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Pests and diseases

Apple trees are susceptible to fungal and bacterial diseases, and to damage by insect pests. Many commercial orchards pursue a program of chemical sprays to maintain high fruit quality, tree health, and high yields. These prohibit the use of synthetic pesticides, though some older pesticides are allowed. Organic methods include, for instance, introducing its natural predator to reduce the population of a particular pest.

A wide range of pests and diseases can affect the plant. Three of the more common diseases or pests are mildew, aphids, and apple scab.

Among the most serious disease problems is a bacterial disease called fireblight, and three fungal diseases: Gymnosporangium rust, black spot, and bitter rot. Codling moths, and the apple maggots of fruit flies, cause serious damage to apple fruits, making them unsaleable. Young apple trees are also prone to mammal pests like mice and deer, which feed on the soft bark of the trees, especially in winter. The larvae of the apple clearwing moth (red-belted clearwing) burrow through the bark and into the phloem of apple trees, potentially causing significant damage.