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Fungal disease control options in grapes

Grape disease

Fungal disease control options in grapes

Getting in front of costly fungal diseases like powdery mildew (Erysiphe necator) and Botrytis before they take hold in your grapevines this season relies on careful planning and integrating best practice control techniques.

Fungicides are only part of the strategy, but they remain important for helping protect the value and quality of your grapes at harvest time, so it pays to select and apply them for maximum effect.

Prolectus® has been described as a multi-tool in the range of resources available for mitigating the risk of Botrytis while maintaining sustainable spray programmes. It’s a protectant treatment with effective curative properties after infection by Botrytis, which can offer flexibility during unpredictable spring weather.

This Group 17 fungicide contains fenpyrazamine, an active ingredient which penetrates quickly into the crop and blocks Botrytis in various stages of its biological cycle. Nufarm Development Manager Alan Cliffe says its multi-site activity makes Prolectus a good rotation partner in a disease management programme to help with fungicides which have a different mode of action.

Prolectus moves rapidly through plant tissue, which helps control infections that may have been missed on the underside of grape leaves during application.

“It also means that it only requires a short drying period. In a laboratory bioassay study using inoculated cucumber leaves Prolectus was rainfast in 30 minutes,” Alan says.¹

As a part of an effective preventative programme for Botrytis, he recommends applying Prolectus at any two of the following critical timings: early flowering (5 percent cap-fall), late flowering (80 percent cap-fall) or pre-bunch closure. The pre-harvest interval is 65 days before harvest.

Digger EW is a broad-spectrum, systemic fungicide with preventative activity against powdery mildew in grapes. This DMI fungicide contains the active ingredient difenoconazole (Group 3) which penetrates grape tissue rapidly to control disease by preventing the development of sterols in the cell wall of the fungus.

Digger is systemic and moves upwards through the plant tissue once applied. Refer to recommended water rates on the label to ensure the canopy is fully wet after application.

For effective powdery mildew control, Alan says growers should apply Digger at critical timings when vines and fruit are most susceptible to infection such as flowering or pre-bunch closure. It may only be used once during the season as part of a preventative programme with fungicides that have a different mode of action against powdery mildew. The pre-harvest interval is 56 days before harvest.

In a 2016 study,² Digger showed high activity and no cross-resistance with other DMI chemistry approved for use in viticulture.

It is also a requirement of Sustainable Winegrowing New Zealand that when using Digger it must be applied in a tank mix with a multi-site powdery mildew protectant like sulphur. Digger should not be applied if a significant powdery mildew infection is already evident.

Other formulations of difenoconazole are registered on a range of crops and diseases in New Zealand, but Digger EW was developed by Nufarm specifically for the wine grape market.

For more information about Prolectus and Digger EW, contact your local Fruitfed Supplies Technical Horticultural Representative.

AVCM registration numbers: Digger EW #P009644, Prolectus # P009146. Read the registered label before use.

1 Sumitomo internal report.

2 “Sensitivity of grapevine powdery mildew to difenoconazole”. 2016 Beresford RM, Wright PJ, Wood PN, Agnew RH.