I don't know about anyone else but I've been really struggling with blackfly this year. Even though the weather has been so cold until recently, the blackfly have been prolific since the last week in May. Unchecked they suck the life out of the growing tips of anything they swarm on. I've been using washing up liquid in water to control them, not being a fan of chemical treatments. You have to spray every few days to keep on top of them but it definitely does the job (it blocks the holes they breath through I believe). I use about 3 times more washing up liquid than I do when washing up, seems to be about the right amount.