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Met your maximum residue limits this season?

Viticulture
11.02.2021
Vine Talk columnist and Syngenta Technical Services Lead Dr Brandy (Belinda) Rawnsley.
Have you heard the latest tips, tricks and industry advice? Vine Talk author, Dr Brandy (Belinda) Rawnsley takes a look at the issues facing grape growers.

Most growers would have implemented a well-planned spray program for pest and disease control this season. As grape harvest approaches, testing by the winery will ascertain if chemicals were applied at the correct application time during the season.

 

There are strict product guidelines for when to apply fungicides, insecticides and herbicides to minimise the risk of chemical residue remaining on the fruit at harvest. Guidelines are set to satisfy the lowest maximum residue limit (MRL) in grapes for any of the major wine markets.

 

If you’ve followed the product guidelines in the AWRI dog book or those set by your winery, the chance of exceeding the required MRL is low.

 

But there may be differences between recommendations on the product label compared to those listed in the dog book.

 

Product labels provide important information on rate, timing and withholding periods that are acceptable for fruit destined for the domestic market.

 

In most instances, labels do not take into consideration where the fruit will be sold. Some countries set lower or no MRLs for chemicals used in Australia, and for this reason, spray timing on the label may be very different than allowed for the export wine market.

 

For example, the product label SWITCH® (containing active ingredients cyprodinil and fludioxonil) states it can be used on two occasions at either 5% capfall, 80% capfall, pre-bunch closure or at veraison. Yet the AWRI restrict cyprodinil use to one spray per season and use no later than E-L 29 (berries pepper-corn size) and not within 60 days of harvest.

Therefore, if you have used SWITCH twice in the season according to the label and not to AWRI specifications, harvested grapes are only suitable for domestic sales.

It is also important to keep up to date with agrochemical updates, as product use patterns can change. In 2020, the use of mancozeb was restricted to three sprays per season and no later than E-L 31 (berries pea-size, not >7mm in diameter).

 

As some countries, such as India and Japan, impose low to undetectable MRLs for many chemicals used in Australia, it’s important to know your market and intended end use. Look at your spray diary and if in doubt, consult your winery.