Grape growing options Flashcards
1
Q
What are the three advantages of conventional viticulture (i.e., monoculture)?
A
- Mechanization (decrease labor costs)
- Reduction of competition from other plants
- Ability to optimize for the specific variety, increasing yields while minimizing costs. Optimization would include:
a. Irrigation
b. Nutrition level
c. Treatments against hazards, pests, and diseases
- Ability to optimize for the specific variety, increasing yields while minimizing costs. Optimization would include:
2
Q
What are the three disadvantages of conventional viticulture (i.e., monoculture)?
A
- Plants are much more prone to disease and pests (due to uniformity), and thus need more treatments or protection
- Nutrients can be depleted as there is no natural ecosystem to replenish nutrients, requiring more applications of fertilizer
- Residual chemicals can contaminate groundwater or air
3
Q
What is the overall approach of sustainable viticulture?
A
Develop and in-depth understanding of the vineyard to predict and prevent a pest or disease before it occurs, and to time applications to when they will have maximum effect, to minimize treatments.
4
Q
What are the four steps of integrated pest management (IPM)?
A
a. Setting thresholds at which action needs to be taken
b. Identifying and monitoring pests
c. Setting up preventative measures
d. Evaluating and implementing control options (if thresholds are exceeded and preventative measures are not effective)
5
Q
What are the four advantages of sustainable viticulture?
A
- A more thoughtful approach, with attention to the economic, social, and environmental impact
- Minimize interventions needed through scientific understanding of pests and diseases
- Reduction of synthetic and traditional treatments
- Cost savings
6
Q
What are the two disadvantages of sustainable viticulture?
A
- Term is not protected and therefore can be used without a set standard
- National rules may be set too low (e.g., in NZ, virtually all commercial growers)
7
Q
What are the 4 key features of organic viticulture?
A
- Application of compost: slow release of nutrients, improve soil structure, and biomass in soil
- Natural fertilizers (animal dung, natural calcium carbonate, etc.): restore natural balance in vineyard
- Cover crops: prevent erosion and contribute to improvement of vineyard ecosystem (e.g., by ploughing in (“green manure”))
- Reduction of monoculture: growing cover crops, planting hedges, and establishing islands of biodiversity
8
Q
What are the 4 advantages of organic viticulture?
A
- Better vine health and disease resistance
- Better soil heath
- No spraying of synthetic chemicals
- Cost savings in not having to buy synthetic chemicals
9
Q
What are four disadvantages of organic viticulture?
A
- Possibly small reduction in yield generally
- Possibly significant reductions in yield in difficult years (e.g., long periods of rainfall or high humidity)
- Increased reliance on copper sprays, which may lead to buildup of copper in soils
- Cost and time in seeking certification [and possibly higher labor costs, which vary based on location]
10
Q
What is biodynamic preparation 500 (horn manure) and what is it said to do?
A
a. Stuffing cow manure into a cow’s horn, burying it in winter, then dynamized (stirring in water, first one way then the other–the water “memorizes the power of the preparation so it can pass it to the vineyard”), then sprayed onto the soil as compost.
b. Said to catalyze humus formation.
11
Q
What is biodynamic preparation 501 (horn silica) and what is it said to do?
A
a. Fill cow’s horn with ground quartz (silica), burying for 6 months, then dynamized and sprayed onto soil.
b. Said to encourage plant growth.
12
Q
What are the advantages/disadvantages of biodynamic viticulture?
A
- Similar to organic (limited research comparing the two)
13
Q
What are the 4 key features of regenerative viticulture?
A
- Restore a vineyard site to a functioning agroecosystem (ecosystem modified for agriculture) to improve resources and limit inputs
- Soil health is top priority, as it will improve the health of the entire vineyard
- Biodiversity (above and below ground) is essential (e.g., encouraging organisms with symbiotic relationships, like mycorrhizal fungi)
- Grape growers improve their well-being by reducing the cost of synthetic inputs and limiting exposure to harsh chemicals
14
Q
What are 4 common practices of regenerative viticulture?
A
- Limit tilling (which sequesters carbon, among other things) and limit irrigation
- Add compost to increase organic matter in the soil and replace nutrients
- Cover crops to prevent erosion and reduce water loss
- Animals (like predators) can create natural controls for pests
15
Q
What are 5 advantages of regenerative viticulture?
A
- Soils rehabilitated, decreasing need for synthetic inputs
- Carbon sequestered
- Vineyards become more resilient (limiting effects of climate change)
- Biodiversity improves along with animal welfare
- Lives of grape growers improve through less exposure to harmful chemicals
16
Q
What are 5 disadvantages of regenerative viticulture?
A
- Not legally defined, so claims may be exaggerated
- Growers need to experiment with what works in their vineyard, which takes time and resources
- Once a plan is established, results take time, which is difficult and costly
- Producers can’t rely on inputs in case of disease or climate issues, which may reduce yields
- Certification costs
17
Q
What is the goal of precision viticulture?
A
The goal is for all key interventions (like pruning, leaf removal, treatments, irrigation, crop thinning and harvesting) to be tailored to small plots, increasing quality and yield and reducing treatments.
* Examples: Changing rootstocks halfway along rows as soil fertility increases, or increasing leaf-stripping in areas of high vigor
18
Q
What are 2 advantages of precision viticulture?
A
- Detailed understanding of variations between and within vineyards
- Variable-rate application technology: Ability to tailor a wide range of interventions (choice of variety and rootstock, canopy management, treatments, harvest dates) to individual blocks or even rows of vines, with the aim of improving yields and/or quality
19
Q
What are 2 disadvantages of precision viticulture?
A
- Initial cost of remote data collection
- Cost of sensors and software and of consultants or trained staff to interpret the data and make interventions based on it.
20
Q
Who practices precision viticulture?
A
Considerable upfront costs means that it is only an option on large scale viticulture or high-value smaller estates (and in practice mostly in CA and Australia)
21
Q
What are the 6 key aims of canopy management?
A
a. Maximize the effectiveness of light interception by the vine canopy
b. Reduce shade within the canopy
c. Ensure the microclimate for the grapes is as uniform as possible so they ripen evenly
d. Promote balance between vegetative and reproductive functions of the vine
e. Arrange vine canopy to ease mechanization and/or manual labor
f. Promote air circulation to reduce disease pressure
22
Q
What 7 factors does the yield that represents a balanced yield (with respect to vegetative vs. reproductive functions) depend on?
A
- Climate (warmer/sunnier/wetter can ripen more grapes)
- Other growing conditions (e.g., soil texture and structure, nutrients, etc.)
