Fall armyworm outbreak in Northern Australia

By Daniel Fitzgerald, Courtney Fowler and Michelle Stanley

The invasive fall armyworm moth has been detected across multiple regions in the Northern Territory and in northern Western Australia, in an outbreak that has surprised authorities.

Armyworms are known to damage more than 350 plant species like maize, sorghum, corn, fruits, and vegetables, and has devastated crops throughout South-East Asia.

The pest has been found in the Darwin, Katherine, and Douglas Daly regions of the Top End just two months after it was first identified on the Australian mainland on Cape York Peninsula.

Northern Territory chief plant health officer Anne Walters said it was "surprising" the pest had spread so far so quickly.

"I probably wasn't expecting it to be quite as widespread as it is at this point," she said.

"But we are seeing this global trend. This particular species does disperse very quickly and has been moving very quickly globally.”

“Within 12 months it can move across continents."

The armyworms were all found in March in pheromone traps set by the NT Department of Primary Industry late last year.

But Dr Walters said it was difficult to know when the pest first entered the Territory.

"We can't age the population so it won't ever be possible for us to know … but we have found larvae as well as adult moths which suggests it has been reproducing here in the Territory," she said.

"We don't think it's been here for a very long time but we do think it's potentially been here for some months."

'Not feasible to eradicate'

The fall armyworm has been deemed by the Consultative Committee on Emergency Plant Pests as 'not feasible to eradicate'.

Now that the fall armyworm had been confirmed in the NT, Dr Walters said the DPI's focus would turn to keeping the pest's numbers down.

"This pest is known to cause significant economic losses overseas and it is important that we work collaboratively to identify and carry out appropriate and effective management activities to support our growers," Dr Walters said.

"We're concerned about all [crops] and it's just a matter of us understanding better what the impacts are so we can ensure the industry can effectively manage this moth as best we can.

"We will be working very closely with the cotton industry and growers to work through if there is an impact on cotton, and what that impact might be."

Dr Walters did not rule out the possibility of the fall armyworm making its way to Central Australia.

"One of the things we will be focusing on is working out the distribution of the pest," she said.

"[We'll be] putting traps throughout the NT to work out whether the pest will disperse all the way through the NT.

"At this stage, not enough is known about the distribution or the biology and ecology of this particular moth in the NT … so we're really learning as we're doing these things at this time."

The Australian Pesticide and Veterinary Medicine Authority is currently assessing additional applications for permits for the use of chemicals against the fall armyworm.

Pest crosses NT/WA border

The fall armyworm has also been found in northern Western Australia, on the same day detections were announced in the Northern Territory.

The pest was found in a surveillance trap in Kununurra, operated by the Department of Primary Industries and Regional Development (DPIRD) as part of the Northern Australia Quarantine Strategy.

"Sentinel trapping in WA is being expanded to help provide early advice to industry about presence of the pest in regional areas," DPIRD chief plant biosecurity officer Sonya Broughton said.

"We have monitored traps in Kununurra since October last year, with an additional 50 lure traps currently being rolled out across Kununurra, Broome, Carnarvon, Geraldton and Kalumburu."

Dr Broughton said the department was working with industry and other state and territory jurisdictions to assist industry in preparing for and minimising the impact of this pest.

She said the integrated pest management approach currently being used by local farmers to control other pests like the heliosis moth, may effectively contain the spread of fall army worm.

The detection has growers concerned for the potential impact to maize, sorghum, cotton and hay crops in the Ord Valley.

"If you don't monitor for this species, it can defoliate your crop very quickly and on something like corn, a 40 per cent yield reduction is not unheard of," Kununurra farmer Fritz Bolten said.

"We were warned that it was coming, and there's things in place but its just come a little bit quicker than what we all thought."

Mr Bolten, who is a second generation farmer in the Ord, said producers had been preparing for the arrival of the pest for years.

"We practice integrated pest management and use soft chemicals and natural products as much possible, and we will continue to use those successful techniques that we've used for the last couple of decades to balance this pest as best we can," he said.

"It will be expensive and we're not looking forward to it, but in agriculture we have this culture and attitude of resilience, we will be able to deal with this."

Industry and agronomists are encouraged to report any unexpected symptoms in the field by phoning the Exotic Plant Pest Hotline on 1800 084 881.