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PR-470

2002 Fruit and Vegetable Crops Research Report

Introduction | Demonstrations | Small Fruits | Tree Fruits | Vegetables | Diagnostic Laboratory | Appendix A

SMALL FRUITS

Blackberry Cultivar Evaluation, Eastern Kentucky

Charles T. Back, William Turner, and R. Terry Jones, Department of Horticulture

Introduction

Blackberry (Rubus), a native plant, grows well in Kentucky, and new improved blackberry cultivars offer a chance for crop diversification and a high income per acre crop for Kentucky agricultural producers. Blackberries have multiple uses including fresh or processed consumption, wine production, and medicinal purposes. Rubus has lower establishment and labor costs than many horticultural enterprises. It is also important to note that blackberries have the potential to be grown on hilly land and strip-mine sites and have a low erosion potential when grown in conjunction with sod strips. With available mechanization, blackberries may be grown on a large scale and mechanically harvested, or they may be grown on a small scale and hand-harvested for local fresh markets.

Materials and Methods

A thorny and thornless blackberry cultivars and advanced breeding selection trial was planted in a randomized complete block experimental design in May 2000 on raised beds. For the thorny cultivars, six plants/replication were planted 2 ft apart in the row. The thornless erect cultivars were planted with four plants/replication at a spacing of 3 ft. Plants of a thornless semi-erect cultivar (Triple Crown) were planted 4 ft apart in the row with three plants per replication. All rows were spaced 14 ft apart. There was a total of five replications with a 3-ft space between replications. The blackberries received a single application of 50 lb actual N/A from ammonium nitrate in March of 2001 and in 2002. The blackberries were evaluated for vigor, winter/spring hardiness, disease problems, as well as fruit yield, berry size, fruit appearance, and firmness.

Results

Many thorny and thornless blackberry cultivars have a tendency to de-harden and break dormancy early in Quicksand where 60° to 70°F in January and February are followed by 10° to 20°F in March and April. This weather pattern occurs at least once every four or five years and did so in 2002. Thornless cultivars such as Hull and Triple Crown, while considered less hardy than thorny blackberries, do very well here under our growing conditions because they are slow to break bud and remain dormant later into the spring. The year 2002 was a year of warm, sunny weather early and cold, overcast weather late in the season. Table 1 shows the bloom development and the presence of floricane injury in early May 2002. Canes showing injury at that time tended to die prior to harvest, reducing yield and berry quality. Once hot, dry weather came in June and July, a lot of floricanes were lost.

Table 1. Percentage of full bloom and floricane injury of 12 blackberry cultivars and breeding selections evaluated on 4 May 2002 at Quicksand, Kentucky.

Cultivar/

Selection*

Percent Full Bloom

Degree of

Floricane Injury

Comments

A1963

0

injured

3 of 5 replications injured

A1539

80

none

 

A2049

48

injured

3 of 5 replications injured

A1857

37

injured

2 of 5 replications injured

A1854

98

injured

1of 5 replications injured

A1960

15

injured

4 of 5 replications injured

A1689

1

slightly injured

1 of 5 replications injured

A1905

6

none

 

Navaho

1

severely injured

4 of 5 replications injured

Kiowa

5

none

double blossom

Shawnee

61

none

double blossom

Triple Crown

0

none

 

*

Selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available in commerce at this time.

The three thorny blackberry cultivars tested are listed in Table 2. Kiowa produced the highest yield (7,185 lb/A) and had the least amount of visible cane injury. Unfortunately, Kiowa is very susceptible to a fungal disease called double blossom. In a warm humid climate, it would be hard to raise Kiowa without having a good fungicide spray program. Kiowa also has a tendency to lay down on the job, and this makes picking and mowing difficult. A-1854 had tremendous fruit set, but the injured floricanes in all five replications slowly declined, resulting in small berry size. Shawnee was also subject to cane injury and had problems with double blossom. In past trials at Quicksand, Shawnee had problems with hardiness and disease and was included in this trial as a check for these problems.

Table 2. Harvest start date, harvest duration, yield, fruit quality, and disease evaluation of three thorny blackberry cultivars and selections, Quicksand, 2002.

Cultivar/ Selection*

Harvest Start1

Harvest Days2

Yield (lb/A)

Fruit

Size

(oz)

Taste3

Appearance4

SS (%)5

Disease Rating6

Remarks

Kiowa

6/27

40

7185

0.32

T

A+

8.0

2.4

double blossom

A-1854

6/18

35

4052

0.12

ST

A

9.0

0.6

 

Shawnee

6/20

36

4010

0.38

S

A

8.4

2.5

double blossom

LSD7

 

 

NS

NS

 

 

 

 

 

*

Selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available in commerce at this time.

1

The first day of harvest for that cultivar.

2

The number of days between first and last harvest for each cultivar.

3

Taste of fresh fruit, T = tart, S = sweet, B = bland.

4

A- = below average; A+ = above average; A = average.

5

SS = soluble solids of fresh berries.

6

Disease ratings are on a 0 to 5 scale; 0 = no disease seen, 5 = 100% of plants have disease present.

7

Least significant difference at the 5% level.

The highest yielding thornless blackberry (Table 3) was Triple Crown (7,623 lb/A). The three cultivars A-1857, Navaho, and A-2049 all suffered severe floricane injury and did not produce well. The fruit from Navaho were so small and dried they were not marketable. The breeding selections A-1689 and A-1905 appeared to suffer less cane injury and produced attractive fruit. The fruit quality of these two selections made them the "pickers' choice" among all the blackberries harvested this past year. No disease symptoms were observed on any of the thornless blueberry cultivars. Additional tests are needed to determine the long-term suitability of any blackberry cultivar to our climatic conditions. Additional evaluations are planned for 2003.

Table 3. Harvest start date, harvest duration, yield, and fruit quality of nine thornless blackberry cultivars and selections, Quicksand, 2002.

Cultivar/ Selection*

Harvest Start1

Harvest Days2

Yield (lb/A)

Fruit

Size

(oz)

Taste3

Appearance4

SS (%)5

Remarks

Triple Crown

7/06

28

7623 A

0.193 A

S

A

10.0

 

A1689

6/30

37

4793 A

0.188 B

S

A

9.3

 

A1905

6/24

41

3472 BC

0.183 C

S

A+

10.2

 

A1963

6/26

33

2165 CD

0.178 D

S

A+

8.3

 

A1960

6/23

40

2103 CD

0.166 E

S

A+

9.9

 

A1539

6/19

43

1873 DE

0.164 E

T

A+

9.2

 

A1857

6/20

26

801 DEF

0.134 F

ST

A

10.9

uneven druplets

Navaho

6/26

23

537 EF

0.010 H

ST

A-

8.8

uneven druplets

A2049

6/21

28

452 F

0.119 G

ST

A-

10.5

 

LSD6

 

 

1369

0.004

 

 

 

 

*

Selections preceded by an “A” and followed by a number are unreleased breeding selections, and are not available in commerce at this time.

1

The first day of harvest for that cultivar.

2

The number of days between first and last harvest for each cultivar.

3

Taste of fresh fruit, T = tart, S = sweet, B = bland.

4

A+ = above average; A- = below average; A = average.

5

SS = soluble solids of fresh berries.>

6

Least significant difference at the 5% level.