- Variety (Cab Sauv will ripen a larger yield than Merlot)
- Rootstock
- Disease
- Vine age
- Style of wine (grapes for rosés can have less ripe tannins)
23
Q
What are the two extremes that are to be avoided in achieving a balanced yield?
A
i. Avoid a vegetative cycle (where too much shade of buds results in lower yields the next year, possibly leading to under-cropping)
ii. Avoid over-cropping, where not enough carbohydrates are stored in the truck, cordons, and roots, which weakens the vine in future years
24
Q
What are 6 effects of promoting sunlight exposure to grapes?
A
a. increased sugar levels in grapes through increased photosynthesis in the vine
b. increased tannin levels and greater polymerisation, leading to less bitterness
c. more anthocyanin (color) development in black grapes
d. decreased malic acid (due to greater respiration and thus metabolism of malic acid)
e. increased levels of some good aroma precursors and aroma compounds (such as terpenes)
f. decreased methoxypyrazines
25
What are 6 ways in which varieties (or clones) can be more or less well adapted to a cimate?
* Time of budding (e.g., early budding more at risk of frost)
* Duration of annual lifecycle (e.g., early ripening better for cool; late-ripening better for warm/hot)
* Tolerance of drought
* Resistance to disease (e.g., Cab Sauv less prone to grey rot than Merlot)
* Winter hardiness
* Vigor (e.g., Sauv Blanc on fertile soils with water requires vigor management)
26
Other then climatic factors, what are 6 other consideration in choice of variety/clone?
* Style of wine
* Yield (aiming for inexpensive, pick high yielding varieties/clones)
* Cost (some varieties, like Pinot Noir, are more difficult/expensive to grow)
* Law (e.g., EU regulations)
* Availability (perhaps limited by high demand or lack of supply)
* Market demand (demand for wine (accounting for fashion) and route to market)
27
What are the 4 criteria for selecting rootstocks?
* Resistance to pests
* Water (tolerant of drought, water-logged soil, or salinity)
* Soil pH (high or low)
* Vigor (high or low)
28
How can rootstocks be better suited to differences in water?
i. Tolerance of drought because of deep/quick rooting: hybrids of V. rupestris and V. berlandieri, such as 110R or 140R
ii. Tolerance of water-logged soil: based on V. riparia, such as Riparia Gloire
iii. Tolerance of salinity: based V. berlandieri, like 1103P
29
What are examples of rootstocks suited to different soil pHs?
i. Low pH: 99R and 110R, both hybrids of V. rupestris and V. berlandieri
ii. High pH: based on V. berlandieri, such as 41B
30
What are examples of rootstocks suited to different vigors and why one would want them?
i. Low vigor (can advance grape ripening in cool climates): based on V. riparia, such as 420A and 3309C
ii. High vigor (can boost vine growth and yields in unfertile and dry soils, or use for sparkling wine aiming for delicate aromas and high acid): based on V. rupestris, such as 140R
31
What is the one advantage and two disadvantages of clonal selection?
* Advantages
a. If all vines grow in a similar way and fruit ripens at the same time, may be simpler
* Disadvantages
a. Perhaps less diversity of fruit, and thus less complexity
b. Perhaps equally susceptible to disease or pest
32
What are the 2 advantages and 2 disadvantages of mass selection?
* Advantages
a. Increases diversity in the vineyard and larger region
b. Vineyard owner uses their own material, which can enhance quality or yield at their site (and used for marketing)
* Disadvantages
a. Selecting and monitoring vines takes work
b. If parent vine is infected by disease, it will likely be passed to the new vines
33
What is mass selection?
A vineyard owner takes cuttings from their own best-performing vines and cultivate them (perhaps sending to a nursery for grafting).
34
What is soil health and what 4 factors contribute to it?
Capacity of soil to act as living ecosystem. Related to:
* Structure of soil (good drainage, water-holding capacity, sufficient oxygen, erosion resistance, root penetration)
* Amount of organic matter and humus in soil (improves structure and water-holding capacity)
* Number of living organisms in soil (like earthworms and microbes that break down organic matter into humus and inorganic nutrients)
* Total amount of available nutrients
35
What are 6 primary interventions with respect to nutrient management?
* Fertilizers
* Cultivation (plow soil to disturb weeds' roots)
* Herbicides
* Animal grazing
* Cover crops
* Mulching (spreading biodegradable materials)
36
What are the two types of fertilizer?
* Organic: derived from fresh or composed plant or animal material, possibly mown and plowed cover crop ("green manure")
* Inorganic (synthetic): Manufactured from minerals extracted from the ground or synthetic chemicals
37
What are 3 advantages of organic fertilizer?
1. Often cheap or free
2. Some high in humus and therefore good for soil structure and water retention
3. Nutrition for soil organisms, promoting living matter in soil
38
What are 3 disadvantages of organic fertilizer?
1. Requires labor to incorporate into the soil
2. Nutrients become available to the vine gradually (which may be a good thing)
3. Bulky and expensive to transport and spread
39
What are 2 advantages and 2 disadvantages of inorganic fertilizers?
Advantages:
* Can be very tailored
* Nutrients readily available to the vines
Disadvantages:
* Do not improve soil structure or ecology (no benefit to soil organisms)
* Often more expensive to purchase (but cheaper to transport)
40
What are two advantages of cultivation of weeds?
i. No chemicals, so can be used in organic and biodynamic
ii. Can incorporate fertilizer and mown cover crops into soil
41
What are 4 disadvantages of cultivation of weeds?
i. Can damage soil structure and ecology by (i) breakdown of organic matter and (ii) disruption of earthworms
ii. Costly: skilled labor and machinery
iii. Buries seeds, encouraging weeds to grow back
iv. Can increase vine vigor, as there is no competition for water or nutrients (not a problem in low vigor sites)
42
What are the three types of herbicides?
i. Pre-emergence herbicides: Persist in surface layers of soil, and (i) absorbed by weeds’ roots and (ii) inhibit germination of seedlings.
ii. Contact herbicides: Kills green parts of weed they contact.
iii. Systemic herbicides: Taken in by leaves, travels up and down the weed in the sap to kill the plant.
43
What are three advantages of use of herbicides?
i. Cheap: little labor and machinery
ii. Highly effective, especially in under-row area
iii. Less damaging to soil structure than cultivation
44
What are four disadvantages in use of herbicides?
i. Risk of poising operator, consumer, and environment, and do not encourage vineyard ecosystems.
ii. Weeds can become resistant, so dosage may need to be increased (example of glyphosate-resistant ryegrass in South Africa).
iii. Can increase vine vigor too much as there is no competition for water or nutrients (not a problem in low vigor sites).
iv. Not allowed for organic or biodynamic.
