Guidelines for agrochemical registrants seeking to have active constituents recommended for export wine included in Agrochemicals registered for use in Australian viticulture (the ‘Dog book’)
This page provides information on the data agrochemical companies are advised to provide for new active constituents to be considered for inclusion in the AWRI’s ‘Dog book’ as recommended for use on grapes destined for export wine. Residue data needs to be provided for both grapes and wine. Where residues are present in grapes, wineries prefer to have information about degradation through winemaking (processing factor) and unless residue limits are globally accepted, a withholding period (WHP) that results in no quantifiable residue in wine should be known.
Trials
Grape and wine residue data from a minimum of six sites covering a range of climates (cool to hot) is recommended. It is preferred that data comes from studies done on Australian sites, but a combination of Australian and overseas data is acceptable.
A climatic classification of some Australian regions are provided as examples:
- Cool: Tasmania, Mornington Peninsula, Yarra Valley, Great Southern
- Warm: Barossa, McLaren Vale, Pyrenees
- Hot: Riverland, Hunter Valley, Swan Valley, Rutherglen
It is preferred that trials are undertaken on grape varieties that are common to the region where the trial is held. The variety of the grapes does not matter for residue testing but the grapes must come from a wine-grape variety (table grapes are not acceptable). One of the six sites should represent grapes destined for sparkling wine that are harvested at a lower ripeness (16–19.5°Brix).
Treatments
At the six test sites there should be a control (untreated) and a treated sample. The treatments should be applied according to directions (e.g. rate, maximum number of applications) that will be on the label. The final application must be applied at the withholding period (WHP) that the registrant feels will yield the appropriate residues to satisfy export markets that do not have an MRL. In most cases, this will be a non-detectable residue. For instance, if E-L growth stage 31 (berries pea-size, 7 mm diameter) is the label WHP, the last application at each of the six sites would be E-L 31. If the registrant is unsure and wants to investigate the residue levels at different withholding periods, then additional treatments will need to be applied and residue tested.
At two of the six test sites, an additional treatment is required. This treatment has the product applied according to label directions but at twice the label rate. This treatment should provide samples containing higher levels of residues than typically expected. Samples from these sites, untreated control (no treatment), Treatment 1 (label rate and recommended WHP) and Treatment 2 (2 x label rate, recommended WHP), should be submitted for a fermentation and wine quality study (see below). This study is used to confirm that at higher residue levels there will be no effect on wine quality. Samples from these sites should be red grape varieties, as this ensures the best quality results from the study.
Samples from each of the six sites should be submitted for processing studies. These should include: the untreated control; label treatment rate at the recommended WHP; and the twice the label treatment rate at the recommended WHP. If the WHP is not known prior to the study, suitable samples should be taken at each WHP being tested to allow for processing samples to be selected once the grape residues have been determined.
Residue data
At the end of the trial, the following residue data should be available:
- Untreated control – six grape samples and six wine samples
- Treated (1 x label rate) – six grape samples and six wine samples
- Treated (2 x label rate) – two grape samples and two wine samples
In cases where data from overseas studies is available, registrants should contact the AWRI to discuss what additional data may be required.
Note: Some regulatory authorities may require residue data on samples of juice and pomace (recycled for animal feed). Consideration may need to be given to the inclusion of these commodities when establishing the study protocol.
Fermentation and wine quality study
Fermentation and wine quality studies are performed to provide the wine industry with the knowledge and assurance that the active constituent or product is not going to have a detrimental effect on fermentation or wine quality. Such an effect could include the formation of off-flavours or aromas due to the breakdown of the active constituent itself.
The fermentation and wine quality study is performed independently of the residue study and a minimum of 20 kg is required for each sample or treatment in the study. Ideally, samples should be taken from both sites where 2 x label rate applications have been implemented, with one acting as a back-up for the other and a minimum of the untreated control, 1 x label rate application and 2 x label rate applications being submitted for the study. If no detectable residues are present in the samples, the study can still proceed based on the possibility that the active constituent may have been converted to a secondary metabolite or broken down to another compound which may affect fermentation or wine quality.
Fruit condition must be sound as wine made from spoiled, mouldy or unripe fruit will not be suitable for a fermentation or wine quality assessment. The grapes should be harvested at commercial quality or ripeness (21–26°Brix) and it is recommended that a °Brix reading be taken prior to harvest. Ideally, the fruit should be at a similar level of maturity (based on °Brix) across the different treatments. It is strongly advised that samples be frozen as soon as possible after harvest as these studies rely heavily on good fruit quality to ensure the best outcome.
The winemaking protocol followed for these studies should reflect that of processing red varieties into wine, considered the worse-case-scenario for residues due to the skin contact employed in the process. This technique is not suitable for white grape varieties and tends to make wines which are quite unpalatable and not suitable for the sensory component of the study. Hence, it is strongly recommended that these studies are conducted with red grape varieties.
Using the above approach enables a residue and processing study to be completed in the same vintage as a fermentation and wine quality study.