Fall Armyworm Management
Integrated Pest Management
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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:
| Crop | Threshold | Notes/Reference |
|---|---|---|
| Wheat and oats | Economic threshold estimated at 10 grubs/m2 (higher than barley because heads are rarely lopped). | https://ipmguidelinesforgrains.com.au/pests/armyworm/ |
| Barley | 2-3 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. | https://ipmguidelinesforgrains.com.au/pests/armyworm/ |
| Maize and sweet corn | At the seedling stage, if more than 5% of plants are cut. | https://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. | 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. https://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. https://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/ |
Soybeans (vegetative) Soybean (budding-podding) | 33% defoliation 3/m2 | Based on S. litura (DAF) https://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/ |
| Pasture (hay production only) | 2-3 larvae /sq foot | No permits currently. https://thebeatsheet.com.au/key-pests/fall-armyworm/faw-management/ |
Insecticides
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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.
| AFFIRM | PER89300 | Group 6 | Canola, pulse |
| AFFIRM | PER89344 | Group 6 | Cotton |
| AFFIRM | PER89371 | Group 6 | Certain cereals, maize |
| PROCLAIM OPTI | PER89285 | Group 6 | Brassica leafy vegetables, leafy vegetables, celery, blueberries |
| PROCLAIM OPTI | PER89330 | Group 6 | Nursery stock (non-food) |
| DURIVO | PER89280 | Group 28 + 4A | Brassicas, leafy vegetables, and fruiting vegetables |
| DURIVO | PER89330 | Group 28 + 4A | Nursery stock (non-food) |
| KARATE ZEON | PER89330 | Group 3A | Nursery stock (non-food) |
| ACELEPRYN | PER89290 | Group 28 | Turf |
Resistance Management
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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.