David C. Ferree, David M. Scurlock, and Rick Evans
A low temperature of -26ºF in January of 1994 resulted in significant injury to grapevines in Ohio and other Midwestern states (1, 4). Of the two most important white French-American hybrids grown in Ohio, 'Vidal blanc' was more severely injured by the low winter temperature than was 'Seyval blanc.' Early spring growth on mature 'Vidal' vines was sparse and weak with some arms showing no growth at all. Some trunks developed longitudinal splits.
In climates where serious injury to trunks can occur, several references suggest leaving multiple trunks (2, 6, 7), but the subject of the best procedure to produce hardy replacement trunks is not addressed. Conventional wisdom suggests allowing several new shoots to develop from the base to avoid the production of very vigorous "bull" canes that lack hardiness. Others suggested allowing everything to grow and then ultimately selecting canes with modest growth characteristics as the replacement trunks.
A series of studies was conducted following the January 1994 freeze episode to evaluate several practices that might moderate growth and result in new trunks that would be hardy. Growth regulators that moderate growth through interruption of gibberellin biosynthesis were tested in the first trial. In the second, different numbers of replacement shoots were retained to determine the effect on growth of replacement trunks. In the third trial, the influence of retaining the top and adjusting it to different crop levels along with growth retardant chemicals was tested. A fourth study evaluating growth-retarding chemicals was conducted in a grower vineyard, near Conneaut, that had significant injury in the vinifera cultivar 'Chardonnay.'
'Vidal' Growth Regulator Trial
Injured trunks along with the entire vine top were removed in mid-May 1994 at a height of approximately 50 cm (approximate snow level when cold event occurred). On June 22, 1995, vines with one to four shoots, approximately 50 cm long and arising from the lower 30 cm of the trunk, were selected and sprayed to drip with a hand-held CO2 pressurized sprayer with the compounds and rates shown in Table 1. Treatments with an x3 designation were repeated on July 22, 1994, and August 22, 1994. The growth-retarding chemicals used were Alar [daminozide (2,2-dimethyl hydrazide)], Ponnax [mepiquat chloride (N,N-dimethyl piperidinium chloride)], and Primo [(4-cyclopropyl-a-hydroxy-ethylene)-5,5-dioxo-cyclohexanecarboxylic acid ethyl)]. BAS 125 (prohexadione calcium) was an experimental gibberellin biosynthesis inhibitor from BASF which was compared with the commercial gibberellin biosynthesis inhibitors Ponnax from BASF and Primo from Ciba-Geigy. Basal shoots were tied up periodically over the summer, first to the cut-off trunk and subsequently to the existing trellis wires. The length of the basal shoots was measured at monthly intervals. Laterals were removed on all replacement trunks until primary shoots reached the top wire, at which time the laterals were allowed to grow. At the end of the season, the diameter and length of the sixth internode, which had formed after treatments began, was measured. Two of the canes were selected as trunks and established as a bilateral cordon in the following spring.
The following spring (1995) when growth had started and cluster development was obvious just prior to bloom, the length of five shoots per vine and all the clusters per vine were counted. The 1995 harvest season was recorded and the studies terminated. Treatments were arranged as a randomized complete block with seven single-vine replications.
'Vidal' Number of Replacement Trunks Trial
Trunks were handled as described previously except that vines were selected that had five or more shoots arising from the lower 30 cm of trunk on June 20, 1994. The number of shoots was reduced to either 1, 2, 4, 6, 8, or 10. Care and data collection were the same as described previously. Treatments were arranged as a randomized complete block with six single-vine replications.
Retaining the Top and Adjusting Crop Level on 'Vidal'
Vines either had the top removed (0 crop load) or the top retained and a crop load of approximately 20 or 30 clusters retained July 5, 1994. On some vines too few clusters were available to achieve the desired level. Retention of 48 shoots was attempted on all vines, but again this was not always possible. Replacement trunks were limited to four per vine and given one of the following treatments applied on June 22, 1994:
In 1995, where possible, all vines retained 48 shoots per vine and were cluster-thinned to 30 clusters per vine. Data, as previously described, was collected with the addition of yield data on the vines with tops retained. Treatments were arranged in a factorial design of 0, 20, 30 clusters per vine and four treatments (Table 3) with six single-vine replications.
