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Fall Armyworm

Fall armyworm arrived in Australia in January 2020, and in less than a year has become established throughout Queensland, the Northern Territory and Western Australia, with seasonal incursions into southern states such as New South Wales.

Syngenta Australia is working with the industry and the Australian Pesticides and Medicines Authority (APVMA) to create solutions, including permits, so farmers can effectively manage this uniquely devastating pest.

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)

 

FAW

Management

Understand your risk with regard to fall armyworm distribution and potential seasonal distribution. If you are within an area of concern, stay abreast of local sightings. Cesar provide an excellent resource with sightings noted on a map: http://cesaraustralia.shinyapps.io/MothTrapVis/

Management

Understand your risk with regard to fall armyworm distribution and potential seasonal distribution. If you are within an area of concern, stay abreast of local sightings. Cesar provide an excellent resource with sightings noted on a map: http://cesaraustralia.shinyapps.io/MothTrapVis/

Integrated Pest Management

As with many pests, fall armyworm will require an integrated approach to management, comprising of cultural, biological and chemical control methods.

Cultural practices can help reduce your risk of fall armyworm populations. This may include reducing host plants (including weeds); managing sowing times to avoid the potential for pests to jump from paddock to paddock; and destroying plant material after harvest. The Fall Armyworm Continuity Plan lists cultural practices that have been used overseas that may have application to certain situations in Australia.

These include:

  • Early harvest of crops in northern Australia
  • Crop rotations with non-host plants, particularly in areas of year-round production
  • Good crop nutrition, and
  • Promotion of beneficial species via provision of non-crop habitat

Fall armyworm has many natural enemies that help reduce their population levels. These include generalist predators (ants, earwigs, etc.), specialised parasitoids (small wasps that kill eggs or larvae), and pathogens (bacteria, virus and fungus). Management decisions that assist in building and preserving beneficial populations include:

  • Provide non-crop habitat as a refuge
  • Releasing beneficial inescts into the crop and/or refuges to augment natural populations, species such as Trichogamma pretiosum, that are available locally are ideal, and
  • Choosing selective insecticides if/when they have to be used, so any impact on beneficial insect populations is minimised.  

Maintaining beneficial populations will contribute towards the management of fall armyworm, but given its explosive population dynamics, it is unlikely that beneficials alone will be able to manage the pest in all situations. Insecticides will also contribute towards the management of fall armyworm and choosing appropriate products to minimise impacts on beneficials, as well as rotating chemical groups according to industy guidelines for resistance management will be crucial.

Monitoring for Fall Armyworm

Regular crop inspection and correct insect identification is critical to effectively manage fall armyworm. Using pheromone traps can provide an early detection system, to trigger an increase in the frequency of crop inspections. Crop inspection technique will vary with the crop. In general, it's best to avoid a 2 metre border around the edge of the paddock and randomly sample 30-50 plants in a ‘W’ or ‘Z’ pattern.

Local research has established thresholds for Australia in some crops. However, some of the thresholds listed below from the US are also a useful guide:

CropThresholdNotes/Reference
Wheat and oatsEconomic threshold estimated at 10 grubs/m2 (higher than barley because heads are rarely lopped).http://ipmguidelinesforgrains.com.au/pests/armyworm/
Barley2-3 large armyworm/m2 of crop (based on ground and plant sampling). 1 head of barley/m2 equals 10 kg grain/ha. 1 larvae/m2 can cause a loss of 70 kg/ha grain/day.http://ipmguidelinesforgrains.com.au/pests/armyworm/
Maize and sweet corn

At the seedling stage, if more than 5% of plants are cut.
At the early whorl stage (knee high), if more than 20% of plants are infested.
At the late whorl stage (shoulder high), if more than 40% of plants are damaged and live larvae are present.
At the tasselling/early silking stage, in sweet corn, if more than 5% of plants are infested and in maize, if more than 20% of plants are infested.

http://www.agric.wa.gov.au/fall-armyworm-western-australia?page=0%2C5#smartpaging_toc_p5_s0_h3
Sorghum

At the seedling stage, if more than 10% of plants are cut.
At the early whorl stage (knee high), if more than 30% of plants are infested.
At the late whorl stage (shoulder high), if more than 40% of plants are damaged and live larvae are present, and

At the panicle emergence stage, if more than 5-10% of plants are infested.

Economic thresholds have not yet been developed for sorghum grown in Australia.  The action thresholds recommended overseas for applying control measures for fall armyworm vary with the growth stage.

http://www.agric.wa.gov.au/fall-armyworm-western-australia?page=0%2C6#smartpaging_toc_p6_s0_h3

Cotton -

Monitor crops for leaf damage and fruiting site feeding. Bollgard 3 will incidentally suppress FAW.

http://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/

Soybeans (vegetative)

Soybean (budding-podding)

33% defoliation

3/m2

Based on S. litura (DAF)

http://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/

Pasture (hay production only)2-3 larvae /sq foot

No permits currently.
Armyworm outbreaks (other species) are not uncommon.

http://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/

 

Insecticides

The Australia Pesticide and Veterinary Medicine Authority (APVMA) has issued a number of emergency use permits so growers can effectively manage fall armyworm on a number of susceptible crops. The permits, plus new ones as they are issued, can be found on the APVMA website (https://portal.apvma.gov.au/permits).

