Not tried them , but am experimenting with two trials this year.
First is the use of two spiderrs who have webs stretching across the
greenhouse, and catch loads of flies,(including me)
The other is the use of citronella candles in the form of tea lights.
Touch wood, no aphids so far, except those caught up in webs.
regards
Cineman

"Easynews" wrote in message
...
Lots of people seem to use parasitic flies to keep greenhouse aphids under
control these days- has anyone experience of using these, and how
effective were they?
Paul D