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The most common issues affecting apple trees in eastern Idaho and how to deal with them

In the Garden

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Fireblight on an apple tree branch | Courtesy Reed Findlay

Apple trees are the most reliable large fruiting trees in eastern Idaho, and since they are planted in almost every yard, there also tends to be a high incidence of apple-related diseases and insect issues since. Here is a short list of the most common issues people have with their apples.


Fireblight is the most common bacterial infection in eastern Idaho. A wet spring, coupled with windy conditions during blossoming creates the perfect storm for a large outbreak of fireblight. This bacteria infects pears, apples, and roses, and if a tree or shrub is infected bad enough, it can kill it. Some of the ways to manage this disease is to prune out infected wood in the correct method, scout for signs of infection throughout the season, and do your annual pruning in March while avoiding any bad storms so the plant has time to dry out the wound after pruning. There are chemical sprays available on the market that can help manage this disease. It is essential to follow label directions exactly if you apply those products.


Woodpecker damage to an old apple tree | Lance Ellis,

Sapsucking woodpeckers can cause unsightly damage to apple trees and while the damage they create may not kill the tree itself, it can open the tree up for infection to pathogens. Woodpeckers are a federally protected species, and cannot be shot or harmed. The best way to reduce their damage is by using scare devices. Contacting the Idaho Fish and Game may be necessary to manage the issue.


Aphid damage on an apple trees first leaves in spring | Lance Ellis,

Every spring there are aphids that attack new apple tree leaves that are just breaking out, causing them to not unfurl correctly and become disfigured on the end of the new leaves. While many people react by getting something out to spray and kill the aphids, you can also just wait for the natural predators, such as ladybugs, to build up in sufficient numbers to take care of it. Additionally, the tree will continue to grow and lengthen its branches and develop new leaves that are not affected. You can also wash off the ends of the branches using a strong stream of water. In the Fall, the disfigured leaves will drop off the tree anyway, and it will be as though the damage never occurred.

Codling moths

Codling moth damage | Courtesy Ward Upham, Kansas State University

In our area, codling moths cause wormy fruit on apple trees. There are several chemical spray options you can choose to control these insects, and specifically, there are a couple of products labeled as being organic insecticides. For best success in controlling these damaging insects, the application timing is critical to stop them from infesting new developing fruit.

For questions on apple tree problems, contact the local county extension office, depending on what county you live in. If you live in Fremont County, you can reach Lance at (208) 624-3102.