Vinews

No. 1 — March 18, 2019

Bud Mortality

Over the past week, I have evaluated a number of grape cultivars for bud mortality from North-central and Northwest Missouri. Anecdotal reports from Northeast Missouri sug-gested that bud mortality was evident. Therefore, in Northwest Missouri, grape cultivars from Clay/Ray, Lafayette and Livingston counties were evaluated. In Northcentral Missouri, grape cultivars were evaluated from Macon county.

Map of Missouri counties. Black circles around Livingston, Macon, Ray, Lafayette counties.
Black circles represent the counties in Missouri in which grape cultivars were evaluated for bud mortality during the week of March 18, 2019.

Results

Primary bud mortality on average was 21 percent of the 18 samples evaluated (Table 1). 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 1. Bud mortality of grape cultivars from northwest and northcentral Missouri during the week of 18 March 2019.

Nearest town County Cultivar Morality %1
Macon Macon Norton 11
Macon Macon Vignoles 8
Macon Macon Chambourcin 75
Macon Macon Chambourcin 66
Macon Macon Chardonel 34
Macon Macon Verona 0
Wheeling Livingston Vignoles 23
Wheeling Livingston Elvira 3
Wheeling Livingston Wine King 22
Wellington Lafayette Norton 11
Wellington Lafayette Chambourcin 14
Wellington Lafayette Vignoles 15
Waverly Lafayette Norton 10
Waverly Lafayette Vignoles 12
Waverly Lafayette Chambourcin 15
Excelsior Springs Clay/Ray Crimson Cabernet 14
Excelsior Springs Clay/Ray Chambourcin 34
Excelsior Springs Clay/Ray Vignoles 9
Average 21%

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

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