THE detection of a new pest in Western Australia this year has entomologists and growers concerned about how far fall armyworm (FAW) could spread and what damage it may cause.
Speaking at the Department of Primary Industries and Regional Development (DPIRD) Grains Industry Day, held at Optus Stadium last month, senior research scientist Helen Spafford said FAW was expected to be mostly a northern pest that could still cause dramas for southern grain growers.
"As part of its lifecycle, FAW doesn't have a diapause, which means it doesn't have a stage in its development which it can stop growing and rest during harsh conditions," Dr Spafford said.
"Because of that, it must have food and suitable conditions in terms of temperature year around, which are expected to be up in the northern parts of Australia.
"However there are also some suitable areas along the coastline around Carnarvon and further south that will also be suitable for FAW year round."
In addition, there are other areas around WA that are predicted to be suitable for FAW, just not for year-round establishment.
It is expected that FAW will live in the northern and coastal areas and then migrate further south and east to establish in parts of the Wheatbelt on an annual basis.
"FAW has a relatively short generation time at suitable temperature and it can go through a full lifecycle within about 30 days," Dr Spafford said.
"Up north we have already seen six or seven generations of FAW since it invaded and if it comes down south and establishes, then there could be three or four possible generations before it gets too cold and the population dies out."
The other issue is that FAW spreads very easily, with an individual able to fly 100 kilometres in a single night and mass migrations occurring at certain times of the year.
Based on that, an annual migration from the north in WA down to the south, even to Albany and Esperance, is within the pest's capabilities. Once it is established, FAW can spread very quickly within an area, with adults migrating and the females laying eggs which leads to patches popping up within a local region.
Dr Spafford said FAW had a wide host range which means as it's migrating, it doesn't necessarily need a crop plant in order to lay its eggs and larvae to develop on.
"Over 350 hosts plants have been noted, with a preference for grasses, however the host range is very wide in that it has been found damaging many crops and pastures overseas," she said.
"Up north we don't grow a lot of wheat and barley, but we have found FAW on maize, sweetcorn, sorghum and Rhodes grass where it has been very problematic.
"The damage is highly variable -we've seen it damage both the foliage, where the young larvae will cause windowing, while the older larvae will completely chew through the leaves and feed in deeper parts of the plant including inside the stalks."
Researchers originally started looking for FAW in October 2019 with two traps set up in the Kununurra region because it was expected that would be where it was first located -which it was in March 2020.
After the detection of FAW in Queensland in February, a far more extensive trapping grid in the Kununurra area was established in March with 45 active traps at the peak.
Additional traps were placed in Broome, Carnarvon, Geraldton and areas within the Pilbara.
"We had detection of FAW in March in Kununurra and Broome and by April it had established at Pardoo and Carnarvon," Dr Spafford said.
"It's now well established in the Tom Price area, plus we had a detection of FAW in surveillance traps in Geraldton and later in October at Gingin, but there is no evidence of establishment yet in either of those areas.
"The DPIRD Grains team set up a trapping grid of 70 traps across the grainbelt this year, located from Geraldton to Esperance, however over the course of the trapping there were no detections in any of those traps."
One of the early challenges that will be ongoing as the pest spreads is identification.
The young larvae are very difficult to identify visually and will need to be sent in for identification, while there are much better characteristics to use for identification of large larvae, but it is still very challenging.
As FAW moves south, growers should be looking in green bridges but also in early-planted crops for the larvae.
Dr Spafford said in terms of management, pesticides had been a primary means of management up north, but there has been variable success, in part due to the cryptic habit of the pest.
"Around the world, FAW has developed resistance to pesticides in almost every group and in some places there is already multiple resistance," she said.
"As FAW had migrated into Australia it has done so with resistance genes present, we have detected genes for resistance to Group 1 insecticides already."
Research is ongoing in Western Australia and other parts of the country to find sustainable ways to manage FAW.
