Join Date: May 2012
Location: CT USA an English transplant
They do seem to work on cluster flies but not the deer fly/horse fly or early biting black fly (flying sharks) which are plaguing us already - sprays, fly sheets and fly hoods seem to be the only defense against them and even then not 100% or even close
The deer & horse flies send my lot hysterical, they cause really nasty wounds that easily get infected and can transmit diseases so best avoided. I find the weathers too hot by then for the fly sheets and the ******s crawl under them anyway and makes things worse. They seem to like damp areas (breeding grounds for them) and trees so if your grazing incorporates those things which mine does it just makes the problem worse
I find the only thing I can do is keep an eye on the horses and as soon as they show signs of 'winding up' I stable them and put them back out in the evening
It is possible to spray pesticides around their hang out spots but that's going to also kill 'nice bugs'.