It's important to have your perimeter pests checked and treated on a regular basis. The frequency of treatment depends on the type of pest and the level of infestation. For example, if you have a problem with mosquitoes, you may need to have your perimeter treated monthly. For termites, quarterly treatments may be sufficient. Ants and spiders can usually be controlled with bi-weekly treatments. If you're not sure how often to have your perimeter treated, ask your pest control professional for recommendations.