Fall Armyworm Q & A

What is fall armyworm?

Fall armyworm is an invasive pest, which has been reported to feed on more than 350 plant species, and impacts economically important cultivated grasses such as maize, rice, sorghum, sugarcane and wheat, as well as fruit, vegetable and cotton crops.

Fall armyworm is native to tropical and subtropical regions of the Americas, and since 2016 has spread to Africa, the Indian subcontinent, China and South East Asia.

Adult moths are highly mobile and can fly long distances with suitable weather conditions. This pest is also prolific, reproducing at a rate of several generations per year.

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

Australia’s climate and the production of suitable hosts are favourable for fall armyworm to establish and spread. Australia’s environment and native flora may also be impacted.

What does fall armyworm look like?

Adults are moths that range from 32–40mm in length (wing tip to wing tip) and typically rest with their wings in a tent-like position. The forewing is brown or grey and the hindwing is white. Male moths have more patterns and a distinct white spot on their forewing.

The larvae are light green to brown with a larger darker head. As they develop, they become darker with white lengthwise stripes and dark spots with spines. Older larvae (30–36 mm) have a distinctive pattern of four spots on the second to last body segment and an inverted ‘Y’ shape pattern on their heads.

The pupae are red-brown, 14–18 mm long and approximately 4.5 mm wide. Pupation mostly occurs in soil under the host plant, and occasionally in host vegetation.

Eggs are pale yellow and 0.4 mm in diameter and 0.3 mm high. They are laid in furry ‘egg masses’, which stick to foliage. There are 100–200 eggs in a ‘mass’.

How does fall armyworm spread?

The adult moths are capable of flying long distances aided by wind currents.  All life stages can be moved on infested plant material.

When is fall armyworm most active?

Adult moths are nocturnal and are most active during warm, humid evenings.

Fall armyworm larvae are most active during late summer and early autumn months, however they can be active year-round in tropical areas.

Fall armyworm is most likely found in warm, moist regions with little forest cover.

What are the symptoms of fall armyworm and what should growers look out for?

Depending on the plant, fall armyworm can cause significant and sudden crop damage and collapse if left unchecked.

Symptoms of fall armyworm include leaf damage such as pinholes, windowing, tattered leaf margins and defoliation of plants.

Growers should also look out for tiny larvae, less than 1 mm, that are more active at night, eating pin holes and transparent windows in leaves and bigger larvae grazing on leaves, stems and fruit, and leaving behind insect excrement.

In grass-like plants, larvae are often in plant whorls where leaves branch from the stalk.

Are any similar pests already present in Queensland?

Fall armyworm can be confused with a number of armyworm species that are present in Australia, however fall armyworm is very different in terms of its impacts.

Distinguishing fall armyworm from similar looking moths or caterpillars requires specialist diagnosis. Common armyworm species include: Mythimna convecta (common armyworm), Mythimna separata (northern armyworm), Spodoptera exempta (dayfeeding armyworm) and Spodoptera mauritia (lawn armyworm).

More information about these species is available at: https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/crop-growing/pests-field-crops/armyworm.

When was fall armyworm detected in Australia?

Fall armyworm was first detected on two Torres Strait islands in January 2020. The first mainland detection in Australia was at Bamaga in February 2020.

Subsequent detections of fall armyworm were on a property in the Gulf country of north-western Queensland, and in South Johnstone, Tolga and Lakeland in North Queensland.

The latest detection is in the Burdekin area in North Queensland.

Can fall armyworm be eradicated?

The Consultative Committee in Emergency Plant Pests has determined that it is not technically feasible to eradicate fall armyworm from Australia.

Fall armyworm moves and reproduces fast, and feeds on a very wide range of plants. It is well established in our nearest neighbours and could be continually reintroduced. It has never been eradicated anywhere else in the world.

How have other countries affected by fall armyworm tried to eradicate it?

No other countries have tried to eradicate fall armyworm. Given how quickly the pest moves, most countries have had little time to respond, and they have moved quickly to pest management.

In well-managed crops, there has been reasonable success using chemical treatment. More work will be undertaken to provide industry with appropriate recommendations for control of the pest.

How can I manage an outbreak?

Early detection is essential. Regularly check all your crops or pastures for unusual insect activities.

Key to the control of any pest is an integrated pest management approach. The Department, in collaboration with industry, is working to identify strategies and tactics for the medium to long-term response.

It is essential with any pesticide use for fall armyworm control that the implications for chemical resistance development in other pests that may be exposed (e.g. Helicoperva) and the potential impact on natural enemies are considered.  Fall armyworm is also known to rapidly develop pesticide resistance.

Currently, the Australian Pesticide and Veterinary Medicine Authority (APVMA) has issued a number of permits (PER88638, PER89259, PER89241, PER85447) for the use of certain chemicals for the control of fall armyworm for a range of plants. It is important that the permits are read in full.

The APVMA is currently assessing, as a priority, additional applications for permits for the use of chemicals against fall armyworm. It is important to check for the latest chemical permits applying to fall armyworm using the APVMA’s permit portal—search for ‘fall armyworm’ and check the ‘pest/purpose’ button. The portal can be found at portal.apvma.gov.au/permits.

What is the Queensland Government doing?

Traps have been established or are being established by the Queensland Department of Agriculture and Fisheries (DAF) at many sites in Queensland, including:

Burdekin, Bowen, Mackay, Richmond, Rockhampton, Longreach, Kingaroy, Emerald, Biloela, Bundaberg, Gayndah, Nambour, Dalby, Goondiwindi, Gatton, Toowoomba and Brisbane.

DAF will continue surveillance and monitoring of the spread of this pest, including for any new introductions/population changes.