Evaluation of Thornless Semi-Erect and Erect Blackberry Training Systems and Varieties for Kentucky

John Strang, April Satanek, John Snyder, Chris Smigell, Phillip Bush, Dave Lowry, and Darrell Slone, Department of Horticulture

Introduction

Blackberries continue to be a popular market item for Kentucky consumers, and most growers find that high quality blackberries are readily marketable. This study is being conducted as part of the New Crops Opportunities Fruit Project at the Horticultural Research Farm in Lexington, Kentucky. One portion of the study has been designed to evaluate two training systems for three thornless, semi-erect blackberry varieties using a double-T four wire trellis. The second portion of the study is to evaluate the use of a plastic bailing twine trellis for cane stabilization versus no trellis for two thornless, erect blackberry varieties.

Materials and Methods

Semi-erect thornless blackberry plants were set the spring of 2000 into black plastic-mulched beds. Each plot consisted of three plants of either Hull Thornless, Triple Crown, or Chester spaced 8 ft apart in the row with 12 ft between rows. Each plot was replicated three times in a randomized block design. All plants were trained on a double-T four-wire trellis with the lower two wires 2 ft apart and the top two wires 4 ft apart. Two training systems were used, a conventional system and the Oregon system.

In the conventional system, primocanes were topped when they had extended 1 ft above the top of the trellis. Dead fruiting canes that had cropped were removed in the fall. During early spring, dormant pruning, spindly canes, and/or those that had red-necked cane borer swellings were removed. Lateral branches were pruned back to 18 inches in length, and those that were within 18 inches of the ground were removed completely.

Primocanes were not summer tipped for the Oregon system. In the spring, canes were not thinned, although those with red-necked cane borer swellings were removed. Low laterals, within 18 inches of the ground, were removed. Laterals above this were not cut back and were wound around, and sometimes loosely tied to the closest trellis wire, extending away from the plant.

Arapaho and Apache erect blackberry plants were set 3 ft apart in the guard rows on the north and south sides of the semi-erect blackberry plot. Trellising treatments (supported and unsupported) and varieties were each replicated three times in a completely randomized design. Plots consisted of three plants of the same blackberry variety. Metal fence posts were set at intervals of 9 ft, and plastic bailer twine was run on both sides of the supported treatment at a height of 3.5 ft.

During the first (2000) growing season, canes were allowed to trail and grow as much as possible. In the spring of 2001, the erect blackberry canes were pruned severely to encourage development of more vigorous shoots for the following season. During the summer of 2001 and 2002, primocanes were tipped at a height of about 3 ft. Spindly canes and those with red-necked cane borer swellings were removed in the spring of 2002. Laterals were cut back to a length of 16 to 18 inches.

The black plastic mulch was removed in the spring of 2001, and plants were watered by hand as needed. The summer of 2002 was dry, and a trickle irrigation system was installed. Plants were fertilized in February with calcium nitrate at the rate of 8 lb/100 ft row (43.5 lb N/A). Weeds were controlled by hand weeding, spot treatment with Roundup, and, in 2002, with Princep 4L. A conventional fungicide spray program using Kocide, captan, Nova, and Benlate was maintained. Japanese beetles and green June beetle pressure was severe in 2002, and both sevin and malathion were used for control. Bird pressure was also severe early in 2002, and an avian alarm was set up.

Plants were harvested in 2001 and 2002. Data were collected for yield, fruit size, and fruit soluble solids. The season in 2002 was hot and dry, which helped to elevate berry sugar content.

Results and Discussion

Statistical analysis was not conducted on the 2001 yield data (Table 1), but trends for berry weight and soluble solids (% sugar) content were similar to those obtained in 2002. Triple Crown tended to be the highest yielding and Hull Thornless the lowest yielding in 2001, while this was reversed in 2002 (Table 2), although there was no significant difference in yield. The fruit load in 2001 could have been responsible for the reversal in 2002. Arapaho and Apache had very low yields in 2001 due to the severe spring pruning.

Table 1. Thornless blackberry yield, berry weight, and soluble solids level, 2001 harvest.

Variety

Avg. Yield

(lb/plant)

Avg. Berry Wt.

(g)

Soluble Solids

(%)

Chester

13.0

5.2

7.6

Triple Crown

14.3

7.6

10.0

Hull Thornless

4.2

5.5

6.5

Arapaho1

1.3

5.3

12.0

Apache1

0.9

4.9

10.8

1

The erect thornless blackberries were pruned severely the spring of 2001.

Table 2. Thornless semi-erect blackberry variety yield, average berry weight, and soluble solids, 2002 harvest.

Variety

Yield1

(lb/A)

Avg. Berry Wt.1

(g)

Soluble Solids1

(%)

Chester

11,027 a

4.9 b

10.4 b

Hull Thornless

13,158 a

5.4 b

8.6 c

Triple Crown

10,150 a

7.5 a

11.4 a

1

Numbers followed by the same letter are not significantly different (Waller-Duncan LSD P = 0.05).

In 2002, there were no significant differences in yield among the three semi-erect blackberry varieties (Table 2) or between training systems (Table 3). Triple Crown had a larger berry size than the other two varieties. Triple Crown berries also had a 1% higher soluble solids (sugar) content than Chester, which in turn had almost a 2% higher soluble solids content than Hull Thornless. The Triple Crown fruit were noticeably sweeter than the other berries. Pickers felt that Triple Crown had the most attractive-looking fruit.

Table 3. Thornless semi-erect blackberry yield, average berry weight, and soluble solids based on training system, 2002 harvest.

Training System

Yield1

(lb/A)

Avg. Berry Wt.1

(g)

Soluble Solids1

(%)

Conventional

10,805 a

6.1 a

10.0 a

Oregon system

12,085 a

5.8 a

10.2 a

1

Numbers followed by the same letter are not significantly different (Waller-Duncan LSD P = 0.05).

Results for the erect blackberries can be found in Tables 4 and 5. Yields were higher for the plants supported by the string trellis for both varieties (Table 5), but there were no differences between training systems for average berry weight or soluble solids. Berry weight was higher for Arapaho as compared to Apache. This is contrary to the variety descriptions in the literature. There were no differences between varieties for yield or soluble solids (Table 4). Bird losses were more severe on the erect blackberries because these were the first to ripen. Pickers felt that of the two thornless erect blackberries, Apache had the more attractive fruit.

Table 4. Thornless erect blackberry variety yield, average berry weight, and soluble solids, 2002 harvest.

Variety

Yield1

(lb/A)

Avg. Berry Wt.1

(g)

Soluble Solids1

(%)

Apache

3,818 a

5.2 b

10.3 a

Arapaho

4,821 a

6.5 a

11.0 a

1

Numbers followed by the same letter are not significantly different (Waller-Duncan LSD P = 0.05).

Table 5. Thornless erect blackberry yield, average berry weight, and soluble solids based on training system, 2002 harvest.

Training System

Yield1

(lb/A)

Avg. Berry Wt.1

(g)

Soluble Solids1

(%)

No trellis

2,707 b

5.0 a

10.7 a

String trellis

5,932 a

6.7 a

10.7 a

1

Numbers followed by the same letter are not significantly different (Waller-Duncan LSD P = 0.05).