Growth Retarding Chemicals on 'Chardonnay' Replacement Trunks
Mature 'Chardonnay' vines on 18815 rootstock that had severe winter
injury in the Markko Vineyard near Conneaut had their tops removed as previously
described. Growth-retarding chemicals were applied to replacement trunk shoots
on June 24, 1994, with a high-pressure hand-gun sprayer until drip. These shoots
averaged 40-50 cm in length. The chemicals and rates used are shown in
Table 4. Four replacement trunk shoots per vine were labeled and measured at
monthly intervals. At the end of the season, the length and diameter of the
sixth internode as well as the basal diameter of each replacement shoot was
measured. The treatments were arranged as a randomized complete block with six
individual vine replications.
'Vidal' Growth Regulator Trial
Only Ponnax applied three times and BAS 125 at the 500 ppm rate significantly increased growth in the first month after application (Table 1). In the second month, Ponnax-treated vines, at 500 ppm and 750 ppm, grew more than the control, with no differences among the other treatments. Primo at 500 ppm and Ponnax at 750 ppm reduced the length of the sixth internode, which formed shortly after the initial treatment was made, while Primo at 250 ppm applied three times reduced diameter growth of this internode. These treatments reduced pruning weight per vine: Alar, 1,000 ppm; Primo, 500 ppm; Primo, 250 ppm applied three times; BAS 125 at 500 ppm; and GA3. Early-season shoot growth the following season was enhanced by Primo at 250 ppm applied three times, Ponnax at 250 ppm, and BAS 125 at 750 ppm. Flower clusters per vine were reduced by these treatments: Primo at 500 ppm and at 250 ppm applied 3 times, GA 4+7, and GA3. Yield per vine in 1995, the year following the treatments, was reduced by these treatments: Alar, 1,000 ppm; Primo, 500 ppm; Primo 250 x 3; and GA3. Interestingly, three applications of GA 4+7 had little effect on yield, while similar treatment with GA3 resulted in the lowest yield of all treatments, showing the sensitivity of grape-flower initiation to GA3.
Table 1. Influence of Foliar Growth Regulator Applications on 1994 Growth of Replacement Trunks of 'Vidal' Grapevines Following January 1994 Injury and Removal of the Top of the Vine. |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Change in Shoot Length (cm) | Sixth Internode | 1995 | |||||||||
| Treatment | Ratez (ppm) | 7/25-8/23 | 8/23-7/25 | Length (cm) | Diameter (mm) | Basal Internode Diameter (mm) | Pruning Weight (lbs/vine) | Shoot Lengthy (cm) | Flower Clusters/Vine | Harvest Cluster/Vine | Yield (lbs/vine) |
| Control | -- | 56.8 c-e | 66.9 b-d | 9.6 a-b | 9.9 a-b | 12.4 | 2.20 a | 18.8 c-d | 56.0 a-c | 34.5 a-b | 14.2 a |
| Alar | 1000 | 32.3 e | 90.8 a-d | 7.5 a-c | 9.3 b-c | 10.6 | 1.51 b-d | 22.3 a-c | 29.1 c-f | 22.4 b-c | 6.6 b-d |
| Alar | 2000 | 98.4 a-e | 88.7 a-d | 7.8 a-c | 8.7 a-c | 10.4 | 1.71 a-d | 21.5 a-c | 38.5 a-e | 26.4 b-c | 9.3 a-c |
