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Record keeping now is critical for future planning

grape vines

By Dave Antrobus
Solutions Development Lead, Syngenta

Powdery mildew was once again one of the key disease challenges confronting growers this season.  If your powdery mildew control wasn’t as effective as it could have been, following are some tips that can help make a difference next season.

  • Harvest is a great time to review the effectiveness of your season’s disease control program, as well as thinking about disease management for the coming season.
  • Disease management, including powdery mildew, begins at harvest. The post-harvest period is a critical time for the vine to store carbohydrates in preparation for dormancy and a functioning, healthy canopy is necessary for this to occur. High-yielding vines may take up to eight weeks to replenish carbohydrate stores in preparation for next season.
  • At harvest, you should start by recording any disease incidence, the severity and its location in the vineyard.

    Taking pictures and recording voice memos with your smart phone is a quick way of capturing this type of information.

  • Determine if the disease is widespread or if it is isolated to a specific area, as this can indicate if it has its own specific microclimate. Note down if the mildew was found on the rachis (the main stem that runs down through the cluster of grapes), the berries or in the top of the vine canopy.

    See if you can identify where the infection on the canes may have started and take photos. This may help identify a distinct point-in-time or growth stage for infection corresponding to a weather event or spray application.

  • Hot spots within a block should be noted along with canopy density at the infection site. This can indicate whether inadequate spray coverage may have been an issue.

Getting into the habit of documenting disease incidence during harvest is important. Having all the relevant information and being able to evaluate details, such as product selection and their effectiveness, will help you to develop a more effective spray program next season.

At times, product quality or access to product can be an issue. Other common issues which can impact the effectiveness of a spray program include spray equipment not being set up correctly for the canopy density or crop load, insufficient water volumes to ensure adequate coverage or too long an interval between sprays, due to the weather or mechanical breakdown.

It’s also worth remembering that powdery mildew is more prone than other diseases to develop resistance to some fungicide groups. Being able to review your selection and rotation of fungicide groups against achieved control will help you to assess any changes required to your strategy for the coming season.

Post-harvest spraying is less common now than it once was. Each spray pass should be carefully considered. The current research highlights the relative importance of early-season fungicide application over post-harvest application.

Finally, ensure you seek professional advice for your specific situation.