When should pyrethrum-based aerosols be used for arthropods associated with bats?

Using pyrethrum-based aerosols after the bats have departed is the appropriate course of action for managing arthropods associated with bats. This approach minimizes the risk of harming the bats, which are protected species in many jurisdictions, including California. Applying such pesticides while bats are present can alter their behavior, harm their health, or kill them, leading to ecological imbalances.

By waiting until the bats have left, it allows for a targeted pest management strategy that effectively reduces arthropod populations without interfering with the bats' activities or their habitat. This practice not only follows ethical and legal guidelines involving wildlife but also ensures that the application of pesticides is done safely and effectively without unintended consequences for the bats or the environment.

Timing is crucial in pest management, and ensuring safety for non-target species is a fundamental principle in environmental conservation efforts.