| Primo | 250 | 43.3 d-e | 83.1 a-d | 7.1 b-c | 8.5 a-c | 10.2 | 1.94 a-c | 20.7 b-d | 59.1 a | 28.2 b-c | 11.6 a-b |
| Primo | 500 | 58.8 b-e | 127.9 a-b | 6.0 c | 7.6 b-c | 9.9 | 1.42 c-d | 19.8 b-d | 25.0 e-f | 22.8 b-c | 7.9 b-c |
| Primo | 750 | 80.5 a-e | 68.0 b-d | 6.6 b-c | 8.5 a-c | 11.0 | 1.97 a-c | 19.5 b-d | 57.7 a-b | 34.7 a-b | 10.9 a-c |
| Primo | 250 x 3 | 35.5 e | 24.3 d | 7.9 a-c | 6.9 c | 10.0 | 1.40 c-d | 25.4 a | 28.5 d-f | 17.7 c-d | 5.2 c-d |
| Ponnax | 250 | 86.7 a-e | 111.9 a-c | 7.8 a-c | 9.1 a-c | 10.3 | 1.74 a-d | 23.4 a-b | 44.4 a-e | 44.0 a | 14.2 a |
| Ponnax | 500 | 112.1 a-c | 141.5 a | 9.1 a-c | 10.0 a-b | 11.6 | 1.64 a-d | 20.6 b-d | 31.7 b-e | 26.5 b-c | 10.9 a-c |
| Ponnax | 750 | 110.0 a-c | 144.8 a | 5.8 c | 10.4 a | 12.3 | 2.04 a-b | 21.1 a-c | 43.2 a-e | 29.2 b-c | 10.9 a-c |
| Ponnax | 250 x 3 | 131.9 a | 86.7 a-d | 8.3 a-c | 10.3 a | 10.8 | 1.81 a-d | 22.4 a-c | 44.4 a-e | 36.0 a-b | 14.0 a |
| BAS 125 | 250 | 94.2 a-e | 94.9 a-c | 9.5 a-b | 9.2 a-c | 11.0 | 1.62 a-d | 20.1 b-d | 38.4 a-e | 27.8 b-c | 9.2 a-c |
| BAS 125 | 500 | 124.3 a-b | 108.7 a-c | 8.6 a-c | 8.4 a-c | 10.7 | 1.28 d | 19.7 b-d | 34.8 a-e | 31.5 a-c | 9.7 a-c |
| BAS 125 | 750 | 83.9 a-e | 99.6 a-c | 7.5 a-c | 8.4 a-c | 11.5 | 1.81 a-d | 23.3 a-b | 55.5 a-d | 25.5 b-c | 9.5 a-c |
| BAS 125 | 250 x 3 | 69.8 a-e | 53.0 c-d | 8.3 a-c | 9.1 a-c | 11.2 | 1.65 a-d | 21.1 a-c | 60.0 a | 30.1 a-c | 10.5 a-c |
| GA3 | 100 x 3 | 86.1 a-e | 65.0 b-d | 10.6 a | 9.2 a-c | 10.7 | 1.21 d | 16.6 9 | 5.7 f | 7.7 d | 2.3 d |
| GA4+7 | 100 x 3 | 106.1 a-d | 123.4 a-b | 10.8 a | 10.2 a | 12.2 | 1.74 a-d | 20.8 b-d | 26.8 e-f | 27.5 b-c | 9.3 a-c |
| z Single applications June 22 except x3 where sprays were repeated at monthly intervals. | |||||||||||
A separate analysis (data not shown), comparing the three antigibberellin materials, indicated that Primo caused slightly more growth reduction than the others. None of the materials demonstrated a significant sensitivity to rate of application, and there was no interaction for any factor measured between chemical and rate of application.
'Vidal' Number of Replacement Trunks
Replacement trunk length declined as expected as the number of retained shoots increased. Growth failed to reach the top wire when eight or more shoots were retained (Table 2). Average basal diameter of all shoots and the diameter of the sixth internode followed a similar linear decline as number of replacement shoots increased. Pruning weight in 1995 was reduced when a single replacement shoot was retained in 1994. Shoot growth and cluster number in 1995 were generally increased as replacement shoot number increased even though only two replacement trunks of modest growth were retained. Although not significantly different from vines with greater number of replacement trunks, vines with two replacement shoots retained in 1994 had the largest sixth internode, the greatest pruning weight, and most flower clusters.