In the medium to long-term DAF will work with industry to:

• identify the crops most favoured by the pest
• assist industry to access appropriate chemical controls
• help industry manage any pesticide resistance.

DAF has:

• disseminated information on the pest and the detections (via email alerts, social media, media releases, fact sheets)
• developed eight fact sheets, covering:
  • wheat
  • maize
  • cotton
  • sugarcane
  • sorghum
  • sweet corn
  • vegetable crops
  • pastures
• drafted fact sheets on sweetpotatoes and melons
• established a Queensland website landing page with information about the pest. The address is business.qld.gov.au/fallarmyworm
• convened an industry/government communications working group to share information
• held a technical workshop with key industry players on Monday 9 March 2020
• held an open, industry webinar on Friday 13 March 2020.

Does it re-establish in crops over time?

As with most insect pests, it will continue to feed on a host until the food source is exhausted.

The pest will likely attack host plants at varying stages and ongoing control is likely to be required throughout a crop’s production.

Are the affected host crops safe to eat if damaged by fall armyworm?

There is no risk to humans from consumption of produce from plants affected by fall armyworm.

However, caution is advised where there are secondary infections resulting from damage and spoilage.

What are the legal requirements around fall armyworm?

Fall armyworm represents a new biosecurity threat for Queensland (and Australia).

It is not currently listed as prohibited or restricted matter in Queensland’s biosecurity legislation, however there are requirements under the Biosecurity Regulation 2016 in relation to the movement of plant material that may carry pests.

Far North Queensland is a high-risk area for the introduction of plant pests and diseases from nearby Papua New Guinea and Indonesia. The spread of pests into the rest of the state poses a significant risk to our agricultural industries.

Two far northern biosecurity zones have been established in the northern half of Cape York Peninsula to control movement of risk items that may carry pests and diseases southwards to production areas. Plants, plant pests, soils and related equipment must not be moved out of these zones without a biosecurity instrument permit.

What can growers / producers do?

Growers and producers should already have strong on-farm biosecurity measures to protect their crops from pests and diseases.

Crops should be monitored for signs of leaf damage leading to defoliation of the crop and report suspected sightings to assist with early detection, and potential treatment.

Good farm hygiene should be implemented for weed control to remove hosts that could build populations.

More information on farm biosecurity is available at farmbiosecurity.com.au or biosecurity.qld.gov.au.

What do I do if I suspect fall armyworm is on my property?

Anyone who comes across fall armyworm is strongly encouraged to photograph and report suspected sightings to the Department of Agriculture and Fisheries on 13 25 23, their agronomist, local biosecurity officer or extension officer.

Images can be sent to the DAF Customer Service Centre; call them on 13 25 23 for advice on how to do this.

Is the egg mass gooey/slimey when wet from rain?

The egg masses have a layer of scales over them and should be fairly resistant to rain and weather. It is unlikely they will become slimey or gooey after rain.

Do FAW only lay on the undersides of host vegetation, or on man-made structures too?

Eggs may be laid on the underside or the top side of leaves. The eggs will look a lot like other endemic armyworm/cluster caterpillar egg masses. As with other endemic Spodoptera species, it is likely they may also lay on man-made structures.

Will fall armyworm affect pastures?

Fall armyworm is reported to feed on tropical and subtropical grasses in grazing systems overseas. It is likely that tropical and subtropical pastures in Queensland will support populations of fall armyworm in suitable seasons.

It is unclear what impact fall armyworm might have on pasture productivity, but outbreaks of dayfeeding armyworm (Spodoptera exempta) have caused significant short-term defoliation in buffel pastures. This defoliation can kill seedlings and retard the growth of established plants. Infested pasture may be reinfested by the offspring of the first infestation.

Grasses that fall armyworm infest overseas include:

• Sorghum haleepense, common name Johnson grass
• Chloris gayana, common name Rhodes grass
• Agrostis spp., collectively called bent grasses
• Digitaria spp., collectively known as pangloa, digit or finger grasses
• Cynodon dactylon, common names include: couch, green couch, couch grass
• Poa spp., common names in Queensland include: annual Poa, winter grass
• Panicum spp., collectively known as panics.

Most of these are common across Queensland, in grazed pastures, hay production, and urban situations.

The potential for fall armyworm to infest other important native (e.g. Mitchell grass, spear grass, blue grasses) and sown pastures (e.g. buffel grass, Rhodes grasses) is unclear, but it is possible these could be suitable host plants.

Hay production, including lucerne, may be at risk of production loss caused by fall armyworm infestation, including irrigated production over winter in warmer regions.

Will fall armyworm affect macadamias?

As fall armyworm is new to Australia, we are relying on information and experience from overseas.

It is expected fall armyworm is unlikely to be an issue for macadamias.

If it breeds in very large numbers and then consumes all of its preferred hosts, it develops an ‘army’ like phase, where it can then attack anything that is in its path. If this were to occur during flowering it could be an issue, but we believe this would be a rare event.

Which fruit and vegetables will fall armyworm affect?

As fall armyworm is new to Australia, we are relying on information and experience from overseas.  The following have been reported overseas as hosts: apple, banana (could be a minor issue), citrus, mango (less preferred), melon (but no crop loss expected), onion, potato, processing tomato, table grape, sweet corn, eggplant, cucurbits.

It is expected that sweetcorn is most susceptible to damage from fall armyworm.  

Where can I source fall armyworm photos for use in communications?

There are a large number of fall armyworm images at the University of Georgia’s bugwood.org site (https://www.bugwood.org/programs_services.cfm) at the insect images section (https://www.insectimages.org/ - search for fall armyworm). The images are free to use with acknowledgement (details with each image). To get the high resolution versions you have to register (it’s free).

Updated 16 March 2020