Fall armyworm

Alert

Have you seen Fall armyworm?

Be on the lookout and report signs to Biosecurity Queensland on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

Early detection and reporting are key elements in controlling Fall armyworm.

Fall armyworm (Spodoptera frugiperda) is an exotic pest that has been reported for the first time in the Torres Strait in January 2020.

Fall armyworm includes two subpopulations, or strains, that are morphologically indistinguishable but differ in their host plant preference and certain physiological features. Diagnosis by a laboratory is required to identify strain.

  • Rice-strain (R strain): feed on rice, millet, pasture grasses.
  • Corn-strain (C strain): feed on corn, cotton, sorghum.

The Torres Strait specimens have been identified as R-strain, however, there is potential for the strains to feed on crops other than their preference in times of scarcity.

The C strain has not been reported in Australia.

Fall armyworm is known to feed on more than 350 plant species, including maize, cotton, rice, sorghum, sugarcane, wheat, and many vegetable and fruit crops, and have caused significant economic losses overseas.

Destruction of crops can happen almost overnight when infestation levels are high.

While this pest is native to tropical and subtropical regions of the Americas, since 2016 it has rapidly spread to and throughout Africa, the Indian subcontinent, China and Southeast Asia.

Scientific name

Spodoptera frugiperda

Other names

  • alfalfa worm
  • buckworm
  • budworm
  • corn budworm or corn leafworm
  • cotton leaf worm
  • grass caterpillar or grass worm
  • maize budworm
  • rice caterpillar
  • wheat cutworm
  • whorlworm

Description

Adults

  • Moth, 15 to 20mm long nose to tail when resting
  • Brown or grey forewing and a white hind wing.
  • Male fall armyworm moths have more patterns and a distinct white spot on each of their forewings.

Larvae

  • Caterpillar-like.
  • When very young are about 1.7mm, light in colour with a larger, darker head.
  • As they develop, they attain a darker greyish-brown colour with paler, slender, lengthwise stripes and small dark spots with spines on their upper surface, with a pale underside.
  • Eventually reach a length of about 34mm.

Pupae

  • Shiny brown cocoon that is formed, usually in soil, but also sometimes in plant debris.

Egg

  • Pale yellow in colour and clustered together in a mass
  • An egg mass can contain 100–200 eggs.
  • Egg masses are usually attached to foliage in a mound, with a silk-like furry substance.

Plant stage and plant parts affected

The larvae can affect leaves, shoots, stems, trunk and fruit. Plants of different ages, from seedlings to mature plants, can be affected.

Plant damage

Fall armyworm larvae initially feed on leaves, creating pinholes and windows in leaf tissue, and giving leaf margins a tattered appearance. In grass-like plants, they often feed within the leaf whorl (where leaves radiate from or wrap around the stem or stalk; see image 2). Insect frass (droppings) is a sign that larvae are present.

Fall armyworm larvae can also eat buds and tunnel into and feed on fruit. Larger larvae can cut plants off at the base.

Many larvae may be present on 1 plant. When the larvae are very numerous they can defoliate preferred host plants and acquire an 'armyworm' habit and disperse in large numbers. Crops have been reported to be destroyed almost overnight.

May be confused with

Fall armyworm can be confused with a number of armyworm species that are present in Australia. If in doubt, contact Biosecurity Queensland on 13 25 23.

Distribution

Fall armyworm is native to tropical and subtropical regions of the Americas. Since 2016 it has rapidly spread to and throughout Africa, the Indian subcontinent, China and Southeast Asia.

Hosts

Depending on the strain of fall armyworm, there are approximately 350 plant species hosts. These include economically important cultivated grasses such as maize, rice, sorghum, sugarcane and wheat but also other vegetable and fruit crops and cotton. View the full list of known hosts.

Life cycle

Watch a video about the fall armyworm lifecycle.

Impacts

Fall armyworm poses a threat to Queensland's agricultural industries.

Damage caused by fall armyworm can reduce plant growth, significantly reduce crop yield and cause plant death. Severe infestations can destroy crops almost overnight.

Since fall armyworm can also graze on native grasses, our environment may also be impacted.

How it is spread

The adult moths are capable of flying long distances. In the Americas, adult moths can undertake annual seasonal migration as far north as Canada.

Fall armyworm can also spread through people movement. It is believed that the arrival of fall armyworm in Africa was on a passenger flight.

Fall armyworm can spread on the illegal importation or movement of infested plant material.

The Australian Government closely regulates approved imports of plant material and monitors for illegal plant movement.

Monitoring and action

Inspect your plants regularly for the presence of unusual pest and disease symptoms.

To help identify symptoms of fall armyworm, examine plants for:

  • leaf damage, including pinholes, windowing, tattered leaf margins, skeletisation and defoliation of plants
  • tiny larvae, less than 1mm, that are more active at night, eating pin holes and transparent windows in leaves
  • bigger larvae grazing on leaves, stems, trunk and fruit, and leaving behind insect frass (droppings)
  • in grass-like plants, larvae are often in plant whorls (where leaves radiate from or wrap around the stem or stalk; see image 2)
  • sudden crop damage and collapse.

If you suspect fall armyworm, report immediately to Biosecurity Queensland on 13 25 23.

Control

Call 13 25 23 if you find a plant you suspect may be Fall armyworm to seek advice on control options.

Legal requirements

The Australian Government Department of Agriculture has import conditions in place for importing plants and plant products.

Further information

Further information about fall armyworm is available in the CABI Invasive Species Compendium.