Thank you for your questions.
Please follow this link for research-based information - http://www.extension.umn.edu/garden/insects/find/lawn-and-turf-insects/root-feeding/
Hope this helps.
With all due respect, you did not respond to my question. You just sent a link to a section of your website, which I had already read. Should I treat the grubs in mid June or mid July? What is a good product to use?