Herpetogramma licarsisalis

Above image courtesy of Michael Welburn 

Sod Webworms are the larvae (caterpillars) of moths (Herpetogramma licarsisalis) native to Australia, tropical Asia, central and northern Africa, and some Pacific Islands. Over recent decades Sod Webworm has become an established pest in Hawaii, northern New Zealand, and parts of Europe.

In Australia Sod Webworm is found throughout Queensland, in NSW as far south as Batemans Bay, and in the top end of the Northern Territory.

Sod Webworm was once viewed as a sporadic pest of pasture and public turfed areas but is now considered a serious pest of warm-season turf grasses especially during the warmer months of January to April. It is the larvae (caterpillars) which cause all the damage. The adult moths are harmless nectar feeders, and may be drawn to outside lights at night.

Best treatment for Sod Webworms

Try Yates Grub Kill and Protect for the control of Sod Webworm larvae in lawns and public turfed areas. The product also controls other lawn caterpillar pests including Lawn Armyworm and Black Cutworm; and lawn beetle pests including Curl Grub (also known as African Black Beetle larvae), Argentinian Scarab larvae, Argentine Stem Weevil larvae, Billbug larvae.

The secret to pest control is to keep an eye on your plants, in this case your lawn, so that you can detect pest incursions early. For example you could keep an eye out (see Monitor) for Sod Webworm damage when mowing your lawn. For this to work you will need to know what to look for (see Symptoms of Sod Webworm Damage). If you find damage you should have a closer look to see if you can find some insects. If you find insects you will need to know what Sod Webworms look like (see Description).

Prevention is always better than cure, and you are more likely to be able to achieve that if you are out and about in your garden regularly. There are several things that you can do to prevent serious damage from Sod Webworm (see How to Prevent Sod Webworm Appearing).

Regular monitoring of your lawn will ensure that a major infestation of Sod Webworm doesn’t occur ‘overnight’. All treatments are way more effective if you can catch an infestation in its early stages.

A well cared-for lawn is more able to resist and recover from Sod Webworm attack. Always water and fertilise appropriately for the type of lawn you have.

What are Sod Webworms and How to Get Rid of Them

Sod Webworms are the larvae (caterpillars) of moths. There are many species of ‘webworms’ and what they have in common is how the larvae use silk (hence ‘webworm’) to form hiding spots of some kind (see Life Cycle).

Description:

Adult moths are greyish-brown, small to medium sized moths with a wing span of about 25mm. When resting the moth has an overall triangular shape. On the upper surface of the forewings there are several faint spots and faint wavy lines. On the hindwings the wavy lines are more distinct.  Unfortunately there are a number of moths which have these distinguishing features; so these characteristics should only be used in combination with other features and behaviours.

Eggs are creamy-white, flattened, slightly oval, and are about 0.7 mm long.

Larvae when first hatched are tiny (1 – 2 mm long) creamy coloured caterpillars with dark-brown heads. Larvae when fully grown are about 20 mm long and pale greenish-brown, with two brown raised spots on each body segment, and a brown head. Larvae have some insignificant short, fine hairs along their body, but overall have a generally smooth appearance.

Pupae are reddish-brown, shiny, and about 10 mm long.

Life Cycle:

Adult moths are active at dusk and fly low over lawns when preparing to lay eggs. Moths hide in long grass and shrubs during the day. Sod Webworm moths live for about 10-14 days, and females lay an average of about 250 eggs over that period.

Eggs are laid on grass blades or in lawn thatch (sometimes singly, sometimes in clusters) in the evening and hatch after a few days.

Larvae grow through 5 moults in about 2 weeks during warm weather. Larvae feed on grass blades and debris at night, and hide in lawn thatch during the day in webbing tunnels made of bits of grass and silk. When disturbed larvae wriggle rapidly backwards in their webbed tunnels.

Pupation occurs in loose cocoons covered in soil particles and other debris within lawn thatch.

The entire life cycle can be completed in as little as 6 weeks during warm weather. There may be as many as 6-10 generations per year in northern tropical regions, and 2 or 3 generations further south.

Due to its short life cycle and large number of generations, when treating for Sod Webworm it would be common to have pests at various stages in the life cycle in your lawn. Yates Grub Kill and Protect stays in the soil and treats them as they emerge from their eggs, getting multiple generations with just one treatment. 

What Plants are Impacted by Sod Webworms

Sod Webworms are pests of warm-season turf grasses including:

  • Couch
  • Kikuyu
  • Buffalo
  • Broadleaf carpet grass

They have also been recorded feeding on rye grasses, grassy crops such as rice, and weedy grasses such as Paspalum dilatatum.

Symptoms of Sod Webworm Damage

  • The more mature (i.e. bigger) the larvae are the more damage they do.
  • Small larvae chew on leaf edges leaving notched and ragged grass blades.
  • Mature larvae consume entire leaf blades and may defoliate patches of turf.
  • Brown patches may appear in turf. Close examination will show green grass blades have all been eaten off and the thatch exposed. If left untreated the brown patches will increase in size.
  • Weeds may establish in defoliated areas.

How to Prevent Sod Webworms Appearing

Monitor

  • Watch for moths fluttering over lawns at dusk.
  • Look for larvae, green larval frass and webbing in thatch.
  • Try using a bucket of soapy water to flush larvae out of thatch.
  • Examine any brown patches which form in lawns.

Prevent

  • Excessive fertilisation may result in thick thatch which encourages egg-laying moths. If this occurs dethatch, reduce fertiliser use, and water deeply rather than frequently.
  • Mowing when grass is long results in lots of debris build-up on the ground, which Sod Webworms like to tunnel in or pupate Avoid this by mowing regularly.

Natural enemies:

  • Several parasitic wasps are known to target Sod Webworm larvae. These wasps need a feed of nectar before laying eggs. You can encourage them by having nectar bearing flowers in the garden for them to feed on.
  • General predators such as spiders, ladybird beetles, ground beetles and predatory bugs will feed on larvae.

Recommended products to control Sod Webworms


More articles

Whitefly Control in Your Garden

Whiteflies are common garden pests that are difficult to detect when immature, but relatively easy to manage. The secret is to take action early.