The rise of the Fall armyworm

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Fall armyworm larva (caterpillar)

Fall armyworm larva / Russ Ottens, University of Georgia, Bugwood.org

The fall armyworm (FAW) is a moth native to the subtropical and tropical Americas, including the United States and Brazil. It poses a significant threat to Australian agriculture and our economy, and it is listed on the Department of Agriculture’s Top 42 Plant Pests. Over recent years this agricultural pest has spread to parts of Africa and Asia and has recently been found in Australia, making the threat very real.

While it’s not currently found in Melbourne, FAW may expand its range into urban areas, not just agricultural areas. Urban areas often support a diversity of plant species that may play host to such a pest. Once an exotic pest establishes in an urban area it can ‘incubate’ and provide a population source from which moth adults can migrate and establish new colonies in agricultural areas. 

A frequent flyer

The fall armyworm (FAW) has the ability to travel far and wide, sometimes covering 100km in one night. In 2016, FAW was detected in West Africa. By 2018, 44 countries across sub-Saharan Africa were invaded, and the first detections in India and Yemen had occurred. Since then, rapid spread has continued to China, south-east Asia, and now, Australia.

Landing in Australia

The fall armyworm (FAW) was first sighted in the Torres Strait Islands of Sabai and Erub in January 2020. Several detections followed across Far North Queensland in February and March 2020, and in the Northern Territory in March 2020, making eradication unfeasible.

Fall armyworm moth (adult)

Fall armyworm moth (adult) / Robert J. Bauernfeind, Kansas State University, Bugwood.org

Spot the difference

The fall armyworm (FAW) can look similar to other armyworms already in Australia, but its feeding habit is very distinct. It is not a picky eater, with a diet that consists of more than 350 plants, including various vegetables (sweetcorn, potato, sweet potato, among others). FAW travel in ‘armies’, and are very destructive. In cases overseas, packs of FAW have stripped entire fields and cost industries millions. 

However, it should be noted that in recent cases overseas such dramatic impacts have often been observed on small-scale subsistence farming operations that are often not representative of Australian farming operations. Further, Australian growers already actively manage other lepidopteran species, such as Helicoverpa armigera. This means that it is difficult to predict the impact that will be experienced on Australian farms. 

So how do I know if I’ve spotted fall armyworm? Well, a good way to differentiate FAW from other armyworms is to look at the larvae. A FAW caterpillar has very distinct, dark raised spots, from which hardened bristles stick out. The most distinctive of these spots are four black spots on its eighth abdominal segment arranged in a square (see larva image above). 

Fall armyworm damage to corn

Fall armyworm damage to corn / University of Georgia, University of Georgia, Bugwood.org

Tips to help you keep an eye out

Community and growers alike should be extremely vigilant of FAW, given that it is now present in parts of Australia.

   – Eggs cluster together in groups of 100-200 on the underside of the leaf encased in a silky, furry substance.

   – Larvae are nocturnal, so most damage happens at nighttime.

   – During the day, the pest will burrow deep inside the plant.

   – As larvae start to grow, they chew through the leaf rapidly.

   – Look for leaf damage such as pinholes, windowing, tattering or complete defoliation of the leaves.

Keeping track of distribution expansion from currently affected areas in Queensland will help us stay ahead of the curve. An important action to take at the moment is for those inspecting crops regularly to become familiar with how to identify fall armyworm and to report suspect sightings in south-eastern Australia to the Exotic Plant Pest Hotline on 1800 084 881.

 Detecting FAW in urban areas will aid protection of our food security.

Fall armyworm tattering leaves of corn crop

Fall armyworm tattering leaves of corn crop / John C. French Sr., Retired, Universities: Auburn GA, Clemson and U of MO, Bugwood.org

Did you know?

FAW might not just spread to new locations by flying, it can also spread by movement of infested produce or cargo!

Useful links

Fall armyworm life cycle
https://www.youtube.com/watch?v=eZxVouWM-t4&t=1s

Fall armyworm larvae guide
https://www.publications.qld.gov.au/dataset/queensland-fall-armyworm-resources/resource/8123f07d-9b73-4788-a252-364c0f45a500

DPIR factsheet
https://dpir.nt.gov.au/__data/assets/pdf_file/0017/810314/ENT-16-fall-armyworm-factsheet.pdf

https://thebeatsheet.com.au/fall-armyworm-should-you-be-concerned/

PestFacts – Southeastern – Issue 1, 2020
http://www.cesaraustralia.com/sustainable-agriculture/pestfacts-south-eastern/issue-1-31-march-2020/the-exotic-fall-armyworm-in-australia-a-south-eastern-perspective/

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