Lawn Grubs & Fungal Disease

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Lawn Grubs & Fungal Disease

16 September 2018 Weeds, Pests & Diseases

This page will help you to identify various types of pests & diseases and provide some advice on how to easily manage them yourself.

ALWAYS read & follow the manufacturers instructions & safety precautions with any herbicide or pesticide.

Lawn grubs

Signs that you may have lawn grubs

Spongy texture has the texture of your lawn become spongy? This texture is a big sign that lawn grubs are feeding on your lawn and affecting the whole structure of your grass.

Discoloured Patches one of the most noticeable signs that lawn grubs are attacking is the brown patches (sometimes right down to dirt) that present on your otherwise healthy lawn, sometimes the leaf & stem is actually missing & have been eaten by the grub and other times it just turns brown because the roots have been eaten away underground.

White, Grey or Brown Moths if you see these moths flying around the surface of your wonderfully healthy lawn around dusk, they could be looking to use your healthy lawn as a place to lay their eggs. The perfect environment gives the larvae the best chance of survival. The larvae will attack your lawn for almost a month before becoming moths and laying more eggs, which will become more larvae, and the cycle continues.

Bird Activity more larvae = more snacks! Birds love to snack on the larvae that eat your lawns, so more of a presence of larvae in your backyard could mean you will also start to notice more birds visiting & pecking at your lawn, too.

Lawn grubs are a problem that needs to be dealt with straight away before they cause any significant damage.

There are three types lawn grub that eat the leaf of lawns in South East Queensland. These are Army Worm, Sod Web Worm and Cut Worm, these are all larvae of small moths that are particularly active from December to May especially after periods of rain. A healthy lawn will easily recover from a mild outbreak of grubs however newly established lawns left unchecked can be completely destroyed in severe outbreaks.

How to check for lawn grubs

  • Walk the lawn in the early evening and look for the presence of the small white moth, this should cause them to fly away, another indicator is the presence of a small red wasp which flies low over the grass during the day, The wasp is searching the lawn for a host grub to lay its eggs into.
  • Another method to check for the presence of lawn grubs is to lay out a wet hessian sack or a large wet rag or towell over the suspected areas in the evening, check under it first thing in the morning and the grubs should still be active in the dark cool environment.

How to treat for lawn grubs

  • For a quick kill, most lawn grub killers are suitable for use on turf, check the label for compatibility with your lawn type, sprays can be toxic so follow the directions on the label carefully,
    • Amgrow Patrol has good effectiveness, it's a safe to use granular product, and the 1.5kg pack is usually enough to do multiple applications,
    • GrubGuard is a 2L pre-mixed spray pack that covers up to 150m2, easy to use & does not require a spray tank.
    • For the true lawn fanatic Acelepryn is very good & has a residual lasting effect, but at a much higher cost (approx $500), it has coverage up to 5,000m2 & needs a spray tank to apply.
  • Ultraviolet bug zapper lights (or similar) are quite effective, they won’t stop the larvae from dropping in and causing some damage, but they will help catch some of the moths before laying eggs in the area, preventing major out breaks.
  • Avoid heavy applications of high nitrogen chemical fertilisers during the summer months, alternatively use organic fertilisers and seaweed based products that strengthen the turf plant making it less desirable for grubs to eat.
  • Lawn Grubs can strike again too! most of the chemicals only kill active insects, so in another 2-3 weeks if you get new larvae laid into the lawn then the chemical will not affect them and the cycle can start over again, so after applying your chosen pesticide it's best to regularly check for new activity & re-apply if necessary, most products reccommend re-application in 7-10 days.

Fungal Diseases

There are many fungal diseases that affect turf such as ‘brown patch’ & ‘leaf spot’, periods of high humidity and excess rainfall increases the chance of infection. Use this identification chart to check if you have any fungal diseases.

Tips to help avoid or treat fungal diseases

  • Avoid fertilizing with high nitrogen fertilizers during these events
  • De-tathcing is a good way to prevent fungal diseases, where there is an excess of thatch, the turf tends to produce roots in the organic layer, the condition of which can fluctuate from saturation to drought, once the thatch is wet, it remains damp for long periods, this favours for the growth of fungi.
  • Ensure sure you are following correct ongoing watering techniques, sometimes regular light waterings can actually be harmful and may create a constantly moist & humid environment which funghi can thrive in, stick to the golden rule of less frequent but heavy watering to encourage a healthy root depth.

Fungicides can be applied if required, as with all fungicides and poison products ALLWAYS CHECK THE LABEL and follow the manufacturer’s instructions, check out the products available at

As always, if you have any more questions please dont hesitate to contact us for free expert advice on 1800ALLTURF (1800255873) or LiveChat with us using the chat box in the bottom right corner of your screen.