Wasps seem to come to life in the spring and die off in late autumn. Unlike bees, they build new nests (aka "bykes" or "bikes") each year. They never use an old byke and the presence of an old one doesn't, of itself, encourage them to use that place again, but what encouraged them to build there in the first place (e.g. proximity of fruit trees) may well still be present. You may have to address this for a complete solution.
The size of the bykes can vary wildly from that of a golf-ball to that of a football. The larger ones can house tens of thousands of wasps. During the winter, the byke will be empty - the queen away hibernating somewhere warm and the workers all dead - so dealing with that [old] byke achieves nothing - indeed, some say that they make very good insulation.
On the other hand, sealing the hole they were getting in by will give that place one less tick in the `Which Byke?' guide. Note that, if the hole is needed for ventilation, some suitably-sized mesh could be used.
In Defence of Wasps
You should think twice before getting rid of a byke unnecessarily as the wasps are hard working gardener's assistants, eating insects, caterpillars and other nasties. You may be well to actually encourage at least one byke about the garden (though not in the house) as they do a fine job of culling greenfly and the like.
Dealing with Them
There follows various ways of dealing with bykes once found. In the DIY section, inclusion does not suggest suitability.
- Professional Exterminators Typically they will come and remove the byke and spray powder insecticide around. This may cost up to UKP 50 +.
- The Local Council Phone the council pest control people and they'll send someone to deal with it. Cost varies from place to place, with some places even doing it free of charge (which sounds like a very good deal to me if it's on offer) but this is getting rarer.
- Your local Angling Club Contact the secretary of your local club. They use wasps as bait and will often come and remove the byke for you free of charge.
- Laisser Faire - If it's late enough in the season and you can stand it, just leave them be. Once the season is over (no more wasps), block the entrance hole (see above) and hope for the best - it worked for me. However, some people are allergic to wasp stings, so this may not be a valid option. For the other methods you need to be able to see the byke, and you need to be active when the wasps aren't, i.e. when it's cold and/or after dark. Some claim to have done this often without once getting stung! But be careful, protect all areas of skin especially the face. Multiple stings can be potentially life-threatening. Whatever you do, don't be a hero!
- Obtain a powder treatment like "Wasp Nest Destroyer" (by Bio). Bearing in mind the precautions above, puff the powder on the entry to the bykes. One application should suffice. An ant-killer powder may be just about as effective.
- You should be able to get an aerosol spray or non-aerosol liquid jet (c. UKP 5) from your local garden centre. Bearing in mind the precautions above, spray the concoction on the byke itself. With the liquid jet you may not have to get any closer that 15ft depending on your ability to aim.
- You can also get an aerosol that emits a freezing blast and literally freezes and stops them in mid flight. You can direct the same product into the byke too. You've still got to kill them but it may give you a breathing space and allow you to do the deed during daylight.
Pedalling the `Byke' Word
uk.d-i-y poster Andy Dingley enlightened (some of) us: "Etymology is unknown, and although it originally applied to wild bees (not a hive or skep of cultivated bees), it also has a long pedigree of application to nests or swarms of wasps, hornets and even flies."