Seasonal update 2022: veraison, tissue sampling and fungal disease management

Wednesday, August 24, 2022

At the beginning of last week, the earliest hybrid grapes started to change their consistency and color, berries are becoming softer and reddish and yellowish tonalities are everywhere, in other words veraison is here! On the other hand, as commonly happens, Vitis vinifera varieties are slightly behind and the first changes might start at the end of this week or beginning of the next one depending on the local conditions. Moreover, this is the proper time to take tissue samples for nutritional analysis and to see if it’s necessary to supply in case of lacking or missing some nutrients. Even though this will sound repetitive for our growers and the loyal Nova Scotia Grape Blog readers, it’s important to keep an eye in the fungal diseases, especially Downy Mildew, and not to forget the applications against Botrytis.

Mentioned at the beginning of this article, veraison started timidly at the beginning of last week in the earliest hybrids, such as Baco noir, Castel or Lucie Kuhlmann. Depending on the location, other hybrids have been moving forward as well, like Marquette, Frontenac and L’Acadie, showing changes in consistency and color. Usually, the beginning of veraison is quite easy to distinguish in red grapes, while in white ones it might be more difficult (depending on each case), but usually they will get softer and translucid. If you’re unsure if these changes have started or you already have veraison, touch the berries to feel the change of consistency, passing from hard berries to softener ones. Meanwhile, Vitis vinifera are still behind in the process, the start of this stage will depend on the location and the variety. For example, one of the earliest varieties which starts veraison will be Chardonnay, while one of the latest Riesling. 

Figure 1. On the left Petite Pearl and on the right Frontenac.

Figure 2. On the left L’Acadie and on the right Chardonnay.

With the arrival of veraison, it’s a good time for tissue analysis for nutritional purposes! Here some information to keep in mind at the time to proceed with the sampling.

How to proceed with this? Please, look at the following video and fact sheet Grape Tissue Sampling to have more information on how to proceed. 

What is the role of the nutrients? You can read a section at the Grape Production guide to get insights about nutrients in grapevines. Please start from page 33 with the Grape Tissue Sampling process.

Mentioned every week in the last month, Downy Mildew pressure is still quite high and, in some locations, also the risk to have Powdery Mildew. Therefore, it’s necessary to keep an eye on the vineyard for symptoms on the canopy or the clusters scouting at least 3 times per week to keep the vines in good health conditions. Moreover, at this time of the year it’s necessary to consider an application against botrytis, especially in varieties and sections in the vineyard where you already have seen the disease previous years. Canopy management practices at the fruit zone will be very helpful to improve the spray penetration, allow morning dew to dry faster, allow breeze and sun exposure to control the diseases and change, according to the wine desired to produce, the ripening characteristics.

Figure 4. On the right berries with Downy Mildew early this season and on the left berries later through the season with Powdery Mildew.

It is recommended to:

  • Scout minimum 3 times per week the vineyard
  • Check the most susceptible varieties, and
  • Spray according to the situation.

Moreover, it’s necessary to check other diseases as well, differentiate with other fungal diseases to spray the proper fungicide to keep control in the vineyard. For this information and to have an access to the Grape Production guide, please check the previous publication about Downy Mildew management tips. In the grape production guide you’ll find information about Downy Mildew and other diseases, such as Powdery Mildew and Botrytis.