Grapes

Lecture Outline

Reading: Chapter 10 in Small Fruit Crop Management

Types of Grapes:

1) European Vitis vinifera

2) American Vitis labrusca

3) French hybrids Hybrids between native American spp. (other than labrusca) and

V. vinifera

Native American Species

V. riparia

V. rupestris

V. champini

V. candicans

1850s - introduction of phylloxera (root louse) and Downy Mildew (fungus) into Europe - major devastation to European wine industry

Selection of ‘Hybrid Direct Producers’ - plants with good fruit quality in addition to phylloxera resistance and disease resistance.

Grafting dying vines onto resistant rootstocks (American spp.)

Breeding to improve rootstocks

Advantages of “French Hybrids”:

Phylloxera resistant

Cold hardy

Disease resistant

Productive (can be excessive)

Good fruit and wine quality

Disadvantages of “French Hybrids”:

Less than excellent wine quality (at least perceived by some)

Can be overly productive so require careful management

4) Rootstocks (derived from wild American spp. x European V. vinifera)

Phylloxera resistance

Increased/reduced vigor

Nematode resistance - virus avoidance

Lime tolerance

Drought tolerance

Resistance to soilborne diseases

5) Muscadine grapes (Vitis rotundifolia)

Subgenus Muscadinia has 2n=40 chromosomes compared to 2n=38 for bunch grapes

Very resistant to common grape diseases

Do not cross readily with bunch grapes

Unique flavor and texture

Grape Production

World (65 mil tons)

Tons of Fruit Wine Production

1. Italy 1. France

2. France 2. Italy

3. USSR (former) 3. Spain

4. Spain 4. US

5. US 5. Argentina

6. Turkey 6. South Africa

7. Argentina 7. Germany

United States 1,004,545 acres 6.8 mil tons

1. California 870,500 6.2 mil tons (86% of US total)

2. Washington 40,700 311,000 tons

3. New York 33,000 135,000 tons

4. Pennsylvania 13,400 60,000 tons

5. Michigan 13,000 55,000 tons

6. Oregon 9,575 22,000 tons

7. Arizona 6,050 25,000 tons

19. Indiana 428 1,485 tons

Grape Cultivars

5,000+ in existence today.... over 7,000 historically.

Only a few (20-30) account for the bulk of the world production

Wine Table (seedless) Juice

Cabernet Sauvignon Thompson Seedless Concord

Chardonnay Flame Seedless Niagara

Merlot others *Thompson Seedless

Riesling

Pinot noir

French Colombard

Chenin blanc

Sauvignon blanc

*Thompson Seedless

French hybrid wine American wine

Seyval Catawba

Vidal Niagara

Marechal Foch Concord

Chambourcin

Chancellor

Raisin

Thompson Seedless

Black Corinth

Muscat of Alexandria

Grape Propagation

Rooting cuttings:

Dormant: common for own-rooted vines or rootstocks

Green: easy

Layering: especially for difficult to root types

Grafting: especially for vinifera where need for phylloxera resistance is important

Bench graft:

Cleft graft:

Chip budding:

Green grafting:

Micrografting:

Grape Culture - Factors affecting cultivar adaptation

Worldwide grapes are produced in regions between 30 to 50˚ N latitude and 30 to 40˚ S latitude.

These regions are referred to as grape belts.

1. Minimum winter temperature

Hardiest -30˚F Most Tender 0˚F

2. Length of the growing season

150 to 180 days - Standard

<150 - early maturing varieties - short season

>200 - late maturing varieties - long season

Standard varieties have uneven ripening, poor fruit quality, low vigor

3. Heat Units - Growing Degree Days

1800 to 2500 American varieties, French hybrids, cool-climate European varieties

2500 to 4000 Most European varieties, French hybrids

Winkler System(50˚F base temperature)

Used to describe regions in California and determine what the best varieties for each region are.

