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Frost in vineyards

By: Diana Fisher, Viticulture Development Officer, Manjimup.

Viticulture in Western Australia

Why are frosts of danger to vineyards?

Frosts can cause serious damage to grapevines during the growing season. They have the potential to kill young vines, reduce or destroy the crop for that season and reduce the potential yield for the following season.

What are frosts?

Frosts are when ground temperatures are 0o C or below (Foley, 1945).

What are the different types of frosts?

There are two types of frost, radiation and advective frosts.

Radiation frosts are caused by inversions and occur on clear nights when radiation from the ground to the sky is not impeded by cloud cover. Radiation frosts occur as land air temperatures increase during the day but decrease with elevation. At night the heat from the land is lost as the hot air rises and the cool air sinks. If this air is too cold the vine freezes. These freezing temperatures tend to occur near dawn.

A cloudy day followed by a cloudless night produces the greatest frost risk. The cloudy day reduces the sun's ability to heat the soil surface and when followed by a clear night what little heat is stored quickly dissipates. Only a small amount of cloud at night is required to prevent a frost from developing.

Advective frosts are also known as freeze or wind frosts. This type of frost is caused by wind chill. If the wind is too cold the vine freezes.

In both situations the vine freezes as plants generate very little heat.

What then are white and black frosts?

Frosts may also be referred to as white or black. This terminology is used to explain the weather conditions that the frost occurred.

White frosts occur under high moisture conditions. The vine tissue being covered in ice crystals typifies these frosts. The crystals form due to water vapour condensing when the dew point is below 0o C.

Black frosts occur under very dry conditions. These frosts are characterized by vine tissue being frozen due to an air temperature drop without sufficient water vapour in the atmosphere to form ice crystals. This frost is difficult to initially identify, as there is no white ice over the vine structure or on the ground before frost damage symptoms begin to appear on the vine.

How do frosts damage the vine?

Frost damage occurs due to the freezing of plant cells. As freezing occurs the ice expands rupturing cell walls, disrupting membrane function and irreversibly denaturing enzymes by dehydration.

What are the visual symptoms of frost damage?

Mild frost injury may appear only in the death of a few leaf cells. Leaves affected have pale yellow or clear, mottled areas within their veins. Some tissue may eventually become necrotic, causing leaf distortion and have the appearance of dead leaf tissue. More severe frozen leaf tissue becomes soft, brown and limp.

What vine tissue is most sensitive to frosts?

In Western Australia it is when the vine is coming out of dormancy that damage to vine tissue usually occurs. Tissue sensitivity to frost differs in grapevines. Leaves are the most sensitive followed by flowers and petioles (Hedberg) 2000). Stems and roots can be damaged by frost but this is not common.

During dormancy grapevine buds differ in their sensitivity to freezing temperatures. The primary latent bud has been recorded as being up to 10o C more susceptible than the secondary latent bud (Stergios and Howell, 1977). Dormant canes are resistant to frost damage. Damage to dormant canes has not been recorded in Western Australia during winter months.

Air temperature indicators when damage to vine tissue may occur are (Hedberg) 2000):

-3.5o C or less woolly bud stage (continued periods can kill the primary bud*)
-2.0o C or less early budburst
-0.6o C or less shoots up to 15 cm long
0o C or less shoots 15 cm and longer

*A grapevine compound bud (winter bud) contains three dormant buds: the primary, secondary and tertiary bud. The primary bud is the one that normally grows. If that shoot is killed the secondary and possibly the tertiary bud will usually develop. However, these other buds tend not to be as fruitful as the primary bud.

What are ice nuclei and cell solutes and what have they to do with frost damage?

Ice nuclei help to change water from liquid to ice. Dust is an ice nuclei that can change rain into hail or snow. Super-cooling is the capability of water to cool to temperatures below zero without freezing. Pure water has been super-cooled to -38o C when ice nuclei were absent (Hedberg, 2000). Super-cooled water will remain unfrozen if it maintains its isolation from any nucleation event. In plants, such as grapevines, the ice nuclei are tiny bacteria from the Pseudomonas family. These bacteria cause the water in the vine to form into ice when climatic conditions are cold enough. When present in large number, plant tissue freezes at temperatures close to 0o C. If ice-nucleating bacteria are not present plant tissue can super-cool to temperatures as low as -5o C without freezing (Lindow and Connell, 1984). Plant cell solutes help to reduce ice formation.

Younger vines can be killed while older vines tend only to have damage on new growth or on immature canes from frost. This is because young vines and new vine tissue contain low levels of plant solutes compared with older vines and mature vine parts and are thus more prone to frost damage.

Are frosts of any benefit to the vine?

Winter chill is required in vines to ensure winter dormancy. Frost on dormant vines in winter help to establish the normal seasonal cycle and help with even budburst (Nash, 1978).

What season are frosts of greatest concern in Western Australia?

Spring frosts are of greatest concern as they are the most common seasonal frosts that occur in vineyards in Western Australia. Spring frosts damage new spring growth. Autumn frosts are also of some concern as they damage leaves and bunch stalks, preventing sugar accumulation in berries. Winter frosts in Western Australia tend not to be of concern, as the air temperatures do not get cold enough to cause damage to the dormant vine parts.

What is freeze injury?

