Special Crop Load Report by Dr. Kevin Ker

 

Crop Thinning for Crop Balance Equals Vine Balance

After the tumultuous year of 2023, most growers are reporting that vines (for the most part) appear to be growing well, especially the hybrids. However, there are also reports of some vines growing poorly or have little crop with good vegetative growth, or in some cases-much more fruit than expected- to the level that the vines are not likely to ripen all of the clusters present.

All of these observations illustrate different ways a vine responds and compensates after winter injury followed by a very wet growing season. 

Poor vine growth is symptomatic of carryover winter injury where trunk injury and/or root damage is finally showing up. Last year, many vines that normally would have collapsed from stress in season did not; the wet conditions and early harvest did not stress the vine, but reserves expected to be accumulated did not happen.

Understanding natural vine biology can help us make sense of what we were seeing, especially where we are seeing lots of clusters. In the wild, grapevines are biennial bearing – meaning a large crop one year followed by a smaller crop the next. Part of this is due to its growth habit and the vine self regulating the balance of shoot and root growth (vegetative) with fruit crop load (reproductive) .

We manipulate the vines through cultural practices and site capacity to strike a balance between canopy growth and crop load to get a consistent crop each year and enable the vines to mature enough and acclimate to survive the maritime winters.  Through canopy management (shoot positioning and thinning, leaf removal, hedging, etc.)  we work to ensure good sunlight exposure on shoots to initiate fruit buds for next year's crop while ripening the hanging crop on the vine this year.

 

How we mange the vines this year can have big implications for fruitfulness for next year if we allow the vines to overcrop

Dropping fruit clusters or fruit thinning in a year after a really poor crop year is the most difficult thing to do when you are looking for a quick financial recovery. However, this short term (one year) gain will lead to long term pain (reduced crop next year) by taking the vine out of balance. As well, excess crop often results in poor fruit quality, delayed ripening, poor vine acclimation for winter and reduced winter hardiness.

Crop thinning to achieve crop balance, fruit bud initiation for next year and vine balance should be your prime objective

Vine capacity (amount of fruit produced that ripens well and achieves maturity) is directly related to cultivar potential, vine age, vine size along with site attributes to achieve adequate vine vegetative growth. Hybrid cultivars can usually carry a much larger crop than vinifera, and hybrid vines are generally larger and more vigorous.

How do I make crop thinning decisions after a poor growing season (2023) and vine injury

The vines in 2024 are still in a recovery phase, and should not be expected nor pushed to crop levels achieved prior to 2023. Many hybrids where trunks were intake and had a moderate crop in 2023 (50-60% of normal) can likely handle a crop of 80 to 90 % in 2024 allowing for more recovery and building of reserves in the trunk and roots for future production. Vinifera cultivars, where fruit is present in 2024, should probably only target at most 50% of a crop or less- if trunk renewal/ re-establishment is taking place.

In literature, viticulturists measure vine crop yields and dormant pruning weights to determine if a vine is weak, moderate or extremely vigorous.  After 2023 season where vines were left “wild” doing pruning weights for 2024 would not have helped us this year. Weak vines have low pruning weights, observed in season with weak or stunted shoots, smaller than normal leaf size and poor leaf colour. All of these attributes are indicative of a damaged vine and is likely carrying too much crop for its capacity. Vigorous vines in season often have very long shoot growth, large numbers of laterals, dark green leaves and often require lots of canopy management and not much crop.

This year, it is highly encouraged for you to get your crop yield, know the actual number of bearing vines in the block and calculate an average yield per vine.  Then in spring you can take some vine weights and  use the information to get crop weight / pruning weight ratio to assess vine balance . This ratio is known as the RAVAZ Index.  A general rule of thumb ratio of 5 to 10 ( 5 to 10 lbs of fruit per pound of pruning weight) is good but this will also depend on the cultivars grown and site capacity.

A generally accepted concept is that a vine needs 15 to 20 mature leaves on a single shoot to ripen a primary cluster on the SAME shoot!

In general, hybrids are very vigorous with multiple lateral shoots growing on the original primary shoot can handle two to three clusters as there are enough mature leaves from veraison to harvest to ripen the fruit. 

On vinifera cultivars, only very strong shoots can carry two clusters to maturity and depends on vine age, overall health and vine density.  In high density situations, many growers often thin to one primary cluster per shoot as overall vine size ( canopy and root system!) is smaller  ( smaller vines should have smaller crop load per vine – optimum  Vine Balance!)

Also. be aware that leaves on a shoot with no fruit does not help mature fruit on neighbouring shoots. It will help feed the trunk and roots and reserves but does not help ripen the current crop on the rest of the vine. 

How do I assess what a vine can ripen? Experience is the best way to understand what your vine can or cannot carry but the following are some generalizations.

