Grub insecticide for lawns 5000 sq ft. Prevent grubs from damaging your lawn with Scotts® GrubEx®1 Season Long Grub Killer. A single application can stop and prevent grubs all season long. Apply during spring or early summer to kill grubs as they develop. Using Scotts® GrubEx®1 Season Long Grub Killer annually can also help control Japanese beetle infestations. Easily apply with a Scotts® broadcast, drop, handheld, or Wizz® spreader and stop grubs before they damage your lawn.