By Philrenshaw
United Kingdom 
We have a grape vine growing on the side of our house. It has become infested with flies such that when we walk past it you are hit by a swarm of flies buzzing around you all the way along which is very unpleasant. Does anyone know of a product that will kill the flies without damaging the vine? (Standard fly spray states that it should not be used over plants.)
30 Jul, 2010
Answers
Good question. We have had the problem at the same time of year for a couple of years, but this year it is particularly bad. The flies seem to be all the way along the vine/the wall as well. The grapes are growing extremely well - they never turn into proper edible ones as we do not get enough sun, but they are looking very good.
30 Jul, 2010
Just answered another question about a hedge which can't be cut because its covered in flies and wasps, with no apparent reason for it. Very weird, perhaps there are just more of them about this year - what are they doing on the vine, are they on the fruit or what?
30 Jul, 2010
They are not on the fruit at all. Rather they are on the leaves. They also seem to be both on the newest and oldest leaves and range from small to large flies.
30 Jul, 2010
How very unpleasant - must be something about the plant that attracts them - I'd be inclined to have it out and plant something else.
1 Aug, 2010
If your vine has been in place there for a while, and you've never had this problem in other years, it might be better to investigate why they're gathering - is there a dead bird or a corpse of some kind in there that's attracting them, for instance.
30 Jul, 2010