FROST CONTROL IN NEW ZEALAND VINEYARDS · FROST CONTROL METHODS Passive methods – cultural inputs ... Practical Considerations for Reducing Frost Damage in Vineyards. Report to

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FROST CONTROL IN NEW ZEALAND VINEYARDSEdited by Ruby Andrew & Dominic Pecchenino

FROST CONTROL IN NEW ZEALAND VINEYARDS

Edited by Ruby Andrew & Dominic Pecchenino

1 New Zealand Winegrowers I nzwine.com

INTRODUCTION

Spring frosts are an annual possibility in almost

all major winegrowing regions of New Zealand

so it makes sense that frost protection should be

incorporated into the routine annual management of

almost every vineyard.

Many experts have noted that the best time

to protect a vineyard against frost is before it

is established. Site selection can be one of the

most critical times for determining a vineyard’s

susceptibility to frost damage. Locating a vineyard

away from areas where cold air ponds, on hillsides

or close to coastal areas can all help in reducing

potential frost risk. If you are looking at establishing

a vineyard and have several options available for

consideration, a 1999 New Zealand Winegrowers’

report provides valuable information on how to

evaluate the frost risk of a site. 1

The present guide, however, reviews the current

options available to New Zealand growers once a

site is established, including:

• Frost forecasting.

• Vineyard monitoring and alarm systems.

• Passive frost protection (actions taken in the

vineyard prior to a frost).

• Active frost protection (including helicopters,

frost fans, water systems and heaters).

• Frost damage mitigation.

• Links to additional resources on New Zealand

Winegrowers’ website (www.nzwine.com).

A short booklet like this can summarise current

best practice, but it cannot provide the level of

technical detail required before making a substantial

investment in a frost protection system. Given the

financial implications of failures in frost protection,

it is important to seek qualified advice before

investing in or relying on any method for protecting

your crop against frost.

TABLE OF CONTENTS

1. TYPES OF FROST Radiation

Advection

Other types

2. CRITICAL TEMPERATURES AND VINE DEVELOPMENT

Growth stage vulnerability to frost

Critical temperature

Defining frost severity

Environmental conditions

3. FROST FORECASTING On-site weather stations and alarm systems

Regional forecasts

Calibrating vineyard temperatures

Calculating risk

4. FROST CONTROL METHODS Passive methods – cultural inputs

Active methods

• Heaters

• Wind mixing (helicopters, frost fans)

• Water systems (overhead and other sprinkler

systems)

5. REDUCING FROST DAMAGE Assessment of damage

Damage in spring

Options for management

Appendix: New Zealand Winegrowers Frost Fan Code of Practice 2014

1 Trought MCT, Howell GS and Cherry N. 1999. Practical Considerations for Reducing Frost Damage in Vineyards. Report to New Zealand Winegrowers.


Figure 1-1. As cold air stays low and warm air rises, the air becomes stratified and

a temperature inversion forms.

ADVECTION FROSTAdvection is the horizontal movement of an air

mass. If the air mass is below 0 °C, an advection

frost results. In New Zealand, advective frosts

generally occur when a cold polar air mass

moves north over the country. They are generally

characteristic of continental climates in New

Zealand. Some radiation frosts can have an

advective component.

OTHER FROST TYPESGROUND FROST

• Occurs when dew freezes.

• Requires a grass minimum temperature of -1 °C or

less.

• Young vines are most vulnerable to ground frost.

SCREEN FROST

• Screen refers to a Stevenson Screen,2 placed

approximately 1.3 metres above ground level –

generally just above cordon height for most New

Zealand vine training systems.

• Screen frost occurs when air temperature at and

below screen height is 0 °C or less.

HOARFROST

• Central South Island only.

• Occurs over a period of days when daytime

temperatures are not warm enough to defrost the

previous night’s frost and another frost occurs.

• Ice crystals form from water vapour, without

going through a liquid phase.

COOL AIR

3o

2o

1o

0o

-1o

-2o

WARMER AIR

I – TYPES OF FROST

Vineyard management in New Zealand focuses on

two types of frost:

1. Radiation frost

(the most common type encountered).

2. Advection frost.

RADIATION FROSTRadiation frosts occur widely throughout New

Zealand. After sunset, when the sky is colder than

the ground, ground temperature will drop and heat

will be transferred (radiated) to the sky above.

When temperatures fall enough, a radiation frost

will occur – often, during clear, settled weather with

light surface winds. Cold air is heavier than warm

air and will settle in areas of lower elevation. As

the cold air stays low and the warm air rises, the

air becomes stratified and a temperature inversion

forms.

Radiation frost is characterised by this inversion

layer and usually a katabatic (downslope) drift.

INVERSION LAYER

The inversion layer can range from five metres to

several hundred metres above ground, although

usually the range falls between 10 to 30 metres.

An inversion can have considerable spatial

variation, and inversion strengths are a function

of topography, katabatic wind speeds and the

moisture content of the air and ground.

It is the inversion layer that is used by helicopters

and frost fans, which move the warm air from the

inversion layer downwards to raise the temperature

of the air around the vines.

KATABATIC DRIFT

Another common characteristic of a radiation frost

are katabatic winds. This is the technical name for

a downward, cooling wind that carries cold air from

a higher elevation down a slope under the force of

gravity. In some instances it is possible to physically

feel the cool katabatic winds as you stand in a

vineyard on an otherwise still, calm night.


Figure 1-2. Hoarfrost at Akarua in Central Otago.

MORE RESOURCES ON NZWINE.COM:Introduction to frost – New Zealand Winegrowers Fact Sheet

Radiation and advection frosts – New Zealand Winegrowers Fact Sheet

Climate and frost risk – New Zealand Winegrowers Fact Sheet

References

• Trought MCT, Howell GS and Cherry N. 1999. Practical Considerations for Reducing Frost Damage in

Vineyards. Report to New Zealand Winegrowers.

2 A Stevenson screen is an enclosure to shield meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely. It forms part of a standard weather station.


II – CRITICAL TEMPERATURES & VINE DEVELOPMENT

Spring frosts are the likeliest to cause damage if a

vineyard is unprotected.

• Critical temperatures are relative to growth

stage(s) of the vine and severity of frost.

• The more advanced the phenological stage (at

least up to flowering) the more susceptible the

grapevine is to frost damage.

Spring frosts can reduce yields and threaten

vineyard productivity, not only for the oncoming

season but also in subsequent years. If one or more

frosts occurs during a susceptible period in the

grapevine’s growing cycle, then crop loss can be

significant.

HOW DOES DAMAGE OCCUR?Dense cold air flows downward into the vineyard.

Frost temperatures cause damage by freezing the

sap inside the conducting vessels of the grapevine.

As the sap freezes, it expands, causing cell walls to

rupture. This can result in tissue damage to leaves,

shoots, buds and vascular tissue. Once the cell wall

has ruptured in Vitis vinifera, it doesn’t repair itself

(unlike other plants).

SEASONAL RISKS

Spring

Swelling grapevine buds or young shoots are

damaged or destroyed when temperatures fall

below critical values for a prolonged period of

time. Damage can affect the current season’s crop,

and can also influence vine productivity in future

seasons.

