Finding a European wasp nest is relatively easy because of two factors:
- they fly in a straight line from feeding to their nest; and
- they are a bit smarter than flies.
When you have a nest within a few hundred metres you will have plenty of them visible in the garden. They're on the lookout for water and food. So the idea is to give it to them and then follow them back to the nest. You may be lucky enough to get a line of flight from something they're already feeding from, e.g. a bird bath.
More likely, you'll need to provide a feeding point and also slow them down a bit at takeoff so you can see which direction they head. This is where the flies come in.
Get hold of one of those fly traps that you half fill with smelly stuff and water in which the flies drown. Get one of the cheap and nasty ones as, in this case, you actually want some wasps to escape from it.
Instead of using the fly bait, half fill your trap with water and dissolve about 5 heaped dessert spoons of sugar in it. Then hang it in a tree or on a fence where you can keep an eye on it. Then go and do whatever it was you were doing; just come and have a stickybeak at the trap every couple of hours.
After a while the word will get around and you'll find wasps in the trap filling up on syrup to take back to the nest. Some of them will drown, but some will (possibly after a couple of days, possibly sooner) manage to get out. As they find their way out they'll stop and then take off, flying in a fairly straight line towards the nest.
You probably won't be able to follow them all the way: they're pretty small and they fly pretty fast. So move your trap about a hundred metres along the line of flight and hang it up again, then come back in an hour or so and watch where they're flying. If they are still flying in the same direction then move the trap another hundred metres down the line.
Sooner or later you'll find that the wasps are flying in a different direction. What that means is that you've passed the nest and you're getting closer. Where the first line of flight and the new line of flight cross is where you'll find the nest. If you want to get another bead on it, move the trap again and get a third line of flight.
Be careful as you move towards the intersection of the lines of flight.
Mostly the nest opening is a small (about 5cm diameter), unobtrusive hole in the ground, often within a few metres of a fence. But it may be above ground, e.g. in a tree. There will be lots of wasps coming and going from it. If you tread on or stumble into the nest you're likely to get stung. If you watch where you're going and keep your ears open for the hum of lots of wasps buzzing, you'll find it without too much bother.
Mark the location and go and call an expert to kill the nest. Alternatively, if you are a licensed wasp killer, go back to the house and tape some red cellophane over a good torch, locate your permethrin-based ant dust and fill in the rest of the day doing what you do. When it gets dark, find your way back to the nest with your red-light torch and give the nest opening a good couple of puffs of the dust.
Job done. The dust works like a charm and kills just about every wasp in the nest. To be sure, go back the next day and have a look. If there's any sign of life, go back at night and give it another puff. Leave the rest to any passing echidna, who will be your friend for life.
You may now resume barbecues and other outdoor work and recreation. If it all happens again next summer, return to the top of the page and start again.