Table 2. Influence of Different Number of Replacement Trunks on Growth of Replacement Trunks on Winter-Injured 'Vidal' Grapevines with the Tops Removed. |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Average Replacement Trunk Length (cm) | Sixth Internode | 1995z | Yield | ||||||||
| No. of Replace- ment Trunks |
6/24 | 7/25 | 10/27 | Basal Diameter (mm) | Length (cm) | Diameter (mm) | Pruning Weight (lbs/vine) | Avg. Shoot Length (cm) | Flower (clusters/ vine) |
(clusters/ vine) |
(lbs/ vine) |
| 1 |
188.4 ay
|
214.6 a-b
|
321.2 a
|
11.1
|
9.5 a-b
|
11.5 a
|
1.38 b
|
21.0 a-b
|
35.7 b
|
17.4 c
|
8.0 b
|
| 2 |
153.8 a-b
|
244.7 a
|
297.7 a-b
|
15.9
|
10.5 a
|
10.9 a
|
2.37 a
|
20.0 b
|
70.5 a
|
30.6 a-b39.4 a
|
15.1 a
|
| 4 |
141.8 a-b
|
189.9 b-c
|
240.5 b-c
|
10.3
|
9.1 a-b
|
9.0 b
|
2.10 a
|
20.4 b
|
57.4 a-b
|
39.4 a
|
14.4 a
|
| 6 |
143.4 a-b
|
187.5 b-c
|
268.7 a-c
|
10.7
|
8.9 a-b
|
8.8 b
|
1.99 a
|
22.1 a-b
|
62.8 a-b
|
29.5 b
|
11.6 a-b
|
| 8 |
132.9 a-b
|
156.1 c
|
197.6 c-d
|
10.6
|
8.8 a-b
|
7.8 b
|
2.05 a
|
22.7 a-b
|
54.8 a-b
|
32.9 a-b
|
13.2 a-b
|
| 10 |
115.3 b
|
166.9 b-c
|
184.4 d
|
10.3
|
8.0 b
|
7.6 b
|
2.02 a
|
23.6 a
|
62.3 a-b
|
36.1 a-b
|
14.2 a
|
| Linear |
*x
|
**
|
**
|
*
|
NS
|
**
|
**
|
NS
|
|||
| Quadratic |
NS
|
NS
|
NS
|
NS
|
NS
|
NS
|
*
|
NS
|
|||
| z Measurements in June 1995 at
full bloom. y Mean separation by Duncan's multiple range test, P=0.05. x NS, *, **, nonsignificant at P ≥ 0.05 or 0.01, respectively. |
|||||||||||
Retaining the Top and Adjusting Crop Load on 'Vidal'
Cutting off the top resulted in the greatest length of replacement trunk, the most growth late in the season, and the largest sixth internode (Table 3). The two crop levels did not differ in their effect on growth or pruning weight. Growth the following season was not affected, but clusters per vine were least where the top had been reduced and new cordons laid down, and highest where a six-ton crop was carried the previous year.
Table 3. Interaction of Removing the Vine Top or Leaving the Top with Two Crop Loads and Applying Growth Regulators on Growth of Replacement Trunks and Vine Performance of Winter-Injured 'Vidal' Vines. |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1995 | ||||||||||||
| Change in Growth (cm) |
Sixth Internode | Yield | Yield | |||||||||
| Factor | 7/25-6/24 | 8/23-7/25 | Basal Diam. (mm) |
Length (cm) |
Diam. |
Pruning Weight (lbs/vine) |
(clusters/ vine) |
(lbs/ vine) |
Avg. Shoot Lengthz (cm) |
Flower (clusters/ vine) |
(clusters/ vine) |
(lbs/ vine) |
| Clusters/Vine | ||||||||||||
| 0 | 105.3 ay | 33.5 | 10.4 a | 9.0 | 8.7 a | 1.51 b | 2.7 b | 0.8 b | 20.6 | 30.9 c | 20.0 b | 6.9 b |
| 20 | 80.8 b | 31.4 | 9.1 b | 7.5 | 6.6 b | 2.54 a | 23.2 a | 8.4 a | 20.1 | 129.2 b | 38.6 a | 16.2 a |
| 30 | 68.7 b | 20.5 | 9.2 b | 8.1 | 6.6 b | 2.60 a | 28.2 a | 9.6 a | 19.5 | 164.7 a | 41.8 a | 16.3 a |
| Treatment | ||||||||||||
| Control-Top Removed | 88.8 | 43.3 a | 9.6 | 9.1 a-b | 8.0 | 2.32 | 21.7 | 7.0 | 20.3 a | 106.5 | 36.1 | 14.4 |
| Pinched top | 97.1 | 7.2 b | 9.7 | 9.5 a | 7.2 | 2.01 | 16.1 | 6.1 | 21.1 a | 113.4 | 30.7 | 12.6 |
| Alar 2,000 ppm spray | 82.4 | 33.4 | 9.2 | 7.5 b-c | 7.0 | 2.25 | 17.3 | 6.1 | 20.6 a | 100.0 | 33.9 | 13.3 |
| Ponnax 500 ppm spray | 70.4 | 34.4 | 9.6 | 6.8 c | 7.0 | 2.25 | 17.0 | 5.8 | 18.1 b | 114.5 | 3.2 | 12.4 |
| z Measured at bloom (June) y Mean separation by Duncan's multiple range test, P = 0.05. |
||||||||||||
'Chardonnay' Growth-Regulating Chemicals
BAS 125 reduced early growth of replacement trunks on winter injured 'Chardonnay' vines at concentrations > 500 ppm (Table 4). A single application of 750 ppm resulted in greater control of growth than did three applications of 250 ppm. The treatments had no significant effect on growth after July. A comparison of effects on the sixth internode, which formed shortly after the initial application, indicated that all treatments except Ponnax at 250 ppm and BAS 125 at 250 ppm applied three times reduced internode length. Internode diameter was reduced by BAS 125 at either 500 or 750 ppm.
