Season two of the fall army worm invasion has descended on NSW maize growers with the confirmation at Croppa Creek of moths found in pheromone traps installed by Local Land Services officers.
This is the season's first sighting west of the dividing range and marks an early start to the pest's incursion after over-wintering in the sweet corn districts of Queensland's Lockyer Valley.
The moths were first detected in Australia's far north in February 2020 and were trapped north of Moree in late September.The pest previously traveled the world and built up tremendous resistance to conventional chemistry.
Coastal producers learned a lot from last year as by the end of harvest Spodoptera frugiperda had affected corn as far south as Shoalhaven.
This season, for the first time in Australia, growers have an alternative control in the form of a naturally occurring virus, manufactured into a convenient spray by the Toowoomba company AgBiTech and imported under APVMA permit from their US facility. It has already made a difference to corn grown in North Queensland and the Ord Valley but has greatest efficacy when caterpillars are small and so growers must monitor their paddocks for emerging grubs and target these - at first and second instar - for best effect.
Phil Armytage from AgBiTech says a single female moth lays 1000 eggs of which only 16 per cent survive. Half of those will be female and in just four generations numbers can swell to 41 million larvae burrowing into the twisted growing centre of corn plants where they and are well shielded from conventional chemicals.
Fawligen works just like Vivus Max, another baculovirus-based biological control made by the home-grown company that began life in an old farm shed in Dalby, Qld. Their US facility grows out a million larvae a day specifically to make the baculovirus to specifically target emerging grubs without harming vital natural predators like highly sensitive parasitic wasps. It can be sprayed from a boom unit attached to a tractor, or from the air or even through irrigation lines in a process known as "chemigation" with each millilitre of product containing 7.5 billion occlusion bodies each one harbouring infectious particles of the host-specific virus.
However this organic spray - a combination of pulverised dead infected caterpillar larvae and water - must be used in conjunction with other management practices to keep the corn loving larvae under control.
Last year's learnings were basic in their premise: Plant corn early when pest pressure is at its lowest and avoid broad-spectrum insecticides.
Paddocks that weren't managed well last year were overrun by grubs, eating their way out of the centre whorl where broad spectrum sprays never penetrated and into an environment where there were no natural predators.
Boambee dairy farmer and corn-silage grower Jason Bake will repeat his efforts of last season which involved extensive moth trapping and grid-pattern monitoring of the crop for early signs of grub followed by a soft spray to keep beneficial insect populations high.
Last year he used Vivus Max to lower the number of common Helicoverpa grubs so that predatory insects could concentrate on FAW. He observed that a high number of little grubs at first were quickly culled by the natural cannibalistic tendencies of the larvae to eat each other.
Richmond Valley corn grower Paul Fleming said last year he experimented with an early spray of DuPont Steward followed by FMC's Altacor but will try the latter chemistry first this year.
"I wouldn't like to say that I know what to do," he admitted. "But Altacor works with a trans-laminar effect, moving through the leaf, whereas with Steward the grubs have got to eat where the chemical lands and if they are in the centre of the growing stalk you won't get it to them.
"My tactic this year will be to not grow as much corn, plant it early in the season, and to spray early with Altacor."
Meanwhile, Mr Armytage of AgBiTech predicted wide-spread resistance to Altacor in four years' time.
"Biological controls are not as effective as conventional chemistry so for that reason those tools should only be used later in the season," he said. "Plant early, control with ultra-soft prevention measures to get a lid on the population and save the hard hitting chemistry closer to tassling.
"We need to protect our critical chemistry so that we can continue to run agriculture," he said.
Another tool is the use of AgBiTech's moth attractant Magnet with a toxin, sprayed in strips over 1.5 per cent of the crop to attract moths and kill them before they lay eggs. Ord River growers got through last winter by using an integrated approach including Magnet and Fawligen.
Mr Armytage warned that chemicals like Corteva Success Neo were hard on wasps but soft on beetles, while DuPont Steward was the other way around with lady beetles more affected and yet that bug was a good predator of FAW.
He said there was some hope that the Australian infestation of FAW goes the way of Helicoverpa in Brazil, where an initial high pest population naturally decreased over time to "settle into a rhythm in the landscape."
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