Damaging white grubs are the larvae of Japanese and masked chaffer beetles. In June they lay their eggs preferable in well maintained lawns because it gives their eggs the best chance for survival. Then in mid to late summer the eggs will hatch and the larvae will feed between right below the surface of the lawn severing the root system from the top growth.
The best way to protect your lawn is to treat for grubs preventatively because they can and will do extensive damage to your lawn before you even know you have a problem. The best time to treat is during early summer stress reducer application.