Freeze injury or winter kill is when very low temperatures damage permanent over-wintering vine parts. Temperatures below -15o C are usually required to cause freeze injury (Mullins et al, 1992) and some grapevines can survive temperatures as low as -20o C at complete dormancy (Hedberg, 2000). Temperatures above this tend not to cause damage because acclimation to freezing temperatures is a normal aspect of grapevine physiology. Dormancy is the period that grapevines acclimatise to frost and freeze injury. These very cold temperatures that cause freeze injury or winterkill also have the capacity to split vine trunks. This gives opportune pathogens an entry point (e.g. crown gall).

How do you predict a frost event?

Three atmospheric indicators can predict frosts (Vagnarelli, 1998). These indicators are:

  • forecasts of a minimum temperature of 2o C or less
  • dew point temperature of 2o C or less and
  • a stationary high-pressure system overhead with a pressure reading of 1025 hpa or more.

The dew point is the temperature that the air is to be cooled for it to become saturated (Penman, 1955). Black frosts occur without dew and are thus not an indicator for these types of frosts.

The reason forecast temperatures of 2o C or less being a frost indicator (even though frosts do not occur until ground temperatures reach 0o C or less) is because the Bureau of Meteorology temperatures are recorded at 1.2 m above ground in a Stevenson screen. Thus, a ground temperature of 0o C may correspond to a screen temp of 2.2o C or more (Linacre et al 1977). As a rough gauge the cordon wire and thus height of the new spring growth would be the same height as the Stevenson screen, except for those vines that have only been planted in recent years.

References and further reading

  • Anon. (2000) A different way to fight frost. The Australian Grapegrower and Winemaker, No. 438, Ryan Publications, Adelaide.
  • Bureau of Meteorology (BoM) http://www.bom.gov.au
  • Cashman, G (2000) Advection frost: a case study of the freeze of 27-28 October 1998 and its effects in the vineyards of the Canberra district. Part 1:Meteorological aspects. The Australian Grapegrower & Winemaker, No. 438, p 74-84, Ryan Publications Adelaide.
  • Cashman, G. (2000) Advection frost: a case study of the freeze of 27-28 October 1998 and its effects in the vineyards of the Canberra district Part 2: Vineyard impacts, The Australian Grapegrower & Winemaker, No. 439, p22-27.
  • Coombe B.G. and Dry P.R. (eds) (1988) Viticulture Volume 1 Resources, Winetitles, Adelaide.
  • Coombe B.G. and Dry P.R. (eds) (1992) Viticulture Volume 2 Practices, Winetitles, Adelaide.
  • Corby, L. (2000) Crystallising protection ideas against frost. The Australian Grapegrower and Winemaker, No. 438, p71-73, Ryan Publications, Adelaide.
  • [Expired]
  • Foley, J.C. (1945) Frost in the Australian Region, Bulletin No. 32, Commonwealth Meteorological Bureau.
  • Grape and Wine Research and Development Corporation Annual Reports
  • Http://www.gwrdc.com.au
  • Hedberg, P. (2000) The key factors influencing frost damage. Australian Viticulture Vol. 4. No. 4, Winetitles, Adelaide, p18-22.
  • Ingels C.A., Bugg R.L., McGourty G.T. and Christensen L.P. (eds) (1998) Cover Cropping in Vineyards - A Grower's Handbook, University of California, Division of Agriculture and Natural Resources, Oakland, Publication 3338.
  • Linacre, E and Hobbs, J (1977) The Australian Climatic Environment, Jacaranda, Wiley Ltd.
  • Lindow, S.E. and Connell, J.H. (1984) Reduction of frost injury to almond by control of ice nucleation active bacteria. J. Amer. Soc. Hort. Sc. 109(1) pp48-53.
  • McAulay, K. (2002) Wind machine principles. The Australian and New Zealand Grapegrower & Winemaker. No. 462. P109-110, Ryan Publications, Adelaide.
  • Mollah, M. (1997) Practical Aspects of Grapevine Trellising, Winetitles, Adelaide.
  • Mullins, M.G., Bouquet, Alain. and Williams, L.E. (1992) Biology of the Grapevine, Cambridge University Press, Cambridge.
  • Nash, G. (1978) Establishing your own vineyard. Thomas Nelson Australia Pty. Ltd.
  • Penman, H.L. (1955) Humidity, Unwin Brothers Ltd, Woking & London.
  • Stergios, B.G. and Howell, G.S. (1977) Effects of defoliation, trellis height and cropping stress on the cold hardiness of Concord grapevines. American Journal of Enology and Viticulture 28, p34-42.
  • Thomas, F., Mayse, A. and Chaney, D. (1993) Cover crop selection and management in orchards and vineyards, University of California, Davis.
  • University of California (1992) Grape Pest Management - Second Edition, University of California, Division of Agriculture and Natural Resources, 3343.
  • Vagnarelli, B (1998) 'Grape production losses usually occur when frost strikes vines. The Australian Grapegrower & Winemaker, No. 415, p69-72, Ryan Publications, Adelaide.
  • ViniCable New Zealand email vini.cable@voyager.co.nz ph +64 025 539 338
  • Walsh, J. (2000) Crucial factors to consider in buying wind machines. The Australian Grapegrower and Winemaker, No. 438, p73, Ryan Publications, Adelaide.
  • Winkler, A.J., Cook, J.A. and Lider, L.A. (1974) General Viticulture. University of California Press.

Page updated September, 2005

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