One of the most gradually destructive threats to dense, healthy lawns is a bug called the “grub.”

Grubs aren’t a particular species of bugs but rather the larval stage of various beetles. They live underground and feed on plant roots before morphing into adult beetles that fly, mate, and lay eggs in the ground that turn into the next round of grubs. These grubs love to feast on grass roots, causing unwanted damage.

Grubs are the ground-dwelling larval stage of beetles and like to feed on grass roots.
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Japanese beetle grubs are prolific lawn-killers east of the Mississippi, but larval (grub) forms of the masked chafer beetle, European masked chafer beetle, and Oriental beetle also commonly cause lawn damage. The grubs themselves are fat, creamy-white, curled, worm-like bugs that do most of their grass-root-eating in late summer to early fall and again in spring before emerging from the ground in early summer as beetles. Their telltale damage is when turfgrass browns and pulls up like loose pieces of carpet. The problem is that the damage usually isn’t apparent until the lawn patch is already dead and the grubs are big, well-fed, and harder to kill.

Preventing grubs

If you’ve had grubs and don’t want to repair a damaged lawn again, the most effective option is applying a "grub preventer". These are granular products that are broadcast over the lawn and watered or rained in so the grub-killing chemicals are active in the root zone as the new, young grubs hatch. That means grub preventers need to be applied at least a few weeks before beetles lay new eggs. That translates into June applications in most of the U.S.

Another positive of grub control products is that they will kill other turf-damaging insects as well, such as armyworms and sod webworms. Be sure to check both the product package label or your county extension agent to be sure any grub-control product will be compatible with your lawn. Of course, the best defense against a grub infestation is a healthy, vigorous, well-watered lawn.