August and September is wasp season in Berlin. This is the time they fling themselves into our food and wine glasses, and generally make a nuisance of themselves at many of Berlin's outdoor restaurants and cafes. I've been stung a few times; and you might think that I hate wasps, but I'm one of their staunchest defenders. You see, wasps eat caterpillars, aphids, spiders, and other things that wreck havoc in the home and garden. They also pollinate food crops and flowers. Moreover, recent research has found that a wasp's venom could cure leukemia, prostate, and bladder cancer. Their venom contains a chemical that selectively targets and destroys tumor cells without harming healthy cells!
If wasps are a problem, one way to discourage them is to burn used coffee grounds. I've seen this done at a few places and it seems to work. The smell is slightly unpleasant but it keeps these troublesome guys far away.