Sun Scald Protection

Sunscald, sunburn and Solar injury are all used interchangeably. Although some research differentiate between them, here we use sunburn, sunscald and Solar injury to refer to damage on fruit and leaves by exposure to solar radiation in addition to excessive heat.

Beyond sunburn symptoms, affected fruit usually show other skin disorders, such as lenticel marking, and sunburn may predispose affected fruit to develop postharvest physiological disorders such as ‘Fuji’ stain, sunburn scald in ‘Granny Smith’ or internal browning. Also, various pathogens may gain entrance into the fruit through the affected area. Most of these disorders make fruit unmarketable.

The economic impact of fruit and plant wastage due to sunburn can be significant, affecting both individual growers and the broader agricultural industry. Sunburn damage occurs when fruits and plants are exposed to excessive sunlight and high temperatures, leading to a range of negative consequences. Temperature threshold can be as low as 28°C for tomatoes and yield might be effected as much as 50%. In most apple orchards, sunburn causes losses averaging 10% annually. In warmer climates such as Australia, South Africa, Spain, Italy, Turkey and Chile losses in unprotected orchards can often reach 30% to 40%

Sunburn Necrosis

It is the most readily visible type of sunburn, with a dark brown or black necrotic spot on the exposed fruit surface In most environmental conditions it occurs when the apple fruit surface temperature (FST) reaches 52 ± 1◦C for only 10 min

Sunburn Browning

It is the most prevalent type of sunburn occurring on attached sun-exposed fruits. The discoloration associated with Sunburn Browning has been correlated to decreased concentrations of chlorophylls and anthocyanins and increased concentrations of carotenoids and quercetin glycosides in the peel

Photooxidative Sunburn

The first symptom of Photooxidative Sunburn is a white spot that appears on previously shade-grown fruits that are suddenly exposed to full sunlight. Research indicates that it is related only to solar radiation in the visible range

Riesling grapes sunburn necrosis

Damage caused by sunburn necrosis in Riesling. 47% of berries were damaged due to a sunburn event occurring on July 25, 2019. Picture was taken on September 30, 2019, at 19.5°Brix in Geisenheim, Germany.

Chemical reflectants such as kaolin and calcium carbonate (CaCO3) have been trialed with success in different fruit crops. Kaolin is an inert white clay that can reflect UV and IR and reduce FST (Fruit Surface Temperature). Application of kaolin reduced FST by 1°C and sunburn severity by 12.5%, while fruit quality remained unchanged or even increased.

Image Caption

Sunburn in Grapes: A Review *

Gambetta JM, Holzapfel BP, Stoll M and Friedel M

CaCO3 acts in a similar way to kaolin.In Red Roomy grapes sunburn incidence was reduced from14.8–15% (control) to 1.7–2% when a 2% CaCO3 solution wasapplied. Results from trials on grapes, as well as on pomegranate fruit treated with kaolin have shown an increase in total polyphenols, anthocyanin, and ascorbate content

Image Caption

Sunburn in Grapes: A Review *

Gambetta JM, Holzapfel BP, Stoll M and Friedel M

Protect Crops with Natural Minerals


Kaolin, an inert, white hydrated alumino-silicate is used to cover susceptible fruits and leaves with a reflective thin film. This film does not restrict breathing of the plant, enhances photosynthesis, protects from parasites and is readily washed away pre or post harvest.

Calcium carbonate

Calcium carbonate provides a white, highly reflective cover on fruit surfaces that increases reflection of solar radiation, a key aspect of reducing sunburn incidence


Similar to other Particle Film Technology minerals, Talc provides decrease in surface temperature and prevents sunburns. Talc has the additional benefit of ease of completely removing the white residues from the stem-end and calyx areas of the fruit at harvest

It's important to note that the effectiveness of these minerals as sun burn protectants can vary based on factors such as climate, solar irradiation, altitude, crop type and management practices. 

Types of sunburns depicted here are excerpted from :Racskó, J. and Schrader, L.E. (2012) Sunburn of Apple Fruit: Historical Background, Recent Advances and Future Perspectives. Critical Reviews in Plant Sciences, 31, 455-504.

doi: 10.1080/07352689.2012.696453

* Excerpted from :Gambetta JM, Holzapfel BP, Stoll M and Friedel M (2021) Sunburn in Grapes: A Review. Front. Plant Sci. 11:604691.
doi :10.3389/fpls.2020.604691