Our main grub problem is the Japanese Beetle larvae with a similar life cycle to our native grub larvae. Grub treatment is not warranted unless there are at least 10-12 grub larvae per square foot! This will only be evident in mid to late summer as you suggest. There has been a decline in grub populations due to the drought of 2012 and the harsh winter soil temperatures, so monitoring grub populations is key to knowing if a treatment is justified. Finally, the active ingredients now available last several months in the soil, so a spring application could be done. This may be an unneeded expense placing pesticides into the environment where no grub management is needed.