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Controlling fungal diseases in wine grapes

wine grape fungicide

Controlling fungal diseases in wine grapes

Babich Wines own and manage seven vineyards in the Wairau, Waihopai and Awatere valleys in Marlborough. For David Bullivant, Babich Wines’ Marlborough Area Viticultural Manager, making sure the vines are protected against major wine grape diseases such as Botrytis and powdery mildew (Erysiphe necator) is a core aspect of their vine management programme.

Both diseases are weather-driven. High humidity or prolonged rain in conjunction with cool or mild temperatures results in persistent moisture on berry surfaces and promotes Botrytis infection and disease development. In a similar vein, high humidity encourages spore formation of powdery mildew then spore dispersal is favoured as the humidity reduces.

David says the 2021-22 growing season was challenging with numerous rain events. Botrytis and slip skin was a problem for growers in the Marlborough district who didn’t apply a suitable protective fungicide.

He addressed the risk of both diseases developing in 300 ha of vines by preventatively applying Miravis® Prime at 80 percent cap-fall.

“Miravis Prime delivered good control of powdery mildew,” David says. “This meant we didn’t have any lesions on the grapes. It’s important to control powdery mildew initially as the berry scarring from this disease creates an entry point for Botrytis.

”David is planning to use Miravis Prime again this season to protect the vines. “Based on its performance against these two key diseases that I’ve seen so far, I’ll also be recommending to our contract growers that they should apply Miravis Prime at the recommended timing this coming season.”

Botrytis resistance management is another aspect David keeps in mind. “A feature of Miravis Prime is that it contains two active ingredients working on multiple sites of the fungi cells. Basically, this combination means the product has built-in resistance management which is helpful from our perspective.”

Following a review of new and existing residue data for Miravis Prime, the 2022-23 New Zealand Winegrowers vineyard spray schedule lists a reduced nil residue pre-harvest interval of 90 days, down from 98 days, or the start of EL25 (80 percent cap-fall), whichever comes first.

Dean Perry, Syngenta Territory Sales Manager, notes that not all countries to which New Zealand wines are exported set Maximum Residue Limits (MRLs) for pydiflumetofen (also known as Adepidyn® technology), the active ingredient in Miravis Prime. “Therefore, wine residues need to be below the limit of quantification, or <0.01ppm.”

The following recommendations have recently been issued in the first update of the spray schedule and should be followed to ensure the limit is not exceeded:
1. Ensure Miravis Prime applications are made as early as possible in relation to the EL25 growth stage (as defined in the spray schedule). The largest berries in the vineyard should not exceed  2 mm in diameter at application.

2. Residue testing final wine lots is recommended where there has been fermentation or maceration on skins. Recognising that application timing isn’t always precise, if application timing has crossed over into EL26 (cap-fall complete), residue testing of all wine lots should be completed.

David says the new 90-day nil residue pre-harvest interval will make a big difference. “It allows much more flexibility to manage the commencement of harvest.”

Other points about Miravis Prime to be noted are that applications should be made preventatively from the start of flowering up to 80% cap-fall and only one application is permitted per season. Use the Grapelink calculator to determine the per hectare rate.

More information on how to use Miravis Prime in your crop protection programme is available from your local Fruitfed Supplies Technical Horticultural Representative.

AVCM registration number: Miravis® Prime #P009724. Read the registered label before use.