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Lawn grubs – is your lawn under attack?

Feb 8, 2018

Tell-tale signs of infestation and treatment for lawn grubs

The warmer months of the year are the peak time for invasion of your lawn by lawn grubs. Find out the tell tale signs of lawn grub attack and how you can rid yourself of these pests before they do too much damage.


There are several types of pests that are commonly referred to as ‘Lawn Grubs’. It is worth noting that Fescue, Kikuyu and Couch grasses are more susceptible to major damage from infestations of lawn grubs, while buffalo species including Sir Walter Buffalo are more tolerant to infestation and will spring back from any damage far better than other grass varieties.


Root feeding grubs are the larvae of various species of scarab beetles, including Japanese beetles, June ‘Bugs’ or cockchafers. Often referred to as white curl grubs, they have a soft, C-shaped body with legs near the head. They are sometimes incorrectly identified as witchetty grubs. Root feeding grubs live under the surface of the soil, feeding on the roots of the grass (and organic matter in the soil), resulting in damage to the structure of the lawn and causing sections of the lawn to die. The grubs are most prolific during the summer months, before becoming adult beetles over the cooler months. They emerge from soil to mate and lay eggs during Spring which hatch into more grubs – and so the cycle continues.


Surface dwelling lawn grubs are the larvae of moths, and include species such as sod webworm, armyworm and cutworm. These caterpillar-like grubs feed on the leaves of the lawn during the night causing damage to the surface of the lawn which may present as brown patches.

Grub types

  • Root feeding larvae
  • Surface dwelling grubs


There are several tell tale signs that may alert you to lawn grub activity.


The presence of small white/grey/brown moths hovering just over your lawn or garden beds in the early evening can be an early sign of surface dwelling grub infestation. These moths target the best, healthiest lawn in the street and lay their eggs en masse. Within 2–5 days the eggs become caterpillar-like grub larvae and start their attack on the lawn. For the next 18-24 days these grubs will feed on the grass, before becoming pupae and then egg laying moths within the next 2 weeks; ready for the cycle to begin again.


Lawn grubs are a tasty treat for birdlife. An increased presence of birds on your lawn during the evening when the nocturnal grubs are emerging, or early in the morning, can be a sign of lawn grub activity.


The activity of root feeding grubs will create spongy patches in the lawn. In some cases, the lawn will even be able to be rolled back like carpet as the root structure anchoring it to the soil has been removed.


An infestation of root feeding or surface dwelling lawn grubs may result in brown irregular shaped patches within the lawn. This will be particularly evident as your lawn comes out of it’s winter dormancy.


  • Increased moth activity
  • Identifying lawn grub activity
  • Increased moth activity
  • Increased bird activity
  • Spongy texture
  • Brown patches


Due to the relatively short life cycle of lawn grubs it is important to treat the problem as soon as possible.

LSA Grub Guard is a fast acting and highly effective treatment for lawn grubs. Because surface dwelling lawn grubs emerge from the soil to feed at night, the most effective time to apply the treatment is in the early evening. To ensure the treatment soaks deep into the soil where root feeding grubs reside, it is important to water the treatment into the soil.

Due to the short lifecycle of the grubs, a second application 2 weeks after the initial treatment is recommended.  This secondary treatment will ensure any moths, beetles, eggs or grubs remaining after the initial treatment are eradicated.

Lawn grubs are a seasonal issue and you may find your experience more than one infestation each spring and autumn. Make sure to keep an eye out for the signs of lawn grub activity and repeat the treatment if necessary.

Fertilising your lawn after the insecticide treatment is a great way to fast track the recovery time. If you have a Sir Walter Buffalo lawn, your lawn is sure to self repair and bounce back quickly after treatment. Other lawn varieties that tend to suffer more severe damage may take longer to self-repair.


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