Kentucky Blueberry Markets Bursting—Consumer Survey Shows Continued Strong Demand

Matt Ernst and Tim Woods, Department of Agricultural Economics

Introduction

A consumer demand analysis was completed during the summer of 2002 on fresh blueberries grown in Kentucky. A very small acreage of blueberries (40 acres) is currently in production, but a number of producers are looking at expanding this enterprise. The demand analysis was conducted to provide market information on consumer willingness to pay for various container sizes. Consumers were evaluated in both a retail supermarket and a farmers' market. Product use, bulk purchase capacity, and interest in pick-your-own were also explored. According to this analysis, consumers in both small and big Kentucky towns are willing to pay well above the grower breakeven price for fresh, high-quality Kentucky blueberries in any size container.

Methodology

A random survey of 137 blueberry buyers was conducted during the first two weeks of Kentucky's blueberry season. Most of the surveys (112) were collected at the Lexington Farmers' Market. There were also 25 surveys collected in Metcalfe County at the "Blueberry Festival" promotion that featured locally grown blueberries in the Edmonton CB Foods grocery store.

The survey took less than two minutes to complete. It included questions about how much consumers were willing to pay that day for retail blueberries, what blueberries were being used for, whether the customer had freezer capacity, and how much customers would be willing to pay for U-Pick blueberries.

Results and Discussion

Lexington Farmers' Market customers surveyed indicated that they would be willing to pay an average of $3.14 per pint of blueberries in season (Table 1). Consumers at the Farmers' Market were accustomed to paying $3.00 per pint for fresh blueberries. Most farmers' market customers, though, said that they were willing to pay whatever the market price was for blueberries on any given day.

Table 1. The MOST for blueberries that I would be willing to pay today.

 

Lexington

Average

Metcalfe County Average

½ pint is

$1.81

$1.17

1 pint is

$3.14

$2.08

1 quart is

$5.48

$3.83

In Metcalfe County, some 150 miles southwest of Lexington, CB Foods featured local, handpicked blueberries for $1.88 per pint. CB Foods is a smaller retail grocer that agreed to feature local blueberries in their produce section. The consumers surveyed there on a Saturday indicated that they would be willing to pay, on average, $2.08 per pint of blueberries (Table 1).

Customers at both the Lexington Farmers' Market and the Metcalfe County grocery indicated that they would primarily use the blueberries purchased for fresh fruit or baking (Table 2). Customers in the more rural Metcalfe County, though, were more likely to have additional freezer capacity beyond a usual household refrigerator (Table 3).

Table 2. My primary use for the blueberries that I am purchasing today.

 

Lexington

Metcalfe County

Baking (pies, muffins, etc.)

20%

50%

Fresh fruit (fruit salad, fresh ingredient)

88%

54%

Preserving (jam/jelly)

6%

8%

Other

2%

0%

Don’t know yet

0%

0%

Table 3. I use a free-standing freezer (deep-freeze) in my home.

 

Lexington

Metcalfe County

Yes

32%

85%

No

68%

15%

The additional amount that consumers would be willing to pay for a quart-size container of blueberries over the pint-size was observed to be largest in the farmers' market, an additional $2.34. This is 78% of the $3.00 price that customers were used to paying at the farmers' market. The supermarket customers, however, were willing to pay an additional 84%, or $3.83, of what they were used to paying per pint for a quart-size container of blueberries (Table 1).

Wholesale prices for local berries at both these markets were well within the $1.25 to $2.00 price per pint that Kentucky's blueberry farmers received in 2002. Blueberry enterprise budget estimates from the UK New Crop Opportunities Center show that blueberry growers can make adequate profits from blueberries at these wholesale price levels. Growers who are willing to market their own berries at "premium" markets (like the farmers' market) can expect to generate significantly greater profits. Farmers' markets offer consistently higher demand, but also have limited volume of product with fewer customers.

U-Pick Promise

Producers willing to tailor their production for U-Pick markets can often capture higher profits than wholesale producers. This is because U-Pick eliminates labor costs, the largest cost for wholesale blueberry production. In fact, according to university estimates, those willing to develop a U-Pick blueberry market in their area can make $800 to $1,500 more per acre over wholesale berry production when charging a price of $1.25 per pint.

The survey indicated that about half the consumers at both markets would be interested in picking their own berries at a nearby farm. Lexington Farmers' Market customers said that they would pay an average of $2.13 per pint for berries that they picked themselves (Table 4). Those surveyed at the Metcalfe County grocery indicated that they would be willing to pay considerably less, $1.24 per pint, for U-Pick blueberries (Table 4).

Table 4. I would be interested in picking my own berries at a nearby farm.

 

Lexington

Metcalfe County

Yes

58%

42%

No

42%

58%

$__/lb willing to pay for U-Pick

$2.13

$1.24

Interestingly, some of those surveyed at the Lexington Farmers' Market indicated that they would be willing to pay more than they were paying at the market just to go to a farm and pick their own berries. Therefore, enterprising farmers willing to provide a hospitable and entertaining environment for U-Pick berry customers may be able to capture additional profits.

Conclusion

Kentucky's blueberry acreage has doubled to 40 acres since 1997 and is expected to double again to 80 acres by 2005. Statewide demand should easily support this acreage increase. Furthermore, this survey indicates that consumers appear to be willing to pay top price for fresh, high-quality Kentucky-grown blueberries. This consumer willingness to pay top price for blueberries should ensure adequate profits for those producers willing to invest the necessary time and capital into this "new" crop for Kentucky.

A complete report of this survey is available online at www.uky.edu/ag/hortbiz.

Blueberry Cultivar Trial—Eastern Kentucky

R. Terry Jones, William Turner, Charles T. Back, and David C. Ditsch, Departments of Horticulture and Agronomy

Introduction

Although blueberries are a native fruit crop, only limited commercial acreage has been established in Kentucky. Blueberries have an excellent potential for local sales and U-pick operations. Recent research into the health benefits of small fruits including blueberries may help increase sales even more. Vaccinium is increasing in popularity in the world of pharmaceuticals. As consumers become more conscious of the foods they eat, they may find themselves eating more blueberries. Scientists attribute the blueberry's healing powers to the flavonoid anthocyanin, which is responsible for the blue berry color found only in the peel. Anthocyanins and other flavonoids could help fight the development of cancer, cardiovascular disease, as well as eye problems such as glaucoma and poor night vision.

The high initial start-up costs for blueberries, approximately $4,000/A, is mainly due to land preparation, plant, and labor costs. However, after the plants reach maturity in approximately five years, the profits should steadily increase to as high as $6,000/A per year. Farmers must make planting decisions based on their own unique situation.

The longevity of a properly managed blueberry crop is similar to that of a well-managed apple orchard. Blueberries require acidic soils with a pH of 4.5 to 5.2, with good drainage and high organic matter. It is best to plant more than one cultivar to ensure good pollination and a continuous harvest of berries. Harvest usually begins in early June and lasts well into July.

