First year with a green house and for most of the summer, my plants have been covered in little black flies. These aren't aphids or "black fly" like you get on beans etc., these are more like fruit flies that fly around you when in the greenhouse. They are all over the soil on my sweet peppers which seem to be suffering the most with lots of little holes in them which then eventually make the fruit rot. Also have some bigger holes on my aubergines, but think this may be a slug that's hiding somewhere!! All other fruits - chilies, cucumbers and tomatoes - seem unaffected, despite the flies being all over the plants.
Does anyone know why I'm getting these flies?