You’ll need to apply Bayer 24 Hour Grub Control right away and water it in with a full inch of water from your sprinkler…don’t think a quick spray or rainstorm will do the job.  That will kill the grubs that are in your lawn now that you should’ve killed last year.  Then you’ll need to re-seed the area and keep it moist until the lawn is up and established…about 6-8 weeks.   Here’s a link about lawn seeding…it was written for end of season seeding but the procedure is the same.  Then you’ll need to treat for the grubs in July with Bonide Annual Grub Beater.  This will kill the grubs as they hatch in August and September.  This kills them before they do all the damage and you won’t ever need to treat in spring again as long as you continue the July treatments every year.  Here’s a blog post all about the proper time and way to treat for grubs.