Autumn

Frost before harvest can cause premature leaf

fall. This may affect vine performance in the

next season, particularly if vines are young. If

the frost is very early, it can prevent wood fully

maturing, leading to decreased tolerance of lower

winter temperatures due to poor carbohydrate

development and storage.

DEFINING SPRING FROSTS BY GROWTH STAGE

Spring frosts can be divided into three subgroups

based on growth stages as categorised by the

Modified Eichhorn-Lorenz (E-L) Phenological

System:

• Early Spring – occurring from E-L 2 (bud scales

opening) to E-L 11 (4 leaves separated, shoots 6-8

cm long).

153

V I T I C U L T U R E 1 : R E S O U R C E S

Figure 7.3 Modified E-L system for identifying major and intermediate grapevine growth stages (revised from Coombe 1995). Notethat not all varieties show a woolly bud or a green tip stage (May 2000) hence the five budburst stages in the modified original 1995system have been changed slightly by removing stage 4 and allocating the definition of budburst to what was formerly stage 5.Revised version of “Grapevine growth stages – The modified E-L system” Viticulture 1 – Resources. 2nd edition 2004. Eds. Dry, P. and Coombe, B.(Winetitles)

1 Winter bud

2 Bud scales opening

3 Wooly bud ± green showing

4 Budburst; leaf tips visible

7 First leaf separated from shoot tip

9 2 to 3 leaves separated; shoots 2-4 cm long

11 4 leaves separated

12 5 leaves separated; shoots about 10 cm long;inflorescence clear



15 8 leaves separated, shoot elongating rapidly;single flowers in compact groups

16 10 leaves separated17 12 leaves separated; inflorescence well

developed, single flowers separated18 14 leaves separated; flower caps still in place,

but cap colour fading from green19 About 16 leaves separated; beginning of

flowering (first flower caps loosening)

20 10% caps off

21 30% caps off

23 17-20 leaves separated; 50% caps off (= flowering)

25 80% caps off

26 Cap-fall complete

27 Setting; young berries enlarging (>2 mmdiam.), bunch at right angles to stem

29 Berries pepper-corn size (4 mm diam.);bunches tending downwards

31 Berries pea-size (7 mm diam.)

32 Beginning of bunch closure, berries touching(if bunches are tight)

33 Berries still hard and green

34 Berries begin to soften;Sugar starts increasing

35 Berries begin to colour and enlarge

36 Berries with intermediate sugar values

37 Berries not quite ripe

38 Berries harvest-ripe

39 Berries over-ripe

41 After harvest; cane maturation complete

43 Beginning of leaf fall

47 End of leaf fall

4 Budburst

Inflorescence clear,5 leaves separated

50% caps off

Young berries growingBunch at right angles to stem

Bunches hanging down

Berry softening continuesBerry colouring begins

Berries ripe

12 Shoots 10 cm

19 Flowering begins

23 Flowering

27 Setting

31 Berries pea-size

35 Veraison

38 Harvest

Sh

oot

and

inflo

rescence

develo

pm

ent

Flo

werin

gB

erryfo

rmatio

nB

erryrip

enin

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escence

MAJOR STAGES ALL STAGESE-L number

Viti 1 Chapter 07 Phenology 27/9/05 10:18 AM Page 153

• Mid Spring – occurring from E-L 12 (5 leaves

separated, shoots about 10 cm long, inflorescence

clear) to E-L 14 (7 leaves separated).

153



1 Winter bud















20 10% caps off

21 30% caps off


25 80% caps off















47 End of leaf fall

4 Budburst


50% caps off




Berries ripe

12 Shoots 10 cm

19 Flowering begins

23 Flowering

27 Setting

31 Berries pea-size

35 Veraison

38 Harvest

Sh

oot

and

inflo

rescence

develo

pm

ent

Flo

werin

gB

erryfo

rmatio

nB

erryrip

enin

gSen

escence



• Late Spring – occurring from E-L 15 (8 leaves

separated, shoot elongating rapidly) to E-L 25

(80% caps off).

153



1 Winter bud















20 10% caps off

21 30% caps off


25 80% caps off















47 End of leaf fall

4 Budburst


50% caps off




Berries ripe

12 Shoots 10 cm

19 Flowering begins

23 Flowering

27 Setting

31 Berries pea-size

35 Veraison

38 Harvest

Sh

oot

and

inflo

rescence

develo

pm

ent

Flo

werin

gB

erryfo

rmatio

nB

erryrip

enin

gSen

escence




3

Grapevines are almost entirely resistant to freezing during frosts of less than -3°C (bud tissuetemperature) by virtue of their ability to supercool (Fuller and Telli, 1999). Dissolved solutesmay lower the freezing point of liquid in bud tissues by 1-2°C through freezing pointdepression. This means that water may be retained in a liquid state at temperatures less than0°C (= supercooling). When water freezes within plant cells it ruptures cell membranes,killing the cells and tissues. Ice nucleation normally occurs when the bud temperature falls to-3°C to -3.5°C. If frosts occur at an early stage of development (up to and including DS02:buds swollen but not yet at cotton bud stage, see Figure 2) then injury is slight and non-lethal.Whereas, if frosts occur when buds are at DS03 or later (DS03: emergence of brown downamong the scales, i.e. cotton buds) then they can be almost completely killed. The freezing ofbuds can be correlated with their water content. During the early stages of development(DS0, DS01, DS02, DS03) the bud water content rapidly increases from approximately 40%to 80% (Figure 2). During this transition, buds gradually lose the ability to supercool and therisk of frost damage increases.

Figure 2. Changes in water content of grapevine buds during initialdevelopment stages (DS), (adapted from Fuller and Telli,1999).

Spontaneous ice nucleation always occurs internally within the canes, before it occurs withinthe buds, during early stages of bud growth. The rate of ice spread in canes is comparable tothe rate of spread in pure supercooled water (0.47 cm s-1), suggesting that the ice is travellingin the bulk water contained within xylem vessels in the canes (Hamed et al., 2000). The lackof a fully functional xylem system between canes and buds, that exists during bud burst, isproposed to act as a barrier to the spread of ice from the canes into bud tissues during thistime.

This report discusses a series of trials that were undertaken on commercial vineyards inHawke’s Bay following the radiation frosts that occurred during spring in 2002. Theobjectives of these trials were to assess productivity, fruit development and fruit qualitycharacteristics of Chardonnay and Merlot vines that were either partially or completelydamaged during spring frosts, compared with vines that suffered no frost damage on the samevineyard, and to evaluate the effects of different post-frost management strategies on yield,fruit development and fruit quality.

Developmental stage

Bud water content (%) 40 55 78 80 85 85

DEGREE OF DAMAGE

The more advanced the phenological stage, the

more susceptible the grapevine is to frost. The

extent of damage will depend on the stage of vine

development and the severity of the frost. Damage

to plant tissue is caused by ice crystal growth – ice

crystals puncture plant cell membranes, causing

cell death. If enough cells die, the bud, leaf or flower

will be destroyed. As Figure 2.1 illustrates, the water

content of grapevine buds increases rapidly during

initial development stages. During this transition, the

risk of frost damage increases.

