Fruit trees can be subject to many different types of pests that severely reduce the quantity of harvestable fruit and even threaten the livelihood of the tree itself. Many insects attack ripening fruit. Birds, deer and other animals are often a nuisance in home gardens and commercial orchards. Fungal diseases affect all types of fruit, from mangos to grapes. And freezing temperatures can decimate an entire orange orchard.
Citrus trees are especially likely to attract aphids, scale insect, spider mites and mealybugs. Slugs and snails can crawl up the tree and eat forming fruit. White flies are a common pest that attacks many types of fruit trees, as are leaf miners. Fruit flies are not picky about the type of fruit they "sting," laying their eggs inside ripening fruit. The eggs hatch into wormy larvae or maggots, which in turn eat the fruit as it ripens. Other bothersome insects include the tarnished plant bug, codling moth, redbanded leafroller, peachtree borer and American plum borer.
Deer often damage fruit trees such as apples by gnawing the bark, young twiggy growth and flower buds. Male deer rub their antlers on fruit trees and can take down a young tree. When bears are present, they also pose a threat to fruit trees, seeking and consuming the sweet fruit. Birds are often a pest in orchards, where they can decimate large numbers of ripe fruit. Opossums will climb fruit trees, even lemon trees, and make large gouge marks on ripe fruit. Fruit bats, common in tropical and subtropical areas, can also inflict major damage on fruit trees.
Fruit trees can develop numerous fungal diseases. Leaf rot, root and fruit rot, apple scab, blights, cankers, rusts, galls, leaf spot, scorch and mildew are some of the most common diseases that can afflict fruit trees. Anthracnose fruit rot is common on mango trees in tropical regions that receive large amounts of rainfall.
Although freezing temperatures are not usually considered a "pest," they kill ripening fruit and can kill some fruit trees, such as citrus, when the mercury drops below freezing for prolonged periods of time. Many entire Florida orange harvests have been ruined over the years by cold weather at the wrong time of year.