45
What are three advantages to animal grazing?
i. Can be used in organic and biodynamic
ii. Animals can provide manure
iii. Animals can be a source of meat
46
What are three disadvantages to animal grazing?
i. Vines must be trained high or grazing must happen out of growing season
ii. Requires labor for animal care if they belong to vineyard owners
iii. Animals are often susceptible to vineyard pesticides
47
What are three examples of types of cover crops?
i. Legumes (beans, clover)
ii. Cereals (ryegrass, oats)
iii. Natural vegetation (but less control)
48
What are four advantages of cover crops?
i. Can be used in organic and biodynamic
ii. Increases soil biological activity and biodiversity
iii. Can influence vigor of vine by introducing competition for water and nutrients
iv. Good surface for machinery, especially in climates with high annual rainfall
49
What are three disadvantages of cover crops?
i. Reduction of vine vigor through competition (not a problem for high vigor sites)
ii. Difficulty of mowing under-row area, which increases time and labor
iii. Not suitable for steep slopes, as slippery when wet
50
What are three advantages of mulching?
i. Can be used in organic and biodynamic
ii. Can reduce water evaporation (good in dry sites)
iii. Can be a source of nutrients and humus, which promotes soil biological activity and good soil structure (esp in poor soils)
51
What are three disadvantages of mulching?
i. Is very bulky, so expensive to transport and spread
ii. Only effective in a thick layer, so a lot is needed
iii. Can increase vigor too much if no competition for water or nutrients (not a problem for low vigor sites)
52
What are the two general approaches to addressing water management?
* Irrigation
* Drainage
53
What are six steps to increasing water efficiency?
i. Use of water-efficient irrigation plus better monitoring (e.g., drip and regulated deficient irrigation)
ii. Use of drought-tolerant varieties (e.g., Granache) and rootstocks (e.g., 140R)
iii. Reducing evaporation (e.g., by applying mulch)
iv. Reducing competition (e.g., removing weeds)
v. Increasing humus in soil to improve retention (e.g., adding organic matter)
vi. Promoting growth of deep vine roots (e.g., through cultivation)
54
What are 4 advantages to drip irrigation?
1. Economic use of water
2. Can control water to individual rows or blocks of vines, tailoring management and possibly resulting in higher yields and quality
3. Can be used to supply fertilizer (“fertigation”)
4. Can be used on slopes
55
What are 4 disadvantages of drip irrigation?
1. High cost of installation; moderate cost of maintenance
2. Clean water required or drippers quickly clog
3. Even with clean water, drippers gradually clog with algae, bacteria, or minerals/salts, so some maintenance is required
4. Can’t be used for frost protection (aspersion)
56
What are 3 alternative irrigation methods other than drip?
* Flood irrigation
* Channel irrigation
* Sprinklers
57
What are the three advantages or disadvantages of flood irrigation?
1. Cheap to install and maintain
2. Inefficient
3. Can only be used on flat or gently sloped land
58
What is channel irrigation, and what is its sole advantage?
Water flows in furrows between rows, which increases efficiency over flood irrigation
59
What are the 3 advantages and disadvantages of sprinklers for irrigation?
1. Expensive to install and maintain due to need for high water pressure
2. Not as efficient as drip
3. Can be used for frost protection
60
What is regulated deficit irrigation (RDI)?
Schedule water deficit between fruit set and véraison to limit shoot growth and encourage grape development (can’t be too much or it will reduce yield and quality)
61
What circumstances are best for RDI and how is it best implemented? What needs to be true for RDI to be worth it?
* Easiest with dry growing season and sandy or loam soils that dry out and can be re-wetted quickly
* Best done with a dripper system to control
* Reduces yields, so increase in quality must make up for lost volume.
62
Is RDI more favored for black or white grapes, and why?
Often favored for black grapes as it reduces grape size, increasing skin to juice ratio, giving increased concentration of anthocyanins and tannins
63
When would artificial drainage be installed and why?
i. In sites with lots of rain and not sufficiently free-draining soils, artificial drainage systems may be installed before planting.
ii. Cost of installation and maintenance typically more than offset in medium term by having healthier, better-balanced vines.
iii. Also aids mechanization by (i) providing better surface to drive on and (ii) reducing soil compaction from driving on wet soils.
64
Besides installing artificial drainage systems, what are other methods to control water available to the vine?
i. Competition for water by cover crops or natural vegetation
ii. Improving soil structure and removing plough pans to better regulate water drainage
65
What are 3 primary considerations in choosing a training and trellising system?
* Vigor of the vine
* Topography of the (many systems can't be used on steep slopes or windy sites)
* Need for mechanization (VSP and other trellising systems are suited for mechanization because fruit tends to be on the same area for each vine)
66
What factors determine vine vigor?
1. Natural resources (temp, water, nutrients)
2. Planting material (variety, clone, rootstock)
3. Presence of disease
67
In addition to factors related to variety/rootstock selection and training/trellising techniques, what two other considerations of how the vineyard is planted are there for canopy management techniques?
* Vine density
* Row orientation
68
What determines optimal vine density?
i. Vigor of the vine (due to variety/rootstock or growing conditions)
ii. Type of trellising system
iii. What access is needed between the vines
69
What are the two types of factors with respect to choosing row orientation?
* Climactic factors
* Logistical factors
70
What are two climactic factors when it comes to choosing row orientation?
1. North-south orientation often provides most even sunlight, though the west side can be warmer (as exposed to afternoon sun) and thus may require more leaf shading.
2. Winds: Often try to orient 90 degrees to prevailing winds
71
What are two logistical factors when it comes to choosing row orientation?
1. Rows parallel to the longest side of the vineyard often most efficient
2. With unterraced slope greater than 10%, have to orient rows up the slope, as machinery may slip.
72
What are the three considerations with respect to the number of buds left after winter pruning?
1. More buds on more vigorous vines
2. Buds left influence number and size of shoots and amount of fruit, influencing vine balance
3. There are techniques to decide how many buds to retain to preserve balance, including yield and weight of pruning cuttings
73
How is replacement cane pruning implemented?
a. 8-20 buds
b. Typically laid down horizontally, and tied to trellis
c. A spur is left, and shoots from the spur will form the next year’s cane
74
What are the three advantages to using trellising?
i. Shoots can be spread out to maximize light interception
ii. Increase air flow in the canopy (reducing fungal disease)
iii. Position fruit in one area, which aid mechanization
75
What are the two disadvantages to using trellising?
i. Expensive to establish (especially for complex systems)
ii. Requires maintenance
76
What are the 3 primary aims of summer pruning?