Materials and Methods

Two blueberry plantings were established in the fall of 1996 at the University of Kentucky Robinson Station and the Laurel Fork Demonstration Site. Growth, yield, and survival of various blueberry cultivars were compared between a normal silt loam site and a disturbed mine site. The plantings consisted of 8 to 12 rows of various cultivars in a randomized block design. Plants were 4 ft apart in raised beds 14 ft apart. Drip irrigation with point source emitters (2 gph/plant) was installed shortly after planting. Plants were fertilized beginning in the spring of 1997. In 2002 one application 5-20-20 (5 lb/100 ft of row) was followed by two sidedressings of 5 lb ammonium sulfate/50 ft of row (at bloom and again two weeks latter). Netting was used at both sites to prevent loss due to birds.

Results

Twenty-one cultivars at Quicksand and 18 cultivars at Laurel Fork were tested, and results are shown in Tables 1 and 2, respectively. This year a cold, wet spring with freezes during bloom (April 6 and 7) may have reduced yield. It is believed that the flower buds of O'Neal, a southern highbush cultivar are not hardy at these locations, and its yield has been very low. The early blooming and maturing cultivar Duke has also continued to do poorly at both planting sites. The Laurel Fork reclamation site is about 500 ft higher in elevation than Quicksand and has much better air drainage. Moreover, based on time of apple tree bloom, plant development at Laurel Fork is about seven to 10 days behind that at Quicksand. As a result in both 2001 and 2002, the blueberry yields were higher on the Laurel Fork disturbed soil site, and the plants had thicker foliage and grew better. This is in contrast to the first harvest season where Quicksand was the more productive site.

Table 1. Yield, average berry size, fruit quality ratings, and earliness of blueberry cultivars, Quicksand, 2002.

Cultivar1

Fruit Yield (lb/bush)2

Berry Size (oz/berry)2

Berry Size Rating3

Taste4

Appearance5

% Harvested6 (first two harvests)

% Harvested6 (first four harvests)

Older cultivars

Brigitta

5.6 A

0.053

L

ST

A+

9

82

Blueray

3.8 B

0.047

L

ST

A+

49

96

Ozark Blue*

3.8 B

0.056

L

ST

A+

2

71

Toro

3.2 BC

0.060

L

SB

A+

44

100

Reka

2.5 BC

0.039

M

ST

A

65

96

Bluejay

2.4 BC

0.028

M

SB

A

39

100

Sierra

2.3 BCD

0.037

ML

ST

A+

44

98

Patriot

2.2 BCD

0.044

L

ST

A+

49

88

Bluecrop

1.8 CDE

0.095

L

SB

A+

39

94

Jersey

1.7 CDE

0.038

M

B

A

22

98

Nelson

1.5 CDE

0.043

L

ST

A+

25

94

O’Neal*

0.6 DE

0.035

M

SB

A

74

89

Duke

0.4 E

0.062

ML

S

A-

90

100

LSD7

1.8

NS

 

 

 

 

 

Younger cultivars

NC1832*

4.6 A

0.030 C

SM

BS

A

0

52

NC1827*

4.2 AB

0.031 C

SM

ST

A

0

73

Ornablue

3.1 BC

0.024 C

S

B

A

31

81

NC2675*

3.0 BC

0.073 A

L

SB

A+

75

100

Bluegold

2.4 CD

0.051 B

ML

T

A+

55

100

NC1852*

1.9 CDE

0.063 AB

ML

SB

A

19

100

NC2852*

1.4 DE

0.033 C

S

S

A

68

99

Spartan

0.8 E

0.066 AB

M

SB

A-

40

100

LSD7

1.4

0.014

 

 

 

 

 

*

These cultivars are 1 year younger than the other cultivars in the trial. Some cultivars were furnished by Hartman’s Plant Company, P.O. Box 100, Lacota, MI 49063. Other cultivars were purchased from Fall Creek Farm & Nursery Inc., 39318 Jasper-Lowell Rd., Lowell, OR 97452.

1

In descending order of yield.

2

Means within a group followed by the same letter are not significantly different, LSD (P = 0.05).

3

Size rated visually. S = small, M = medium, L = large, VL = very large.

4

S = sweet, T = tart, B = bland.

5

A- = below average, A = average, A+ = above average.

6

Harvest dates 6/07, 6/14, 6/21, 7/01, 7/04, 7/08, and 7/15, a 38-day harvest season.

7

Least significant difference (P = 0.05).

Table 2. Yield, average berry size, fruit quality ratings, and earliness of blueberry cultivars, Laurel Fork, 2002.

Cultivar1

Fruit Yield (lb/bush)2

Berry Size (oz/berry)2

Berry Size Rating3

Taste4

Appearance5

% Harvested6 (first two harvests)

% Harvested6 (first four harvests)

Older cultivars

Bluecrop

4.8 A

0.047 B

M

B

A+

54

80

Nelson

4.6 AB

0.063 B

L

S

A+

59

84

Bluejay

4.6 AB

0.039 B

M

B

A

71

92

Blueray

3.7 ABC

0.058 B

M

BS

A

77

91

Toro

3.3 BC

0.074 AB

L

S

A+

86

97

Sierra

3.2 BC

0.066 AB

L

S

A+

77

95

Ornablue

3.1 C

0.030 B

S

BS

A

75

91

Patriot

3.1 C

0.044 B

S M

T

A

80

94

Brigitta

3.1 C

0.050 B

L

S

A

18

69

Bluegold

3.0 C

0.047 B

M

S

A

75

92

Reka

2.7 C

0.038 B

S M

B

A-

79

97

O’Neal*

0.3 D

0.109 A

M

B

A

95

99

Duke

0.3 D

0.055 B

M

B

A+

100

100

LSD7

1.5

0.044

 

 

 

 

 

Younger cultivars

NC2675*

1.0 A

0.040 B

M

ST

A

31

67

NC1827*

0.8 A

0.023 C

S M

ST

A

41

95

NC1852*

0.8 A

0.046 A

M

BS

A

96

100

NC2852*

0.5 A

0.041 AB

S

S

A+

92

100

NC1832*

0.3 A

0.025 C

S

S

A

13

75

LSD7

0.7

0.00468

 

 

 

 

 

*

These cultivars are 1 year younger than the other cultivars in the trial. Some cultivars were furnished by Hartman’s Plant Company, P.O. Box 100, Lacota, MI 49063. Other cultivars were purchased from Fall Creek Farm & Nursery Inc., 39318 Jasper-Lowell Rd., Lowell, OR 97452.

1

In descending order of yield.

2

Means within a group followed by the same letter are not significantly different, LSD (P = 0.05).

3

Size rated visually. S = small, M = medium, L = large, VL = very large.

4

S = sweet, T = tart, B = bland.

5

A- = below average, A = average, A+ = above average.

6

Harvest dates 6/07, 6/14, 6/21, 7/01, 7/04, 7/08, and 7/15, a 38-day harvest season.

7

Least significant difference (P = 0.05).

At Quicksand, Brigitta was again the highest yielding cultivar followed by Blueray and Ozark Blue. Brigitta's yield was significantly higher than those of the other 12 cultivars initially planted at Quicksand. Brigitta is an attractive, large-fruited cultivar that matures in late mid-season in Kentucky with 82% of the fruit picked during the first four harvests. Ozark Blue is another attractive, medium to late maturing berry. Even though the Ozark Blue plants were a year younger than the initially planted blueberry cultivars, it had the fourth highest yield in 2002. Two North Carolina cultivars, NC-1832 and NC-1827, gave relatively high yields at Quicksand. They had small to medium size berries with a pleasant but distinctive taste. NC-1832 tends to flower heavily and set fruit in the fall. Several other North Carolina numbered cultivars also appear to be later maturing than the named cultivars in this trial. Plants of all five North Carolina selections grew rapidly this past summer and are going to be much larger plants than the named high bush cultivars. Late maturing blueberries in Kentucky will require protective sprays to prevent damage by Japanese beetles.

