Fall armyworm (FAW) is a highly migratory, invasive pest that was first reported in Australia in February 2020 and quickly established across parts of northern Australia’s tropical and sub-tropical regions, including northern Queensland, the Northern Territory and northern parts of Western Australia.
It has now been detected in southern WA, NSW and Victoria.
CSIRO researcher Wee Tek Tay said the research provided evidence that two geographically separated populations — a WA population from Kununurra in the Kimberley region and a north Queensland population from Walkamin in the Tablelands region — show variable levels of sensitivity to insecticides.
“Geographic variability in insecticide responses is not unexpected and is commonly observed in the closely related species Helicoverpa armigera,” Dr Tay said.
“The current findings don’t necessarily indicate distinct genetic differences in the populations — results of genomic analyses are pending — but they do have implications for growers trying to manage FAW in the field.”
NSW DPI researcher Lisa Bird said an independent and complementary study of FAW susceptibility in five populations from north Queensland and one population from Kununurra also revealed geographic differences in sensitivity to some synthetic insecticides.
Both the CSIRO and the NSW DPI studies found FAW populations were between 50 and 150 times less sensitive to the pyrethroid alpha-cypermethrin compared with susceptible strains of H. armigera.
Both researchers found similar levels of variability in sensitivity to methomyl, ranging from three to 11 times less sensitive, in populations from north Queensland compared with susceptible strains of H. armigera. In contrast, CSIRO found its WA population to be 52 times less sensitive.
Grains Research and Development Corporation biosecurity manager Jeevan Khurana said these results provided evidence that geographically different FAW populations in Australia can vary in their responses to insecticide.
“This new knowledge helps to guide insecticide choice,” Dr Khurana said.
“As always, growers are encouraged to judiciously select and rotate products to reduce selection pressure.
“While these studies don’t directly reflect field rates and conditions, it is important for growers to consider insecticide sensitivity when making decisions about product choice.
“Always use the full rate as stated on the label or permit. Where a rate range is specified, such as on current FAW permits for indoxacarb and chlorantraniliprole in maize, it is recommended to use the higher rate in accordance with the permit instructions.”
Growers are encouraged to monitor crops to identify signs of infestation early.
If you suspect FAW, report immediately to the Exotic Plant Pest Hotline on 1800 084 881.
26°C