* enhancing grape ripening
* reducing fungal disease
* making vineyard easier to manage
77
What is involved in disbudding?
1. Remove excess buds (e.g., those left in case frost killed buds)
2. Remove poorly positioned buds (facing down or too close together)
3. Remove buds of non-fruit-bearing shoots (which may compete with grapes for resources)
78
What is involved in shoot removal?
Removal of shoots, often laterals, that are infertile or poorly positioned
79
What are the 7 kinds of summer pruning?
* Disbudding
* Shoot removal
* Shoot positioning
* Pinching
* Shoot trimming
* Leaf removal
* Crop thinning/green harvesting
80
What is shoot positioning?
Shoots tucked into the trellis wires
81
What is pinching?
Removing shoot tips at flowering to improve fruit set
82
What is shoot trimming and why would one do it?
Cutting shoots to limit growth and reduce canopy thickness
Why you'd do it:
* enhances fruit ripening (as less competition for carbohydrates from shoots) and
* lowers disease pressure (better air circulation and spray penetration)
83
Why would one engage in leaf removal?
Removing leaves to reduce shading and lower disease pressure (better air circulation and spray penetration)
84
What is crop thinning/green harvesting, and what are two reasons why would one do it?
Removal of bunches of grapes to increase ripeness of those left.
Two reasons:
* If timed near véraison, can enhance ripening.
* Can remove less ripe fruit (due to uneven budburst or fruit set, or presence of bunches on lateral shoots), enhancing quality
85
What are the 4 harvest practices for sweet wines?
1. drying grapes on the vine
2. drying grapes off the vine (appassimento)
3. noble rot
4. freezing grapes on the vine
86
What are 9 hazards (not including pests or diseases)?
* drought
* excess of water
* untimely rainfall
* freeze
* frosts
* hail
* sunburn
* fire
* smoke taint
87
What are 9 types of pests or diseases?
* Phylloxera
* Nematodes
* Grape moths
* Spider mites
* Birds
* Mammals
* Fungal diseases
* Bacterial diseases
* Viral diseases
88
What are 6 example of fungal diseases?
* Powdery mildew
* Downy mildew
* Grey rot
* Eutypa dieback
* Phomopsis cane and leaf spot
* Esca
89
What are two examples of bacterial diseases?
* Pierce’s Disease
* Grapevine yellows
90
What are two examples of viral diseases?
* Fanleaf virus
* Leafroll virus
91
What is phylloxera and how is it spread?
a. Aphid-like insect feeds and lays eggs on the roots
b. Insects can spread through crawling but most commonly transported by humans (on roots, soil, equipment, or irrigation water)
92
What are five symptoms of phylloxera?
a. Vines die of drought in patches that increase in size year by year
b. Vine roots covered with insects surrounded by yellow eggs
c. Swellings on older roots
d. Pale green leaf galls on under-surface of the leaves
e. Slow, stunted shoot growth and leave yellowing appears around three years, and the plant dies after around five years
93
How is the threat of phylloxera managed?
a. Initial solution was grafting to American rootstocks, but this causes problems in calcareous soils of Europe—chlorosis.
b. Hybrid rootstocks, balancing resistance to phylloxera with resistance to lime.
c. Rootstock selection nowadays is very complicated and growers get professional advice to match the soil, pests to be combatted, and level of vigor desired.
94
What are nematodes (and two examples of them) and how do they damage vines?
Microscopic worms. Examples:
* Root-knot nematode
* Dagger nematode
Damage:
* Can feed off vine roots, reducing yields and vigor (slow, gradual decline)
* Some spread viruses (like dagger nematode spreading fanleaf virus)
95
How is the risk of nematodes managed?
* Once present, can only be managed, not eliminated
* Take soil samples to identify numbers and type present
* Fumigate the soil
i. Used to be chemicals, but now mostly banned.
ii. Plough in a cover crop of mustard plans, which has compounds that work as biofumigants.
* Use nematode-resistant rootstocks from nurseries that heat treat vines to kill nematodes.
96
How do grape moths harm vines, and what are three examples of the moths?
* Feed on flowers and grapes, creating wounds vulnerable to bacteria and fungi (including botrytis) leading to significant crop loss.
*Examples
i. Australia: light brown apple moth
ii. Southern Europe: European grapevine moth
iii. Central and Eastern North America: grape berry moth
97
What are four methods to control grape moths?
* Biological controls
i. Bacillus thuringiensis (which produces toxins for the moths)
ii. Pheromone capsules to disrupt mating (sexual confusion)
iii. Natural predators (parasitic wasps, green lacewings, some spiders)
* Insecticides
98
How do spider mites harm vines, and where do they thrive?
* Feed on surface cells of leaves, leading to discoloration, reduction in photosynthesis, delayed ripening and reduction in yields.
* Most damaging with water stressed vines.
* Thrive in dusty conditions.
99
What are four ways of managing spider mites?
a. Reduce dust by using sprinklers and/or cover crops or mulches
b. Encourage predatory mites (by planting host species) that feed on spider mites
c. General pesticides (but can kill beneficial predatory mites)
d. Specific pesticides that kill only problematic mites (but expensive)
100
How do bird damage vines, what vineyards are especially vulnerable, and what is one example of a problematic bird species?
a. Can destroy entire crops as they ripen
b. Isolated vineyards in particular danger
c. Damage to bunches can lead to bacteria and fungi
d. Example: starlings
101
What are three ways of managing birds?
a. Total netting in high value areas (e.g., Mornington Peninsula) or where birds are major threat
b. Bird scarer or noises, but must be rotated regularly
c. Sometimes falcons
102
What damage do mammals cause to vines?
a. Damage to shoots, grapes, leaves
b. Damage to trellising
103
How does one manage mammals?
Fencing—high and sunk into the soil
104
How is fanleaf virus managed?
* No cure--eventually affected vines will have to be removed
* Before replanting, soil should be tested and only clean planting material used
105
How is leafroll virus managed (overall approach and 2 specifics) ?
No cure--eventually affected vines will have to be removed
* New planting material should be clean
* Control the vector (mealy bugs) by (i) opening the canopy to reduce the humid environment they prefer and (ii) encourage its natural predators (e.g., ladybugs, lacewings). Spraying not effective due to their waxy coating.
106
How it powdery mildew managed?
* Preferred: keep an open canopy to reduce share and density of leaves
* Apply sulfur to prevent and treat disease, from a couple weeks after budburst up to veraison (spray early--easier to prevent than contain)
* Systemic fungicides can be effective, but only limited treatments to avoid building resistance
107
How is downy mildew managed?
