Any residual pesticide that contains permethrin is ideal for eliminating cluster fly infestation. This pesticide can be applied outside with a sprayer to eliminate cluster flies from entering and laying eggs.
Along with permethrin, sprays that include lambda-cyhalothrin have been shown to help eliminate cluster flies. The best time to spray pesticide for cluster flies varies depending on region, but is generally between the end of August and the beginning of September. During this time, the flies move indoors to lay eggs. To prevent this, the outside of the house should be sprayed around window seals, under the awning and around doorways.
It is important to seal any entry points into the house. Sealing cracks and windows should be done during the summer when any dormant eggs have already hatched. If not, any flies that have not yet hatched will be forced to find their way into the house.
For infestations that are already occurring, it can be necessary to use a chemical "fogger" or "bug-bomb". This process is used as a last resort, as it requires all residents to evacuate during the extermination process. In such cases, it is best to try the use of electronic fly traps or homemade fly traps constructed of finely powdered eggshells. This method is simple and requires no electricity, but can take a substantial amount of time to do the job.