Vine observation	# clusters to keep on a shoot
·      Stunted shoot growth in mid July (< 50 to 60 cm) ·      No new tendrils growing on shoot tips ·      Few lateral shoots growing ·      Shoots less than pencil size diameter ·      Poor leaf size and colour	NO FRUIT
·      Moderate primary shoot growth (1 to 1.25 meters) ·      Some lateral shoot development on primary shoot ·      Pencil size shoot diameter or slightly above ·      Normal leaf size and leaves with dullish green appearance	1 to 2 clusters per shoot
·      Vigorous primary shoot growth (more than 1.5 meters) ·      Numerous lateral shoots growing vigorously ·      Large leaves with deep green colour ·      Large diameter shoots (>15 mm) “bull wood developing”	2 to 3 clusters per shoot

 These are just generalizations and grower experience will always be more accurate than any formula. Site history (crop production records) and capacity is your best information to guide ongoing and future production.  The following are some additional web resources on this topic.

 

·      Cluster Thinning – Cornell University  (PDF)   Cluster Thinning (cornell.edu)

·      Hellman, E.W. and T. Casteel. “Crop Estimation and Thinning” in Oregon Viticulture, ed. Edward Hellman. Oregon State University Press, 2003. http://winegrapes.tamu.edu/grow/tentative%20pdf/thinning.pdf

·      Pool, R. 2001. Estimating and adjusting crop weight Finger Lakes vineyards. http://www.fruit.cornell.edu/grape/pool/cropsize.html

·      Skinkis, Patty. 2019. “ Basic Concept of Vine Balance”  http://www.extension.org/basic-concept-of-vine balance/

·      Skinkis, Patty. 2019  “Crop Thinning: Cluster Thinning or Cluster Removal”  http://www.extension.org/pages/31767/crop-thinning:-cluster-thinning-or-cluster-removal 

Rain, Rain Go Away!

Happy Friday Dear Readers!

I hope this rain has not put a damper on your spirits.

For this post, I will continue to focus on disease prevention as precipitation will very likely continue into next week.

Diseases:

Please be vigilant and stay on the look-out for Downy and Powdery mildew as the inoculum would still be present from last year. If you have had issues with Black Rot in the past, please ensure that your spray regime is tight as it will take time to decrease the inoculum to less severe levels. Pesticide groups 3 and 9 are effective for Black Rot control; group 7 is weak on Black Rot in high pressure situations like what we are currently experiencing.

With so much rain over the last two weeks, please ensure that your spray windows are tightened- the 8-10 day interval for systemics and 5-7 for protectants can be narrowed as 200mm of rain will have had a negative effect on product efficacy.

In about 10 days or so, you should also be considering botrytis sprays – just before bunch closure- to ensure the clusters are protected from inside the cluster and out. With the onset of ripening come wasps and other pests, so sour rot may also become an issue.

As always, please consult the online spray guide tool for products and rates.

As we are dealing with several diseases, my next installment will explain the life cycles of these blights, so to give a better understanding as to why we utilize certain practices at particular times of the year.

Growth Stages and Vineyard Practices:

In terms of growth stages- we are getting close to the lag phase- the ideal time for cluster thinning and leaf removal. To save time, if able, mechanically thin initially, then at a later date, go back in by hand and remove more if needed. Leaf removal will help with air movement in the canopy and allows your clusters the sunlight they need to ripen.

Again, to ensure a consistent crop load year after year, it is advisable not to over-crop the vines. Remember that 15-20 leaves are necessary to ripen one cluster on one shoot.  

Pre-Harvest Considerations:

Hedging:

·       Tucking, hedging and leaf removal are to be done now. Please avoid hedging 30 days prior to harvest- the canopy is needed to ripen the clusters.

Communication:

·       Contact your grape buyer and verify their guideline on the date of the last spray. The products may indicate three weeks, however, your requirements may be specified otherwise.

Please note:

As harvest time approaches, I may be putting out more than one weekly post to keep themes more concise, timely and not overwhelming.

Please see below for growth stages, GDD and Precipitation as provided by Jeff Franklin at the Kentville Research Station.

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
September	104.1
October	115.8

*Up to July 18, 2024

Growing degree days, base of 10 °C starting on April 1
Current Year	10-Year Average
562.5	455.8

*Up to July 18, 2024

Date of Assessment	Marquette	L’Acadie blanc	New York Muscat
18-July	50% Berries at pea size, 50% Berry touch	75% Pea Size, 25% Berry touch	Berry touch

 

  

                   Chardonnay                             L'Acadie                               Marquette

                                                                                   

 

                                     Frontenac Gris                  Pinot Noir                          New York Muscat                                                                                                                                 

 As is visible above, in the valley, Marquette and Frontenac Gris are close to full berry touch, L’Acadie is at pea size to berry touch, Pinot Noir and Chardonnay are at pea size and New York Muscat is at about 8-10mm size. Remember that loose cluster varieties may not see the “berry touch” phase.