* Traditionally, sprays from copper salts (like Bordeaux mixture, of copper sulfate and lime). Only organic option. But only work until 20mm of rain has fallen. (EU is trying to reduce and eliminate due to buildup of copper in soil.)
* Other fungicides might be used
* Good drainage and an open canopy that dries quickly
108
How is grey rot managed?
* Most important: (i) select varieties with small grapes and thick skins (like Petit Verdot) and (ii) protect the grapes against other pests that could split skins
* Keep open canopy and remove leaves around bunches
* Fungicide sprays
* Biological control, like antangonistic bacteria (e.g., Bacillus subtilis)
109
How is eutypa dieback managed? Four things
* Difficult to control, but pruning late and applying fungicide to pruning wounds is effective
* Affected trunks cut back 5-10 cm beyond visible symptoms and treated with fungicide (with cuttings burnt).
* Some biological controls (like Bacillus subtilis) may be effective
* If the plant is badly affected, then (i) retrain from a sucker (a shoot that grows from the base of the vine) or (ii) uproot and replace
110
How is phomopsis cane and leaf spot managed? Three things
* Fungicides applied 3 weeks after budburst and then every 2 weeks if wet conditions continue
* Diseased and dead wood removed during pruning, and then burned or buried
* Canopy management to improve air flow may help
111
How is esca managed (overall approach and 5 specifics)?
No chemical controls; focus on prevention
* Source disease-free stock
* Trying new pruning techniques
* Not pruning in rain
* Removing prunings promptly
* Disinfecting pruning wounds
* (Research into biological controls like Bacillus subtilis.)
112
How is Pierce's Disease managed (overall approach and 4 specifics) ?
No chemical control for bacteria; focus is on reducing vector
* Removing vines close to rivers (as the blue-green sharpshooter, a vector, lives there)
* Chemical insecticides
* Biological control of vector (wasp that feeds on sharpshooter eggs)
* Strict quarantine for plants
* (Work on developing resistant vines.)
113
How is grapevine yellows managed (overall approach and 3 specifics)?
No control against bacteria; focus is on controlling vector
* Insecticides to kill leafhoppers
* Removal of cover crops that host leafhoppers
* In nursery, bathe pruning wood in hot water
114
What 2 varieties are more susceptible to powdery mildew and what 2 varieties are less?
More:
* Chard
* Cab Sauv
Less:
* Pinot Noir
* Riesling
115
Where does powdery mildew attack vines and what damage does it cause?
* Overwinters in buds and on canes
* Attacks young, green parts
* Dull grey patches become black as they advance
* Damages young shoots, inflorescences, and grapes, reducing yield and splitting grapes at veraison (opening up to other infections)
116
What conditions encourage powdery mildew?
* Optimum temp around 25 C
* Shady
* Does not require high humidity
117
Where does downy mildew live, what does it look like, and what damage does it cause?
* Mold lives in the vine tissue (not surface)
* Yellow circular "oil spots" and then white downy growth on underside of leaves
* Attacks green parts, esp young leaves and flowers, reducing yield via defoliation
* Can also attack grapes, but less important
118
What conditions encourage downy mildew?
* Rainfall and warm temps (20 C)
* High risk: warm springs and stormy but warm summers
119
How does grey rot damage vines?
* Damages grapes
* If flowers affected, fungus can stay dormant and emerge after veraison
120
What conditions encourage grey rot?
* Grapes have a point of entry (rubbed against each other or punctured)
* Rainfall and high humidity
121
What effect does grey rot have on the wine?
* Loss of yield
* Drop in quality (color, body, and aroma/flavor)
122
What does eutypa dieback attack and what impact does it have on the vine?
* Leads to rotten wood
* Reduces yields significantly and kills vines over 10 years if not eliminated
* In spring: stunted shoot growth and yellow leaves
123
How does eutypa dieback spread?
* Spores spread by wind over long distances
* Infection through pruning wounds in moderate temps and especially during rain
124
What varieties are esp susceptible to eutypa dieback, and where is it esp prevalent?
* Grenache, Cab Sauv, Sauv Blanc
* South Australia, SW France, parts of California
125
What does phomopsis cane and leaf spot look like and what parts of the vine does it attack?
* Infected canes whiten and break off easily
* Shoots growing from these canes develop brown cracks at their bases
* Leaves affected too
* Yields reduced
126
What conditions encourage phomopsis cane and leaf spot?
* Cool and wet springs followed by humidity and mod temps
127
What is 1 example of a variety esp susceptible to phomopsis cane and leaf spot, and 1 example less so?
* Very susceptible: Grenache
* Less so: Cab Sauv
128
Where does esca thrive, how does it enter the vine, what does it look like, and what is its impact on the vine?
* Warmer and drier climates (like southern Europe and California)
* Enters vine through pruning wounds
* Tiger-striping of leaves and spotting inside wood
* Reduces yield and leads to death of vine within a few years
129
What spreads Pierce's Disease?
* Sharpshooters, especially the glassy-winged sharpshooter
130
Where does Pierce's Disease live and what does it do?
* Bacteria live in sap channels, which it clogs, leading to grape shriveling, dropping leaves and death of vine in 1-5 years.
131
Where is Pierce's Disease present and what varieties are more vulnerable?
* Southern USA and Central America, and now California
* Chard and Pinot Noir
132
How is grapevine yellows spread?
* Insect vectors like leafhoppers
* Nurseries selling infected stock
* Cover crops can harbor bacteria
133
What are 4 symptoms of grapevine yellows?
* Delayed budurst
* Drooping posture (as new shoots fail to become woody)
* Canopy turning yellow (in white varities) or red (in black varieties)
* In some strains, the vine dies; otherwise it might recover
134
What two varieties are most vulnerable to grapevine yellows and what is the impact on grapes?
* Chard and Riesling
* Drastically reduced yields and lower quality (high acid and low sugar)
135
How was readiness for harvest originally measured?
* Potential alcohol
* Rule of thumb of 100 days after beginning of flowering
136
What are three reasons why potential alcohol is no longer used for determining harvest date?
a. Warmer climates, making it easier to ripen grapes in cooler climates
b. Better viticulture, enabling the vine to ripen grapes fully
c. Focus on aroma and tannin ripeness, as this may be more important than sugar ripeness (as sugar can be adjusted)
137
What are three measures of ripeness and how are they measured?
* Sugar levels
i. Determined by handheld refractometer
* Acidity levels
i. Measured by titration or a pH meter
* Aroma and tannin ripeness
i. Determined by experienced taster
138
What 4 steps can be taken to improve the quality with machine harvesting?
