Seasonal update 2022: GDD, veraison is starting, preparing for tissue sampling and fungal disease management

Wednesday, August 17, 2022

Jeff Franklin, from AAFC Kentville, is sharing with us this week weather information with increasing growing degree values. Precipitations have helped to refill the soil profile, grapevines are showing a positive development, grapes are still growing and, in some cases showing the first signs of veraison. In specific cases it’s possible to observe vines with sun burn from previous weeks, which is minimum and nothing to compromise this year’s production.

The first table shows the temperature base 5⁰ C and 10⁰ C from 2019 until 2022 accumulated from March 1 until August 16. At the end of each section, it’s possible to see the average of the last 5 and 10 years respectively.






5 year average

10 year average

Plant development (Base 5ºC)







Insect development (Base 10º)







Figure 1. Degree day accumulations as of August 16, 2022.  All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

At this time, we can see 2022 with almost the values than 2021. Compared to the 5- and 10-year average, 2022 maintains a higher accumulation in these last 7 days. In cases where the grapes are exposed to the sun, locations with higher accumulation of degrees and where early varieties are present, it’s possible to see the first berries turning color.

In the following column graph, you can see the values from 2004 until 2021 and at the end the average of the last 5 and 10 years respectively.

Figure 2. Degree day accumulations as of August 16, 2022 base 10⁰ C. All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

The trend is similar to last week, values have increased and it’s almost like 2021. Currently, 2022 is higher than the 5- and 10-year average. Compared to previous seasons, 2020 and 2018 are slightly higher than the current season and the most notorious years are 2021 and 2006. Let’s keep an eye on how moves the rest of the week!

Last week we’ve seen the damage caused by the sun on the exposed grapes through the heat wave. This damage can stay on the grapes, it’ll be mainly on one side of the bunches, the side with more exposure to the sun. In the following photo, it is possible to see a bunch with sun burn and mechanical damage.

Figure 3. Bunch with sun burn and mechanical damage.

Last week we shared that many hybrids reached bunch closure and some of them were in progress. At the beginning of this week, it was possible to see the first berries starting veraison in the earliest hybrids, such as Castel or Lucie Kuhlmann. On the other hand, vinifera are still in progress with good berry development and in some cases even at bunch closure. In places with the most suitable conditions, the next 2 weeks it might be possible to see veraison. Moreover, with veraison approaching, it’s important to remind that this is a good time for tissue sampling for nutritional purposes. How to proceed with this? Please, watch the following video and fact sheet Grape Tissue Sampling to have more information on how to proceed.  

Figure 4. On the left Castel and on the right Lucie Kuhlmann starting veraison.

Figure 5. On the left Chardonnay and on the right Riesling.

Quite repetitive the last month, Downy Mildew pressure has been quite high with the current conditions, high moisture, and warm temperatures. Even though the conditions have been changed to less humidity and warmer, such as last week, these conditions can be suitable for other diseases such as Powdery Mildew. It’s necessary to keep an eye in the vineyard for symptoms on the canopy or the clusters, please take a look at the following pictures.

Figure 7. Leaf and berries with Powdery Mildew this week.

It has been recommended the last couple of weeks 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 in the following link about Downy Mildew management tips