Following Veraison: Updates

Tuesday, September 3, 2024

 

Hello Dear Readers!

I hope you had a good week and enjoyed the long weekend. Last two Thursdays, Kevin, Lisa and I visited sites around the Valley and Bear River to check in on growers to see the seasonal progression. Saying we are very pleased is an understatement. With a good crop load and by all accounts, the season is early by about a week.

Thank you for attending the GGANS Summer Tour. I appreciate seeing you again and learning alongside with you. Thank you also to those who attended the Best Practice session at Luckett Vineyards. For reference, I will post the berry/ cluster sampling protocol in the Fact Sheet Section of the Perennia Website.   

As previously mentioned, I began sampling and recording the maturity progression (sugar accumulation) from several cultivars. The information is vital to the concept of precision viticulture and will be used to inform and optimize many decisions including pruning time, pesticide spray time, fertilization, harvest... Data and knowledge improves efficiency and efficacy, so I hope that you would help me by recording the growth stages from your own site starting next spring if you haven’t been doing it already.   

In preparation for harvest, for the follow-up blog post, I will send along some information about using a refractometer for brix measurements and a quick overview of the cluster sampling protocol.

Below are the Brix and Total Acidity results I collected from sites in the Valley. I will be posting this information in the weekly blog until harvest.

Please keep in mind that these values are site specific, so your numbers may vary somewhat. These are a guidelines only.



Method of collection: randomized cluster sampling; chemical analysis provided by Acadia ALab.

As you can see, Marquette is quite far along in terms of sugar accumulation while Chardonnay is just starting to go through veraison.

Marquette 28 August 2024

 

Below are precipitation, GDD, Phenology, Sugar and Total Acidity (TA) results from the Kentville Research Station

Table 1.  Precipitation totals for the Kentville Research and Development Centre by month.

Month

25-Year Average

(mm)

Current Year

(mm)

April

81.5

54.0

May

74.0

29.8

June

95.5

83.0

July

81.3

201.7

August

94.5

30.1**

September

104.1

 

October

115.8

 

                                                         **Up to August 29, 2024

Table 2. Growing Degree Days

Single sine degree days, base of 0 °C starting on April 1

Growing degree days, base of 10 °C starting on April 1

Current Year

10-Year Average

Current Year

10-Year Average

2349.9

2246.4

1000.2

894.6

 

Table 3. Phenological stages of three varieties of grape by date for the KRDC Research Vineyard. Bud break for all three varieties was between May 18 and May 20, 2024.

Date of Assessment

Marquette

L’Acadie blanc

New York Muscat

29-August

Berries with intermediate sugar values

Berries with intermediate sugar values

Berries with intermediate sugar values

Table 4. Post-veraison brix and acid values of three varieties of grape, by date, for the KRDC Research Vineyard. TA is the total acidity expressed in grams per litre and measured by titration using a Hanna (model#  HI 84502) titrator.  Brix is total soluble solids expressed as % and measured with an Atago Digital Hand-Held Pocket Refractometer.

Date of Assessment

Marquette

L’Acadie blanc

New York Muscat

Brix (%)

TA (g/L)

Brix (%)

TA (g/L)

Brix (%)

TA (g/L)

29-August

17.6

23.0

11.5

21.1

13.0

15.1

Follow up posts will also focus on Botrytis. We have been lucky with the weather lately, so I hope you have been vigilant about your sprays and following the pre-harvest intervals according to your contractor’s wishes.

Thank you all for your time, and I hope you enjoy your week.

Cheers!

Katarina


Katarina Vucic MSc DipWSET

Viticulture Specialist
Perennia Food and Agriculture
Email kvucic@perennia.ca
Office 902-678-7722

Cell 902-599-1390


 

 

 

Downy Mildew: Environmental Conditions, Developmental Cycle and Possible Solutions

Tuesday, August 20, 2024

 

Hello Dear Readers!

As promised, this post will focus on Downy Mildew. The weather- here in the valley and province in general, is warm, humid which unfortunately makes it very easy for Downy Mildew to take hold.

This post will detail why this disease is so destructive, the development cycle, and possible preventative solutions. As mentioned in the previous post, it is much easier to prevent a disease than to react to it once it is established. So please, as always, go into veraison and harvest clean to maintain the best crop quality possible, and into the dormant season with healthy vines.

Acknowledgement to Wendy McFadden Smith of Brock and Katie Gold of Cornell University for their research and publications on the topic. Please refer to these links for further reading:

·        The lowdown on downy mildew in grapes – ONfruit

·       Grape Disease Control, Spring 2021 | Cornell Fruit Resources: Grapes

Additional citations are at the end of this article.