* Select out fruit by hand before machine harvesting
* Using bow-rod shaking machine: gentler and can be set to be more selective
* Using very latest machines with (i) optical sorting, (ii) crush white grapes and (iii) add SO2 to limit oxidation.
* Rigorous sorting on arrival at winery
139
What types of wine is machine harvesting the default option for?
Inexpensive to mid-priced wines and for larger-scale production (exception of South Africa, where labor is cheap)
140
What are four advantages of machine harvesting?
* Significantly faster and much cheaper in large vineyards designed for it (in CA, can be 1/3rd the cost)
* Avoids lack of availability and unreliability of casual workers
* Harvesting can happen at night, and grapes kept up to 15 C cooler (reducing microbial spoilage and oxidation, increasing fruitiness for white wines, and saving cost on refrigeration)
* Harvest can be timed precisely because it is so quick and reliable
141
What are seven disadvantages of machine harvest?
* Less gentle than hand harvesting, so may crush some grapes and introduce oxidation and extraction of phenolics
* Rental or ownership of machines not cost effective for small vineyards
* Not suitable for growers with grapes ripening at different times in the same plot
* Not suitable on steep slopes or with limited access
* Quality only as good as skills of operator
* If harvester not owned, possible competition for rentals at best moment for harvest
* Purchasing a harvester is a major investment
142
What are three advantages of hand harvesting?
* Pickers can be very selective at bunch level to remove under or extra ripe fruit at harvest
* Pickers can deal with steeper slopes, irregular rows, mixed plantings
* With care and small crates, can avoid crushing grapes and release of juice
143
What are three disadvantages of hand harvesting?
* More expensive for medium to large vineyards
* Available workforce (and training and supervision) required
* Daylight harvesting is easier, which means warmer grapes (though it can be done by flashlight)
144
What are four examples where hand harvesting is required?
* Premium sparkling wines where whole bunch pressing is required (e.g., Champagne)
* Carbonic or semi-carbonic maceration
* Styles that require selective harvesting (e.g., botrytis-affected bunches for TBA Riesling)
* Vineyard characteristics: Steep slopes, uneven land, bush vines
145
What are the two types of frosts?
a. Advective: Large volumes of cold air moving in from very cold areas.
b. Radiative: Heat lost on still, cool nights (especially cloudless).
146
What are five ways to reduce risk of frost?
a. Site selection
b. Delaying pruning postpones budburst
c. Choosing a late-budding variety (like Riesling)
d. Training high off ground
e. Bare soil between vines (no cover crop)—more heat absorbed during day that is radiated at night
147
What are three ways to deal with frost when it threatens?
* Water sprinklers--on until temp rises (ONLY SOLUTION FOR ADVECTIVE FROSTS)
* Wind machines (often 3-5 C warmer 10m above ground)
* Oil or propane gas burning heaters (smudge pots) or wax candles (bougies) (expensive, low efficiency, and pollution)
148
How does frost harm vines?
* Kills young shoots and buds.
* The vine may put out more shoots from secondary buds, but they are less fruitful and will take longer to ripen (possibly running into late season frost or rain).
149
What are four ways to manage the risk of hail?
* Rockets fired into thunderclouds seed with silver iodide, cause rain instead of hail
* Net the fruit zone (though this causes shading, so ok in Mendoza but not Burgundy)
* Own a number of plots in in different areas
* Crop insurance
150
What is the impact of hail on vines?
* Can damage all parts of the vine (and grape damage invites botrytis).
* Yields can be seriously reduced in the first and following seasons.
* If damage is early, may be able to reshoot from existing buds.
151
Why are grapes susceptible to sunburn?
Grape transpiration is more limited and thus less effective than leaf transpiration, so grapes can reach a higher temperature than leaves.
152
What damage does grape sunburn cause to grapes, and what is the impact on the wine?
* Scars on skin of grapes and eventual death of grapes.
* Potential issues: browning, bitter taste, increased susceptibility of rot.
* Sunburnt grapes need to be removed by sorting, which reduces yields.
153
What are four ways to manage the risk of grape sunburn?
* Row orientation and aspect: in Northern Hemisphere, avoid East-West orientation so that south side of row is not subject to day-long sun
* Canopy management to shade fruit
* If a heatwave is forecast, additional irrigation to reduce water stress
* Agricultural sunscreen spray or shading the vines with cloth or net
154
What are three ways of managing fire risk?
a. Install fire detectors and sprinklers
b. Install and maintain water tank
c. Employee training for action in event of emergency
155
What factors increase risk of fire?
a. Vineyards near woodland, pastures, or other crops may be more at risk.
b. Cover crops may increase risk.
156
What four ways is smoke taint managed?
* Musts can be tested analytically or by micro-vinifications in days leading up to harvest to establish extent of problem
* Minimize extraction of precursors inside skin
* Flash détente and reverse osmosis can also help, but will not remove the taint completely
* Blending with unaffected wines
157
What is smoke taint?
a. Smokey or plastic aromas.
b. Smoke compounds bind to sugars in grapes to produce aroma-less precursors, that become aromatic through the fermentation process.
c. Aromas can increase during maturation and bottle ageing as more precursors break down and become aromatic.
158
What are three ways to manage winter freeze?
* Site selection (hillsides can be warmer, large water moderates nearby, vines planted where snow settles most thickly)
* Choice of variety
i. Some varieties more resistant (e.g., Cab Franc or Riesling)
ii. Some American and Mongolian species and hybrids very resistant (e.g., Concord)
* Protecting vines
i. Hilling up around vine graft
ii. Burying vines in the most extreme climates
159
What are the three times when untimely rainfall can cause harm, and what harm does it cause?
* During pollination and fruit set
i. Millerandage
ii. Coulure
* During the summer
i. Reduce rate of ripening
* Close to vintage
i. Swells grapes (reducing concentration and thus quality)
ii. Splitting grapes (leading to grey rot)
iii. Makes working harvest difficult (difficulty using machinery or allowing pickers to access vineyards on clay soils)
160
What two ways can untimely rainfall risk be managed?
* Site choice (climate in general, slope), condition of the soil, choice of whether or not to grass the land between rows of vines and the adequacy of drainage
* Monitoring weather forecasts: Choose whether to harvest early
161
What three ways can drought risk be managed?
a. Irrigation, where allowed
b. Choose drought-resistant rootstocks (Examples include rootstocks from V. rupestris and V. berlandieri parentage (e.g. 110R and 140R).)
c. Choose drought-tolerant varieties like Garnacha
162
How much water do vines need and does drought impact vines?
