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WEATHER DAMAGE



A leaf with a mosaic pattern of frost damage either in the bud or later
A leaf with a mosaic pattern of frost damage either in the bud or later
Photo credit: Peter Magarey
Look For Look For Notes

   LOOK FOR

    Look for in shoots
  • HEAT STRESS
  • Shoot tips, tendrils and shoot internodes that dry out in hot weather leaving a collapsed pith
  • Frost in autumn or winter
  • Portions of arms or canes in spring without shoots or with stunted growth
  • Frost in spring
  • Shoots, leaves and bunches which turn chocolate-brown to black within hours of a severe spring frost
  • LOWER PARTS OF THE TRUNK
  • Buds that fail to burst or produce stunted shoots
  • Restricted growth of shoots along some arms or canes
  • WIND
  • Light brown superficial markings of irregular shape on leaves, shoots or bunches
  • Partly broken shoots with:
  • - patchy or evenly-yellowed (or reddened) leaves
  • - bunches that shrivel, especially after flowering
  • - leaves that curl downward and colour later in the season
  • Completely broken shoots with leaves and bunches that collapse and rapidly dry to light brown. Leaves remain attached.
  • HAIL
  • Pitted and broken shoots
  • Irregular, raised callus around circular pitted marks, mainly on the windward side of shoots and canes
  • LIGHTNING
  • Shoots with green nodes and brown internodes
  • Dry shoots with a brown and separated pith

    Look for in leaves
  • HEAT STRESS
  • Young leaves that dry out and die
  • SUNBURN
  • Light brown patches on the backs of leaves
  • Frost in autumn or winter
  • Dead buds
  • Distorted leaves with irregular yellow-white speckling between the veinlets
  • HAIL
  • Torn or shredded leaves
  • LIGHTNING
  • Partially brown and wilted leaves, tendrils and bunch stems

    Look for in bunches
  • HEAT STRESS
  • Shrivelled bunch tips
  • Bunches with severe shrivelling after a heatwave
  • SUNBURN
  • Browning and shrivelling of berries

   CONDITIONS

  • HEAT STRESS
  • More likely when vines are water-stressed
  • Muscat, Gordo, Calmeria and Red Globe are particularly susceptible to water stress and heat damage.
  • SUNBURN occurs when shaded leaf or bunch tissue is exposed to direct light.
  • Sunburn typically occurs when foliage is repositioned during training or by the weight of crop neat harvest.
  • FROSTS & FREEZES
  • Cause ice to form inside cells, killing parts of the vine
  • Buds that freeze during a severe autumn or winter frost may die or produce stunted shoots or speckled leaves. Symptoms will appear after budburst.
  • Young shoots and bunches can be killed by frosts in spring. Symptoms will appear within 12 hours of the frost.
  • LOWER PARTS OF THE TRUNK can be killed by severe autumn or winter frosts in dry seasons. This disrupts the supply of water and nutrients to buds and young shoots, restricting growth in spring. The extent of symptoms, sometimes known as restricted spring growth, will vary between vines according to vine vigour or soil moisture content.
  • WIND
  • Usually seen only when both vine and crop are damaged
  • HAIL
  • Causes variable damage that may lead to botrytis infection of shoots, leaves and bunches
  • LIGHTNING
  • Dramatically kills vines in a small area
  • Damage may not be noticed until 5-10 days after a strike.

OTHER WEATHER DAMAGE IMAGES

Shoot-tip shrivel on succulent foliage after hot drying winds Sections of heat stressed shoots showing corky brown pith Developing tips of young bunches may die after a hot windy day, causing affected berries to raisin Extreme heat when berries are pea-sized can cause severe shrivelling on the exposed side of bunches Sunburn on the back of a recently exposed leaf Mild sunburn Green berries shrivelled by a heat wave just prior to berry softening Heat stress may only discolour berries when they sugar up Blackened sunken spots on Calmeria caused by heat damage Frost damage to young spring growth An example of restricted growth of shoots caused by freeze damage to lower trunks during dormancy An example of restricted growth of shoots caused by freeze damage to lower trunks during dormancy An example of restricted growth of shoots caused by freeze damage to lower trunks during dormancy A shoot bent over a wire by wing has restricted sap flow. Leaves (red varieties) have reddened and, being late season, have rolled downward A shoot nearly broken through by wind damage. Leaves (white varieties) turn yellow and later in the season will roll downward Close up of the damaged part of the shoot pictured at left Severe shoot damage from wind blown hail Hail usually damages only single shoots and some leaves Botrytis infection following hail damage Lightning often burns many vines in a row Brown internodes with green nodes and burnt leaves are typical of lightning damage Shoots affected by lightning have brown pith On vines struck by lightning, bunch stems turn brown and berries later shrivel and die

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