At Laurel Fork, Bluecrop was the highest yielding blueberry (Table 2) followed by Nelson, Bluejay, Blueray, and Toro. The largest berry sizes were those of O'Neal, Toro, and Sierra. However, O'Neal had very few berries, which may have resulted in larger average berry size. At Quicksand, Patriot and NC-2675 had the largest berry size. Based on appearance, the most attractive blueberries at Quicksand were Brigitta, Blueray, Ozark Blue, Toro, NC-2675, and Bluegold. At Laurel Fork, Bluecrop, Nelson, Toro, Sierra, Duke, and NC-2852 were judged to be the most attractive. At the Quicksand blueberry site, Jersey, Toro, and Sierra have suffered some plant loss due to Phytophthora root rot. These results represent the third harvest of these cultivars after 4½ to 5½ years' growth. Additional harvests and observations will be needed to determine which cultivars are the best performing over time in Kentucky.

Highbush Blueberry Cultivar Trial—Western Kentucky

Joseph G. Masabni, Gerald R. Brown (Professor Emeritus), and Dwight Wolfe, Department of Horticulture

Introduction

The blueberry is native to North America. At present, Kentucky has a small acreage of commercial blueberry production. Blueberries have recently been touted for their health benefits because of their high levels of antioxidants. Also, highbush blueberries have been a good supplemental crop for Kentucky growers who want to take advantage of land not suitable for tillage. For these reasons, this study was initiated in order to evaluate highbush blueberry varieties for adaptability to Kentucky soils and climatic conditions. This report updates earlier results, presented in previous issues of the Fruit and Vegetable Research Reports (1).

Materials and Methods

This trial, established in the spring of 1993 at the UK College of Agriculture Research and Education Center (UKREC), in Princeton, Kentucky, consists of eight cultivars spaced 4 ft apart within rows spaced 14 ft apart. There are 3 bushes of each cultivar per replication. Prior to planting, the pH was reduced from above 6.0 to 5.4 with elemental sulfur. The trial is mulched yearly with sawdust and is trickle-irrigated using 1-gph vortex emitters. The trial is netted in the last week of May, and fruit is harvested from the first week of June through the first week of July.

Results and Discussion

Cumulative yield from 1995 through 2002, the 2002 yield, percent ripe fruit, and berry size are presented in Table 1. Sierra, Duke, and Nelson cultivars have yielded the most fruit to date. Duke and Sunrise are the earliest ripening cultivars in this trial with 63% and 64% ripe fruit by the first week of June, respectively. Relatively little harvesting is done for all other cultivars up until the second week of June. Fruit harvest is finished for most cultivars by the end of June. One exception is Nelson, which is picked throughout the first week of July.

Table 1. Yield parameters of the highbush blueberry cultivar trial established in 1993 in UKREC, Princeton, Kentucky.

Cultivar1

Cumulative Yield

1995-2002

(lb/bush)

2002 Yield

 

Percent Ripe Fruit

Berry Size (g/berry)

lb/bush

T/A2

June 7

June 21

Sierra

60.9

9.6

3.7

 

0

91

1.9

Duke

59.9

9.7

3.8

 

63

100

2.0

Nelson

59.3

10.5

4.1

 

0

80

2.0

Toro

57.4

11.0

4.3

 

0

80

2.1

BlueCrop

56.5

11.5

4.5

 

0

82

1.7

BlueGold

50.5

8.1

3.1

 

17

100

1.7

Sunrise

36.3

7.3

2.8

 

64

100

1.6

Patriot

34.2

8.7

3.4

 

0

100

1.7

LSD (5%)

8.7

2.7

1.0

 

6

NS

0.2

1

Data are presented by cumulative yield in descending order.

2

Plant spacing is 4 ft by 14 ft, equivalent to 778 plants/acre.

Another factor to be considered in selecting a cultivar is berry size (Table 1). Our data indicate that berry size can vary from the size of a pea to that of a cherry. Typically, small berries are often preferred for cooking, while larger ones are preferred for fresh consumption.

Finally, when selecting a cultivar for planting, growers should also consider the difficulty of harvest. Blueberry pickers ranked the following cultivars from easiest to hardest to pick: Toro, Duke, Sierra, Sunrise, Bluecrop, Bluegold, Nelson, and Patriot.

These results should be useful to growers in selecting a blueberry cultivar. Avoiding labor peaks and harvest times conflicting with the production and/or harvest of other crops may have to be weighed against the highest yielding cultivar.

This article describes the results of the first seven harvests from this planting. Other factors important to cultivar selection are discussed in other publications (2, 3).

Literature Cited

  1. Dwight Wolfe and Gerald R. Brown. 2001. Western Kentucky Blueberry Cultivar Trial. 2001 Fruit and Vegetable Crops Report, PR-452:22.
  2. John Strang, Terry R. Jones and G. R. Brown, 1989. Growing Highbush Blueberries in Kentucky. University of Kentucky College of Agriculture Cooperative Extension Service, publication HO-60.
  3. Joseph G. Masabni and Dwight Wolfe. 2002. Blueberry Cultivar Trial. Kentucky Fruit Facts. August/September 2002, 8/9-2.

Pierce's Disease, a Disease of Grapes in Kentucky and Indiana

John Hartman, Claudia Cotton, Chris Smigell, and Julie Beale, Departments of Plant Pathology and Horticulture and Hancock County Extension Office

Introduction

Pierce's disease, caused by the bacterium Xylella fastidiosa, is a threat to grapes in California and in southern states from Florida to Texas. Disease symptoms vary with species and cultivar, but are typified by marginal browning of leaves and death of vines. This disease is favored by the warm winter temperatures and long growing season found in the southeastern United States. Last year, Pierce's disease was found for the first time in Kentucky (1, 2).

Symptoms of Pierce's Disease

Symptoms vary with the different species and cultivars. Symptoms in spring and early summer include delayed shoot growth, leaf mottling, and dwarfing of new shoots. Late summer and fall symptoms are more dramatic and include burning, scorching, or drying of leaves; wilting or premature coloring of fruit; and uneven cane maturity. Scorching begins near the margin of the leaf blade where tissues become completely desiccated and die. As summer progresses into fall, scorching progressively spreads inward in concentric zones until the entire leaf blade is affected. Leaf blades often fall from the vine at the point of attachment to the petiole, leaving the petiole still attached to the shoot.

The disease progresses along the grape vine with symptoms developing in adjacent leaves along the shoot both above and below the point of initial infection. Flower clusters on infected vines usually dry up. Late in the season, wood on affected canes fails to mature normally, leaving green "islands" of tissue that persist into the dormant season and can be seen on canes throughout the winter. Tips of shoots often die the first year the vine is infected. Initially, only one or a few canes on a vine show foliar and wood symptoms. Symptoms are more pronounced in vines that are stressed by high temperatures and drought conditions.

