I still have 20, 15,000 ft2 lawns that I need to apply Merit/fert still. No rain in 21 days, lawns are non irrigated and no chance the homeowners will water fertilizer in after it is applied. I just need some rain so I can apply Merit so it gets watered in. How long to you think I have until my effectiveness window expires? I know that the grub pressure will be low since these lawns are non irrigated, just looking at timing-Thanks!