We tend to see a lot of people putting in the hard yards and proudly showing off their achievements to then be brought undone by what is more commonly known as Lawn Grub.

What is Lawn Grub? (AKA Armyworm)

Lawn Grub (Armyworm) scientifically known as Spodoptera maurita, is one of many pests of turfgrass that can destroy your lawn in a matter of days and bring a grown person to tears.

Armyworm is a caterpillar, and it can become a major problem in your lawn if not controlled. Armyworm’s appearance can vary in colour between shades of green and brown with very distinctive dots (markings) down the length of their body. On average an Armyworm will grow to around 40mm long. As harmless as they sound don’t be fooled.

So why are they called Armyworm?

Armyworm is the larvae of the of the adult moth, yes, those moths that you see on dusk hovering over your lawn. Seeing these moths about is a sure indication that activity is present.

A single moth upon can lay up to and exceed 500 eggs a day for several days, and that there should ring alarm bells. This is the start of the population of Armyworm, and as they mature and feed they congregate forming a formidable plant eating force devouring your lawn as they travel across it.

armyworm eggs

Armyworms can cause severe damage in little time, with the ability to destroy a lawn by feeding on the plant leaves and stems with most damage occurring in the early stages of an Armyworm’s life.

What to look for and simple ways to test for Armyworm...

Visually Armyworm can be difficult to detect, their distinctive markings help them hide very well. During the day the Armyworm will retreat to soil level to avoid heat and direct sunlight, then at dusk and beyond it is party time for the masses, coming to the surface to feed on your lawn.

A few ways to detect and determine if Armyworm is present is by inspection and observation.

1. A typical symptom of Armyworm damage is areas of turf that becomes damaged becoming brown and dry looking.
2. Look for chomp marks on damaged leaf, like any other caterpillar they will leave evidence of chewing.
3. Bird activity, if suddenly, your lawn becomes an aviary it is time to act as they are there feeding for a reason.
4. Moth activity at dusk and at night, with a torch stroll out on to your beloved lawn shining the torch whilst walking looking for the hovering little moths
5. Cocoons, one of the most obvious.There is no place that is out of limits, inspect your eaves, gutters, clothesline and any solid structure for these hairy, pale brown cocoons as these are packed with caterpillar larvae waiting to hatch. Use your broom or hose to remove these as soon as you see them to help with control.
6. A practice that has been around for a long time when it comes home testing, is to saturate an area you believe may be under threat with a bucket of water and dishwashing detergent. Pour on to the surface and wait for the Armyworm which should rise to the surface if present. Now just because you tested one area with zero results it does not mean you are safe as they could be active in a different location within your lawn.

    Life of an Armyworm...

    As mentioned before the temperatures are on the way up and now is when moth activity becomes more prevalent. The warmer temperatures and higher humidity forms the base of an active season.

    armyworm moth

    The simplest way to understand the lifecycle of an Armyworm is; The adult moth looks to lay the eggs by way of cocoon, these eggs can take up to 3 weeks to hatch.

    The small larvae then hatch from the cocoon and make their way towards to your lawn by way of silk threads. Depending on the wind strength at the time the larvae can be spread over a fair area therefore allowing more widespread damage over the coming weeks.

    As the Armyworm matures it progresses through many stages known as (instars) which will take approximately 4 to 5 weeks.

    Once mature, the well-fed Armyworm retreats into the soil profile up to depths of 80mm where it pupates, in other words starts a new cycle.

    Now that this new cycle has been created it only takes a matter of weeks and moths will appear again. While it is an easy cycle to understand, it also highlights how you can be targeted several times throughout the season.

    How to control Armyworm...

    We will keep this brief.

    The most common and highly effective way of control of this lawn pest is obviously insecticides. Insecticides are available from many outlets.


    The biggest selling knockdown products containing Bifenthrin (e.g. ProForce Rumbler). Bifenthrin is known for its quick knock down ability, remembering that the residual effects of these products are limited and constant and repeat applications are the only way to combat an infestation.

    When using such products ensure you maintain regular applications as you will need to break the cycle of the Armyworm to succeed.


    If you are looking for a residual product there is only one, Acelepryn, which is a trusted and proven product throughout the world. Acelepryn offers 6-month protection and is widely used in the professional turf market due to its quality, and therefore it has a price tag to go with it.

    The pros when it comes to this product far out way the cons. Acelepryn is a non-scheduled chemical with very low toxicity, and therefore poses very little harm to birds, fish and bees unlike some other insecticides.

    When it comes to selecting a product to treat your lawn research is the key.

    Important -

    • Please select your treatment carefully, understand the product and its precautions before you start applying.
    • Do not exceed label rates as they are written and tested for a reason. Abide by re-entry periods, and as always use correct PPE as tabled by your chosen product.
    • Don’t run the gauntlet, if you build it they will come, you are actively creating a buffet for these pests when establishing a healthy lawn and they will oblige. By protecting yourself and putting all the right measures in place not only will you have a pest free lawn you will be able to enjoy your prized plot as well.