Big humongous horse flies--the size of small mice--are attacking my horse. I've used all kinds of fly sprays and they still go after him. I was thinking about trying one of those fly nets that goes over the rump. I'm concerned about attaching it to my Bob Marshall treeless and wonder about the crupper under his tail. Anyone use one of these or have any other suggestions? Thanks in advance. 

Like anything they need to be introduced to in in a safe enviroment such as a round pen would be my suggestion and maybe a stall.  But personally I need fly protection under the belly and legs were we ride...and what I've seen of those not user friendly under saddle.

Yesterday at a show there was one of those mouse-sized horseflies on Love. I sat spraying it with flyspray for at least 5 sprays, turned to stream, not fine mist, and it just sat laughing at me! I use some oil base in my mix and I think it finally started suffocating before it decided to fly off. I also see them munching on Zan with flysheet on all the time, but tho he may be retired from back leg issues he is still so flexible that he just swings his head around to knock them off. They are so nasty!

Okay, that's not going to be good then since he's green and I'm just coming back from an injury and haven't ridden for many years. "User friendly" would probably not be a good idea. 

Yikes. Munching on him right through the fly sheet. That's bad. I'm trying to figure out how I can ride this morning with them out there.... what can I put on him? Someone mentioned to me smearing his rump with poultice....

Yep it has been black bomber season in Jersey for weeks.. Nothing keeps them off. My method is get on and trot - don't walk or stop. 

If one lands quickly take ball cap (or hand) and try and kill it before horse tries to unload.  Other option is to ride after dark or hot sun. Seems like early and late day is the worst time for them.

Put a cow fly tag in his tail up by the tailhead.