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Ministry of Agriculture, Food and Rural Affairs

SUN BURN (sun scald)


  • Grape berry surfaces become brown and shriveled
  • Flesh of berries may be discoloured (browning)
  • Affected area may sink down to the seed and become flattened
  • On the portions of the cluster exposed to direct sunlight

Often Confused With
Hail – occurs after severe weather; often leaves will also sustain injury

Black rot – black fruiting bodies; infected berries on both sun and shaded sides of cluster

Sun burn can be a significant problem following extreme heat spikes - particularly after veraison when berries begin to soften. Direct sunlight on unprotected clusters, typically on clusters that had previously been in shade, is common. Drought conditions may worsen the effects, as well as management practices like substantial leaf removal, excessive summer pruning, and shoot positioning that moves clusters from shaded positions in the canopy to full sunlight exposure.

Affected berries contain less soluble solids (sugars) and tartaric acid than normal, and alcohol and acetaldehyde accumulate in the affected tissues.

Period of Activity
After leaf removal, summer pruning, shoot positioning or other canopy management practices in mid-to late season.

Scouting Notes
Injury may be more severe on the west and south sides of the canopy on fully exposed clusters after recent leaf removal and several hot sunny days.

Management Notes
Remove leaves near clusters early in the growing season (after bloom and no later than pea size berries) to enable clusters to acclimate to high levels of sunlight and temperatures.

Remove leaves only on the east side of the canopy for white cultivars.

Do not completely strip the fruiting zone of leaves.

Sunburn on berriesClick to enlarge.