These photos were taken on the 17^th July 2024.

In terms of pests, phylloxera and Erineum Mite are prevalent- Japanese Beatle as well but to a lesser extent.

Again, please consult the online Pest Management guide and follow label directions for any sprays you may use. 

Lastly,

Our Cover Crop Information Session is on the 24^th July 5-7:30pm. To register, please use the link below:

https://www.perennia.ca/eventer/growing-between-the-vines-cover-crops-in-vineyards-panel-discussion/edate/2024-07-24/

Thank you all for your time this week, and I look forward to seeing many of you next Wednesday.

Cheers!

Katarina

Viticulture Specialist

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

Cell 902-599-1390

www.perennia.ca

 

 

 

Precipitation Warning and Canopy Practices

 

 Greetings Dear Growers,

Apologies for the late posting; I was away for a conference last week.

With rainfall totaling over 200 mm in some areas this past week, many of you had questions about spray products and frequency. Just a reminder that it is very unlikely that any effective fungicide residue remains on the vines after that significant rainfall; keeping on top of disease pressure is paramount.

As we should be receiving more rain this week, here are some guidelines and recommendations provided by Dr. Kevin Ker:

Please remember: It is highly encouraged to have re-applied fungicides in advance of upcoming rain events to maintain high levels of disease protection.

Water Use:

Be sure you are also using enough water to thoroughly cover all susceptible tissues. With rapidly expanding and near-full canopies now present, you should be using at least 500 L of water per ha or more to provide proper spray coverage. At vigorous locations with big canopies, 750 L of water per hectare is preferred.

 

Water is the primary carrier of pesticides from the spray tank to the plant tissues and should be continually adjusted to match the canopy development at your farm. If you are identifying disease infections in hidden/hard to reach areas of the canopy or on the backside of clusters, you are not achieving optimal spray coverage and should consider increasing your water output.

 

Disease pressure:  

Berries are highly susceptible to infections from Downy Mildew, Powdery Mildew and Black Rot until veraison is well underway. Green tissues such as leaves, petioles, shoots and rachis tissues are also highly susceptible to mildew and black rot infections, so it is important to recover following wash-off rain events, keep tight spray intervals of 7-9 days and continue using good locally systemic fungicides where possible.

Vineyard Practices:  

Carry on with your fruit zone leaf removal activities as this will open the fruit zone allowing for better air flow and spray penetration around berries. It is advised to remove basal /fruit zone leaves that are layered in stages on white cultivars, so they have time to adapt to the new conditions.

Risks Associated with excessive leaf removal:

If you are too aggressive in leaf removal around clusters, leaving the fruit fully exposed in white cultivars, you risk burning or baking the newly exposed berries. It is common to remove leaves on the east side of the row first then follow-up by removing leaves on the west side 7-10 days later. You can be more aggressive in your first leaf removal pass in red cultivars, removing leaves from both sides of the row.

As previously mentioned by Dr. Deb Moreau, sightings of Japanese Beetle and

Phylloxera are increasingly prevalent.

 

                               Japanese Beetle Leaf Damage               Phylloxera Damage

If you have previously used Movento for phylloxera control, please consult the Perennia online pest tool to evaluate other products if you need follow up sprays. Read and follow the label rates.

 

Below, please see the Precipitation, GDD and Phenological Observations, provided by the Kentville Research Station up to July 11^th, 2024.

 Table 1: GDD:                                                                                   

Growing degree days, base of 10 °C starting on April 1
Current Year	10-Year Average
462.5	379.0

 

 

 

 

Table 2: Precipitation:  

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	99.8 **
August	94.5
September	104.1
October	115.8

Table 3. Phenological stages of three varieties . Bud break for all three varieties was between May 18 and May 20, 2024.

Date of Assessment	Marquette	L’Acadie blanc	New York Muscat
11-July	BERRIES PEA SIZE	BERRIES PEPPER CORN TO PEA SIZE	BERRIES PEPPER CORN TO PEA SIZE

 

Our observations: Date of Assessment: 11 July 2024.

•        Frontenac

Berries pea-size

•         Pinot Noir

Setting: Young berries growing; bunches are at right angles to the stem.

•         Chardonnay

Setting; some berries >2mm

Lastly, a gentle reminder about the Cover cropping info session next Wednesday at 5:30pm at Benjamin Bridge winery.

 

Thank you all for your time this week, and looking forward to seeing many of you at the info session next week.

Cheers!

Katarina Vucic

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

Cell 902-599-1390

 

www.perennia.ca