We don’t sell that product but I’d suggest following the directions on the label.  This would be a good question for the people at the place where you purchased it.  We sell Bonide Annual Grub Beater which should be put down and watered in with a full inch of water during the second two weeks of July.  Applied properly and watered in immediately after application Grub Beater will kill over 90% of the grubs that hatch during August and early September.  One application every July is all that is needed.  HERE’S a link to more on grub control.