Table 4. Influence of Growth-Retarding Chemicals on Replacement Trunk Shoots of Winter-Injured 'Chardonnay' Vines. |
|||||||
|---|---|---|---|---|---|---|---|
| Change in Length (cm) | Sixth Internode | ||||||
| Treatment | Rate (ppm) | 7/27 - 6/29 | 8/24 - 7/27 | 10/27 - 8/24 | Length (cm) | Diameter (mm) | Basal Node Diameter (mm) |
| Control |
69.0 az
|
26.9
|
1.3
|
5.8 a
|
7.8 a
|
11.3 a
|
|
| Alar |
1000
|
49.1 a-b
|
20.8
|
5.5
|
3.8 b
|
6.6 a-b
|
9.4 a-b
|
| Ponnax |
250
|
55.0 a-b
|
9.9
|
0.6
|
4.3 a-b
|
7.1 a
|
10.3 a-b
|
| Ponnax |
500
|
56.3 a-b
|
3.2
|
3.2
|
3.6 b
|
6.6 a-b
|
9.5 a-b
|
| BAS 125 |
250
|
39.6 a-b
|
21.4
|
12.2
|
3.6 b
|
6.1 a-c
|
10.6 a-b
|
| BAS 125 |
500
|
8.1 c-d
|
4.5
|
3.5
|
2.6 b
|
4.8 b-c
|
8.8 b
|
| BAS 125 |
750
|
2.0 d
|
22.0
|
9.1
|
2.9 b
|
4.5 c
|
9.7 a-b
|
| BAS 125 |
250 x 3
|
31.2 b-c
|
11.9
|
0.3
|
4.1 a-b
|
6.3 a-c
|
10.2 a-b
|
| z Means separation by Duncan's multiple range test, P = 0.05. | |||||||
The 1994-1995 winter was mild, and significant winter injury did not occur to test the survivability of the replacement trunks that developed. The effect of the gibberellin-inhibiting growth regulators was modest. Primo was the only inhibitor that tended to reduce cluster development. However, the application of
gibberellins that were included in this trial to potentially enhance vigor and produce undesirable replacement trunks had minimal effect on growth, but GA3 did reduce flower clusters. It appeared that GA3 tended to cause a greater reduction in flowering than GA4+7. Studies (3, 5) have shown that grapes are very responsive to GA3.
Results of these studies suggest that "conventional wisdom" was correct that growth is moderated by leaving a greater number of replacement trunks than ultimately desired. This practice resulted in increased pruning weight, cluster number, and yield the following season, with yield peaking when originally four replacement shoots were retained. Although these replacement trunks were not tested by severe cold, a general recommendation from this work to moderate growth of these new trunks would be to retain and tie up approximately four replacements and then select two with moderate growth characteristics for retention after the first year.
Another practical outcome from these studies on 'Vidal' was that it would be wise not to be in a hurry to cut off trunks of partially injured vines. Retaining the tops resulted in a partial crop the year of the injury and a 60% larger crop the following year compared to vines from new replacement trunks laying down new cordons. The majority of the 'Vidal' vines with the top retained following injury have recovered and have remained productive. A few have lost a cordon, and the new replacement trunk was used to replace the injured portion.