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About the Fall Armyworm

What is fall armyworm?

Order: Lepidoptera

Family: Noctuidae

Scientific name: Spodoptera frugiperda (J. E. Smith)

Common Name: Fall armyworm

Fall armyworm is an important lepidopteran pest in the Americas. During the mid-19th Century it was reported attacking maize, sugarcane, rice and grasses in the southern United States of America.

The name, fall armyworm is derived from its annual rapid range expansion northwards into North America where it lays eggs, and the larvae develop throughout the fall (autumn).

In the last four years fall armyworm has spread from its native Americas, across Africa and throughout Asia, threatening millions of small holder farmers and triggering emergency responses from multiple governments and agricultural industry bodies.

Likely distribution in Australia

Fall armyworm is a migratory species that utilises prevailing winds. If conditions are suitable it can travel more than 100 kilometres in a single night.

Its year-round distribution is expected to be restricted to relatively warm and moist areas closer to the coast. However, the geographic range of fall armyworm is expected to expand and contract based on climatic variability and available hosts.

Population modelling for fall armyworm using CLIMEX (estimates climate-related species distribution) suggests this pest has the potential to migrate to southern Australia during the warmer summer months.

Source: http://www.planthealthaustralia.com.au/wp-content/uploads/2020/11/Fall-Armworm-Continuity-Plan-2.pdf

Host range and lifecycle

Fall armyworm is a polyphagous pest with the potential to damage more than 350 different plant species, including a mixture of both crops and weeds.

While its ability to feed on weeds might not seem that important, it is these hosts that allow the pest to survive when commercial crops are no longer suitable or not available. For this reason, effective weed control will ultimately help restrict population growth.

In Australia, fall armyworm is likely to target key broadacre crops including cereals, cotton, maize, sorghum and soybeans. Horticultural crops are also susceptible, while it has been reported extensively on sweetcorn, other potential hosts include brassicas, cucurbits, fruiting vegetables and potatoes.

Identification

Fall armyworm is a notifiable plant pest, it must be reported to the Exotic Plant Pest Hotline on 1800 084 881.

Moths

Source: https://www.planthealthaustralia.com.au/wp-content/uploads/2020/11/Fall-Armworm-Continuity-Plan-2.pdf

 

Eggs

Larvae

Source: D Visser ARC-VOP Roodeplaat (https://www.grainsa.co.za/upload/Fall-Armyworm-Identification-Presentation.pdf)
 

​Early instar larvae (L1 – L3) are often lighter in colour compared to the older caterpillars. The colour can be variable, however green and/or yellow colours are common.

Source: D Visser ARC-VOP Roodeplaat (https://www.grainsa.co.za/upload/Fall-Armyworm-Identification-Presentation.pdf)

Late instar larvae (L4 – L6) also vary in colour from light to dark brown. Darker individuals appear when overcrowding occurs. The spots on the body are not always equally clear or apparent.

Source: D Visser ARC-VOP Roodeplaat (https://www.grainsa.co.za/upload/Fall-Armyworm-Identification-Presentation.pdf)