* Vines need at least 500mm per year in cool climates and at least 750mm in warm climates.
* Lack of water causes leaves to close stomata to limit water loss, which reduces photosynthesis, which:
i. Impairs growth of plant
ii. Reduces grape size
iii. Slows ripening
163
What are three problems with excessive water?
a. Too much vegetative growth: compete with grapes and shade fruit too much
b. Increase fungal disease pressure
c. Waterlogging soil: reduced oxygen (slowing growth and eventually killing vine) and compaction of soils (difficult to work) and uncontrolled water runoff
164
What are two ways to manage the risk of excess water?
a. Planting on a slope or on free-draining soil
b. Construction of a drainage system
165
What is the grape grower's aim?
Produce the largest possible crop of grapes that are of suitable ripeness and quality for the intended style
166
In organic viticulture, what remedies are available for pests?
* Traditional sprays, like sulfur and copper sulfate
This may be bad, because of (i) buildup of copper in soil and (ii) need to use tractors to spray often because it doesn't last long
* Natural predators and ecosystem mechanisms (like Bacillus subtilis (competes with Botrytis) or sexual confusion)
167
Who certifies a vineyard as organic?
Different standards around the world, but all should meet the standards of the International Federation of Organic Agriculture Movements (IFOAM)
168
What vineyards use biodynamic viticulture?
smaller growers, including some of the most prestigious in Burgundy
169
* What are two types of sensors in precision viticulture?
* How is their data often presented?
Types of sensors:
* Remote (e.g., aircraft)
* Proximal (e.g., on a tractor or in the field)
Presented visually on a map
170
What are four categories of data collected in the vineyard in precision viticulture?
* Soil
* Vine vigor
* Topography
* Plant growth
171
Who are the two founders of biodynamic viticulture?
Rudolf Steiner and Maria Thun
172
Biodynamic adds what to organic viticulture? Give two examples.
Grape growing practices coincide with the cycles of the planets, moon, and stars
Examples:
* When moon is ascending ("summer mood" and "sap is rising"): take cuttings for grafting, but avoid pruning
* When moon is descending ("winter mood" and "roots are favored"): time to plant vines or prune
173
In site selection, other than natural resources, what are six additional factors to consider?
* Price of land in desirable GIs is much more expensive (so probably need to make PDO-qualifying wine that sells at a premium)
* Location, layout, and topography of the site may have cost implications (e.g., frost or disease prone sites)
* Steep slopes may be unsuitable for mechanization (and labor may be expensive, slow, and hard to obtain)
* Irrigation water availability and cost
* Ease of access to vineyard site and distance from winery (focus on healthy grape delivery with little oxidation or microbial spoilage)
* Proximity of vineyard and winery to population centers for labor, supplies, cellar door customers, retail or distribution businesses
174
What are four things to assess and possibly rectify with soil preparation of a new vineyard?
* Drainage and structure of soil
* Mineral composition of soil
* Presence of pests or unwanted plants
* Modification of topography (e.g., terraces)
175
When preparing for a new vineyard, what are three ways to rectify the mineral composition of the soil?
* Manure, compost, and fertilizers to increase nutrients and organic matter
* Ploughing to incorporate these additions
* Adjustment of soil pH (e.g., for acidic soils in Beaujolais, lime can be spread and ploughed in)
176
What are seven factors that go into deciding on an approach to viticulture?
* overall approach (including worldview and ethical concerns)
* desired level of production
* intended quality
* return on investment
* cost
* availability of labor
* environmental impact
177
What are the two primary aims of conventional viticulture?
* raise production levels
* reduce labor requirements
178
What are the four ways in which the aims of conventional viticulture were accomplished?
* mechanization
* chemical inputs (herbicides, pesticides, fertilizer)
* irrigation
* clonal selection
179
What are the five aims of sustainable viticulture?
* promote natural ecosystems in the vineyard
* maintain biodiversity
* manage waste
* minimize applications of chemicals and energy use
* reduce impact of viticulture on the wider environment
180
Under IPM, what is the threshold above which action will be taken?
Only when the level of damage will exceed cost of intervention
181
What are the intended effectsof organic viticulture?
Improve (i) the soil and (ii) the range of microbes and animals in it,
thereby increasing health and disease resistance.
182
What are two reasons why the additional expense of organic viticulture differs around the world?
* Climate may drive reliance on chemical sprays
* Differing labor costs
183
What is the leader of organic viticulture, and how much?
Europe, with 84% of organic viticulture
184
What are the six largest markets for organic wines?
* Germany
* France
* UK
* USA
* Sweden
* Japan
185
What country is the leading producer and exporter of organic wines, and what percentage of vineyards does it have?
* Italy
* 15.8%
186
What is the overall aim of biodynamic viticulture?
* Seeks to achieve a balance between the physical and higher, nonphysical realms
* Vineyard soil is seen as part of a connected system with the Earth, other planets, and the air
187
What are biodynamic preparations with respect to compost?
* Compost must first be "activated" by a series of starters in tiny quanities
* These starters assist with decomposition
* Starters: yarrow, chamomile, nettle, oak bark, dandelion, or valerian
188
What is regenerative viticulture?
A method of farming that aims to continually improve upon environmental, social, and economic measures. It works to improve resources like soil and water (rather than just maintain them).
The term was coined by Rodale Institute in the 1980s.
189
Where is precision viticulture most effective?
Where date collected is used to systematically control treatment application rates or irrigation rates
190
What three things does precision viticulture seek to do?
* respond to variations within the vineyard
* reduce the variations, if possible
* identify different quality zones in the same vineyard
191
What other approaches to viticulture is precision viticulture often used with?
* Sustainable
* Organic
192
What are three key types of decisions when it comes to vineyard establishment?
* Site selection
* Soil preparation
* Planting materials
193
What are the three major influences when it comes to site selection?
* Style
* Quality
* Price
194
What are three examples of definitions of terroir?
* Physical: Wine shows the climate soil, aspect, elevation
* Physical plus vineyard management, like planting density, type of trellising, etc.
* Minerals in the soil are in the wine (like chalk in Chard--doubtful)
195
What do many commentators believe can mask terroir?
Overly zealous winemaking, like picking over-ripe fruit or ageing in new oak.
196
Other than adjusting soil nutrients and pH, what are four other interventions in soil preparation?
* Removing very large rocks at or near surface
* Subsoiling: removing a plough pan
* Removing old roots and burning them
* Systemic herbicides if weeds are a problem
197
How can a viticulturist quickly capitalize on a change in fashion in varieties? What is one disadvantage of this practice?