Figure 2.1. CHANGES IN WATER CONTENT OF GRAPEVINE BUDS DURING INITIAL DEVELOPMENT STAGES

CRITICAL TEMPERATUREThis refers to the lowest temperature plant tissue

(such as a bud) can endure for 30 minutes or less

without injury. It is the temperature within the plant

rather than atmospheric temperature that is critical.

It provides crucial information when determining

when to activate frost protection systems. Table 2.1

shows critical tissue temperatures observed in Pinot

Noir.

• Dormant tissue may be able to withstand

temperatures as low as -15 °C.

• Developing buds, depending on the stage of

development, may withstand temperatures from

-9.5 °C to -3.0 °C.

• Young tissues (new leaves and flowers) are

susceptible to temperatures only slightly

below 0 °C.

In the vineyard, the presence of surface moisture

increases the susceptibility to frost injury

(see Table 2.2).

Table 2.1. CRITICAL TISSUE TEMPERATURE (°C ) AT WHICH DAMAGE IS OBSERVED IN PINOT NOIR

Stage of development50% tissue death No damage

Dormant enlarged -14.0

Green swollen -3.4

Shoot burst -2.2 -1.0

First leaf -2.0 -1.0

Second leaf -1.7 -1.0

Fourth leaf -1.2 -0.6

Source: Trought, 2003 (from Gardea 1987)

Table 2.2. ROLE OF SURFACE MOISTURE

Stage of development

Modified E-L scale

Influence of surface moisture

WET DRY

Scale crack 2 -5.5 -9.5

First swell -4.5 -8.5

Full swell 3 -3.5 -7.0

Burst 4 -3.0 -6.0

Source: Martin, 2013

Source: McCartney, Chatterton and Good, 2003


DEFINING SEVERITY OF THE FROSTA simple way of quantifying the intensity of a

frost event is to accumulate the (screened) air

temperatures below zero on an hourly basis

(Figure 2.2).

For example, if during a three-hour frost the

temperatures recorded each hour were -1 °C, -2 °C

and -2 °C respectively, the accumulated degree-

hours would be -5 °C. Figure 2.2 provides an

estimation of frost damage (frost intensity is to

screened air temperature).

ENVIRONMENTAL CONDITIONSFrost risk may be reduced if it is windy, because air

movement reduces the insulation effect of still air,

helping to raise plant tissue temperature.

Under still conditions, the internal bud temperature

may end up 2 °C to 3 °C lower than the air

temperature. Wind speeds of 3 to 4 kilometres

per hour (kph) will minimise this effect, with air

movement around the bud bringing bud and air

temperatures much closer together.

Frost risk is lowered when there is free water in the

soil during a radiative frost. Heat is released from

this water into the air, reducing the affect of freezing

temperatures.

Free water on buds, however, will increase

susceptibility to frost damage.

No or light damage

Moderate damage

Severe damage

-15

-10

-5

Fros

t Int

ensi

tySu

m o

f deg

ree

hour

s bel

ow ze

ro (C

°)

1 5 10 15 25

Modified Eichhorn-Lorenz (E-L) Growth Stage

20Budburst FloweringInflorescence clear

Frost Severity Estimation ChartFigure 2.2. FROST SEVERITY ESTIMATION CHART

MORE RESOURCES ON NZWINE.COM:

Damage processes and symptoms – New Zealand

Winegrowers Fact Sheet

Post-frost event – preparing for the next year

after a frost, Damian Martin (Grape Days 2013:

Presentation notes and video)

References

• Trought MCT, Howell GS and Cherry N. 1999.

Practical Considerations for Reducing Frost

Damage in Vineyards. Report to New Zealand

Winegrowers.

• McCartney S, Chatterton D and Good M.

Dealing with frost: describing vine response

to frost damage and the impact of post-frost

management on vine performance, October

2003, Report to New Zealand Winegrowers.

• Trought MCT, 2003. New Zealand Winegrowers

Romeo Bragato Frost Workshop, Wellington.

Source: Martin, 2013


III – FROST FORECASTING

No frost protection method will protect against

all types and severities of frost. Knowing the

conditions that occur most frequently in your

vineyard is the first step in determining which

system to use.

• Compare the frosts that are forecast to the

temperatures at your vineyard.

• Understand the importance of your canopy/

cordon height and the impact this has on

temperature.

PLANNINGKnowing what the night’s minimum temperature is

likely to be – and how it might change – is essential

to frost management.

Vineyard managers should be actively involved in

frost forecasting and frost protection. Forecasting is

not something that can be left to weather stations

and frost alarms alone. Data collected from on-site

weather stations can be used to determine:

• What types of frost occur.

• What type of frost protection will be effective.

• Where to apply frost protection.

Weather station data can also be used during

frost events to determine when and for how long

protection is required.

Creating a frost protection plan is a good first step

in determining frost protection requirements. A

site map will outline areas with varying conditions

(such as elevations, temperature extremes, timing

of budburst) and historical frost protection methods

used, if any. Maps should be based on weather data,

topographic information, personal observations

over time and vine management records.

FORECAST SOURCESON-SITE FORECASTING

While off-site regional forecasts provide valuable

information, including historical data, they are

seldom specific to your vineyard block(s).

Minimum temperatures can differ widely within a

region. Factors that affect temperature, humidity,

wind speed and inversion strength at your site may

result in several mesoclimates, with differing risks in

terms of the potential for frost damage.

Many vineyard managers supplement off-site

forecasting with on-site weather stations.

Figure 3.1. On-site weather stations often include temperature and humidity

sensors, as well as reporting and alarm systems.

In recent years, technological advances have

brought sophisticated weather stations within the

financial reach of many growers. While the makeup

of these weather stations varies between services,

they commonly have:

• A solar-powered wireless base system with a

range of sensors including temperature and

humidity sensors.

• A data reporting system (often to a web page via

a weather database and server).

• Alarm systems that send text, voice or email

messages when conditions fall outside specified


thresholds (which can be configured to each

location). Alarm systems are now available with

multiple sensors that can be placed in a variety of

locations throughout the vineyard.

Depending on the model, these units can also:

• Activate frost fans or sprinkler systems (auto

start).

• Monitor the performance of frost fans or sprinkler

systems (for example, fuel level and engine rpm

of frost fan and pump performance of sprinkler

systems).

• Activate strobe lighting in specific areas to direct

helicopters being used for frost protection.

OFF-SITE FORECASTING

Off-site weather forecasting tools and services

are offered by the NZ Meteorological Service

(MetService) and NIWA (National Institute of

Weather and Atmospheric Research). You can learn

more about the online tools available by visiting the

websites below:

• Rural regional forecasting at MetService

http://metservice.com/national/home

• Web-based weather forecasting at NIWA

http://www.niwa.co.nz/online-services/niwa-

forecast

There are also private companies that provide frost

forecasting services, either as part of a customised

product or as a standalone service.

CALIBRATING ON-SITE CONDITIONSIf you are not using on-site weather stations,

regional frost forecasts form the start of your frost

forecasting process.

Your first step – which only needs to be done once

unless you make major changes to your site – will be

to modify the expected minimum temperature from

the regional forecast to the local conditions of your

own vineyard by monitoring on-site and over time

with some form of temperature measurement.

