Apple Tree Diseases & Insects

Updated February 21, 2017

Whether you have only a couple apple trees in your yard or an entire orchard on your property, you have to be willing to give your trees some extra care to protect them from insect invaders and diseases. When you focus on the proper care of apple trees, you can expect to be rewarded with a delicious fruit crop and attractive, healthy trees.


Several diseases have the potential to harm your apple trees and crops. Fire blight, powdery mildew and apple scab tend to attack early in the growing season and can result in malformed fruit, loss of leaves, and shoot and branch dieback. Some cultivars of apple, Jonathan among them, are susceptible to cedar apple rust, which causes yellow spots on fruit and leaves.

According to the North Carolina State University Plant Pathology Extension, the warm months of summer can bring black rot, white rot and bitter rot, along with sooty blotch and flyspeck. Sooty blotch and flyspeck cause cosmetic damage to apples, while white rot, black rot and bitter rot begin with a blemish on the skin of the fruit, working its way into the flesh of the apple.

Insect Pests

According to the Colorado State University Extension, codling moth, apple maggot, spider mites, scales, aphids, and white apple leafhoppers are the main insect pests of apple trees.

The larvae of the codling moth is what we normally refer to as the worms in "wormy" apples. Apple maggots tunnel through fruit leaving dark trails behind them. Spider mites, leafhoppers and scale insects suck on plant juices and cause poor yields and diminished tree health. Aphids can cause an apple tree to develop misshapen and mottled fruit.


Control of apple diseases and pests involves the use of fungicidal applications for apple diseases, and applications of horticultural oil, insecticidal soaps or insecticide sprays for insects, depending on the pest. Insect traps may also be used to help with timing of insecticidal sprays. Applications usually begin early in the season and may continue through harvest.

It is important to note that fungicides or insecticides, whether organic or inorganic may not be effective unless applied at the correct time, and at regular intervals thereafter. Also, insecticides should not be used until after petal fall, to reduce the prospect of killing pollinating insects.


Prevention is as important to controlling apple tree insects and diseases as using chemical controls. According to the Ohio State University Extension, many of the pests and diseases that attack fruit trees overwinter in or near the tree. By practicing good sanitation habits, you can eliminate much of the risk of pest and disease damage, removing the problems before they get a chance to attack.

Control weeds around trees, rake up and dispose of any leaf and tree litter on the ground, and prune and dispose of any dead, injured, or diseased branches and limbs.

Resistant Varieties

Planting disease-resistant varieties of apples will help you keep disease problems at bay, helping to reduce or eliminate the need for extensive spraying for fungal problems. Liberty, Goldrush and Empire are among the types of apple trees that have good resistance to a variety of diseases. Trees that are less prone to disease problems are generally better equipped to withstand insect attacks.

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About the Author

Leslie Lane has been writing professionally since 2007. Her areas of expertise include landscape and garden design; trees, shrubs and perennials; plant care; and plant pests and diseases. An education in landscape horticulture from Lansing Community College is paired with several years experience working for one of Michigan's premier wholesale/retail nurseries and growing farms.