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Pre-harvest herbicide applications

21/9/2021

Pre-harvest herbicide application or “crop-topping” can be a good opportunity to reduce weed seed numbers for the following year. Due to the products registered and the nature of the applications it is important that growers consider the impact of these late applications on chemical residues in grain. In order to ensure that residues do not exceed Australian MRLs it is critical that all applications are conducted in adherence with the product label. Growers are encouraged to discuss pre-harvest herbicide application with their agronomist to choose the most appropriate course of action.

Registered Products

Use only registered products, this is a legal requirement and will help ensure that Australian MRLs are not exceeded. The tables included in this document state the registered products by crop current as of September 2021. Consult the individual product labels via the APVMA website to confirm registrations have not changed:

Public Chemical Registration Information System Search - portal.apvma.gov.au

Rates, Timings and WHPs

Labels may have a rate range stated, applying at the minimum label rate required can help to minimise residues in grain. Application timing is always stated on the label and must be adhered to as this can have a significant impact on chemical residues in grain. Withholding Periods (WHP) can be found below the directions for use table and may differ between crop types.

Seed Set Management or Harvest Aid

Understanding whether the herbicide is being applied to control seed set of weeds or as a harvest aid either drying out weeds or crop will determine the most suitable herbicide for the planned task. For weed seed set control the aim is not to kill the weed, but to sterilise the seed.

Glyphosate on Barley: Declaration on Delivery

If glyphosate is applied to feed barley it is important to declare this on the CDF when delivering to CBH. This allows CBH to segregate glyphosate treated feed barley where necessary. Glyphosate is not registered to be applied to malt barley, so it is important that glyphosate treated barley is not delivered as malt. Maltsters and brewers require non-treated barley due to residues and germination issues.

For more detailed information refer to the product labels and consult with your agronomist.

Public Chemical Registration Information System Search - portal.apvma.gov.au

Lupins

Active

Product example

Rate

Timing

Withholding Period

AU MRL mg/kg

EU MRL mg/kg

Paraquat

Gramoxone, Shirquat

400-800 mL/ha

(250 g/L ai)

80% leaf drop onwards

7 days

1

0.02

Diquat

Reglone

2-3 L/ha

Full Maturity

1 day

1

0.2

Saflufenacil

Sharpen

34 g/ha + 1% MSO

80% leaf drop

7 days

0.03

0.03

Pyraflufen-ethyl

Sledge

200 mL/ha

80% leaf drop onwards

14 days

0.05

0.02

Glyphosate

(Permit)

Roundup UltraMAX

645-2150 mL/ha

Full Maturity

30% moisture

7 days

5

10

 

Wheat

Active

Product example

Rate

Timing

Withholding Period

AU MRL
mg/kg

S Korea MRL
mg/kg

Glyphosate

Roundup ULTRAMAX,

CRUCIAL

850 mL/ha-3.4 L/ha

(570 g/L ai)

28% grain moisture

(Late dough)

5 days

5

5

Diquat

Reglone

1-3 L/ha

Full Maturity

2

2

Saflufenacil

Sharpen

34 g/ha + 1% MSO

Z71-83, From watery ripe

7 days

0.6

0.5

Pyraflufen-ethyl

Sledge

200 mL/ha

Z71 onwards

 

0.05

0.01

2,4-D

Estercide Xtra 680

1.7 L/ha

(680 g/L ai)

After firm dough stage

 

0.2

2

 

Barley

Active

Product example

Rate

Timing

Withholding Period


AU MRL
mg/kg

Japan MRL

mg/kg

*Glyphosate

Feed Barley Only

Roundup UltraMAX

1.62 L/ha

(570 g/L ai)

28% grain moisture

(Late dough)

5 days

20

30

Diquat

Reglone

1-3 L/ha

Full Maturity

5

5

Saflufenacil

Sharpen

34 g/ha + 1% MSO

Z71-83, From Watery ripe

7 days

1

1

Pyraflufen-ethyl

Sledge

200 mL/ha

Z71 onwards

 

0.05

0.08

2,4-D

Estercide Xtra 680

1.7 L/ha

(680 g/L ai)

After firm dough stage

 

0.2

0.5

*Although glyphosate use for feed barley is now on label this still needs to be DECLARED at point of delivery.

Canola

Active

Product example

Rate

Timing

Withholding Period


AU MRL
mg/kg

EU MRL mg/kg

Glyphosate

Roundup ULTRAMAX,

CRUCIAL

1.2-3.4 L/ha

(570 g/L ai)

20% Seed colour change

20

10

Diquat

Reglone

1.5-3 L/ha

70% of pods yellow

4 days

5

1.5

 

Oats

Active

Product example

Rate

Timing

Withholding Period


AU MRL
mg/kg

EU MRL mg/kg

Diquat

Reglone

1-3 L/ha

Fully mature

4 days

5

1.5

 

 

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