Grape Susceptibility and Disease Spread

Some grape cultivars are very susceptible, usually dying within two years. Most French (vinifera) varieties die within two to five years, while American (labrusca) varieties often live longer than five years. French-American hybrids are intermediate in susceptibility. Pierce's disease is spread by several types of sharpshooter leafhoppers, spittlebugs, and grafting.

For many years, trees, especially oaks, in Kentucky landscapes have suffered from bacterial leaf scorch disease, also caused by X. fastidiosa but a different strain from the one that causes Pierce's disease. Leaf scorching symptoms associated with this disease annually appear in late summer. Symptoms are quite striking on pin and red oaks, with individual leaves turning one-third to two-thirds brown on the leaf ends and margins. The causal agent of bacterial leaf scorch is also vectored by leafhoppers or other xylem-feeding insects. As far as is known, the grape pathogen is the same species as the tree leaf scorch pathogen, but is a different strain. Thus, the disease would not be spread from trees to grapes.

The objective of this study was to begin a survey of vineyards in Kentucky (and of one vineyard which we were called to in southern Indiana) to determine where Pierce's disease was occurring.

Materials and Methods

Grape leaves showing leaf burning symptoms or dead areas on the leaf were collected from vineyards statewide and in one southern Indiana county and delivered to the UK Plant Disease Diagnostic Laboratory. Petioles from affected leaves were crushed with a mortar and pestle so that the extract could be tested for presence of the pathogen using a special laboratory test, an enzyme-linked immunosorbent assay (ELISA) developed for X. fastidiosa ("Pathoscreen-Xf," Agdia Inc., Elkhart, Ind.). Color reactions for the ELISA test were evaluated visually.

Results and Discussion

In all, 42 grape specimens from 13 vineyards were assayed in the laboratory. They included the cultivars Chancellor, DeChaunac, Foch, Mars, Merlot, Riesling, Vidal, and other cultivars, and also wild grapes where they were found near the vineyard.

From these tests X. fastidiosa was detected in Mars grapes from Hancock County and in Chancellor grapes from southern Indiana. Thus, although Pierce's disease is not yet widespread in Kentucky, it is now confirmed still to be present in Kentucky and is found for the first time in Indiana.

In the laboratory, we are developing a PCR test that we hope will tell whether the grape strains of X. fastidiosa found here are the same or different from X. fastidiosa in landscape trees in the region. This disease can be devastating to grape production, and much more Kentucky research is needed. Studies are also under way to determine which leafhopper vectors might be spreading Pierce's disease in Kentucky. Where the disease is isolated, removal of infected vines should keep further spread to a minimum.

With an emerging grape industry developing in Kentucky, it is important that growers and County Extension Agents be on the lookout for this disease. Personnel in the UK Plant Disease Diagnostic Laboratory can run the specialized tests needed to determine the presence of the Pierce's disease bacterium.

Literature Cited

  1. Bachi, P.R., J.W. Beale, J.R. Hartman, D.E. Hershman, W.C. Nesmith, and P.C. Vincelli. 2003. Plant Diseases in Kentucky—Plant Disease Diagnostic Laboratory Summary, 2002. UK Department of Plant Pathology (in press).
  2. Hartman, J.R., D. Saffray, D. Perkins, J. Strang, and J. Beale. 2002. Pierce's Disease, a new Disease of Grapes in Kentucky. University of Kentucky 2001 Fruit and Vegetable Crops Research Report, PR-452, 19-20.

TREE FRUITS

Rootstock and Interstem Effects on Pome Fruit Trees

Joseph G. Masabni, Gerald R. Brown (Professor Emeritus), and Dwight Wolfe, Department of Horticulture

Introduction

Although apple is the principal tree fruit grown in Kentucky, the state's hot, humid summers and heavy clay soils make apple production a more difficult task for Kentucky growers than for growers in the major apple-producing regions having more favorable conditions. The hot and humid summers are also a factor in the high disease and insect pressure on orchards in Kentucky.

In spite of these challenges, productive orchards are one of the highest per-acre income enterprises suitable for rolling hills and upland soil. Furthermore, in these sites orchards have a low potential for soil erosion. Still, Kentucky imports more apples than it produces.

Continued identification of improved rootstocks and cultivars is required for growth of the Kentucky fruit industry. For this reason, Kentucky cooperates with 39 other states and three Canadian provinces in the Cooperative Regional NC-140 Project titled "Rootstocks and Interstem Effects on Pome Fruit."

The NC-140 trials are of utmost importance to Kentucky growers in terms of gaining access to and testing new rootstocks from around the world. The detailed and objective evaluation of these rootstocks provides growers with valuable information needed to select the most appropriate rootstocks when they become commercially available.

The 1994 and 1999 apple rootstock trials are designed to compare the adaptability of the slender-spindle and the French vertical-axe systems in orchards grown on our fertile soils. In addition, the semi-dwarf rootstocks in the 1999 apple rootstock trial will provide information on the ability of these rootstocks to support themselves without a trellis. The 2002 apple trial will provide us with information on the differences in performance among clones of rootstocks.

The NC-140 orchard trials are used regularly as demonstration plots for visiting fruit growers, Extension personnel, and research scientists. The research data collected from these trials will help establish base-line production and economic records for the various orchard system/rootstock combinations that can be utilized later by Kentucky fruit growers.

Materials and Methods

Scions of known cultivars on various rootstocks were produced by commercial nurseries and distributed to cooperators for each planting. The University of Kentucky has three NC-140 rootstock plantings at the UK Research and Education Center at Princeton (UKREC):

I. The 1994 apple rootstock trial consists of Red Gala on six rootstocks and 10 replications per rootstock. Trees are spaced 13 ft apart within rows 18 ft apart. Trickle irrigation was installed, and a trellis system was constructed in 1995.

II. The 1999 dwarf and semi-dwarf apple rootstock trial consists of two groups:

i) 11 dwarfing rootstocks with six replications per rootstock. Trees are planted on a 10-ft by 16-ft spacing.

ii) six semi-dwarfing rootstocks with six replications per rootstock. Trees are planted on a 13-ft by 20-ft spacing.

III. The 2002 apple rootstock trial consists of Buckeye Gala on nine rootstocks with seven replications per rootstock. Trees are spaced 8 ft apart within rows 15 ft apart.

The experimental field is laid out as a randomized block design. Orchard floor management consisted of a 6.5-ft herbicide strip with mowed sod alleyways.

Trees were fertilized and sprayed according to local recommendations (1, 2). Yield, trunk circumference, and maturity indices were measured.

Results and Discussion

The winter of 2002 was mild, followed by a wet spring and below-normal rainfall from June through August. Summer temperatures were above normal. Rainfall was moderate to above normal throughout the remainder of the growing season. An early spring hailstorm severely damaged the fruit in the 1999 NC-140 trial. Several trees were also blown over.

I. 1994 Apple Semi-Dwarf Rootstock Trial

This is the first orchard trained to the French vertical-axe system at this station. It includes a number of new rootstocks, along with others that have performed well in previous trials at this location.