CALCULATING RISKCalculating frost risk will help to determine when to

activate frost protection and several approaches are

available.

DEW POINT ESTIMATES

The dew point is the temperature at which the

relative humidity reaches 100% as the air cools. At

this point, water vapour in the air condenses into

fog or dew, which gives off heat, slowing the drop in

temperature.

The dew point temperature measured at 3 p.m.

provides a useful estimate of the upcoming

minimum temperature under clear and calm

conditions. The dew point can be estimated by

measuring relative humidity and air (dry bulb)

temperature, or air and wet bulb temperature.

Using these measurements, the dew point

temperature can be read from prepared tables

(such as those provided on MetService at http://

about.metservice.com/about-metservice/

learning-centre/frost/) or accessed from freely

available online calculators (such as http://www.

dpcalc.org/).

For example, the MetService table indicates that

a 3 p.m. temperature of 11 °C and a 50% Relative

Humidity results in a dew point of 1 °C. Deducting

4 degrees from an estimated overnight low of 1 °C

gives an estimated ground minimum temperature of

-3 °C. In other words, a moderate frost that could be

damaging in spring.

While the 3 p.m. dew point temperature provides an

indication of the expected night-time low, the actual

temperature may be lower, particularly if the night is

calm and clear and is longer than 12 hours.

OVERNIGHT MINIMUM GRASS TEMPERATURE

An alternative method is to predict the overnight

grass minimum temperature using predictive

models such as those provided by MetService and

NIWA (mentioned earlier).


EXCEL-BASED PROGRAMMES

More precise local forecasts can be made using a

pair of freely available Excel-based programmes

developed by meteorologists at the University of

California and Lisbon Technical University:

o FFST_M uses historical records of air and dew

point temperatures to forecast the minimum

temperature from inputs of air temperature alone

or with dew point temperature measured two

hours after sunset.

o FTrend_M uses forecast minimum air temperature

and dew point temperature to determine the air,

wet bulb and dew point temperature trends during

a radiation frost night, giving you an indication of if

and, as important, when during the night you need

to activate your active frost protection (such as a

sprinkler system or frost fans).


Forecasting – New Zealand Winegrowers Fact Sheet

References



• Snyder RL and Paulo de Melo-Abreu J. 2005. Frost Protection: fundamentals, practice, and economics

(Vol. 1). Food and Agriculture Organization of the United Nations, Rome.

http://www.fao.org/doCrep/008/y7223e/y7223e00.HTM


IV – FROST CONTROL METHODS

Given the financial implications of failures in frost

protection, it is important to take qualified advice

before relying upon any method for protecting your

crop against frost.

Before investing in a frost protection system,

growers should also review the New Zealand

Winegrowers Code of Practice (at the end of this

booklet), which discusses related issues such as

district plan requirements.

Table 4.1

FROST CONTROL METHODS

Passive ActiveGroundcover / soil management

Air mixing – frost fans or helicopters

Delayed pruning Sprinkler systems

Trellis height Heaters

PASSIVE METHODS

Available to every grower, passive control methods

are effective and often help prevent frost damage in

a vineyard.

GROUNDCOVER / SOIL MANAGEMENT

Prepare the vineyard floor:

• Ensure inter-row grass or cover crops are closely

mown (generally to less than 5 cm), and soils are

moist and firm.

• Keep on top of weed growth.

Loosely cultivated soil or deep inter-row herbage

provide an insulating layer on the soil surface that

will restrict heat absorption during the day and

restrict the ground’s ability to re-radiate heat out

during the night.

An absolute focus on keeping on top of weed

growth and achieving a short sward can secure

up to a 1 oC elevation in canopy temperatures on a

frost-prone site.

Removing all ground cover (compacted bare earth)

enhances frost protection further by completely

removing the insulating layer. To increase the

temperature by about 0.5 oC, the soil surface

will have to be firm. Ground preparation must be

done well before a predicted frost – ideally, before

budburst.

Ice-nucleating bacteria are plant pathogens that

cause freezing injury. The concentration of ice-

nucleating bacteria on grass and ground covers is

typically high.

DELAYED PRUNING

• Employ late spur pruning to delay budburst,

reducing the vulnerability of developing shoots to

frosts.

• Leave additional canes post-pruning, which may

or may not be used in the event of a frost. This

will allow additional shoot selection should a frost

occur, optimising vine yield.

TRELLIS HEIGHT

• Raise fruiting wires. For every 100 mm the wire is

above the ground the temperature will increase by

approximately 0.2 oC.

Figure 4.1: Canopy management can be used to fight frost. For every 100 mm

the wire is above the ground, the temperature will increase by approximately 0.2 oc.


ACTIVE METHODS

Active frost protection measures are implemented

just before and during frost events to mitigate the

risk of damage. Active methods rely on a range of

technologies, and include:

• Diesel return stack heaters.

• Air mixing by helicopters and frost fans.

• Application of water through sprinkler systems.

No system, however, is able to guarantee crop

protection against frost damage.

HEATERS

Diesel return stack heaters provide frost protection

by directly heating the air in the vineyard, which, in

turn, provides some radiant heating of the vines.

Quantity is critical: approximately 150 to 200

heaters per hectare may be required in colder

regions to achieve a level of frost protection.

Positioning of heaters is also critical. If placed

downwind in the vineyard, the heating benefits may

go to your neighbour’s block rather than your own.

Pros:

• Are proven to protect against typical radiation

frosts.

• Provide some protection under advective frost

conditions.

• Flexibility of placement enables targeting of frost

pockets within the vineyard.

Cons:

• Very high operational costs.

• Labour intensive.

• Protection is based on combustion, increasing

carbon footprint.

Figure 4.2

Diesel return stack heaters provide frost protection by directly heating the air in the

vineyard, which, in turn, provides some radiant heating of the vines.

FROST DAMS

Because cold air drains downhill much like water,

vineyard managers have used vegetation, buildings

and other structures to protect against frost. This

can be done by erecting frost dams upwind to

block the flow of cold air or by removing shelter

and/or providing gaps downwind to drain cold

air away from vines. Berm walls, fences and other

structures have been used to redirect cold air and

provide a measure of frost protection.

Foliar applications such as urea and copper

sulphate may provide limited frost protection, but

they must be applied before frost occurs.


Modifying sites to reduce frost risk – New Zealand


Choosing sites with low frost risk – New Zealand


References

• Trought MCT, Howell GS and Cherry N. 1999.

Practical Considerations for Reducing Frost

Damage in Vineyards. Report to New Zealand

Winegrowers.


FROST FANS

Two- and four-blade machines remain the most

popular form of fixed protection in NZ vineyards,

partly because of cost (they cost roughly half

as much per hectare as a water-based sprinkler

system). Frost fans (also known as wind machines)

are also easier to maintain and service and are

relatively straightforward to manage during a frost

event. They are not suitable for every site, however,

particularly where inversion conditions are weak.

Depending on the make and model, one frost fan

can protect 4-plus hectares under ideal conditions.

Air mixing technologies do not add significant

amounts of heat. They simply redistribute heat

by mixing the warmer upper layer with the cooler

ground layer, thereby raising the temperature at the

vine level during a radiation frost.

