Not GREENFLY control, although they're a pest as well. I'm talking about fruitflies, mainly. I left a bag of rhubarb in the kitchen when we went away on holiday and when we got back the kitchen was full of fruitflies. I don't really want to use poison to eliminate them, so instead I got rid of the rhubarb and anywhere else they could live, such as the compost bucket, and hung up flypapers.
If you're not familiar with flypapers, they're incredibly sticky strips that you hang up. As soon as a fly blunders into one, it gets stuck for good. Frankly, they're a bit gross, but they're better than having flies everywhere.
One final thing - under no circumstances allow small children to "help mummy with the dusting" anywhere near them. Last year Sam was playing with my genuine ostrich feather duster and got it tangled with the flypapers. By the time I had cut all the sticky bits off my duster, it was so badly maimed I was forced to do the merciful thing.