Anyone know how to treat black fly without chemicals?

Something else you might consider is untreated Diatomaceous Earth. It is a natural insect killer. It is the little skeletons of microscopic diatoms. Apparently it scrapes the waxy protective coating on the insects shells and they dehydrate. They cannot become immune to it. It is completely harmless to humans. In fact some people take it orally for health. Apparently it is good for your digestive system. We used it last year and were pleased with the results in the garden. I haven't started using it on myself though. Treated Diatomaceous Earth is used in pool filters and you should stay away for that stuff. Make sure if you use this stuff you get the food grade variety.

I have crushed a couple of cloves of garlic into a spray bottle and let it stand for a few hours. I then sprayed the solution on to my roses beforethe black fly attacked them and they stayed clear of black fly and green fly. My neighbours roses were attacked as usual and he used chemicals. I then continued to spray them all summer and they came on really well. Once they flowered though, I didn't spray the garlic on the plants. I was afraid that the scent would be ruined by garlic, but I don't think I needed to worry though because I didn't smell garlic on those plants at all. - Derek

I've heard the same thing, also adding cayenne pepper to the mix, but I've never tried it myself.

I think washing the leaves gently with dishwashing liquid is the best that you can do. I guess that there are probably other ways to get rid of the problem but that is what I would recommend at this time. Most of the other solutions would involve chemical means.

Dilute washingup liquid is what I was going to suggest. I just put a tiny bit in water and squirt it in one of those plantsprays when the plants aren't in the sun. It seems to work with whitefly and greenfly anyway.

I guess it is very hard to kill black fly without chemicals but if you are patient enough you may keep the area clean so they will have no place to live in.

Try to have a habit of burning leaves at evening to let them have a smoke for them to flew away. Wash it with soap with water so that the blackflies will go out . Or get the house where they used to stay so that they will run away in the plants.

you may want to try hanging one or two of those sticky fly strips near your plants, they work really well. good luck.