Bringing warm air from above the inversion down

to the ground typically increases temperatures by

about 1 oC to 2 oC, but there must be an inversion

present. Air mixing does not work for advective

frosts.

Placement is critical: the upper gearbox rotation

time should be close to or less than the industry

standard of 6 minutes and 40 seconds. Individual

manufacturers’ standards may vary. Air is drawn

down from heights of 20 m+ by blades slightly

angled towards the ground and mixed with colder

air near the surface.

Information on the strength of an inversion layer

at a specific site should be determined before any

purchase or installation of a fixed frost protection

system.

Helicopters and frost fans protect less area

when inversion conditions are weak or surface

temperatures are very cold.

Figure 4.3 Two- and four-blade frost fans remain the most popular form of fixed

protection in NZ vineyards.

Figure 4.4 HOW DO FROST FANS WORK?Air mixing technologies do not add significant amounts of heat. They simply redistribute heat by mixing the warmer upper layer with the cooler ground layer, thereby raising the temperature at the vine level during a radiation frost.


Activation

Fans are usually started while the temperature

measured at 1.5 m height is still above the critical

damage temperature – typically, fans are set to

auto start at 0.5 oC, but growers can adjust them to

vineyard conditions (usually, from 0.3 oC to 1.5 oC).

In areas where wind speeds during frost can be

a problem, the frost fan should be fitted with an

auto anemometer. This will shut the fan down when

wind rises above a set maximum speed and start it

again when the wind returns to below-critical levels.

Run your fans according to the manufacturer’s

specifications.

Pros:


frosts.

• After installation, are always available and can be

set to start automatically (auto start).

• Have relatively low running and maintenance

costs (between 19 to 34 litres of diesel per hour

per machine, depending on the make and model)

and a low energy cost compared to heaters.

Cons:

• Are not effective under advection frost conditions.

• Have relatively high capital cost (approximately

$50,000 to $60,000 per machine – which

converts to somewhere between $7,500 to

$12,500 per hectare protected, depending on the

make and model).

• Some machines emit noise that can be a problem

near dwellings and may limit installation consents.

• Not recommended when wind speeds exceed 7 kph

(see the Appendix: New Zealand Winegrowers

Code of Practice 2014).

Frost fans must be monitored during the night. They

must be switched off if wind gets up too much or it

starts to get foggy or snows. Frost fans can fail due

to blade-icing (observed in Central Otago).

The auto start feature on all frost fans can also fail,

either initially or once it has run.

HELICOPTERS

Like frost fans, helicopters redistribute heat by

mixing the warmer upper layer with the cooler

ground layer, thereby raising the temperature at the

vine level during a radiation frost.

Bringing warm air from above the inversion down

to the ground typically increases temperatures by

about 1 oC to 2 oC, but there must be an inversion

present. Air mixing does not work for advective

frosts.

Figure 4.5 Like frost fans, helicopters redistribute heat by mixing the warmer

upper layer with the cooler ground layer, thereby raising the temperature at the vine

level during a radiation frost.

Estimates vary, but the coverage area protected by

one helicopter can range from between 10 to 40

hectares. The area protected will depend on the size

and weight of the helicopter, the power and thrust

from the blades, and on weather conditions. As the

temperature falls, helicopters protect significantly

less area.

Ideally, helicopters should have a return period of

no more than five minutes to the same point – and

certainly no more than 30 minutes (this determines

the number of helicopters required). Flight paths

should be in a zigzag pattern into the prevailing

katabatic drift and flight height is usually about 15

metres above ground.


Use coloured frost lights as a guide for pilots.

As the temperature drops, colours will change,

signalling areas requiring attention.

Figure 4.6: Helicopter operations fighting frost in a New Zealand vineyard.

Ground temperature needs to be monitored as the

helicopter passes above to ensure that temperature

rises rather than falls. If the inversion layer weakens

too much (typically just before sunrise, when it is

coldest) air mixing can do more harm than good.

Having a temperature sensor on the helicopter

is also helpful. Maintain communication with the

helicopter pilot at all times.

Pros:


frosts.

• May provide some protection even under very

weak inversion conditions.

• Need only pay for when called.

• No need for additional infrastructure in the

vineyard.

Cons:

• Are not effective under advection frost conditions.

• Have to be booked in advance of a frost, and

standby costs apply even if not used.

• Availability during frost season not always

guaranteed.

• Relatively high running costs and noise emissions.

• Almost never available for the unpredicted frost.

WATER APPLICATIONS

Sprinkler irrigation for frost protection works

because water releases heat when it changes

from a liquid to a solid (ice). In cold conditions,

the clear ice that forms on the crop as a result of

sprinkler applications serves as a good conductor

of heat. However, ice does not act as an insulating

layer to prevent frost damage. Rather, it facilitates

freezing of crop tissues unless a film of continuously

freezing water is maintained on the surface of the

ice, releasing sufficient latent heat to maintain

temperature just below 0 oC.

Today there are a range of sprinkler systems used

in frost protection. Vineyards in New Zealand

commonly use one or more of the following:

1. Traditional, full cover (overhead impact) sprinklers

that are fixed in place and completely wet the

plants and soil, providing 100% coverage (typically

manufactured in brass).

2. Targeted micro or mini sprinklers, which apply

water only to the vines, rather than the entire

vineyard (typically manufactured in plastic).

3. Hybrid full cover impact sprinklers (metal and

plastic materials, depending on componentry).

Note: Full cover overhead sprinklers offer the

only reliable protection under both radiation and

advection frost conditions, provided a sufficient

amount of water is applied. They are not suitable

for every soil type, however, and may have high

water storage requirements.


Full cover sprinklers

These systems will work in advective or mixed

events where frost fans or helicopters won’t.

Dew point is critical. Vineyard managers need to

monitor the dew point and turn on sprinklers before

the damage point is reached for the current growth

stage. This is likely to be different at both ends

of the season – in spring, it’s typically -0.5 oC but

can be as low as -2 oC during autumn. The water

rate should increase as temperature decreases. Ice

formation should remain clear. If ice turns opaque,

there is insufficient water application and damage to

sensitive plant tissue may occur.

Figure 4.7: Overhead sprinkers will work in advective or mixed events where

frost fans or helicopters won’t.

Figure 4.8: Ice formation should remain clear. If ice turns opaque, there is

insufficient water application and damage to sensitive plant tissue may occur.

The accompanying tables were established by

bio-meteorologist Richard Snyder (University

of California) to indicate when to start and stop

sprinklers for frost protection based on temperature

and humidity (that is, the critical damage

temperature for the current growth stage).

You must run the sprinklers until all the ice has

melted from the protected area of the vineyard –

otherwise tissue damage will occur.

Note that you will need a site-specific means of

measuring dew point if you are using water as your

means of frost protection.


Select a wet bulb temperature that is above the critical damage temperature for the pertinent growth stage and locate the appropriate column. Then choose the row with the correct dewpoint temperature and read the corresponding air temperature from the table to turn your sprinklers on or off. This table assumes a barometric pressure of 1013 millibars (101.3 kPa).