Survival of trees on M.26 EMLA rootstock (10% survival) differed significantly from trees on the other three rootstocks (90% survival). Cumulative yield, yield in the year 2002, trunk cross-sectional area, fruit size, flesh firmness, and number of root suckers varied significantly among rootstocks (Table 1). No significant differences were observed for percent soluble solids (data not shown). Trees on CG.30 and V.2 rootstocks have been the most productive in this trial. On the other hand, trees on B.9 rootstocks have been the least productive.

Table 1. Results of the year 2002 for the NC-140 1994 apple semi-dwarf rootstock trial, UKREC, Princeton, Kentucky.

Rootstock*

Cumulative

Yield

(lb/tree)

2002

Yield

(lb/tree)

Trunk

Cross-Sectional

Area (in.2)

Fruit Size

(oz/fruit)

Flesh

Firmness

(lb)

Number

of Root

Suckers

CG.30

758

159

11.5

5.0

15.2

7

V.2

633

128

6.5

5.3

17.0

2

M.26 EMLA

465

79

7.3

4.2

13.4

0

B.9

302

62

4.0

4.6

14.3

1

Average

549

145

8.8

4.9

15.4

3

LSD (5%)

216

97

2.6

0.8

2.0

6

*

Arranged in descending order by cumulative yield.

II. 1999 Dwarf and Semi-Dwarf Apple Rootstock Trial

This trial consists of two groups of apple rootstocks, a dwarfing group with 11 rootstocks, and a semi-dwarfing one with six rootstocks. Eight of the dwarfing and three of the semi-dwarfing rootstocks had not been tested previously at UKREC. At planting time, we received 90 trees of a possible 102 for this trial because 12 trees were not available for our site (one each of G.16N, CG.6814, and CG.5202, two CG.4013, three CG.3041, and four CG.30N). Furthermore, three trees never leafed out after planting (one G.16T, one G.16N, and one CG.3041). Five trees in the dwarf planting (one each of CG.5179, G.16N, G.16T, and two of CG.5202) and seven trees in the semi-dwarf planting (one each of CG.6814 and M.26, two CG.7707, and three Supporter 4) broke off at either the roots or the graft union this summer. No statistical differences in mortality were observed among the rootstocks for either group.

For both groups, significant differences were observed for trunk cross-sectional areas, yield in 2002, and cumulative yield (Table 2). The number of root suckers, flesh firmness, and the percent soluble solids varied significantly only among the dwarf rootstocks. Average fruit weight did not vary significantly by rootstock for either the dwarf or semi-dwarf group. Twenty-two of the 31 semi-dwarf trees planted are now supported by tree stakes due to their lean exceeding 30° from vertical. Some of these trees have blown over, breaking at the roots or at the graft union.

Table 2. Results of the year 2002 for the NC-140 1999 apple dwarf and semi-dwarf rootstock trial, UKREC, Princeton, Kentucky.

Rootstock

Cumulative

Yield

(lb/tree)

2002

Yield

(lb/tree)

Trunk

Cross-Sectional

Area (in.2)

Number

of Root

Suckers

Flesh

Firmness

(lb)

Percent

Soluble

Solids

Fruit

Weight

(oz)

Dwarfing*

CG.4013

89.9

64.4

5.3

14.0

20.3

13.7

5.0

G.16T

80.9

57.1

4.2

1.8

20.5

14.1

4.8

CG.5202

67.5

62.6

4.1

8.3

20.3

13.3

5.0

G.16N

64.2

37.5

29.0

2.3

22.5

14.1

5.1

M.9 NAKBT 337

57.8

48.9

16.8

2.8

20.1

13.3

5.5

Supporter 2

54.2

33.7

20.1

0.3

20.9

13.7

5.0

M.26 EMLA

51.1

46.5

18.7

1.7

19.8

13.6

5.4

Supporter 3

50.9

23.8

18.9

2.0

23.1

15.2

4.8

CG.5179

48.3

41.0

20.5

2.4

20.3

14.1

4.8

Supporter 1

47.2

23.4

19.7

3.7

22.9

14.6

4.8

CG.3041

31.7

13.4

26.7

0.5

22.5

11.7

5.6

Average

58.4

41.0

22.4

3.3

20.9

13.9

5.0

LSD (5%)

20.5

26.5

5.9

5.9

2.4

1.5

NS

Semi-Dwarfing*

CG.30N

66.1

48.9

5.2

5.5

20.9

12.8

6.2

CG.4814

60.0

58.4

4.0

9.3

20.3

14.6

5.5

M.26 EMLA

34.8

24.7

3.2

0.4

21.4

14.5

5.9

CG.7707

31.7

29.5

5.7

4.8

21.2

14.1

5.8

M.7 EMLA

28.0

20.1

5.1

25.2

21.4

15.0

5.4

Supporter 4

23.4

12.1

2.7

9.3

23.6

16.1

4.9

Average

37.9

30.4

4.3

10.3

21.4

14.6

5.6

LSD (5%)

26.9

24.3

1.9

NS

NS

NS

NS

*

Within groups, arranged in descending order by cumulative yield.

III. 2002 Apple Rootstock Trial

This trial compares nine rootstocks consisting of three clones of M.9, two clones each of B.9 and M.26, and one clone each of Supporter 4 and of P.14. Sixty-three trees of Buckeye Gala, nine different rootstocks and seven replications per rootstock, were planted in a randomized complete block design in a block of seven rows with a pollenizer tree at the ends of each row. A trellis was constructed and trickle irrigation installed a month after planting. To date, all trees are alive and growing vigorously.

Significant differences were observed for both spring and fall trunk cross-sectional areas and for the change in trunk cross-sectional area from spring to fall. No differences were observed in number of feathers or number of suckers (Table 3).

Table 3. Results of the year 2002 for the 2002 NC-140 apple rootstock trial, UKREC, Princeton, Kentucky.

Rootstock*

Spring

Trunk

Cross-Sectional

Area (in.2)

Fall

Trunk

Cross-Sectional

Area (in.2)

Growth**

(in.2)

Number

of

Feathers

Number

of

Suckers

M.26 NAKB

0.26

0.67

0.41

2.3

0.0

M.26 EMLA

0.22

0.62

0.40

1.4

0.1

P.14

0.26

0.62

0.36

1.9

0.0

Supporter 4

0.26

0.54

0.28

1.0

0.4

B.9 Treco

0.20

0.47

0.27

0.0

0.0

M.9 Nic29

0.26

0.50

0.24

2.4

0.6

M.9 T337

0.18

0.42

0.24

0.6

0.0

M.9 Burg 756

0.20

0.41

0.21

1.4

0.0

B.9 Europe

0.20

0.39

0.19

0.4

0.0

Average

0.23

0.52

0.30

1.3

0.1

LSD (5%)

0.04

0.11

0.10

NS

NS

*

Arranged in descending order by growth of trunk cross-sectional area.

**

Growth in trunk cross-sectional area from spring to fall, 2002.

