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Market Diseases of Apples, Pears, and Quinces
Formaldehyde Injury (Halo Spot) |
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Long exposure to low concentrations of formaldehyde will cause injury to Golden Delicious apples. The numerous, uniformly distributed brown to black spots are centered at the lenticels. They range from less than 1/16 to more than 1/8 inch in diameter. In the larger lesions the much-darkened lenticels are surrounded by halos of lighter brown tissue (see photo). Moisture loss from the injured tissues causes the larger spots to become slightly sunken. Formaldehyde liberated from urea-formaldehyde resins in packing materials has been found to be the cause of this type of injury. A switch to other types of resins for wet-strength in trays and cartons has virtually eliminated this problem.
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