Source: Snyder, 2005

Table 4.3 DEW-POINT TEMPERATURE (OC) FOR A RANGE OF AIR TEMPERATURE AND RELATIVE HUMIDITY

Relative humidity Temperature (oC)

% 0.0 2.0 4.0 6.0 8.0 10.0

100 0.0 2.0 4.0 6.0 8.0 10.0

90 -1.4 0.5 2.5 4.5 6.5 8.4

80 -3.0 -1.1 0.9 2.8 4.8 6.7

70 -4.8 -2.9 -1.0 0.9 2.9 4.8

60 -6.8 -4.9 -3.1 -1.2 0.7 2.6

50 -9.2 -7.3 -5.5 -3.6 -1.8 0.1

40 -12.0 -10.2 -8.4 -6.6 -4.8 -3.0

30 -15.5 -13.7 -12.0 -10.2 -8.5 -6.8

Select a relative humidity in the left column and an air temperature from the top row. Then find the corresponding dew point in the table.

Source: Snyder

Table 4.2: MINIMUM TURN-ON AND TURN-OFF AIR TEMPERATURES (OC) FOR SPRINKLER FROST PROTECTION

Dew-point temperature Wet bulb temperature (0 oC)

0 oC -5.0 -4.0 -3.0 -2.0 -1.0 0.0 0.0 0.0

-1.0 -1.0 0.7

-2.0 -2.0 -0.4 1.3

-3.0 -3.0 -1.4 0.2 1.9

-4.0 -4.0 -2.5 -0.9 0.8 2.4

-5.0 -5.0 -3.5 -1.9 -0.4 1.3 2.9

-6.0 -4.5 -3.0 -1.5 0.1 1.8 3.4

-7.0 -4.1 -2.6 -1.0 0.6 2.2 3.9

-8.0 -3.6 -2.1 -0.6 1.0 2.6 4.3

-9.0 -3.3 -1.7 -0.2 1.4 3.0 4.7


Water volume requirements

For effective frost control using full cover overhead

sprinkler irrigation, growers must apply water at a

rate:

• High enough to release sufficient latent heat that

temperatures are prevented from dropping much

below 0 oC.

• Low enough to avoid unacceptable levels of

waterlogging of the soil (see the New Zealand

Winegrowers factsheet on soil water status).

A useful rule of thumb is that each millimetre of

water applied per hour can be expected to maintain

plant temperatures one degree above the frost

temperature.

For example, an application rate of 4 mm/hr can

hold plant temperatures at -0.5 oC to 0 oC in a

-4 oC frost. However, higher sprinkling rates will be

required to ensure protection in situations where

sprinkler cover on the crop is not uniform and/or in

wind conditions where evaporative cooling becomes

a factor. In such conditions, sprinkling rates of 1.5

mm/hr or more may be required to achieve a 1 oC

rise in plant temperature.

You can easily check that the correct temperature is

being maintained by looking at the ice being formed:

• When sprinkling rates have been acceptably high

and freezing is continuous, the crop is covered in

icicles of clear ice (as shown in Figure 4.9).

• When sprinkling rates have been insufficient for

continuous freezing, icicles tend to be absent

and trapped air in the ice makes it white; tissue

damage is likely to have occurred.

The total volumes of water required for sprinkler-

based frost protection are greater than those

needed for irrigation (see Table 4.4). As the whole

protected area needs to be wetted at the same time,

the overall pumping capacities required far exceed

those for systems used solely for irrigation.

Typical weather patterns in New Zealand can

produce a series of potentially damaging frosts

over several days, so the necessary amount of

water needs to be available for several nights

in succession. Planning for water storage and

pumping capacity sufficient to provide protection

under realistic worst-case scenarios for frost risk is

an important part of the design of sprinkler frost

irrigation systems. Plan for three consecutive nights

of frost protection, with refilling of the reservoir

beginning as soon as frost protection starts.

The water rate required will depend on the sprinkler

system’s rotation rate plus the wind speed and the

dew point temperature. Evaporation increases with

wind speed and decreasing dew point temperatures.

The goal is to re-wet the vines frequently so that the

interval when tissue must withstand temperatures

below the critical damage threshold is short (no

longer than 60 seconds).

Correct engineering design is essential to match

application rates to frost risk. A report prepared

for Hawke’s Bay Winegrowers, Improving Sprinkler

Frost Control In New Zealand Vineyards provides

comprehensive coverage on this topic (see

‘References’ at the end of this section for the

complete notation).

Figure 4.9: Ice-encased leaves and flower following overhead sprinkler frost

protection – note the clear ice which is indicative of near continuous wetting.


Tissue Temperature

Wind Speed ( Km h-1 )

0-1.5 3.0-6.5 8-13 15-22 29-32 48

-2 - - - - - -

-3 0.25 0.25 0.36 0.50 1.00 1.50

-4 0.25 0.40 0.75 1.00 2.00 4.00

-5 0.30 0.60 1.25 1.50 3.00 4.50

-6 0.35 0.70 1.40 1.80 3.65 5.25

-7 0.40 0.75 1.50 2.00 4.00 6.00

-8 0.50 1.00 1.75 2.50 5.00 7.50

-9 0.65 1.75 2.25 3.30 6.60 10.00

Source: Trought, 1999 (modified after Gerber, 1970)

Pros:

• The only frost protection method that reliably

protects under both radiation and advection frost

conditions is the full cover sprinkler.

• Provided sufficient water is available, water

pumping costs are lower than the energy costs of

heaters for frost protection.

• Application rates can be refined to reduce costs

and water.

Cons:

• Require large volumes of water that necessitate:

o Appropriate water storage (dams/reservoirs).

o Consent for using the water.

• High water use can waterlog soils, potentially

creating problems with:

o Soil structure.

o Soil and plant health.

o Access for machinery.

• Relatively high installation costs (these will

vary depending on the water storage capacity

required) and high maintenance costs.

Under canopy micro or mini sprinklers

Micro or mini sprinklers use less water than full

cover overhead sprinklers. They may provide a

useful, but limited, temperature rise that can help

protect against damage from light frosts or increase

the efficacy of frost fan protection.

Pros:

• Little additional capital costs are incurred because

existing irrigation systems can be used.

• Low running costs.

Cons:

• Provide limited protection that tends to be useful

only in radiation frosts.

• Usually made of plastic and typically require more

maintenance than metal full cover sprinklers.

Table 4.4 SPRINKLING RATE (MM H-1) NECESSARY FOR COLD PROTECTION


CHECKLIST BEFORE FROST FIGHTING

• Make sure your frost alarm or weather station sensors are working and information is going to the correct

staff.

• Know how many litres of fuel per hour your machine uses and ensure that there is enough diesel for the

following night by dipping the tanks and prioritising refills at the end of the frost fighting session.

• Frost fans should also be checked prior to running – remove bird nests, which may catch fire and damage

the engine.

• Ensure that frost fan batteries are fully charged.

• Frost fans should also be run monthly to ensure oils and water circulate and should be calibrated by ice

twice a year to ensure preparedness for spring and autumn frosts.

• Subscribe to an area-specific forecast.