* Head grafting (or top grafting): Cut the original vine at the trunk and graft a bud from a new grape variety on top
* Disadvantage: the rootstock may not be well matched, as it wasn't selected with the variety in mind
198
When choosing planting material, what three things can be chosen?
* Variety
* Clone
* Rootstock
199
What are two attributes of the best cover crops?
* Quick to establish
* Adapted to soil and climate
200
What is mulching?
Spreading of matter (usually biodegradable, like straw or bark) to suppress growth of weeds
201
What are two water quality problems?
* High in dissolved solids: can block irrigation systems
* High in salt (esp with drip irrigation, as the salt stays in the root zone rather than washing out)
202
Describe installation of drip irrigation
* Narrow water pipe laid on each row, typically tied to lowest trellis wire
* Drippers position far enough away from vines to encourage roots to seek out water
203
What is flood irrigation and what is its advantage?
Water stored behind a sluice and released at scheduled time to flood the vineyard. It is cheap to install.
204
What is dry farming and why would one do it?
* Not using irrigation in areas with limited rainfall in growing season
* Lower yields but possible improvement in quality
205
What is bud fruitfulness?
The number of inflorescences developing inside a latent bud
206
What are two ways in which canopy management can reduce fungal disease pressure?
* Better air circulation can help canopies dry after rainfall or morning dew
* Open canopies can ensure better access to fungicide sprays
207
What are the four steps in the vegetative cycle?
* **Shade**: Depresses budbreak, bunch initiation, fruit set, berry growth
* **Fruit weight per shoot**: Reduced
* **Shoot growth**: Stimulated due to less fruit growth
* **Canopy density**: Increases due to more leaf area
208
What are four steps in a balanced cycle?
* **Light**: Stimulates budbreak, bunch initiation, fruit set, berry growth
* **Fruit weight per shoot**: Increased
* **Shoot growth**: Depressed due to more fruit growth
* **Canopy density**: Decreases due to less leaf area
209
What are two ways that yield is measured?
* Weight per vine (e.g., kg per vine)
* Weight over a set area (e.g., kg per hectare)
210
What two factors does yield over a set area depend on?
* Yield per vine
* Planting density
211
What are five categories of canopy management techniques?
* vine training
* winter pruning
* vine trellising
* overall plant vigor mangaement (nitrogen fertilization, irrigation, cover crop, etc.)
* summer pruning
212
What is vine training, and what are the two categories?
* The shape of the permanent wood
* Head training; cordon training
213
How can a head trained vine be pruned?
Either spur-prined or replacement cane-pruned
214
How can a cordon trained vine be pruned, and what is one disadvantage relative to head training?
* Usually spur-pruned
* Takes longer to establish due to amount of permanent wood
215
How many buds does a spur have?
2-3
216
Which winter pruning technique can be mechanized?
Spur pruning
217
What are two advantages and two disadvantages of bush vines?
Advantages:
* simple, and therefore easy and inexpensive to develop
* shoots may droop down to shade grapes (helpful in hot and sunny regions)
Disadvantages:
* not suitable for mechanization
* only suitable for dry conditions (wet would encourage vigor and too much shade, and would also increase fungal pressure)
218
How are bush vines trained and pruned?
Head trained and spur pruned
219
When VSP is used on replacement-cane pruned vines, what is it called?
Guyot training
(Single/Double Guyot if one/two canes are kept)
220
How much vigor is VSP best suited for?
Low to moderate vigor
221
What types of trellising is necessary for vines that are more vigorous, and what are examples?
Split horizontally:
* Geneva Double Curtain (GDC)
* Lyre
Split vertically:
* Smart-Dyson
* Scott-Henry
222
What is the disadvantage of complex trellising systems?
More difficult to manage and mechanize.
223
What are the only two summer pruning techniques that can't be mechanized?
* Pinching
* Disbudding
224
What are four ways to minimize extraction of smoke precursors inside skins?
* hand harvesting
* gentle or whole bunch pressing
* lower ferm temp
* reduced maceration
225
How does phylloxera harm vines, and what is its effect?
* Damages roots, (i) reducing update of nutrients and water, (ii) vulnerable to bacteria and fungi.
* Reduces growth and yield and then kills vine.
226
What are two examples of nematode-resistant rootstocks?
Ramsey and Dog Ridge (both Vitis champini)
227
What are examples of spider mites?
* California: Pacific spider mite
* Europe: red spider mite and two forms of yellow spider mite
228
What are six examples of mammals that are pests?
* deer
* rabbits
* kangaroos
* raccoons
* wild boar
* baboons
229
What fungus causes powdery mildew?
Erysiphe necator, also called Oidium tuckeri
230
What fungus causes downy mildew?
Peronospora
231
How is fanleaf virus spread?
* Inadvertent use of infected plant material
* Spread slowly by dagger nematode
232
What symptoms does fanleaf virus cause?
* Early shoot growth is stunted
* Canes can grow in distorted ways
* Leaves appear very pale, malformed, and can look like a fan
233
What is the effect of leafroll virus on vines and why does it do this?
Does not kill vines, but:
* Surviving fruit can take several additional weeks to ripen and has more acid, less color, and lower sugar
* reduce yield by up to half
Why:
* Slows down growth of roots and shoots
* Reduces stores of carbohydrates
234
How is leafroll virus spread?
* Grafting
* Mealy bugs (in South Africa, Mediterranean, Argentina, and parts of CA)
235
What are the symptoms of leafroll virus?
* Downward rolling of vine's leaves occurs in autumn
* Leaves change color in autumn to red (for black varieties) and yellow (for white)
236
Why does leafroll virus negatively affect vines?
* Slows down growth of roots and shoots
237
What are four examples where style impacts harvest date?
* Growers in Loire picking Chenin Blanc over 4-6 weeks (starting with sparkling, then dry and off-dry, then late harvest and botrytis)
* Zinfandel in CA: (i) white vs red Zinfandel and (ii) decision what to do with uneven ripeness (e.g., keep shriveled grapes?)
* Residual sugar: (i) multiple passes for botrytis wines and (ii) specific requirements for icewine
* Continuing "hang time" debate
238
How is hand harvesting done?
Teams of harvesters remove whole bunches by cutting the stem of each bunch with secateurs
239
When used against grey rot, what sprays are applied and when (4 times)?
Fungicides (not sulfur or copper), applied (i) when flowering is nearly complete, (ii) at end of grape formation, (iii) at bunch closure (when grapes get large enough to touch each other), and (iv) at veraison. (But too much leads to resistance.)
