Armyworms are on the march across the Gympie region after their numbers have exploded int he ideal conditions.
Armyworms are on the march across the Gympie region after their numbers have exploded int he ideal conditions.

Grubby pests cause chaos on lawns - here's how to stop them

RAINFALL across the region has been gratefully received, but it has caused an explosion of the menace now attacking lawns and fields only recently brought back from the dead.

Unusually high numbers of armyworms, or lawn grubs as they are commonly referred to, are on the march across the Gympie region.

READ MORE: Lawn grubs march through One Mile

One Lawrence Street resident said half her lawn disappeared overnight aon Saturday.

"It was Sunday morning we noticed they were there when they hadn't been there the night before. The grass that was there the day before was suddenly gone," she said.

CLICK HERE: Chook tractor gets rid of armyworms

Armyworms are not to be confused with fall armyworms,which are an invasive pest that feeds on 350 plant species including maize, rice, sorghum, sugarcane and wheat, other horticultural crops and cotton. They have been detected in Far North Queensland and pose a significant threat to Queensland agriculture.

Armyworms. Pics from Peter Notman.
Armyworms. Pics from Peter Notman.

Lawn grubs can vary in colour from green to brown to black, can reach up to 4cm in length, and get plump as they feed and mature.

Their large numbers are possible due to the moth parent being able to lay up to 500 eggs in a single laying, and then repeat the same process the following night.

This is where this lawn grub gets its name, it forms a large army, lays devastation to an area, and then quickly moves on to the next lawn.

The ABC has reported today that hundreds of residents from Gympie to Brisbane have reported the worms after noticing their once-green grass turn brown almost overnight.

Armyworms. Pics from Peter Notman.
Armyworms. Pics from Peter Notman.

John McDonald, biosecurity manager at Greenlife Industry Australia - the national peak body for the nursery industry - said the armyworms in the south-east appeared to be in "unusually high numbers", the ABC reported.

He said while the grass was not dead and would grow back, it could be distressing for residents.

They are even being reported in some Brisbane lawns for the first time in 20 years.

Mr McDonald said armyworms were a natural biological process throughout Queensland and the rain and cooler weather in recent weeks had provided ideal conditions for them.

"When all the conditions are right you get these blooms of the population.

"Then they'll move on once they've pretty much chewed up the food source, you'll see the numbers decline," he told the ABC.

Armyworms. Pics from Peter Notman.
Armyworms. Pics from Peter Notman.

What can you do?

The website says there are two main methods to check for armyworms.

The first method involves using a bucket of soapy water which has been mixed-up with dishwashing detergent. The mixture is then poured over the lawn in a small area. The area is then monitored over the next 10 minutes to check for caterpillars which are rising to the surface.

The second method involves going out onto the lawn at night time. With a good torch in hand, get down low onto the lawn and carefully run the torch over it looking for caterpillars feeding or moving. Begin the search at the damaged area of turf, and spread outwards from there.

Another sign of possible caterpillar infestation is to leave the outside light on at night for a few hours. Then go outside every so often and check for moths flying around the light. If a multitude of moths are present, then this may be a sign of possible lawn caterpillar problems which will require further investigation.

If you do find caterpillars, it would be best to capture a few to take to the local nursery for positive identification. This will help the staff member to recommend the right insecticide for the caterpillar type.

A lawn decimated by thousands of army worms
A lawn decimated by thousands of army worms

How to kill armyworms

Once armyworms have been identified, they are treated with a lawn insecticide which is freely available for purchase from garden stores and nurseries.

The insecticide is mixed-up and applied to the lawn just before dusk. Ensure to allow yourself enough time to finish the entire lawn treatment before dark. The treatment is then lightly watered into the lawn so it can reach down to the base of the thatch layer. The poison is then ingested by the Army Worms as they are feeding on the lawn. Be careful not to over water, this will simply wash the poison away, and it will not be ingested by the caterpillars.

Repairing damage from armyworms

Army Worms will not generally kill a lawn by it's feeding, but it will become heavily damaged, which if left untreated could cause patches of lawn to die. The only real thing to do at this time is to follow good lawn care practices and apply a quality fertiliser, and ensure it is getting adequate water. This will allow the lawn to best repair itself.

There is no need to over-water or apply excess fertiliser, doing either will not aid the lawn in repair, but may even cause further damage. Always apply fertilisers at manufacturer's recommendations.