What are you interested in controlling ? the grubs or the beetles?
The grubs feed on underground plant tissues for a far longer period
than the adult beetles and milky spore works pretty damn well albeit
slowly at first.
Mind the imidacloprid if it gets into flowering plants it's very hard
on pollinators because it also gets into the nectar.
As for the beetles, traps and hand picking will beat the wholesale
application of pesticides.
Allowing your cool season grasses to go dormant tis time of year will
mean more beetles will lay their eggs in the lush green irrigated lawns
of your neighbors.
Cutting a test patch of turf and inspecting the soil for grubs is a
good idea, you really need to take no action below the presence of
about 10 grub/square foot.
I have no experience with benneficial nematodes but I hear there is
some control from them as well.