 

Downy Mildew (P. Viticola)-Developmental Conditions:

Downy mildew is caused by a fungal-like pathogen and thrives in warm, humid regions. Out of all seasonal diseases, mismanaged downy mildew is the only one that can result in total vine loss.

The optimal temperature for P. viticola growth is 25°C; however the infection is able to begin at 10°C. Rain is the main factor responsible for the epidemics.

The growth of P. viticola may be slow to begin in northern regions, where sufficiently high temperatures are not reached in the spring.

Damage:

Under the right conditions, downy mildew infections can cause pre-mature defoliation, which at best impedes critical post-veraison ripening, and at worst makes them more susceptible to winter injury/kill.

Downy leads to organoleptic defects (changes in grape flavour profile), productivity reduction and significant yield losses.

Please Note:

Severe downy mildew pressure in the prior season will likely result in an abundance of primary inoculum in the following year’s early season.

Infection Sites:

Downy mildew infects all green parts of the grapevine, including leaves, young stems and grapes, but leaves were found to be the main source of spores due to surface size, and the lack of protection against invasion of the pathogen. The disease is characterized by oily patches on the upper face of leaves that develop a dull green or yellowish color while the underside of the leaf exhibits a white growth.

Infection of P. viticola causes: leaf discoloration, necrosis and defoliation. Together this damage reduces nutrient composition, sugar accumulation in berries, capacity for buds to overwinter and crop loss.

When infected, young berries become brown and are covered by white powder resulting from sporulation. As berries ripen, they become less susceptible to the infection, but rachis infections can spread into older berries.

 

Figure 1.                                                              Figure 2.



Fig 1: Multiple infections lead to a large number of lesions that may coalesce. (Courtesy G. Ash) https://www.apsnet.org/edcenter/disandpath/oomycete/pdlessons/Pages/DownyMildewGrape.aspx#:~:text=Although%20all%20green%20parts%20of,oilspots)%20(Figure%202).

Fig 2: After suitably warm, humid nights, a white downy fungal growth will appear on the underside of the leaves and other infected plant parts.

 Figure 3.                                                                                                      Figure 4.               


     








Figure 5.                                                            Figure 6.   

  
Figure 5. Symptoms of late downy mildew infection, where the lesions of disease are restricted by the leaf. (Courtesy G. Ash) https://www.apsnet.org/edcenter/disandpath/oomycete/pdlessons/Pages/DownyMildewGrape.aspx#:~:text=Although%20all%20green%20parts%20of,oilspots)%20(Figure%202).

Disease Cycle:

In the spring, spores are released and infect vine tissue through rainfall.

Downy spores can land in the soil, where they remain inactive until favorable conditions occur. It will then transfer onto a host plant and start to grow. The life cycle of this pathogen consists of primary and secondary infections. It overwinters as oospores (resting sexual spores) in leaf litter, shoots, and soil.

It takes about 7–10 days for symptoms of primary infection to appear on the leaves, typically as yellow areas or “oil spots” that later turn brown due to necrosis as the disease progresses.

Early Season Infection:

Primary infections begin when spores spread from leaf litter on the ground to young leaves and clusters, beginning about 2-3 weeks before bloom. Suckers are often the first infected because they’re closest to the ground. Berries are infected and support profuse sporulation until 2 weeks post-bloom. Pedicel tissue remains susceptible until 4 weeks post-bloom.

Unfortunately, sanitation and dormant sprays have no effect on downy mildew, but early season cultural management for other diseases provides an opportunity to scout for these primary infections to see if your management to date has been effective.

Early season downy mildew management is essential for effective season-long management.

If downy mildew is mismanaged in the early season and becomes established, infections will produce secondary inoculum season-long whenever conditions become conducive, resulting in cascading late season epidemics.

Secondary Inoculum

Secondary inoculum release is triggered by warm, humid nights with rain shortly thereafter. Without rain, most secondary inoculum will stay in place and die the next day when exposed to bright sunlight. However, spores can survive and remain infectious for several days between rainfalls if conditions remain cloudy.

The requirements for sporulation and secondary infection are:

  • Humidity of at least 98%
  • Temperature of 13°C or above (optimum 20–25°C)
  • At least 4 hours of darkness
  • Leaves are wet for 2-3 hours pre-dawn.

All V. vinifera clusters are highly susceptible from first shoot appearance through approximately 4-5 weeks after bloom. Berries become resistant to direct downy mildew infection at this time, but pedicels and foliage remain susceptible long after.

Multi-year Infections:

Oospores can survive for up to 2 years in the soil and can produce sporangia throughout the growing season whenever conditions are suitable. Late summer infections are new ones coming from oospores on the soil or in leaf litter rather than earlier lesions on grape tissues. So not only can grapevines be infected by the repeating cycle of sporangia on lesions, they can also be infected by new sporangia from oospores.

