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Wasps represent a danger both to residents and visiting contractors. Contractors visiting premises often encounter them in confined spaces like lofts, lift motor rooms and gardens. This can delay essential works and lead to serious accidents. Residents too can encounter problems when they nest in air vents or fly into buildings when attracted by lights at night.

Biology

Wasps are omnivorous, feeding on fallen fruits and nectar but mostly catching other insects like greenfly early on in their life cycle. Queens emerge from hibernation in the spring to build new nests. Initially the queen lays 10-20 eggs. When they hatch into larvae she will feed them until they become workers. The workers forage for food, feed the new larvae and defend the nest against predators. A nest may contain thousands of workerwasps.In late summer the colony produce males and new queens, which fly away and mate. Only the fertilised queens survive winter hibernation.

 Behaviour

Wasps are not normally aggressive. However, they become more aggressive if interfered with, as a result of overcrowding and high temperatures. A wasp’s nest is 5-10°C above the outside temperature. In summer thetemperature inside a nest can be very high indeed. Slight irritation can cause an aggressive response. The stingof a wasp is a modified egg laying device. The male wasp is unable to sting. The base of the sting is a venom-containing sac, containing a pheromone (a chemical scent signal acting as an alert to other wasps in the area).

 Treatment

Wasp’s nests are treated with an insecticide dust, which is lethal. It does not work instantly. The wasps take a few days to die. The nest will disintegrate by itself and the insecticide used will evaporate away after a few daysleaving behind a chalk carrier dust only. The nest does not need to be removed since wasps never use them twice.

 Access

Good information from the managing agent is necessary to carry out a treatment. A key component of costs is access to the location needing treatment.