The Mantis 10 x 17 Glue Board (Pack of 6) (Boacha 850) does not contain any chemicals.
The Mantis 10 x 17 Glue Board (Pack of 6) are replacement glue boards for the Mantis 1x2 and the Uplight Sconce fly light systems and would would be good choices for horse fly control.
Per the manufacturer, good structural exclusion practices are effective (such as serviceable screens and a "no open door policy"). However, once inside, horse flies would be attracted to properly placed insect light traps. On the exterior, the Titan 200 IP could be placed to attract flies away from the structure or intercept flies before reaching the structure.