It is recommended to apply Tick Killz starting early spring to early winter for the best protection from mosquitoes, fleas, ticks, and other pests. Apply every 3 to 4 weeks to continue to protect your lawn as this interrupts the pests' gestation cycles. Since Tick Killz is an organic pesticide, it will break down with the weather, so if you get a heavy rainstorm, you may need to reapply the product. Refer to the application instructions for more details.