Heaters for active frost protection – New Zealand Winegrowers Fact Sheet

Wind machines and helicopters for active frost protection – New Zealand Winegrowers Fact Sheet

Overhead sprinkler irrigation for active frost protection – New Zealand Winegrowers Fact Sheet

Soil water status – New Zealand Winegrowers Fact Sheet

Under-canopy sprinkler irrigation for active frost protection – New Zealand Winegrowers Fact Sheet

REFERENCES

• Yule I, Eastwood CR, Murray RI, Lawrence HG, Johnson G, Impact of topography on frost protection

machine performance, Report to New Zealand Winegrowers, 2003.

• Woodhead I, Richards S, Hayward A. Improving Sprinkler Frost Protection in New Zealand Vineyards,

Summary Report from 2004-2007 Data. Report to Hawke’s Bay Winegrowers.

• Ireland W. 2005. Frost and Crops: Frost prediction and plant protection. ISBN 0-473-10108-4.

• Snyder, R.L. and de Melo-Abreu, J.P. 2005. Frost Protection: fundamentals, practice, and economics

Volume 1. FAO. ISBN: 92-5-105328-6 http://www.fao.org/doCrep/008/y7223e/y7223e00.htm#Contents


V – REDUCING FROST DAMAGE

Frost damage is most likely to occur in spring,

during early growth stages.

Damage may not be immediately apparent.

Consider waiting before taking any action.

Symptoms of frost damage may take one or more

weeks to appear and will indicate which remedial

actions are appropriate.

The goal is to:

• Maximise crop for the current season if possible.

• Ensure the vine is in the best possible position for

the following season, so that crop and vine health

are not compromised.

POST-FROST

A frost event has occurred. The question now is,

‘What should I do next?’

If frost protection has been unsuccessful, damage

in the spring can reduce the current crop as well as

reduce the crop in following seasons.

ASSESSMENT OF DAMAGE

Frost damage may not be immediately apparent.

Consider waiting until symptoms of frost damage

appear. There is a trade-off, however, between

waiting to see the outcome and a quick response to

minimise frost damage.

• Leaf damage is usually evident. Loss of

chlorophyll, transparent sections on leaves or

bubbling on the leaf surface may be observed.

• Young succulent shoots will wilt once the frost

thaws, but older hardened shoots will take longer

to show symptoms.

• Frosting of inflorescences may not be

immediately apparent. Later, they begin to dry out

and individual flowers start to fall off, particularly

when handled.

Figure 5.1 Leaf damage is usually evident. Loss of chlorophyll, transparent

sections on leaves or bubbling on the leaf surface may be observed.

FROST DAMAGE IN SPRING

DETERMINE OBJECTIVES FOR THE REMAINDER

OF THE SEASON

The chosen approach will depend on a range of

factors:

• The severity of the frost.

• The phenological stage when the frost occurs.

• The rapidity with which vines are growing and

how much water they have in them.

• The region and length of growing season available

after the frost.

• The pruning system.

• The grape variety.

• The targeted wine style (which may change

following the frost).

Assess cropping potential – the impact of variety

and training system need to be factored into your

predictions. Most grape varieties have fruitful

secondary buds that can produce a smaller crop

(in the case of some varieties, much smaller).

On some training systems, fruitful shoots may

arise from bud positions other than those on

canes retained and counted at pruning. Check

whether there will be enough growing season to


allow any new bunches to fully ripen. Bear in mind

that a reduced crop might mature faster than an

undamaged full crop.

Strategies for maximising crop in the current year

will differ from strategies to produce good canes for

pruning in winter.

The following checklists for managing frosts of

different severity at different points in the growing

season were prepared by Damian Martin, Science

Group Leader Viticulture & Oenology at Plant &

Food Research, and first presented to the wine

industry at New Zealand Winegrowers’ Grape Days

events in 2013.

OPTIONS FOR MANAGING FROST DAMAGE

LIGHT EARLY-SEASON FROST DAMAGE

• Many primary buds will survive and crop normally.

• The vine’s reserves are likely to still be abundant.

• Not usually necessary to promote shoot growth of

replacement canes.

• Fruit that forms on secondary buds are

comparable to second set.

• Manage according to the variety and targeted

wine style.

• Premium red wines – green-thin fruit at veraison.

• White and sparkling-based wines – input is

probably not warranted.

SEVERE EARLY-SEASON FROST

• Virtually all primary buds will be destroyed.

• Crop will only come from unburst primary buds

and secondary/tertiary buds.

• Fertility of secondary and tertiary buds is modest;

they are never as fruitful as first buds and

fruitfulness will vary by variety. A good rule of

thumb is to allow only one small bunch for every

two shoots.

• The spring development of new shoots will be 3-4

weeks behind the pre-frost growth stage.

• Still enough time for the replacement canes to

develop fully and harden.

• Crop may also still ripen and be relatively uniform.

• Pruning input not necessary.

Following an early frost, applications of nitrogen

fertiliser and water can help regrowth and restore

the vine’s reserves.

MODERATE MID- TO LATE-SEASON FROSTS

• Well-developed shoots only partially damaged.

• Lateral growth is strongly stimulated.

• The spring development of new shoots will be 4-8

weeks behind the pre-frost growth stage.

• Priority is to ensure that there are good quality

replacement canes or spurs available for winter

pruning.

• Replacement canes with multiple lateral branching

and poorly matured wood (laterals harden off less

well than primary shoots).

• Current season’s crop becomes secondary

priority.

• Pruning input is recommended (see Table 5.1). The

focus is to ensure replacement wood.

SEVERE LATE-SEASON FROSTS

• Well-developed shoots only partially damaged.

• Lateral growth is strongly stimulated.

• Vines’ reserves are greatly depleted and regrowth

can be very late and/or slow.

• Even more important to direct the remaining

reserves into the replacement canes.

• Current season’s crop should be forgotten

altogether.

• Major pruning input is recommended

(see Table 5.1).


Table 5.1: PRUNING AFTER A FROST

Early Spring Mid Spring Late Spring

LIGHT DAMAGE No pruning N fertiliser and water still recommended.

No pruning N fertiliser and water still recommended.

No pruning N fertiliser and water still recommended.

MODERATE DAMAGE No pruning N fertiliser and water still recommended.

Prune the partly damaged green shoots back to 5 mm above the crown to stimulate growth of primary and tertiary buds. Breaking off shoots may damage replacement buds. Prune damaged shoots close to the head to ensure replacement canes are not dominated by laterals.

Prune the partly damaged green shoots back to 5 mm above the crown to stimulate growth of primary and tertiary buds. Breaking off shoots may damage replacement buds. Prune damaged shoots close to the head to ensure replacement canes are not dominated by laterals.

SEVERE DAMAGE No pruning N fertiliser and water still recommended.

Prune the partly damaged green shoots back to 5 mm above the crown to stimulate growth of primary and tertiary buds. Breaking off shoots may damage replacement buds. Prune all damaged shoots to promote secondary and tertiary buds and maximise cropping potential.

Prune canes midway along to reduce the bud load. Promote new shoot growth from the base of the cane and the head. Priority is replacement canes.

