Pre-harvest herbicide applications

29/8/2022

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 August 2022. 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	7 days	0.05	0.02
Glyphosate	CRUCIAL	600-1600 mL/ha	Full Maturity 30% grain 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

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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