Ripe weather conditions in south-east Queensland are being blamed for an "explosion" of armyworms chomping through lawns within days.

Key points: There are numerous species of armyworm that feed on foliage and grass, decimating backyards

There are numerous species of armyworm that feed on foliage and grass, decimating backyards They are different to the declared pest fall armyworm which was recently found in north Queensland

They are different to the declared pest fall armyworm which was recently found in north Queensland Residents say their lawns have been decimated within days — it will grow back, eventually

Hundreds of residents from Gympie to Brisbane reported the worms after noticing their once-green grass turning brown almost overnight.

It's important to note that they're not the notorious fall armyworm that poses a serious threat to agriculture and was recently detected in north Queensland.

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".

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

"We are seeing pockets of armyworms exploding in recent weeks and those populations … people have not witnessed that before."

Armyworms collected this week from a Sunshine Coast lawn. ( ABC Sunshine Coast: Annie Gaffney )

Mr McDonald said he even had them at his Brisbane home for the first time in 20 years.

"In recent weeks we've had hundreds end up in our pool, so we've never seen that before.

"It was somewhat of a surprise to see such large numbers and find them moving out of the neighbour's yard into ours."

Nambour resident Katelyn Efremoff had a similar experience when she noticed her neighbour's lawn turn brown days before the worms munched through hers.

"I thought it was insane that a caterpillar could decimate the entire front and back lawns in such a short period of time."

Nambour resident Kiah Thompson says her turf, laid in November, was doing fine until two weeks ago. ( Supplied )

Once the armyworms finish with a food source — i.e. your yard — they march onto the next. Hence their name.

The larvae, or caterpillars, often shelter during the day and feed at night, leaving residents shocked at what they find in the morning, as they told ABC Sunshine Coast:

"Victim of the little bastards here. Our yard flooded really badly, so initially I thought a few patches were where the water had been lying for a long time. Woke up on Saturday morning and it was all dead." — Ange Gillham, Yandina

"We were pretty shocked to have a nice green lawn after all the rain and then literally overnight it was demolished. Nothing I've seen before." — Jen Rickards, Palmwoods

"Destroyed ours in less than two weeks." — Sarah Campbell, Coes Creek

Ripe conditions bring devastation

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."

Peregian Springs resident James Willey found armyworms under a hessian sack he put on the lawn overnight.

Mr McDonald said the armyworm's life cycle took just a couple of weeks.

"The moths are the adult — they'll fly, land and lay eggs. The eggs hatch, which become caterpillars and the caterpillars do the chewing.

"They will pupate and they will move on and another adult will form and that'll be a moth and fly off."

Because the process happens so quickly, residents often don't notice until their once-green grass is a mass of brown, dead-looking foliage.

"They [the caterpillars] are probably there for a day or so and then people start to see the evidence," Mr McDonald said.

"It happens quite quickly and it comes down to numbers, so the more numbers, the more rapid they will chew through the food source."

Ange Gillham was surprised to find armyworms in her Yandina backyard. ( Supplied: Ange Gillham )

What can you do?

Horticulturalist Paul Plant said there were organic and chemical treatments available. People should seek advice at their local garden centre or hardware store.

He said some chemicals included chlorpyriphos as an active ingredient but should be used with caution and under advice to reduce the impact on other animals and ecosystems.

Non-chemical treatment options, he said, included a registered neem insecticide.

To remove a small patch or test whether you have armyworms in your lawn, place a wet blanket, hessian sack or cloth on the lawn in the evening.

"The armyworms will think it's still dark so they'll come up to the surface of the lawn but under the blanket," Mr Plant said.

"You'll see the armyworms right there on the surface, and if you've got chooks, they'll come over and eat all of those little blighters."

Some residents have also reported that pouring diluted eucalyptus wool wash over the affected area can help treat small patches, by forcing the worms to the surface where they can be removed by hand.

Jen Rickards from Palmwoods says since the armyworms moved on, only weeds have regrown. ( Supplied: Jen Rickards )

Mr Plant empathised with residents and said it was a vicious cycle.

"We've already had three times the amount of rainfall than what we had last year," he said.

"The moist soil and plenty of food source is an ideal environment for the grubs, which means they are growing, more moths are breeding, eggs are being laid, and it's this constant cycle that's really prevalent right now."

He encouraged residents to be on the lookout for moth eggs, which resembled a cotton wool bud, that may be laid around foliage and grass or near the house.

"Their eggs will be popping up constantly along the fence line close to the house where the light is, because moths are attracted to light, so they will come towards your house.

"Then the caterpillars, after hatching, will march past progressing away from the house."

And because the armyworms attack the leaves and usually leave the root system in place, Mr Plant said the lawn would grow back — eventually.

"If you want it to look good within two months, I would be [buying in fresh turf], but if you're willing to wait eight months, I'd be patient."

Not the fall armyworm

Mr McDonalds said while the two armyworms were similar in appearance, the fall armyworm had a more ferocious appetite.

The fall armyworm caterpillar is capable of destroying crops of rice, wheat, cotton, and sorghum overnight. ( Supplied: Daniel Rodriguez )

"It's been recorded on things as diverse as eucalyptus, tomatoes, blueberries, chrysanthemums, cabbages through to grapes.

"They're not necessarily its favoured food, but it seems to at the moment have an appetite to move across a diverse range of plant families."

He said the "aggressive" fall armyworm — whose adult moth can fly about 500 kilometres in its lifetime — was likely to move down the east coast quite quickly.

"How far? We're not too sure, but based on international info, I believe they will comfortably survive through New South Wales."

Concerns about fall armyworms should be raised with the Department of Agriculture and Fisheries on 13 25 23.