 The Rain Effect:

It’s not just the amount of rainfall that has an effect on sporangium release.  The intensity of rain (millimeters per hour) has a key role in splashing water drops from the ground to grape leaves; increasing intensity results in an increased coverage by splashed drops, as well as an increased number and size of the splashed drops.  As rain intensity increases, mean raindrop size increases and more splash drops are formed. Raindrop size influences both the numbers of spores dispersed, and the distance dispersed.  Large raindrops are more effective than small ones because they carry more spores and can splash them farther.

Diagram of Downy Mildew Development:

 

Prevention and Control:

Practices that encourage air circulation and quicker drying time can reduce disease pressure but will not replace the need for chemical control. Plant debris should be removed from the area around the plant and buried or burned.

All systemic fungicides for downy mildew management are prone to disease resistance development and should be used in rotation within a sound, integrated pest management program. Protectants used to control Phomopsis and/or black rot early in the season, will also provide good preventative control of downy mildew.

  • Please consult the Perennia Pest Management Guide for effective products.
  •  Ensure complete coverage when spraying
  • DO NOT skip rows.
  • Tighten spray window if we receive excessive precipitation.
  • Adhere to pre-harvest spray intervals.

I do hope that this post well illustrates why early Downy Mildew control is essential in vineyards.

Downy, Black Rot… these diseases have found ways to overwinter and survive into the following season. It is up to us to be vigilant in preventing it. Remember that young vines- inter-plantings and new plantings require additional care as they are getting established. They too require sprays- especially because they are trying to establish themselves while dealing with environmental stressors.  

Thank you all for your time, and look out for the follow up post on pre-harvest updates this week.

Cheers!

Katarina Vucic

Viticulture Specialist
Perennia Food and Agriculture
Email kvucic@perennia.ca
Office 902-678-7722

Cell 902-599-1390


Sources:

·       Downy Mildew of Grape, by Ash G. Downy mildew of grape (apsnet.org) Charles Sturt University, Wagga Wagga, New South Wales, Australia​.

·       Koledenkova, Kseniia  et al. Plasmopara viticola the Causal Agent of Downy Mildew of Grapevine: From Its Taxonomy to Disease Management. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9130769/

 

Hedging Vines at Veraison

Friday, August 9, 2024

 

Hi Dear Readers!

From this point on in the Blog series, I will be focusing on pre-harvest practices. This canopy management post may be seen as reaching you a little late, but as we should avoid hedging or topping after Veraison, there is still room for this discussion. 

The information from the following posts was gathered from several sources. Please see the bottom of the article for links and more information.


Why focus on hedging specifically?

Most of us take on the practice, but we may not understand that the timing of the practice has important implications for fruit quality.

By this time of the season, most canopy management practices may be finished- or if not – completed very soon. Shoots should be tucked (to avoid “scalping when hedging!)  and leaf removal/hedging close to completion.

What is Hedging/Topping?

Hedging is the removal of about 25 cm or more of the shoot apex (shoot tips) of vigorously growing primary shoots (these may be lateral shoots if growing rapidly) and non-fruitful shoots. It is a practice that can be used at various times throughout the season to provide an adequate microclimate for developing clusters and open up the canopy for good pest control and spray coverage.

  
                   Not Hedged                                                                                      Hedged


Physiology Behind Hedging

The rationale behind hedging is to avoid excessively dense canopies (shading of fruit and internal leaves), to allow for ease of movement through the block especially for vigorous hybrid cultivars and to encourage movement of carbohydrates from new leaves at shot tips  and directing those sugars toward the grapevine clusters as well as the trunk and roots (vine reserves for overwintering and vine hardiness).  From veraison onwards, the sinks for photosynthates are expanding shoot tips, bunches, shoots and roots.  Generally, 50% of the carbohydrates go to the clusters and the other 50% go to the permanent vine structure (reserves).   Our objective is to optimize the clusters as sinks and ensure that the bunches achieve optimum maturity.

Timing is Important

To reap the benefits of hedging, or of any cultural practice for that matter, good timing is essential.

Primary Goal of Hedging at Veraison

Crowded, dense canopies result in shaded fruit with low sugar accumulation, high acidity and delayed ripening.

It takes about 15 to 25 mature leaves (depending on leaf size and cluster size) to ripen each grape cluster.  Leaves above the cluster provide the sugars for ripening and those below, send their sugars essentially to the shoots, trunk and roots. Hedging during Veraison encourages the sugars to travel to the berries, encourages periderm formation ( cane maturity)  critical for winter hardiness for overwintering canes (as FYI:  this is not lignification – that is part of xylem activities and not part of what we see externally – lignin is colourless!) . Be sure to avoid where possible hedging withing 30 days of harvest to avoid stimulating new shoot growth which will complete for carbohydrates that we want destined for the clusters.

