Preen has long been the smart gardener's secret weapon against weeds. It stops weeds before they start. It stops them when they're seeds. Preen Weed Preventer plus Ant, Flea and Tick Control also contains a powerful insect killer. It kills invasive ants on contact. It kills biting fleas before they can lay eggs or infest your home. It kills the ticks that may transmit Rocky Mountain spotted fever and Lyme disease.