Grubs are a Beetle’s larvae. You will recognize them as white-colored worm, with a dark end. Grubs considered a delicacy amongst Raccoons, Crows and Skunks…
The beetles lay their eggs during June and July, which hatch towards the end of June early August. That’s when most of the damage is done to the lawn, and also the best time to treat against them.
The best (and legal) option to treat against them is with Nematodes – a microscopic worm “designed” to consume… Grubs. Nematodes are sensitive to heat and sun, and so best to apply them (mixed in water) on a rainy and cloudy day (not a problem in the Toronto area in August!).
The government of Ontario has a great web page with more detailed info on Grubs here.