Phosphorous acid is a registered fungicide with post-infection capabilities for downy mildew on grapes, with a withholding period of ‘DO NOT apply after E-L 33’.
Phosphorous acid residues in wine are to be expected if it is used at any time during the growing season. For this reason, many exporting wineries have no tolerance for fruit that has been treated with this active ingredient.
The ‘Dog book’ recommendation states that phosphorous acid should not be applied to fruit destined for export wines. Growers should contact their winery or grape purchaser prior to any phosphorous acid application.
Tolerance for phosphorous acid residues varies across Australia’s export markets. Accordingly, grapegrowers and winemakers should exercise care if intending to use phosphorous acid on grapes eventually destined for export, and ensure they are aware of the limits that apply for each relevant export market.
AWRI’s agrochemical online search facility provides the latest information on MRLs in different markets. This information is presented below for phosphorous acid by grouping markets with similar MRLs :
Group A
Three export markets − European Union member countries, New Zealand and United States of America − accept residue levels equal to or greater than the Australian MRL of 200 mg/kg of phosphorous acid (phosphonate) in grapes.
- If grapes are being grown for the domestic market or for export to these three markets only, the only requirement regarding the use of phosphorous acid is that label directions are followed.
- In New Zealand and the USA, phosphorous acid is exempt from the requirement of an MRL.
Group B
11 export markets – Great Britain and Turkey (100 mg/kg); Japan (70 mg/kg); Chile, Malaysia, Philippines, Russia, Singapore, Thailand, Turkey, Vietnam (60 mg/kg) − accept phosphorous acid residue levels greater than 50 mg/kg but less than 200 mg/kg.
- If exporting to these markets it is recommended that no more than three phosphorous acid sprays are applied and the last spray is applied no later than E-L 33, berries still hard and green.
Group C
Eight export markets – Korea and South Africa (25 mg/kg); LCBO** [temporary] and Canada (21 mg/kg); Taiwan (20 mg/kg); Hong Kong and India (10 mg/kg); China (T 7.5 mg/kg) – have residue tolerances lower than 50 mg/kg.
- Trials indicate that residues of phosphorous acid are highly variable and a reliable recommended use for phosphorous acid cannot be made for these markets.
** The LCBO has temporarily matched the MRL for phosphorus acid to the Canadian MRL, subject to its further review. As such, the LCBO will accept Australian wines produced from vintages leading up to and including the 2025 vintage, provided that:
- any phosphorous acid residues found in the finished, commercial wines imported by the LCBO are within the MRL of 21 mg/kg expressed as phosphorous acid (or 30 mg/kg expressed as fosetyl-Al)
- prior to export, prospective Australian exporters test their wines (that have been produced from grapes that have had phosphorous acid applied) to ensure compliance with the relevant MRL
- exporters provide the LCBO with a copy of the relevant Certificate of Analysis, upon the LCBO’s request.
Group D
Four export markets – Argentina, Indonesia Brazil, Israel – have no or very low tolerance for any phosphorous acid residues.
- Phosphorous acid should not be applied to grapes when final wine is destined for these markets.
This information is correct as of November 2024.