Residual wall sprays last three to four weeks and are applied to areas where flies rest. Knock-down sprays supply a quick but temporary removal of flies from lots they must be used daily. Feed additives can be an option, however the active ingredients are deposited in manure, thus, they won t control flies developing in other breeding materials. These wasps attack and destroy flies. They ve been useful in poultry confinement buildings, however, their use in feedlots is somewhat limited.
Studies are underway to determine why they don t work as well in feedlots.
Using this method requires a lot of management, because a person needs to know where, when, how many and how often to release the wasps. It s probably not the most feasible choice for Iowa feedlots. None of the techniques listed have changed much over the past 20 years.