Quick Identification Guide to Apple Postharvest Defects & Disorders Cards

Fruit Finish

The Fruit Finish section of the card set includes sun and heat induced disorders found in Washington apples. This includes sunburn browning, sunburn necrosis and photo-oxidative sunburn (previously refered to as Type III sunburn). At a later date more cards may be developed for this section which would include any emerging or reclassified disorders. For ordering information vist the Additional Information section of the Introduction. The cards shown below are slightly modified to accomodate web formatting. Figures may appear fragmented in some browsers. Please report viewing problems here. Any reproduction of the card images or content without permission is in violation of WSU Copyright policies.

FRUIT FINISH : Sunburn Browning
	Sunburn browning is the most common form of sunburn. The symptoms appear as a yellow, brown or dark tan spot on the sun-exposed side of the apple. This disorder is induced by ultraviolet-B radiation from sunlight along with high fruit surface temperature. The sunburned area may contain desiccated lenticels depending on severity.
*Figure 1:* Sunburn browning on Golden Delicious. *Figure 2:* Sunburn browning on Fuji.

FRUIT FINISH: Sunburn Necrosis

Sunburn necrosis is heat-induced while the fruit is on the tree. Like Sunburn browning, it occurs on the sun-exposed part of the fruit, but UV-B is not a major factor. When the fruit surface temperature exceeds 126 degrees F for as little as 10 minutes, skin cell death occurs, resulting in a dark brown or black (necrotic) spot that appears later. Cracking of the affected area is common.

Figure 1: Sunburn necrosis on Granny Smith.

Figure 2: Sunburn necrosis on Red Delicious.

Figure 3: Sunburn necrosis on Gala.

return to top

FRUIT FINISH: Photo-oxidative Sunburn

Apples that are suddenly exposed to sunlight after growing in shade, as would occur with hand thinning or late-season pruning, may develop photo-oxidative sunburn. Unlike the previously mentioned sunburn forms, this is neither surface temperature, nor UV-B dependent. In addition to happening on the tree, it can also occur after harvest if apple bins are left sitting out in the sun in the field, on a truck, or at the loading dock.

Appearance of photo-oxidative sunburn varies by severity. In general, it appears first as whitened peel (i.e., photo-bleaching) with browning appearing later.

Figure 1: Photo-oxidative sunburn on Granny Smith with slight browning.

Figure 2: Photo-oxidative sunburn on Red Delicious with darker browning.

return to top

Secondary content using h2 tag. Column 2

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Heading using the h3tag

Tree Fruit Research & Extension Center, 1100 N. Western Ave, Wenatchee, WA, 509-663-8181, Contact Us

Tree Fruit Research & Extension Center