Tips For Cedar Apple Rust Control

by johnah on November 20, 2020

Cedar apple rust control is one of the most common problems in our country. Caring for your trees and their branches from cedar apple rust is not easy, but it’s doable if you have good knowledge and care. If you are looking for something to protect your trees from cedar apple rust, then this article will give you some ideas about what can be done to prevent or treat cedar apple rust on apples.

What Is Cedar Apple Rust?

Cedar apple rust (aka “carpenter apple”) is a fungal disease that affects both hardwood and coniferous trees. It is caused by the fungus Phytophthora ramorum. The infection causes dark brown spots on leaves and fruit. Trees infected with cedar apple rust often die within two years after being affected, while healthy trees may live for several decades without any symptoms at all.

The main symptom of cedar apple rust is the appearance of dark brown spots on leaves and fruit. These spots are actually small clusters of spores called mycelia. Mycelia produce tiny roots that feed off nutrients in the soil, which eventually lead to new infections spreading throughout the tree. Once infected, trees become weak and eventually die due to lack of energy. Some species such as Douglas firs may survive up to five years before they succumb completely to cedar apple rust.

Where Did The Name Cedar Apple Rust Come From?

The name cedar apple rust is a result of the common host for the fungus. While it is possible for many species to get infected by cedar apple rust, such as junipers and apples, it is most commonly found on true firs and apples.

True firs and apples both belong to the rose family. Their leaves are actually very similar at times, which is why the fungus easily invades them. The apple trees provide a growth medium for the fungal spores to grow and spread, while the firs provide a nutritious food source for the fungus.

What Trees Are Susceptible To Cedar Apple Rust?

There are many trees that are susceptible to cedar apple rust. True firs, Douglas firs, balsam firs, and cedars are the most common types of trees to get infected. Other types of trees that are susceptible to cedar apple rust are:






Ash trees

How To Prevent Cedar Apple Rust Infection?

There are several ways to protect your trees against cedar apple rust. These are:

1. Plant New Trees Away From Infected Ones

If you have an infected tree in your yard, it is best to plant new trees at least 50 feet away from the infected ones. New trees have stronger immune systems and are less likely to get infected with cedar apple rust.

2. Cut Down Infected Trees

If you have an infected tree, it’s best just to cut it down and remove it from your yard. Make sure to dispose of the wood properly to prevent the spread of cedar apple rust. Dispose of it by either chipping it or putting it in the dump. Don’t just leave the wood on the ground as this can lead to new infections in your area.

3. Apply Lime Sulphur Or Herbicide

Once a year, apply either herbicide or lime sulphur on your trees. This helps kill off fungal spores that could lead to infection. It’s important to note that this isn’t a perfect solution as some fungal spores can still survive. The herbicide is only effective for one year, so you will need to re-treat the trees after a year to ensure none of the spores have survived.

4. Plant Susceptible Trees Away From Infected Ones

If you only have a few infected trees in your yard it might be best just to plant new trees away from the infected ones. This ensures that your new trees aren’t exposed to the fungus until they are big enough to resist it.

5. Bake Seeds Before Planting

If you get seeds from an infected tree, it’s important to either bake them or soak them in water before you plant them. This ensures that the seeds aren’t viable and can’t grow into fungal infected trees.

6. Dispose Of Sawdust Properly

When you perform routine tree cutting in your yard, make sure to dispose of the sawdust properly. Don’t just leave it on the ground as this can lead to new fungal infections in your trees and other parts of your yard.

7. Plant Deciduous Trees

Because the fungus only becomes a problem in the summer months, you can get away with planting deciduous trees. These trees lose their leaves during the summer months and don’t get the nutritional benefit from the leaves that the fungus needs to grow. This prevents them from getting infected.

What Are The Symptoms Of Cedar Apple Rust?

There are several different signs to look out for if you think your tree is infected with cedar apple rust. These include:

Tips For Cedar Apple Rust Control at

Unexplained yellowing of leaves in the summer

Red or orange spots on the leaves

Browning and dying of branches

Unexplained apples with red spots on them

How To Treat An Infected Tree?

If you think you have an infected tree in your yard, there are several steps you can take to try to stop or slow down the spread of cedar apple rust. These include:

1. Weekly Watering Of Trees

One of the best ways to try to stop the spread of cedar apple rust is to ensure your trees are constantly hydrated. This means watering your trees every single week during the summer when the fungus is most active. Keep an eye on your lawn to see if it’s getting dry and then water accordingly. Keep doing this all the way up until harvest time when you pick your apples.


Sources & references used in this article:

Susceptibility of selected juniper cultivars to cedar-apple rust, Kabatina tip blight, Cercospora needle blight and Botryosphaeria canker by NA Tisserat, JC Pair – Journal of Environmental …, 1997 –

The hosts, life history and control of the cedar-apple rust fungus Gymnosporangium Juniperi-virginianae Schw by IH Crowell – Journal of the Arnold Arboretum, 1934 – JSTOR

Evaluation of alternative fungicides for organic apple production in Vermont, 2007 by ML Cromwell, LP Berkett, T Ashikaga, HM Darby… – Plant Dis. Mgt. Rpt, 2008 –

Gymnosporangium juniperi-virginianae (cedar apple rust) by IS Compendium –



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