AMISTAR WG FUNGICIDE
- APVMA no.
- 50519
- Registrant
- SYNGENTA AUSTRALIA PTY LTD
- Formulation
- WATER DISPERSIBLE GRANULE
AMISTAR WG Fungicide is a broad-spectrum, protectant fungicide formulated as a water dispersible granule containing 500 g/kg of the active constituent azoxystrobin. It is widely utilised across Australian horticultural and agricultural districts, including avocado and mango orchards in the Atherton Tableland and Bundaberg, as well as viticultural blocks in Sunraysia and the Yarra Valley.
The product functions primarily as a preventive application to protect developing foliage, canopy growth, and fruit from target fungal pathogens such as anthracnose in tropical fruit and powdery and downy mildew in grapevines. Azoxystrobin offers systemic and translaminar activity, distributing locally within treated foliage to help defend leaf surfaces.
To ensure consistent efficacy and preserve long-term disease management options, this fungicide should be integrated into a strategic crop protection programme. Spray timings should focus on protecting vulnerable tissue ahead of critical infection windows, implemented alongside orchard or vineyard sanitation practices and rotated with alternative fungicide modes of action.
Active constituents
- AZOXYSTROBIN500 g/kg
Registered uses
| Crop | Pest or disease |
|---|---|
| Avocado | Anthracnose |
| Grape | Downy mildew |
| Grape | Powdery mildew |
| Mango | Anthracnose |
Withholding period
WHP: Avocados: Do not harvest for 7 days after application. Cucurbits Passionfruit Tomatoes: Do not harvest for 1 day after application. Grapes: Do not harvest for 14 days after application. Mangoes: Do not harvest for 3 days after application. Poppies: Do not harvest for 6 weeks after application. Potatoes: Not required when used as directed.
The withholding period (WHP) text defines the mandatory harvest intervals required between the final spray application and crop harvest. Harvest withholding intervals specified on the label range from one day for cucurbits, passionfruit, and tomatoes; three days for mangoes; seven days for avocados; fourteen days for grapes; to six weeks for poppies. For potatoes, a specific withholding period is not required when the product is used strictly according to label directions. Note that domestic withholding periods may differ from Export Withholding Periods (EWPs) or trade requirements for fruit sent to overseas markets; growers supplying export supply chains should verify destination standards prior to application.
Mode of action
Azoxystrobin belongs to the quinone outside inhibitor (QoI) class of chemistry and is designated as a Group 11 fungicide. It acts by inhibiting mitochondrial respiration in target fungi, blocking electron transfer and energy production. This biochemical mechanism prevents fungal spore germination, zoospore motility, and early germ-tube development, making it most effective when present on host plant tissue prior to pathogen infection.
Resistance management
Fungal pathogens carry a high risk of developing resistance to Group 11 fungicides if chemistry from this group is used repeatedly in isolation. Agronomists and growers should strictly follow resistance management strategies established by CropLife Australia and detailed on the approved product label. Key practices include limiting consecutive applications of Group 11 products, incorporating non-cross-resistant protectant or curative fungicides into spray programmes, and adhering strictly to seasonal application limits.
Tank-mix compatibility
Physical and chemical compatibility depends on water quality, formulation types, tank agitation, and atmospheric conditions during mixing and application. Always perform a physical jar test before broad-scale tank mixing when combining products for the first time. Exercise caution when mixing water-dispersible granules with emulsifiable concentrates or adjuvant oils under hot, dry conditions, as this can increase the risk of foliage or fruit damage. Consult the approved product label and mix partner labels for specific mixing instructions and compatibility warnings.
Handling and environment
Operators must read and observe all safety directions, personal protective equipment (PPE) requirements, and re-entry considerations set out on the approved product label. Take precautions to minimise spray drift beyond the target orchard block or paddock, avoiding contamination of waterways, aquatic ecosystems, and non-target crops. Store product in its original sealed container in a cool, well-ventilated location away from direct sunlight, seeds, fertilisers, and foodstuffs.
Common questions
- How does translaminar movement assist disease control in dense tree canopies or viticulture?
- Translaminar activity allows the active constituent to penetrate the upper leaf surface and move through leaf tissue to the underside. In dense crop architectures, such as mango blocks in Bundaberg or grapevine canopies in the Riverland, this local movement helps protect leaf surfaces that may not receive direct spray deposit.
- Why is preventive application critical when using Group 11 fungicides?
- Group 11 fungicides are most effective at inhibiting fungal spore germination and early cellular establishment. Applying the product preventatively before disease symptoms appear yields superior disease control and reduces the selection pressure for resistant pathogen populations compared to spraying established, severe infections.
- What steps should be taken to confirm compatibility before tank-mixing?
- Review the approved labels of all prospective tank-mix partners for specific cautions or prohibitions. Perform a small-scale jar test using water from the spray source to check for physical incompatibility, such as flocculation, settling, or separation, before filling the main spray rig.
- Where should growers verify export withholding standards before harvest?
- Export Withholding Periods (EWPs) and destination market Maximum Residue Limits (MRLs) may differ from Australian domestic WHPs. Viticulturists should check AWRI dog-book guidelines, while fruit growers should consult their industry peak body or packing shed exporter before scheduling late-season applications.
- What is the proper procedure for dissolving water dispersible granules (WG) in the spray tank?
- Ensure the spray tank is clean and filled to at least half capacity with water under active agitation before adding the water dispersible granules. Allow the granules to fully disperse throughout the spray solution before adding any liquid formulations, emulsifiable concentrates, or adjuvants.