Vinews

No. 2 — March 25, 2019

Bud Mortality Update

Over the past week grape cultivars were evaluated for bud mortality from Central, East Central and South Western Missouri. Counties include Boone, St. Charles, Gasconade, Franklin, Washington, Ste. Genevieve and Lawrence.

Map of Missouri counties. Black circles around Livingston, Macon, Ray, Lafayette counties. Red circles around Boone, Gasconade, Franklin, St. Charles, Washington, Ste. Genevieve, and Lawrence counties.
Black circles represent the counties in Missouri in which grape cultivars were evaluated for bud mortality during the week of March 18, 2019. Red circles represent counties in Missouri in which grape cultivars were evaluated for bud mortality during the week of March 25, 2019.

Results: Week of March 25, 2019

Primary bud mortality on average was 22 percent of the 31 samples evaluated (Table 1). Traminette, four Vitis vinifera cultivars combined, Chambourcin and Chardonel had the greatest bud mortality. Traminette had a bud mortality of 30 percent. Bud mortality for Chambourcin ranged from 11 to 39 percent, with the average of 9 samples being 24 percent. Chardonel bud mortality ranged from 12 to 46 percent, with the average of 5 samples being 29 percent. The average bud mortality of the four V. vinifera cultivars was 28 percent, whereas Concord had a bud mortality of 4 percent.

Table 1. Bud mortality of grape cultivars from northwest and northcentral Missouri during the week of 25 March 2019.

Cultivar County Morality %1
Chambourcin Franklin 11
Franklin2 24
Gasconade 37
Gasconade 19
Gasconade 20
Lawrence 33
St. Charles 39
Ste. Genevieve 15
Washington 15
Average 24
Chardonel Boone2 28
Gasconade 29
Gasconade 31
St. Charles 12
Ste. Genevieve 46
Average 29
Concord Gasconade 4
Norton Boone2 15
Gasconade 8
Average 12
Traminette Boone2 30
Vidal blanc Boone2 14
Washington 8
Average 11
Vignoles Boone2 16
Franklin2 14
Franklin 37
Gasconade 16
Lawrence 19
Washington 24
Average 21
Vincent Gasconade 15
Cabernet Franc St. Charles 34
Lemberger St. Charles 18
Saperavi St. Charles 32
Viognier Ste. Genevieve 32
Average 28

1 % based on the examination of 100 buds from 20 randomly selected canes. Five count buds were examined per cane for primary bud mortality.
2 Bud mortality submitted by collaborators.

Results: Week of March 18, 2019. Reprinted for comparison

Primary bud mortality on average was 21 percent of the 18 samples evaluated (Table 2). Chambourcin and Chardonel had the greatest bud mortality. Bud mortality for Chambourcin ranged from 14 to 75 percent, with the average of 5 samples being 41 percent. Only one sample of Chardonel was evaluated, and the bud mortality was 34 percent. Bud mortality for Vignoles ranged from 8 to 23 percent, with the average bud morality being 13 percent among five samples. Three samples of Norton were evaluated and the average bud mortality was 11 percent.

Table 2. Bud mortality of grape cultivars from northwest and northcentral Missouri during the week of 18 March 2019.

Cultivar County Morality %1
Chambourcin Clay/Ray 34
Lafayette 14
Lafayette 15
Macon 66
Macon 75
Average 41
Chardonel Macon 34
Crimson Cabernet Clay/Ray 14
Elvira Livingston 3
Norton Lafayette 11
Macon 11
Waverly 10
Average 11
Verona Macon 0
Vignoles Clay/Ray 9
Lafayette 12
Lafayette 15
Livingston 23
Macon 8
Average 13
Wine King Livingston 22

1 % based on the examination of 100 buds from 20 randomly selected canes. Five count buds were examined per cane for primary bud mortality.

Assessing bud mortality in your vineyard

To accurately assess the health of the bud tissue use a sharp razor blade and make a cross-section cut about 1/3 to 1/2 of the height from the bud tip. Realize the primary bud is in the center of the bud, the secondary bud is located towards the base of the cane and the tertiary bud is located towards the tip of the cane (Figure 1). If the center of the primary bud is brown or black in color the primary bud is dead. Careful not to cut to deep or you will reveal the bud plate which will be green. A quick assessment of 10 to 20 count buds in the vineyard will provide you a rapid assessment. If damage is found then you should evaluate 100 count buds to get an accurate assessment of primary bud damage.

cross-section of Chambourcin vine's dead primary bud cross-section of Norton vine's live primary bud
Figure 1. Chambourcin (A) with dead primary bud, and Norton (B) with live primary bud. Photo credits: Dean S. Volenberg

How to manage vines with bud mortality

Primary bud mortality, % Adjustment to dormant pruning
0 to 15 none
20-30 Add 20-30% more count buds
40-50 Double count buds
60+ No dormant pruning

Table adopted from “Assessing and managing grapevines in response to winter injury” by Thomas J. Zabadal, MSU Department of Horticulture: https://www.canr.msu.edu/uploads/files/Vineyard_management/AssessWinterInjury.pdf

Managing bud mortality commentary

If your vines have experienced primary bud mortality between 20 to 30 percent, then it would be best to leave approximately 30 percent more count buds. If, on the other hand, you have completed pruning and your vines have experienced primary bud death, what is the solution? Looking back to what occurred during the Easter freeze of 2007 does provide some insight. My good friend Eli Bergmeier reminded me that both Chambourcin, Chardonel and Vidal blanc will produce some fruit from secondary buds. In fact, when most of the primary shoots were destroyed during the Easter freeze of 2007, Chambourcin, Chardonel and Vidal blanc had crop levels of approximately 60 percent, compared to normal (Understanding and preventing freeze damage in vineyards, University of Missouri-Columbia, Dec. 5-6, 2007). You may then raise concern about asynchronous ripening of fruit produced from shoots from primary and secondary buds. There may be some lag time from fruit developing on secondary bud shoots. However, most of Missouri experiences more than enough GDD to ripen fruit (except for the northern areas), more than likely the fruit clusters produced on secondary shoots will approach harvest maturity shortly after the clusters on the primary shoots.

If your vines experienced extreme primary bud mortality, then there likely is another issue that you need to concern yourself. In most cases, when primary bud mortality is above 60 percent and the temperatures during November through February were not extreme, a vascular problem is the likely culprit. For Chambourcin, the most likely culprit is Crown gall. The solution to Crown gall is to start bringing up new trunks if your Chambourcin in growing on its own roots.

Also, if your vines experienced primary bud mortality greater than 60 percent, then consider simply hedging the vines to approximately five-bud canes. This results in keeping the vines in better balance in the future years.

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