How to get rid of grubs in your lawn

June 23, 2015

If a patch of lawn is brown and spongy and can be rolled back like a carpet, it may be infested with grubs. Find out which grubs you need to watch for and what you can do to prevent, and fight, an infestation, if necessary.

How to get rid of grubs in your lawn

About grubs

Grubs are the larvae of the Japanese beetle, June bug, rose chafer and other beetles.

  • They are fleshy, grey-white, worm-like creatures about 2.5 centimetres long, with six legs and brown heads.
  • They curl into a circle when disturbed. Grubs live in the soil, feeding on grass and weed roots. Some species feed for one to three years before becoming adults.

Checking for grubs

To check for grubs, cut a square of sod about 10 centimetres  wide and lift it up.

  • If you see five or more grubs, that's enough to warrant treatment with milky spore disease, beneficial nematodes or an insecticide containing imidicloprid (which won't kill beneficial earthworms).

Controlling grubs

  • Another strategy is to water your lawn deeply but infrequently, letting it dry out between waterings.
  • Beetles like to lay their eggs in moist soil; a dry lawn surface will discourage them and is inhospitable to any existing eggs.
  • You also can use beneficial nematodes (Heterorhabditis spp.), which are microscopic parasites, to combat grub infestation. After you spread them on the lawn, they will begin infecting and killing grubs within a few days. Both controls are generally available from garden centres and mail-order sources.

Trap potato-eating wireworms

  • Trap potato-eating wireworms, which are the larvae of click beetles, by scooping out small holes in the soil in several places.
  • Toss in chunks of potato and cover with boards — the "nests" will attract swarms of wireworms.
  • Every few days, collect the infested potatoes and drop them into a pail of soapy water.
  • Wireworms like moist soil, so you can deter them by improving drainage with organic matter or sand. Or, plant mustard, buckwheat or alfalfa in late summer and turn it under in spring. These green manures repel the pests and condition the soil.

Set the chickens loose

Country gardeners may have a built-in pest fighter: the chicken.

  • Turn the soil, and chickens will eagerly scavenge for cutworms, wireworms and grubs.

Squash the squash vine borer

  • Find the worm's entry hole in the vine and poke a piece of wire inside to kill it, or slit the stem open and remove the pest.

Afterward, you can bury the wounded stem section of buttercup squash; it will often develop new roots. Butternut squash are resistant to squash vine borers.

Band fruit-tree trunks

  • Band fruit-tree trunks with corrugated cardboard to trap codling moth larvae as they move down the trees to spin cocoons.

Check for and destroy any pests weekly.

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