps and ants in having no typical "wasp waist". The giant wood wasp is a very conspicuous insect approximately 5cm in length (including the egg-laying tube), with a shiny black thorax, a yellow band where the waist would be, a longer black band on the upper abdomen and the final three segments of bright orange-yellow. Even the legs are banded black and yellow. Although a fearsome-looking insect the wood wasp is quite harmless to humans, and the female uses her long rigid ovipositor to lay eggs inside freshly felled trees where the grub takes up to three years to develop. Occasionally, adult wood wasps emerge inside buildings from timber used in flooring and roof structures. Therefore, they most commonly occur in new premises within a year or so of completion.

 

Wasp Mimics
Hoverflies Syrphidae (a family of flies, Diptera) . Many hover flies are banded in clear yellow and black, sometimes with shades of orange, but are easily distinguished from wasps by their flight pattern: alternately darting and hovering. They have only one pair of wings, which may be folded when at rest, but are sometimes held out at right angles to the body. They have uniformly mid-brown legs, and no "wasp waist". They are the gardener's friends: their larvae are voracious eaters of green fly and black fly (aphids).

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