We were at a Turf Seminar earlier this year Sponsored by Landscape Ontario. Pam from the Guelph Turfgrass Institute and OMAFRA presented her research findings on nematodes. Under her laboratory conditions she was getting 50-60% control of the grubs. (Okay it is an outdoor laboratory, but the conditions are somewhat controlled and everything is done according to specifications.)
So under real life conditions, we are are going to be lucky to get 50% control.
And we have found that nematodes take 4 weeks or more to kill the grubs.
Unfortunately, sometimes the skunks and raccoons will dig up a lawn even if the midnight buffet is not a plentiful as it was before.
If we remove soil, will we be getting rid of some grub eggs?
There is not benefit in terms of grubs to removing soil. Grub eggs are laid in the lawn in June-July. Any that did not hatch last year are no longer viable. When the adults lay eggs this summer there is no way of knowing which spots they will decide to lay their eggs.
On the other hand, if the lawn is too high and needs to be re-leveled, or lowered or even raised up with more soil, this may be an opportune time to re-grade the level of the lawn.