Literature Cited

  1. G.R. Brown, R.T. Jones, J.G. Strang, L.A. Lester, J.R. Hartman, D.E. Hershman, R.T. Bessin. 1998 Commercial Tree Fruit Spray Guide. University of Kentucky College of Agriculture Cooperative Extension Service, Publication ID-98.
  2. Midwest Tree Fruit Handbook. University of Kentucky

Optimal Training of Apple Trees for High Density Plantings

Joseph G. Masabni, Gerald R. Brown (Professor Emeritus), and Dwight Wolfe, Department of Horticulture

Introduction

Kentucky apple growers often have a problem with excessive vegetative growth or vigor of their trees, which greatly reduces the production that can be achieved from high density apple plantings. Early production and optimal fruit size on vigorous sites are obtained when photosynthates are balanced properly between flower bud initiation and vegetative growth. Pruning and training are possibly the most important operations performed by growers to maintain the proper balance between flower bud initiation and vegetative growth. Identification of effective pruning and training techniques for vigorous sites is required for continued expansion of apple production in Kentucky. The University of Kentucky College of Agriculture (UK) and the Kentucky State Horticultural Society (KSHS) have made long-term commitments to help meet this need and are cooperating in this ongoing research, the purpose of which is to determine the best training and pruning practices needed to obtain early production and optimal fruit size from trees trained to the slender-spindle or the French vertical-axe system.

Materials and Methods

One hundred-sixty trees of Golden Delicious on M.9 rootstocks were planted in May 1997 in a randomized complete block design consisting of five rows and 32 trees per row. At planting, trunk circumference at 12 inches above the soil surface averaged 2.4 inches and did not vary significantly among rootstocks. A trellis was constructed, and trickle irrigation was installed. Trees were spaced 8 ft apart within rows 16.4 ft apart. Orchard floor management was a 6.5-ft herbicide strip with mowed sod alleyways. Trees were fertilized and sprayed according to local recommendations (1, 2). Beginning in 1998, yield, trunk circumference, and maturity indices such as soluble solids and flesh firmness were measured after harvest.

The trees were trained according to detailed treatment protocols presented in Table 1. Trees began to fill their allotted space in 1999, and leader management was modified to maintain leaders at specified heights (Table 1). Limbs of one tree that overlapped or touched those of adjacent trees were headed back to two-year-old wood.

Table 1. Details of pruning and training treatments of the 1997 apple training study at UKREC, Princeton, Kentucky.

System

Amount of 1-Year-

Old Wood Left After

Heading at Planting

Pruning

 

Training

Level

Interval

in Weeks

Limb

Angle1

Limb

Management2

Leader Management

19993

20004

French Axe

Not headed

Light

1

 

45

No

D

12

French Axe

12-16 in.

Moderate

2

 

45-60

Yes

C&D

11

French Axe

12-16 in.

Moderate

1

 

45-60

Yes

D

11

French Axe

8-12 in.

Heavy

1

 

60-90

Yes

D

10

Slender Spindle

Not headed

Light

1

 

45

No

A

9

Slender Spindle

14-20 in.

Moderate

2

 

45-60

Yes

B

9 Y

Slender Spindle

14-20 in.

Moderate

1

 

45-60

Yes

B

9 Y

Slender Spindle

10-14 in.

Heavy

1

 

60-80

Yes

C

9 Z

1

Angle at which limbs are positioned.

2

French Axe: remove overly vigorous branches with narrow angles when 3 to 6 inches long. Slender Spindle: remove branches that compete with leader. In 2000, for both training systems, limbs overlapping or touching those of adjacent trees were headed back into 2-year-old wood.

3

A = weak leader renewal and new leader headed at 12 inches. B = bend leader at 60̊ angle, alternating direction with every 18" of new growth. C = leader bagged 1 month prior to bud break and bag removed at appropriate time. D = leader bent to horizontal, alternating direction after buds break on top side.

4

Leaders were maintained at specified heights (ft) by cutting to an alternate leader when necessary. Y = Alternate leader was bent to horizontal for 6 weeks. Z = Alternate leader was “snaked” throughout growing season. Leader management was the same in 2002 as in 2000 and 2001.

Results and Discussion

No significant differences were observed between the French vertical-axe and the slender-spindle training systems for any of the measured variables. Therefore, all data are presented as the combined values for both systems. No differences among the four pruning levels were observed for cumulative yield (1998-2002), yield in 2002, fruit weight, and trunk circumference (Table 2).

Table 2. Effects of pruning and training treatments on yields of the 1997 apple training study at UKREC, Princeton, Kentucky.

Pruning1

Level

Interval in Weeks

Yield (lb/tree)

2002

Cumulative Yield3

(lb/tree)

Fruit Weight

(oz)

Trunk

Circumference (in.)

1998

1999

20002

2001

2002

Light

1

1.3

19.8

11.2

92.7

39.2

167.0

5.46

9.33

Moderate

2

2.0

22.0

23.4

83.1

51.1

179.8

5.36

9.10

Moderate

1

2.4

17.1

23.7

85.8

54.8

180.4

5.04

8.95

Heavy

1

0.2

20.5

21.4

80.4

53.1

177.3

5.41

9.24

Average

 

1.5

19.8

19.9

85.7

49.4

176.0

5.33

9.16

LSD (5%)

 

0.9

NS

6.60

20.7

NS

NS

NS

NS

1

Pruning level represents combined values for Slender Spindle and French Vertical Axe.

2

Starting in 2000, the pruning protocol was changed to once early in the season for all treatments.

3

Yield is the sum of picked and dropped fruit. Dropped fruit averaged 9.1 lb/tree in 2002.

Pruning time per tree was not analyzed statistically; thus, no LSD values are presented in Table 3. Even though pruning time per tree appears to be the highest for the heavy pruning level, this difference was not significant to the pruning crew. Pruning time, when adjusted for pounds of fruit produced, did not differ among the four treatments (Table 3). Total pruning and training periods were 14 weeks in 1997, 12 weeks in 1998, 18 weeks in 1999, four weeks in 2000, four weeks in 2001, and one week in 2002.

Table 3. Time required for pruning and training of the 1997 apple training study at UKREC, Princeton, Kentucky.

Pruning1

Level

Interval in Weeks

Minutes per Tree

Total Minutes per Tree

Minutes per Pound of Fruit

1997

1998

1999

20002

2001

2002

Light

1

12.2

10.2

18.2

4.4

9.6

6.1

60.7

0.36

Moderate

2

9.6

8.6

16.5

3.4

9.6

6.6

54.3

0.30

Moderate

1

11.4

11.1

19.1

2.1

9.6

5.6

58.9

0.33

Heavy

1

11.9

12.0

21.6

2.5

9.5

7.0

64.5

0.36

Average

 

11.3

10.3

18.9

3.0

9.6

6.3

59.4

0.34

1

Pruning level represents combined values for Slender Spindle and French Vertical Axe.

2

Starting in 2000, the pruning protocol was changed to once early in the season for all treatments.

This planting has been regularly used as a demonstration for visiting apple growers, Extension personnel, and research scientists. The data collected in these trials have helped establish baseline economics and production methods for the various orchard system/rootstock combinations that can be utilized by Kentucky fruit growers.

Literature Cited

  1. G.R. Brown, R.T. Jones, J.G. Strang, L.A. Lester, J.R. Hartman, D.E. Hershman, R.T. Bessin. 2002 Commercial Tree Fruit Spray Guide. University of Kentucky College of Agriculture Cooperative Extension Service, Publication ID-98.
  2. Midwest Tree Fruit Handbook. University of Kentucky College of Agriculture Cooperative Extension Service, Publication ID-93.


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