One of the most asked gardening questions on my website is "How do I control grubs in my lawn?"  Time was (not that long ago) there were chemicals available on the retail market for this purpose.  Now we apply dormant nematodes.  They are microscopic sized insects that feed on the backs of the grubs.  You purchase nematodes from a bar fridge at your local Home Hardware or independent garden retailer.  
Mix them with water according to directions and spay evenly over your entire lawn, concentrating on the infected areas.  
Be sure to water your lawn for 2 or 3 hours before you apply and 2 hours afterwards.  This will drive the nematodes deep into the root zone of your lawn where the grubs are most active."
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