Common Name: Sunburn/sunscald
Type: Plant Damage
Major Identifying Features: Solar radiation
Life Cycle: Not considered as a pest
Pest Rating: Not considered as a pest
Management Rating: Very difficult
Host/Season/Outbreak Information: Summer, exposure to sun, unhealthy roots, sunscald in winter (Sierras and mountains)
Damage Information: Damage to bark, foliage, fruit, and other aboveground plant parts caused by excessive exposure to solar radiation. Injury mostly on the south or west sides of plants and on the upper side of horizontal branches, sunscald can resemble certain canker disease pathogens, water deficit, and certain other disorders. Sunburn may discolor bark and bark can ooze sap, it can crack, peel and become susceptible to pathogens. Broadleaf foliage may appear silver, glazed, or reddish-brown, necrosis can appear on tips, margins and between veins. Young stems and bark is very susceptible to sunburn, especially when they were grown close together in the nursery. The removal of structures and trees that provide shade can also lead to sunburn. Sunburn is common in new plantings that lack a solid root system. Anything that makes roots unhealthy or prevents them from absorbing water can lead to sunburn.
Sunscald is winter injury to bark caused by rapid temperature fluctuations, most common in mountain areas
Management Options: Plant where roots will have adequate soil volume and sufficient growing space. Choose plants that are well adapted to local conditions, plant properly and provide proper cultural care including over irrigation. Encourage desired plant structure by pruning when plants are young, retain branches that shade the trunk, avoid pruning during summer and do not remove more than 20% of plant tissue per growing year. Apply mulch to retain soil moisture, apply white interior (not exterior) latex paint diluted with water to young trees and plants, provide partial shade. Some companies are inventing plant-based or clay-based substances that can be sprayed onto plants in order to protect them from sun radiation.
Dreistadt, Steve H., and Jack Kelly Clark. Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide. Oakland, CA: U of California, Agriculture and Natural Resources, 2016. Print.