Source: Martin 2013

AUTUMN FROSTS

If fruit has been frozen, it should be harvested immediately. If only the leaves are killed, the sugar

concentration in the fruit will increase slowly through dehydration of the berry. Deciding when to harvest

must be weighed against the possibility of another frost and further reductions in fruit quality. Canes in

autumn should be sufficiently hardened to provide good canes and spurs for pruning in winter.


Post-frost event – preparing for the next year after a frost, Damian Martin

(Grape Days 2013: Presentation notes and video)

Damage processes and symptoms – New Zealand Winegrowers Fact Sheet

References




NEW ZEALAND WINEGROWERS

FROST FAN CODE OF PRACTICE 2014

Introduction

The New Zealand Winegrowers Frost Fan Code of Practice 2014 (the Code) represents a standard of good

practice in the safe operation of frost fans and takes the form of recommendations.

The intent of the Code is to provide guidance to the wine industry on the safe operation of frost fans:

a) when climatic conditions necessitate their use;

b) in accordance with local council rules; and

c) in a way that minimises risk and disturbance.

In accordance with section 3.1 of the Guidance on Planning for the Wine Industry (Ministry for the

Environment, Guidance Note, 2007), it is noted that any standards regulating the use of frost-protection

devices should recognise the infrequent occasions on which these devices may need to be used, typically

dependent on factors beyond a grower’s control.

It may be that, in some situations, strict compliance with all recommendations is impracticable. In such

circumstances, every endeavour should be made to observe the intent of the Code.

The good practice recommendations in this Code are voluntary and do not displace the obligation on

members to comply with the rules contained in the District or Unitary Plan of their relevant regional authority

or not to engage in any other conduct which may be in breach of the Resource Management Act 1991. In

particular, we draw attention to the relevant rules in each region on noise limits and location of frost fan from

boundary.

1 OPERATING ENVIRONMENT

1.1 Avoid operating a frost fan in the following conditions:

• fog;

• rain;

• when winds are at 7km/h or greater; or

• when there is no risk of frost (except for maintenance purposes, which should be conducted at a time

/ duration to minimise intrusion).

1.2 Where possible, shield the frost fan engine from vineyard sprays and/or irrigation sprinklers.

1.3 In order to prevent inadvertent start up the frost fan should be disarmed during periods when no frost

threat exists.

2 PRE-USE INSPECTION

2.1 Before operating the frost fan (or activating the ‘Operator Assist’ or ‘Automatic’ function), check the

following levels:

• fuel level (never allow the fuel tank to run out of fuel when frost fan is operating);

• oil level;

• coolant level; and

• battery voltage levels.

2.2 Conduct a visual inspection of the gear box and fan for cracks, debris, tree branches and/or birds’ nests

that might impede the operation of the frost fan.


2.3 When performing pre-use inspections:

• always keep the tower between yourself and the fan; and

• never adjust, alter or modify any part of the frost fan.

2.4 In order to avoid toppling the tower, only authorised and suitably trained people should climb frost fan

towers.

3 WARM UP

3.1 It is essential to safely warm up a frost fan before use. Refer to the operating manual supplied by your

manufacturer for the appropriate warm up method for your machine.

3.2 If set to ‘Operator Assist’ or ‘Automatic’, the machine should engage the warm up procedure

automatically.

4 ON-SITE SUPERVISION

4.1 Always supervise a frost fan during operation.

4.2 During operation, ensure that there is access to the following:

• a set of jumper leads or spare battery;

• hand held thermometer; and

• portable fuel supply or regular delivery order from local fuel supplier.

5 DURATION OF USE

A frost fan may potentially operate for hours, after starting automatically at 1°C, even though no frost

has occurred. The 1°C frost threshold is not absolute; the risk of frost may vary by variety, time of

year, air temperature immediately preceding the temperature drop and proximity to sunrise (generally

the coldest part of the day). Assess the conditions of each frost event in order to avoid unnecessary

operation.

5.1 A frost fan should only be operated during a frost danger period.

This generally means:

• the air temperature has reached a critical level as determined by you and based on your experience of

past frost events.

5.2 Where these conditions no longer prevail and you are confident that the temperature within the

vineyard is stable, shut the frost fan down manually.

6 SHUT DOWN

6.1 When shutting down a frost fan, follow the procedure for shut down as directed by the operating

manual supplied by your manufacturer.

6.2 If set to ‘Operator Assist’ or ‘Automatic’, the machine should engage the shut down procedure

automatically.

7 ANNUAL MAINTENANCE

7.1 Ensure that the frost fan is serviced annually by a suitably qualified person.

Please note that this document does not constitute advice on how to comply with your obligations under

the Resource Management Act or your local district plan. You should check with your local Council

regarding the requirements for frost fan operation that apply in your area.


Photo and Image Permissions

Cover: Photo courtesy of Wither Hills

Figure 1-2: Photo courtesy of Akarua Winery

Figure 3-1: Photo courtesy of Harvest

Figure 4-3: Photo courtesy of NZ Frost Fans

Figure 4-4: Diagramme courtesy of NZ Frost Fans

Figure 4-5: Fairfax Media New Zealand / Marlborough Express

Figure 4-6: Fairfax Media New Zealand / Marlborough Express

Figure 4-7: Photo courtesy of NZ Irrigation Services

Figure 4-8: Photo courtesy of NZ Irrigation Services

New Zealand WinegrowersPO Box 90-276 Victoria Street WestAuckland 1142New Zealand

The New Zealand wine industry relies on research

leading to technical innovation to enable winemakers

and grapegrowers to stay ahead in a competitive world.

New Zealand Winegrowers works to ensure its levy-

funded research programme provides and promotes a

technological basis for the New Zealand grape and wine

industry to remain internationally competitive as the

leading producer of premium quality wines.

This booklet is part of New Zealand Winegrowers’ levy-

funded research programme.

www.nzwine.com

DISCLAIMERWhile care has been used in compiling this booklet, New

Zealand Winegrowers gives no prediction, warranty or

assurance in relation to the accuracy of or fitness for any

particular purpose, use or application of any information

contained in this document. To the full extent permitted

by law neither New Zealand Winegrowers nor any of its

employees shall be liable for any cost (including legal

costs), claim, liability, loss, damage, injury or the like, which

may be suffered or incurred as a direct or indirect result of

the reliance by any person on any information contained in

this document.

© New Zealand Winegrowers 2014. All Rights Reserved.

ACKNOWLEDGMENTSThis booklet summarises New Zealand Winegrowers’

research and literature that explores the many issues

related to frost prevention and management in the

vineyard. The website (www.nzwine.com) provides a

wealth of related material, including fact sheets and

research reports, and these are highlighted in each chapter

under the heading, “More resources on nzwine.com.”

The editors gratefully acknowledge the contributions of all

the authors whose work (commissioned by New Zealand

Winegrowers) has been incorporated into this summary,

which is made possible by NZW funding. We would

also like to acknowledge the direction we have received

from Dr Simon Hooker, General Manager Research, and

the valuable technical review provided by New Zealand

Winegrowers Research Committee.


nzwine.com

Documents

FROST CONTROL IN NEW ZEALAND VINEYARDS · FROST CONTROL METHODS Passive methods – cultural inputs ... Practical Considerations for Reducing Frost Damage in Vineyards. Report to