Horses don’t lie, right? So this one has to be true. Popcorn told me so! When covered in mud the flies are naturally repelled. Don’t belive me? When the flies were driving my old horse (19 yrs) Scrapper CRAZY I went into the pasture near the recently emptied water trough and painted him with mud over his rear where he must be extra tasty-look at the size of that biting fly! But he couldn’t get through the mud. I am thinking of creating a big mud spot in the turnouts and seeing what the horses do with it. What do you use for defense against flies in the summer?