Monday, June 18, 2012

Protect Against Sunscald on Fruit

Sunscald on raspberries
One of the many frustrating things about producing fruit or vegetables is having perfect growth and the harvest which then can be a loss in sales. Sunscald is such a disorder.

Sunscald occurs on the south side of the plant and on one side of the produce. It affects many fruits and vegetables including apples, cucumbers, grapes, pepper, raspberry, squash, tomato and watermelon. In each case the symptoms are a bit different and create varied overall results on the harvest.

Tree fruit will show brown or gold skin that usually has a corky area below. The fruit is still edible and pathogens usually don’t attack. On vegetables and most small fruit, the area becomes bleached or tan and is often sunken into the vegetable. The area becomes susceptible to pathogens and will quickly rot and decompose. Raspberries are an exception as each individual drupelet becomes white and hard.

Exposure to sun and especially to long intervals of heat has the greatest affect on tissue. When the temperatures remain above 85° for as little as three days, the plant canopy is weak and there is a lack of cloud cover, sunscald may be an issue. Temperature is a force that cannot be changed but the amount of shade on the produce can.

A healthy plant that has a mass of leaf cover has fewer issues associated with sunscald damage. Good nutrient management and ample water supply as the plant develops will create a good canopy that can protect developing fruit and vegetables. If that leaf cover is not present then shade cloth is a possible solution to combat sunscald.
(by Sarah Denkler, MU Extension Southeast Regional Horticulture Specialist)

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