Sodium orthophenylphenate (SOPP) is the fungicide most widely used to control decay in apples and pears. It is highly alkaline and is likely to cause injury if the fruits are exposed to it for several minutes, or if a clear water rinse does not follow treatment. Injuries from overexposure are brown to black. They range from less than 1/16 to more than 1/8 inch in diameter. Injuries may develop around the lenticels or at breaks in the skin, or larger areas of skin may be killed and discolored. The underlying tissues are usually unaffected, but the spots may become sunken when moisture is lost through the injured skin. An injury associated with both overexposure and failure to rinse after treatment occurs in the calyx (see photo). The fungicide absorbed by persistent calyx parts kills the skin around the calyx. Subsequent desiccation results in shrinking and cracking of affected tissues, producing a sunken, brown area up to 1/2 inch in diameter around the calyx.
This injury can be prevented by manually removing and rinsing fruits from the disinfecting section of a packing line during equipment failures, and by using sufficient water in the rinse to reduce residues below toxic levels.
Sodium orthophenylphenate injury