When selecting an insecticide to manage fall armyworm it is important to:

  • Conduct regular fall armyworm monitoring for insects and damage.
  • If you are going to spray, target early instar larvae before they become entrenched. Smaller larvae (1-2 instar larvae, <6 mm) are more susceptible to insecticides.
  • Before spraying, consider the beneficial insects that have been recorded in the crop and any impact the spray may have on that population, which also contributes towards the management of fall armyworm.
  • Ensure you ONLY use an insecticide when fall armyworm populations are at a level where economic injury is likely to occur (action threshold).
  • If an action threshold has not been established for your crop, in your region, consult your local Agricultural Department for advice.
  • Rotate insecticides with different modes of action to avoid selection for resistance. Refer to the CropLife fall armyworm strategy and regularly check for updates on the latest research and advice from state agricultural departments, CSIRO, GRDC, AUSVEG and other industry bodies as listed in the Resistance Management tab. 
  • Consider all other insect pests that might be present within the crop, where they exist, and follow existing CropLife resistance management strategies for that pest.

Syngenta products approved for the management of fall armyworm

Syngenta Australia has an accelerated fall armyworm research and development program including both seed treatments and foliar insecticide solutions.

In the interim, the APVMA has issued several permits that allows the use of certain Syngenta Australia products for the control of fall armyworm. Growers must follow all instructions as outlined in the permit, including the permitted crops, the rates and application methods. Note: Victoria is not included in these permits, as their Control-of-Use legislation means a permit is not required to legalise this off-label use in that state.

AFFIRMPER89300Group 6Canola, pulse
AFFIRMPER89344Group 6Cotton
AFFIRMPER89371Group 6Certain cereals, maize
PROCLAIM OPTIPER89285Group 6Brassica leafy vegetables, leafy vegetables, celery, blueberries
PROCLAIM OPTIPER89330Group 6Nursery stock (non-food)
DURIVOPER89280Group 28 + 4ABrassicas, leafy vegetables, and fruiting vegetables
DURIVOPER89330Group 28 + 4ANursery stock (non-food)
KARATE ZEONPER89330Group 3ANursery stock (non-food)
ACELEPRYN PER89290Group 28Turf

Resistance Management

Globally, fall armyworm has evolved resistance to multiple insecticides including Bacillus thuringiensis toxins in some genetically modified crops. Recent Australian research indicates that some populations of fall armyworm collected in northern Australia in 2020 carried genetic markers for resistance to organophosphates (Group 1B) and carbamates (Group 1A).

To help manage resistance, it is important to rotate the insecticide mode of action groups and incorporate other controls where viable options are available. After applying an insecticide, growers should monitor the crop to establish the effectiveness of the treatment  and to determine further actions if required.

CAUTION: A spray failure does not necessarily mean that the pest has developed resistance to a product or insecticide group and further testing may be required to confirm this. A spray failure could also eventuate from incorrect spray timing of the insect life stage (i.e. targeting larger larvae) or crop stage for the product. Furthermore, growers should also confirm that the spraying conditions and their spray equipment has been properly set up to ensure good coverage of the target area. Always use the recommended rates and follow any other directions of use that are outlined in the permit.

In conjunction with growers, researchers and agronomists, the CropLife Australia Insecticide Resistance Management Review Group (IRMRG) has developed an insect resistance management strategy for fall armyworm. The aim is to minimise the development of insect resistance to insecticides. These strategies outline the guidelines for insecticide use (and other methods) for sustainable insect control. 

Managing your program from a Mode of Action perspective will help ensure appropriate rotation of chemistry. Please refer to the DPI website where there is a table that identifies the Modes of Action available for use in each crop. 

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Durivo

Horticulture
Nursery stock (non-food)

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A full list of products for Emergency Permit use is listed on the APVMA website.

Further information

Information on fall armyworm is growing very rapidly with sources being made available around the globe.

A recording of a Growcom webinar and most of the facilitated session on R&D gaps analysis was made. To view the recording, click here

An earlier series of webinars on fall armyworm was presented by AusVeg. These can be accessed here

Some industry resources are listed below. This is not a comprehensive list, but a more focussed, localised collection of knowledge.

Queensland Department of Agriculture and Fisheries Crop Fact Sheets

Queensland Department of Agriculture and Fisheries Fall Armyworm information

Full list of host plants (CABI)

Life cycle of the fall armyworm video (CABI)

Sugar Research Australia fact sheet

Cotton Info fall armyworm ID guide: From Endemics to Exotics

The Beatsheet: Pest Management for the Northern Grain Region

Helicoverpa Economic Threshold Calculator

Queensland DAF Farm Biosecurity advice

Grains Farm Biosecurity Program

Farm Biosecurity (Grains)

For more information

Contact your local Syngenta representative, call 1800 022 035 or click on the link below.