flies

Question: I have an office building that has been infested by cluster flies. We've had exterminators out who have sprayed, this did not help. We have purchased two fly machines with sticky papers, this is collecting some flies but not solving the problem. Tenants are still being bugged. Do you have any suggestions?

Answer: Our company does not run across this problem too often but I have done some research that you may or may not already know. Cluster flies enter structures during the fall in order to over winter. They will typically occupy attics and wall voids which receive the most sunlight. They are also known to use the same structure year after year to over winter.

The best method of control is a preventative spray to the vertical walls on the outside of the building before they have a chance to enter the structure. Timing of the preventative spray is very important and depends on your location. Since the flies are already in your building, this preventative treatment will not help you this year but you may want to consider it for next year.

You have already taken some steps which can be helpful. Some other methods involve sealing openings in light fixtures and any other openings which can give flies in the attics or wall voids access to your rooms. This could be very time consuming and expensive. Another method involves space sprays (fogging) the rooms, attics and even in the wall voids that the flies occupy. Since the flies do not reproduce indoors, this could be an effective way to eliminate a large percent of the current infestation. Dead flies can attract dermestid beetles so be sure to vacuum any flies you can reach after the treatment.