Apples regularly come in contact with chemicals that are used to control diseases and to prevent insect injuries. Occasionally they also come in contact with chemicals in packing materials, in connection with refrigeration, or from some other source. A small amount of chemical injury may occur when chemicals are used under ideal conditions, but the chances for injury are much greater when pesticides are used carelessly, if unusual weather conditions follow spraying, or if the fruits are accidentally exposed to a toxic material. Chemical injuries that occur in the orchard generally do not reach the market, because the damaged fruits are removed during packing. However, injuries that occur during or following packing are frequently found on the market. Similarities in the response of fruits to several kinds of chemical injury make it difficult to determine the cause of the injury unless the history of the fruits is known. Several materials may cause identical injuries at the lenticels, while higher concentrations of some of the same materials or some entirely different ones may kill and discolor large areas of the skin or even penetrate the flesh.
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