Wednesday, February 3, 2010

Wasp Stings and How to Avoid Them

Common and German wasp colonies increase in size through the summer and will peak over the next couple of months. Nests can contain as many as five thousand individuals by late summer and the nests can be the size of a beach ball. These shiny black and yellow striped wasps were accidentally introduced to New Zealand and have found the conditions here very much to their liking. In particular the honey dew in beech forests provides the workers with the high energy carbohydrate food to keep them active and wasp densities can become very high. Also the milder winters in New Zealand compared to their native European habitat means that some colonies can survive through the winter and produce huge nests the second year.

Nests of both common and German wasps are usually in underground cavities or holes in trees, but they frequently set up home in the roof voids or subfloors of houses and other buildings. The entrance to the nest can be identified by the stream of wasps entering and leaving in warm weather. There is almost always only one entrance/exit.

The sting of the wasp is painful and will cause redness and swelling. Wasps, unlike bees can sting multiple times. Some people are particularly sensitive to the stings and anaphylactic shock can result. Susceptible people should carry adrenalin for use in an emergency.

I have been stung many times in the past while dealing with wasp nests. Almost all the stings have occurred late in the season when wasps change their feeding habits towards higher levels of protein. Wasps will catch other insects, even catching flies on the wing. The change in feeding seems to make wasps more aggressive. Using liquid insecticides on wasp nests also has the effect of making the wasps angry. Powder type insecticides are recommended as they help to keep the wasps calm in a similar way to the smoke beekeepers use when handling their hives.

If a wasp lands on you try not to react violently. I appreciate that this is easier said than done but violent movement is only likely to result in a sting. Stay calm and move away from the nest, the wasp is likely to leave.

When controlling a wasp nest use powder insecticide such as NO Wasps Insecticidal Dust or Carbaryl Insect Control (aka NO Wasps Carbaryl). Use the NO Wasps puffer pack to pump the powder into and around the entrance to the nest. If wasp activity is high leave treatment until darkness has fallen and activity has dropped. Do not use the powder when it is raining or rain is due. Wet powder will not be picked up as effectively on the wasps to be carried into the nest.

If the wasp nest is in the eaves of a house it can be difficult to get powder in the nest if the wasps are entering via a hole under the eaves. In this case use NO Insects Carbaryl 80 as a spray and spray the areas where wasps are landing and entering.

NO Wasps powder is 4% carbaryl so that wasps do not detect it and will land on it and take it into the nest. Carbaryl 80 is 80% carbaryl and is effective where the wasps cannot avoid it when entering the nest.

Stay sting free this summer.

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