As part of a horn fly control program many producers feed a loose mineral or some other type of supplement with an insect growth regulator (IGR) such as methoprene or diflubenzuron.

Insect growth regulators do not kill adult flies but will prevent larvae and pupae in the manure from turning into adult flies.

For insect growth regulators to be most effective, cattle need to consume a minimum dose for their weight on a regular basis. In many loose mineral supplements, methoprene is included at a rate of 0.010% or 0.014%; the higher rate is targeted for cows over 1,000 pounds.