Ortho Home Defense MAX Insect Killer Granules starts to work after the application has been watered in.  How long it takes insects to die after they come into contact with a treated area will depend on a number of factors, such as the type of insect, the life stage of the insect, and how long the insect stayed in contact with the treated area.  It can take anywhere from a couple of hours to a day or so for the insect to die.