Grape and Wine Institute

University of

Vinews

No. 5 — May 25, 2020

Contents:

Update on the Frost Freeze Impact

Close-up of a brown, shriveled bud sprouting offf a Norton cane.
Figure 1. A Norton bud killed by freeze events on April 17-18, 2020. This vineyard sustained more than 90% loss of primary buds. Photo credit: D. Volenberg

This week I visited a couple of vineyards in Boone County, Missouri, that had sustained major damage from the cold temperatures on April 17-18, 2020. Both of the vineyard sites were planted on slopes and had good air drainage. The first vineyard was an approximately 6-acre block of Vivant. I estimate that approximately only 10% or less of the primary buds survived. There was extensive non-count basal buds breaking at spur positions. Fortunately the basal buds of Vivant are fruitful and there will be a crop to harvest.

The second vineyard was an approximately 3-acre block of Norton. The Norton vineyard was approximately 5 miles from the Vivant vineyard. Similar to the Vivant vines, only about 10% or less of the primary buds survived to produce primary shoots (Figure 1 & 2). There were a lot of non-count basal buds breaking at spur positions (Figure 3). Unfortunately, non-count basal buds of Norton do not produce fruit.

The most interesting thing I observed in both of these vineyards was the absence of secondary buds breaking on spurs. I collected six spurs from different grapevines in the Norton and seven spurs from the Vivant vineyard. The spurs ranged in count buds from two to five count buds for Norton, and three to five count buds for Vivant. In total, for Norton and Vivant, I dissected 20 and 25 count buds, respectively (Figure 4 & 5). For Norton, 100% of the primary buds were dead, 95% of the secondary buds were dead, and 85% of the tertiary buds were dead (Table 1). For Vivant, 100% of the primary buds were dead, and 96% of the secondary and tertiary buds were dead (Table 2).

Understandably, some vineyards were not damaged by frost or freeze events that took place in April and May 2020, whereas other vineyards like the two documented above sustained serious frost freeze damage. It is important to document and report these damages since there may be at some point this year on opportunity for grape growers that have sustained frost freeze damage to apply for certain government programs. At this time we all just have to wait and see what transpires going forward.

Besides grapes, a number of specialty crops in Missouri were damaged by the frost and freeze events in April and May. These include peaches, cherries, apples, blackberries, and strawberries, to name a few. Additionally, border states to Missouri, as well as states in the upper Midwest all the way east to New York, were impacted by the April and May frost freeze events. Widespread frost freeze damage over a large geographical area may result in the development of government assistance programs. I appreciate all of you who have taken the time to report frost freeze damage to me over the past few weeks.

A Norton branch in focus, showing green leaves but no buds, with other rows of vines in the background
Figure 2. Norton spurs that failed to bud out that were damaged by frost/freeze events in April and May 2020, Boone County, Missouri. Photo credit: D. Volenberg
CLose-up of a Norton spur that has green leaves but no count buds
Figure 3. Basal buds on Norton spur growing although all count buds were dead as a result of frost/freeze events in April and May 2020, Boone County, Missouri. Photo credit: D. Volenberg

Figure 4. Norton bud cross-sectioned revealing dead primary, secondary and tertiary buds. Photo credit: D. Volenberg cross-section of Norton bud shows rings
Table 1. Norton buds scored as dead or alive from six different spur canes. Buds were cross-sectioned and buds that were brown were scored as dead and buds that were green scored as alive.
Bud number Cane Bud position on cane with 1 being nearest cordon Primary bud Secondary bud Tertiary bud
Dead/Alive
1 1 1 Dead Dead Dead
2 1 2 Dead Dead Dead
3 1 3 Dead Dead Dead
4 2 1 Dead Dead Dead
5 2 2 Dead Dead Dead
6 2 3 Dead Dead Dead
7 3 1 Dead Dead Dead
8 3 2 Dead Dead Dead
9 3 3 Dead Dead Dead
10 3 4 Dead Dead Dead
11 3 5 Dead Dead Alive
12 4 1 Dead Dead Dead
13 4 2 Dead Dead Alive
14 4 3 Dead Dead Dead
15 4 4 Dead Dead Dead
16 5 1 Dead Dead Dead
17 5 2 Dead Dead Dead
18 5 3 Dead Dead Dead
19 6 1 Dead Alive Dead
20 6 2 Dead Dead Dead
100% 95% 85%