Secondary Goals:

Removing excess primary and lateral shoot growth from the top and sides of the canopy prevents shading and entanglement of shoots between vine rows and allows workers and tractor traffic through the vineyard.

Other Benefits of Hedging:

Ø  It improves the micro-climate of the canopy: it encourages better light penetration, good air movement through the canopy and clusters and helps minimize humid environmental micro-conditions which favor the development of various diseases.

If you have any questions about this information, please don’t hesitate to contact me.

 

A quick note about netting:

Netting:

Netting should be done with the onset of Veraison. Depending on the netting methods used, you may be able to still complete hedging (topping), but spraying may be more difficult. If using  “over the canopy” netting, you may to be able hedge if needed. Still, please ensure that your spray coverage is not affected- or affected as little as possible.

 

GROWTH STAGE REPORT

Phenological stages of three varieties of grape by date for the KRDC Research Vineyard. Bud break for all three varieties was between May 18 and May 20, 2024.

Date of Assessment

Marquette

L’Acadie blanc

New York Muscat

1-August

Berries beginning to soften

Berries still hard and green-beginning to soften.

Berries still hard and green-beginning to soften.

Personal Observations:

Chardonnay and Pinot Noir are at bunch closure- still green and firm to the touch.

Marquette- Berries are beginning to soften- in the Kentville/ Wolfville area. North and South shore – berries are still green and hard to the touch.

Frontenac Blanc, L’Acadie Blanc and New York Muscat are also green and hard to the touch.

Be on the lookout for these varieties as they will be coming most likely within the next week or so-in the valley:

  • Lucy Khulman,
  • Petit Milo,
  • Marechal Geoffrey
  • Baco Noir
  • and Osceola Muscat


PRECIPITATION AND GDD: 

(All temperature data were recorded at the Kentville Research and Development Centre).

Month

25-Year Average

(mm)

Current Year

(mm)

April

81.5

54.0

May

74.0

29.8

June

95.5

83.0

July

81.3

       201.7

August

94.5

         10.7**

September

104.1

 

October

115.8

 

                         *Up to August 8, 2024                       


Growing degree days, base of 10 °C starting on April 1

Current Year

10-Year Average

795.7

687.1

         *Up to August 8, 2024

PESTS:

         


Sphinx Moth Caterpillar                                                         Phylloxera

Phylloxera: Currently present in Ontario, will be here again in approximately two weeks. Please keep on top of your sprays.


DISEASES:

Black Rot: 

Following through on the last blog- please ensure that your spray intervals are tight, and you are rotating between products. With the rain this weekend, we will be seeing this blight continue to surface and inflict damage. Spray every row, and ensure complete coverage.


Downy Mildew

This is prime infection time for Downy Mildew- the upcoming blog will delve deeper into the pathology of the disease, but with the humidity, heat and rainfall- these are the prime conditions for the blight to develop.

Ensure proper ventilation of the canopy with leaf pulling if not already done so. Please consult the Perennia Pest Management Guide for pesticide information. And please, rotate the sprays and ensure full coverage.


We are in the home stretch!

Go clean into veraison and stay clean throughout. Don’t stop spraying too soon. 

The crop is looking great this year- from all sides of the province. Let’s ensure that we continue the trend. Do look out for pre-harvest intervals and make sure you comply with the labels and contractors purchasing your fruit.

Thank you all for your time, and I look forward to seeing you in person next week at the GGANS Summer Tour.

Cheers!

Katarina Vucic

Viticulture Specialist


References and Acknowledgements: Hedging information is gathered by the following sources: Please see these links for further information:

Hedging and Canopy Management in Grapes: https://onfruit.ca/2020/07/17/hedging-and-canopy-management-in-grapes/

https://www.guadoalmelo.it/en/cosa-stiamo-facendo-ora-in-vigna-giugno-e-le-cimature/#:~:text=Let's%20go%20into%20detail%3A%20why%20do%20we%20do%20the%20topping%3F&text=The%20topping%20makes%20the%20vines,for%20the%20available%20water%20resources.

To Hedge or Not to Hedge: https://lodigrowers.com/to-hedge-or-not-to-hedge/

Koblet, W. (1987). EFFECTIVENESS OF SHOOT TOPPING AND LEAF REMOVAL AS A MEANS OF IMPROVING QUALITY. Acta Horticulturae, (206), 141 156. doi:10.17660/actahortic.1987.206.8 10.17660/ActaHortic.1987.206.8

Perennia Food and Agriculture
Email kvucic@perennia.ca
Office 902-678-7722

Cell 902-599-1390

 www.perennia.ca