Region GDDs (base 50)

I <2500

II 2,500 to 3,000

III 3,000 to 3,500

IV 3,500 to 4,000

V 4,000+

Effects of climate on winegrape fruit quality

Cool season low sugar, high acid

Warm season high sugar, lower acid

Hot season high sugar, too low acid

4. Relative humidity and rainfall: (incidence of fungal diseases)

Low humidity, dry, hot (SW U.S. and Calif) - European varieties are best adapted

High humidity, warm, moist (SE US) - Muscadine and American varieties

Midwest & Northeast (MO, IL, IN, OH, MI, PA, NY, etc.) - American, French hybrids, and European varieties

Moderate to high RH during most of the growing season

Some regions are Cool Climate (Region I or II) (NY, MI), others are typified by warm summers and cold winters (Region II or III)

Indiana climate

GDDs = 2,500 to 3,800 (Region II and III)

Growing season = 150 to 200+ days

Minimum winter temperatures: Zone 6b (0 to -5˚F) to Zone 5a(-15 to -20˚F)

Site Selection for Grapes

1. Length of the growing season >165 frost free days

elevation

proximity to large bodies of water

slope aspect

<150 days - American or French hybrids - Early maturing

150 to 160 - Most American and some French hybrids

160 to 170 - American , French hybrid, early European

170 to 180 - American, French hybrid, European

180+ - Best for French hybrid and European

200+ - Best for late European and muscadines

2. Minimum winter temperatures (for the East and Midwest US)

Excellent: -5˚F (3/10 years) -10˚F min

Good: -5˚F (5/10 years) -15˚F min

Acceptable: -5˚F (10/10 years) -15˚F min

Poor: -10˚F (5+/10 years) -15˚F min

Response to low temperatures

Hardiness of tissues:

Trunks > Canes > Buds

@ 0˚F Some bud injury to tender varieties

@ -10˚F Bud and cane injury to tender types

Some bud injury to moderately hardy types

@ -15˚F Bud, cane, and trunk injury to tender types

Bud and cane injury to moderately hardy types

Vineyard layout

Plant spacing: 5 to 8 feet apart in rows

Row spacing: 9 to 12 feet apart (standard) as close as 4 feet in high density

Plant/row spacing depends on potential vigor or ‘vine size’

1. Vigor of variety

rootstock

scion

2. Soil fertility

soil type

depth

3. Equipment size - especially row spacing concerns for clearance

Row orientation:

North-South is preferred for maximum sunlight interception

Cross slope row orientation becomes important to reduce erosion

Pruning grapevines

Must be done each year

Most important cultural practice for maintaining vine productivity

Most expensive (labor intensive) cultural practice

Purpose of pruning:

1. Regulate the size of the crop - MOST IMPORTANT

Maintain proper balance between vegetative growth and fruit production

2. Select fruiting wood

quality

position (density/placement)

amount

3. Maintain vine shape and form

conform vine to training system, fill the trellis evenly for maximum sunlight utilization

Types of pruning

1. Cane pruning - retain long (10 to 15 node) canes

2. Spur pruning - retain short (2 to 6 node) spurs

3. Machine pruning (can either approximate hand pruning or be minimal)

approximate hand pruning:

- hedged with cutter bars, some hand follow-up

minimal pruning

- hedged or skirted with cutter bars, no hand follow-up

Leads to high number of buds compared to hand pruning

- vines compensate for large number of buds retained over a period of years

- Mid-season crop adjustment is usually necessary to prevent overcropping

Balanced Pruning Concept

Sheppard - Michigan State and Shaulis - Cornell (New York)

Pruning according to a formula developed for each variety to ‘balance’ the amount of vegetative growth with the amount of fruit produced.

Developed on Concord and works best on American varieties

Balance Pruning Procedure

1. Prune the vine leaving enough extra buds to provide a margin of error

2. Weigh the 1-yr old canes (only what grew last season) to obtain ‘Vine Size’

3. Apply Vine Size weight to the formula to determine how many buds to retain.

Example calculation of balanced pruning formula:

Concord: formula is 30 + 10

We leave 30 buds for the 1st pound of prunings and 10 buds for each additional pound

So, if we prune a vine and estimate the Vine Size to be 4 lbs, then we would leave

30+10+10+10 = 60 buds total on the vine for a proper balance of fruit and vegetation.

Balanced Pruning does not work in every situation:

Highly fruitful varieties - especially certain French hybrids - produce clusters from secondary buds and non-count buds (those on wood older than 1 year, and those at basal nodes)

On these varieties, removal of some of the clusters (cluster thinning) or some of the shoots (shoot thinning) must be done to maintain the proper crop load

Crop Load (Yield of fruit / weight of one-year cane prunings)

Very important concept in balancing the fruit production to the vegetative vigor. If properly balanced, vines will bear consistent yields and maintain adequate vigor.

