Don’t let crop residues spoil your harvest
By Brandy Rawnsley
With harvest drawing ever closer, it’s time to make sure the use of all agrochemicals in your vineyard have been recorded in your spray diaries.
It is the grape grower’s responsibility to keep any residues within the legal limit of the intended market. These are known as Maximum Residue Limits (MRLs).
The level of chemical residue remaining on your fruit at harvest can depend on several factors including; type and formulation of chemical; application rate; time of application and crop stage; number of applications; use of adjuvants; and weather conditions, at or after application.
Strictly following product labels helps ensure these MRLs are not exceeded and meet CropLife Australia’s agchem industry fungicide resistance management strategies. Yet, these restrictions may not meet the requirements for grapes used for export wine.
This is where the well-known ‘Dog Book’ (Agrochemicals registered for use in Australian viticulture), published annually by the Australian Wine Research Institute (AWRI), is vital. Following the Dog Book helps minimise the risk of exceeding the MRL in export countries and can be more stringent than the product label.
For example, the label for SWITCH® (active constituents cyprodinil + fludioxonil) states that applications can be made at 5% capfall, 80% capfall and pre-bunch closure or veraison for botrytis bunch rot control. This use is only suitable for fruit used in the domestic wine market.
For export purposes the Dog Book states SWITCH can be used no later than E-L 29 (berries peppercorn size; 4 mm diameter) and not used within 60 days of harvest. Furthermore, for resistance management, SWITCH should not be applied at both flowering and growth stage E-L 29.
The Dog Book withholding period is longer to minimise the likelihood of residues having negative effects on fermentation and not exceed standards set in overseas markets.
MRLs are legal limits. A late chemical application to grapes destined for the export market is likely to be detected. Up-to-date spray diaries are vital.
Biological and biorational products are highly beneficial for late season disease control and provide a viable option when traditional chemistry is restricted for use close to harvest. TIMOREX® GOLD is an excellent new option in this space. You can use a product that is not listed in the Dog Book as long as it is in consultation with the winery/grape purchaser and used according to approved product label.
It is important to keep up-to-date with latest information provided by the AWRI. A list of MRLs established for domestic and export wine grape markets can be found at the (AWRI) website at: http://www.awri.com.au/industry_support/viticulture/agrochemicals/mrls/
Electronic versions of the ‘Dog book’ (pdf, online search and app) are all updated regularly.
Dr Belinda (Brandy) Rawnsley is a Syngenta Technical Services Lead for Viticulture and Horticulture.