Lawn Chafer Grubs

When you do get your nematodes, you'll first need to water your lawn for 2 hours before you apply the dormant nematodes and again for 2 hours afterwards.  The idea is to get the nematodes to multiply (which they do on contact with water) and to drive them deep into the soil where the grubs live. That way you'll get the best bang for your buck, so to speak.  If you're getting a lot of rain, then hold off until you can control the watering or your nematodes will simply be washed away.

Here's more info on grubs: HERE and HERE