Fall armyworm workshop

Bringing together research and grower experiences from across the agriculture sector is critical to developing better management techniques for fall armyworm. 

Growers across the country have been struggling to deal with a resurgence of Fall armyworm this year, with numbers of the exotic pest bouncing to their highest levels since it was first detected in Australia in 2020. 

Initially a problem in northern growing regions, Fall armyworm has now been detected in all states and territories except South Australia. Equally concerning is its appearance in a range of additional crops, well beyond the sweetcorn, maize and sorghum that had previously borne the brunt of Fall armyworm damage. 

Fall armyworm (Spodoptera frugiperda) is a difficult pest to manage. It’s a highly invasive and destructive caterpillar native to tropical and subtropical regions of the Americas, with a fast reproductive cycle and the ability to travel long distances in its moth stage. 

It prefers grass species with whorls like sweetcorn, maize and sorghum, but in recent years it has also caused damage in brassicas, capsicum, melons, cucumber, eggplant, heliconia and okra. 

Helping growers to handle the new pest is the focus of a levy-funded project being run by the Queensland Department of Agriculture and Fisheries, called the National Fall armyworm innovation system for the Australian vegetable industry (VG22006). Starting in 2023, it follows a previous project that was launched in the wake of the initial Fall armyworm detection. 

Many growers are getting their first introduction to Fall armyworm this year as it spreads to new areas, and they are having to learn management techniques quickly, according to Dr Melina Miles, Principal Entomologist with the Queensland Department of Agriculture and Fisheries. 

“Fall armyworm arrived in Australia in 2020, and was first detected in Far North Queensland,” she says. “It was detected in January, and by September it had made an appearance across most of eastern Australia. It’s now in every major growing area.” 

The infestation in northern regions was severe in 2020, but the following few years were comparatively quiet. The situation changed this year, however, with the pest getting started early after a mild winter and warm spring. The result has been a significant infestation, with some sweetcorn growers in Queensland reporting large losses. 

Dr Melina Miles
Dr Melina Miles speaks to growers at a Fall armyworm workshop in NSW.

“From the beginning of 2024, we’ve seen pressure, numbers, densities, and damage that we haven’t seen in previous years,” she says. “It’s been quite a wake-up this year.” 

Best practice management of Fall armyworm in Australia is still rapidly developing. It varies between crops, depending on how the caterpillar attacks each crop and how much damage that crop can sustain before it becomes unmarketable. 

“The response of sweetcorn to Fall armyworm is much more severe than, say, in maize and sorghum,” says Dr Miles. 

“From a broadacre point of view, we went very well in the past two years with minimum chemical intervention and a move to early planting, so planting in spring rather than planting in summer.” 

“That has meant that the majority of crops have avoided higher Fall armyworm pressure. This year the pressure has been so high, and we’ve also had a lot of late cropping, so a lot of crops have experienced really high Fall armyworm pressure. There’s been a lot more spraying as a consequence across broadacre and horticulture.” 

A rigorous insecticide spray regime has proven the most effective management practice so far. Fall armyworm has shown resistance to synthetic pyrethroids, organophosphates and carbamates, but insecticides like chlorantraniliprole, indoxacarb, spinosyns, and emamectin benzoate offer viable options. 

Natural enemies of Fall armyworm can also help, including ladybirds, spiders, native earwigs, predatory shield bugs, assassin bugs, and tachinid flies, and endemic parasitoids like the trichogramma family. 

Due to the broad range of Fall armyworm host crops and the significant threat posed by the pest, research into management practices has been taking place across different industries and regions. Dr Miles says a key goal of the current project is to bring that research together and disseminate findings to growers across the affected industries. 

“This Fall armyworm area wide management project brings together the industries with an understanding that fall armyworm doesn’t recognise industry boundaries,” she says. 

“It’s focused on learning the biology, the ecology, the interaction, the natural enemies of Fall armyworm – the common threads, whether you’re growing sweetcorn or maize, whether you’re feeding it to people or animals.” 

In March 2024, Dr Miles presented on Fall armyworm management techniques at a field day run by VegNET New South Wales and NSW Local Land Services. 

Held in Richmond on the outskirts of Sydney, the NSW Vegetable Growers and Sweet Corn Field Day brought together growers and agronomists from the Sydney basin to discuss the pest, which has only recently started to have an impact in the region. 

The event was one of many the Fall armyworm project team is taking part in. 

“The real emphasis is on bringing people together to communicate the outcomes of research that is going on currently, but also to share the experiences growers are having and what is, or isn’t, working for them.” 

For sweetcorn, a theme for upcoming research that has emerged out of the higher pest pressure this year is understanding how much damage is too much from an economic point of view, following a similar research thread in sorghum and maize. 

Dr Miles says the goal for sweetcorn is to develop thresholds that will help growers make rational economic decisions around whether they can afford to spray a Fall armyworm-affected crop, or if the economic return will be outweighed by the cost. 

In sweetcorn, that threshold could actually be quite low. Other endemic caterpillar species typically damage the tip of a sweetcorn cob, which can be trimmed off in processing. Fall armyworm caterpillars can chew into the cob from the base, sides or tip, however, in which case the cob can’t be used for the fresh or processing markets. 

“Sweetcorn looks to be much less resilient to Fall armyworm compared with maize and sorghum, so you can’t allow much damage in the vegetative state,” says Dr Miles. “It doesn’t leave very much wiggle room in terms of minimising insecticide use.” 

Find out more:

Head to the Fall armyworm engagement hub

National Fall armyworm innovation system for the Australian vegetable industry is funded by Hort Innovation using the vegetable industry research and development levy and contributions from the Australian Government.
Project Number: VG22006

Watch the video on Youtube

This article first appeared in Australian Grower Winter 2024