General Rule: Crop load should be in the range of 5 to 10

Crop load is the ration of lbs fruit : lbs prunings and varies among varieties, but in general falls within the range of 5 to 10 for vinifera varieties, probably a little higher (e.g. 12-15) for American and French hybrids.

Relationship between yield and fruit quality

GENERAL STATEMENT: As yield increases, quality decreases

However, fruit quality is dependent on several factors:

Canopy microclimate

Leaf area to fruit ratio

Genetic potential of the variety

Potential of the site: Climate and Soils

Intended use of the fruit

Training Grapes

Training grapevines is done to properly display fruit and foliage to sunlight, and provide renewal zones that will lead to sustainability of the system.

Trellis support facilitates production, management, disease control.

Trellis system:

Wood posts: 20-30 feet apart (depends on vine spacing)

@ 8 ft vine spacing posts are 24 ft apart

Wire: 9 to 12.5 gauge galvanized or high-tensile used to support trunk,

cordons, canes, and shoots

Training Systems:

Cane pruned:

Kniffen systems

Umbrella

4 cane

California mid-wire

Pendlebogen (half-bow)

Keuka high renewal

Fan

Spur pruned:

High cordon - Bi-lateral cordon or single curtain for procumbent growing cultivars

(esp. American and French-American hybrids)

Mid-wire cordon - Vertically shoot positioned for upright growing cultivars

(esp. vinifera)

Low cordon - Vertically shoot positioned for cold-tender cultivars (esp. vinifera)

Divided canopy systems: (May be spur or cane pruned or a combination of each)

Horizontally divided -

Geneva Double Curtain

Lyre

Vertically divided -

Scott Henry

Smart-Dyson

Other training systems

Overhead arbor

etc. etc. etc.

Grape Diseases and Control

Diseases are a major concern for grape production worldwide. Most can be controlled through cultural and chemical means.

Most important diseases are caused by fungi:

Powdery mildew - #1 worldwide

Downy mildew

Black rot

Botrytis bunch rot

Phomopsis cane and leaf spot

Eutypa dieback

etc.

Others:

Viruses (most vectored by insects or nematodes)

Grape fanleaf

Peach rosette mosaic

Rupestris stem pitting

Chrome mosaic

etc.

Bacterial

Crown gall - Agrobacterium vitis closely related to A. tumefacians

Pierce's Disease - xylem-limited, rickettsia-like organism

Control of virus and bacterial pathogens is accomplished through planting ‘clean’ disease-free planting stock, and control of vectors.

Grape Fungal Disease Control

Accomplished by a combination of cultural and chemical methods.

Cultural methods:

Varietal resistance

Site selection

Good air movement

Full sun exposure

Canopy management

Training systems

Pruning strategies

Leaf removal

Hedging

Chemical methods:

Protectant fungicides

- applied routinely (calendar basis) to prevent disease infection

- non-systemic - cannot stop disease after infection

- usually broad spectrum (control many different fungi)

Curative fungicides

- applied in response to climatic conditions conducive to infection

- systemic - can 'cure' disease by killing or inhibiting fungi after infection occurs

- Usually narrow spectrum (specific for certain pathogens). Many are sterol inhibitors - work on only certain fungi. Because of a 'single site' activity can be subject to development of pathogen resistance

Effective chemical control depends on:

Proper identification of disease

Thorough understanding of pathogen biology

Selection of proper chemical

Proper timing of application

Thorough coverage of susceptible parts

Disease control strategies:

Preventative

Grower relies on frequent application of protectant fungicides to prevent any

infections from occurring

Curative (post-infection)

Grower relies on accurate disease forecasting: weather monitoring and

disease modeling to predict when infects are likely to have occurred, then

applies a curative systemic fungicide to stop the infection before disease symptoms and damage occur.

Commonly used program in the Midwest based on pathogen biology

Early season - grower applies protectant (and curative) chemicals from early

budbreak to two weeks after bloom on a regular (7-10 day) basis.

This prevents primary inoculum from starting disease and subsequent epidemic.

Mid season - grower switches to curative chemicals only, applying only when

disease forecasting indicates problems, or when disease outbreak

occurs.

Late season - near harvest grower may apply specific chemicals to prevent

Botrytis or other fruit rots.

Post-harvest - after harvest grower applies broad spectrum protectants to maintain

healthy foliage through fall to optimize winter hardening.