Table 2. Vivant buds scored as dead or alive from seven different spur canes. Buds were cross-sectioned and buds that were brown were scored as dead and buds that were green scored as alive.
Bud number Cane Bud position on cane with 1 being nearest cordon Primary bud Secondary bud Tertiary bud
Dead/Alive
1 1 1 Dead Dead Dead
2 1 2 Dead Dead Dead
3 1 3 Dead Dead Dead
4 2 1 Dead Dead Dead
5 2 2 Dead Dead Dead
6 2 3 Dead Dead Dead
7 2 4 Dead Dead Dead
8 3 1 Dead Dead Dead
9 3 2 Dead Dead Dead
10 3 3 Dead Dead Dead
11 4 1 Dead Dead Dead
12 4 2 Dead Dead Dead
13 4 3 Dead Dead Dead
14 5 1 Dead Dead Dead
15 5 2 Dead Dead Dead
16 5 3 Dead Dead Dead
17 5 4 Dead Dead Dead
18 6 1 Dead Dead Dead
19 6 2 Dead Dead Dead
20 6 3 Dead Alive Alive
21 7 1 Dead Dead Dead
22 7 2 Dead Dead Dead
23 7 3 Dead Dead Dead
24 7 4 Dead Dead Dead
25 7 5 Dead Dead Dead
100% 96% 96%

close-up of Vivant cane shows branch section where a bud should be, but is dead cross-section view shows dry, brown, dead bud spots
Figure 5. Vivant bud on cane 4 bud 2 (left) and a cross-section (right) revealing the dead primary, secondary and tertiary buds. Photo credit: D. Volenberg

Managing Vineyards That Have Frost Freeze Damage

Understandably, vineyard owners of vineyards that have sustained excessive damage as a result of frost freeze damage want to reduce inputs to maintain a bottom line. There is the short-term vision to reduce inputs, but this short-term vision will have consequences in the longer term. I would strongly suggest that vineyards that were damaged by frost freeze events continue to be protected from pathogens. Keep protecting the crop at least until after fruit set at which time revisit and evaluate the crop. Understand that flowering and fruit set will be prolonged since secondary and in some cultivars basal buds will flower later than shoots that developed from primary buds.

For those of you who experienced the Easter freeze of 2007, a lot of data was collected from damaged vineyards that provided some tid-bits of a silver lining. If you have not looked back at this report in the past 13 years, it would be worth the read. Nevertheless, I will highlight some of the results.

  • Depending on the cultivar, fruitfulness of secondary and basal buds was not high. Certain cultivars such as Chambourcin, Chardonel, and Vidal blanc typically produced ≥60% of a crop.
  • Even though fruit clusters were produced from different buds (secondary and basal) at harvest the fruit quality parameters were similar. Although brix and pH did not vary greatly between clusters produced from different buds at harvest, TA was typically higher from fruit that was delayed in maturity.
  • Fruit produced on count buds had similar fruit quality to fruit produced on secondary and basal buds at harvest maturity even through there were major differences in fruit quality at the onset of veraison. One caveat, remember in 2007 that most of the primary count buds were killed. In vineyards that experienced frost freeze damage this year, there is a going to be a crop produced on primary, secondary and basal buds depending on the level of frost/freeze damage to the vineyard and the cultivars ability to fruit on basal buds.
  • The 2007 freeze did some damage to the vines vascular system in cordons and trunks. The 2020 frost/freeze events occurred when some cultivars were at bud-break and the temperatures did not get low enough to cause damage to cordons or trunks. Most damage in 2020 was to primary buds in most vineyards that were ad-vanced in phenology.
  • The 2007 freeze resulted in buds breaking from blind wood in cordons. Blind wood is where a spur at one time was present but over time no buds appeared to replace the spur position. This is exactly what I observed in the Norton vineyard in the article above. A number of basal buds were breaking where along the cordon where no spur position had been present in the past few years.

You can revisit the 2007 PDF report: Understanding and Preventing Freeze Damaage in Vineyards. I suggest reading “What we learned from the Easter freeze in Missouri” by Any Allen.

Another good resource for managing cold damaged grapevines is the PDF “Assessing and Managing Winter-Damaged Grapevines Part II: Early Spring” by Imed Dami et al.

Cumulative Growing Degree Days for the Seven Grape Growing Regions of Missouri from April 1 to May 23, 2020

Region Location by County Growing Degree Days1
2020 2019 30-year Average
Augusta St. Charles 458 595 622
Hermann Gasconade 445 589 600
Ozark Highland Phelps 474 662 648
Ozark Mountain Lawrence 497 654 630
Southeast Ste. Genevieve 480 632 654
Central
 Boone 470 578 591
Western Ray 453 506 565

1 Growing degree days at base 50 from April 1 to May 16, 2020. Data compiled from Useful and Useable at https://mrcc.illinois.edu/U2U/gdd/. Click on link below to determine growing degree days in your area.

To determine the number of growing degree days accumulated in your area since April 1, use this tool.

Weather Outlook

Weather Outlook for June 1-5

  • Above normal high temperatures predicted in the lower to mid 80°F.
  • Below normal precipitation predicted.

May highlights

  • This past week was the first time that 2-inch bare soil temperatures were above normal for the month of May. Soil temperatures ranged from 68 to 70°F across Missouri
  • Both southern and northern Missouri had normal to above normal precipitation in May. Wet!
  • West Central, Central, and East Central Missouri had below normal precipitation in May.