Do your trees have cedar apple rust?

Cedar apple rust
The galls of cedar apple rust resemble an orange gelatinous mass when active. John Zvirovski / The Sun

Every year each of us is faced with different issues in the garden. There is always a challenge we may face from year to year. Many of us know what they are as they always present many solutions on how to deal with them. One of those challenges happens to be that of the cedar apple rust on our cedars, junipers and various apple species.

At first we are not sure what we are dealing with as they mimic many other issues. But cedar apple rust attacks the leaves first and then moves from there. Within a couple of weeks of infection, small yellow spots begin to appear on the leaves eventually turning to orange or brown. Sometimes there is a combination of the colors on the leaves. Eventually, this fungus infection will cause the leaves to drop prematurely. In apple species, it will affect the production of fruit also as it attacks early on when the trees are in bloom.

In order for this fungus to occur, two host plants are necessary within a 1-2 mile radius. In the urban setting that is not difficult to come by. Two host plants would include a juniper species, an apple tree or crabapple tree, a hawthorn or a quince. Two of these items are what is required for the fungus to move back and forth by spore in order for the fungus to actively take effect.

The spore moves either via insect or wind from a juniper species to one of the others. Then they return to the original plant to produce a hard round formation called a gall. This gall will begin as the size of a pea and may grow from there. The first year it just attaches to the branch and is not activated until the following year when the warm spring rains begin.

The gray- to brown-colored galls when inactive are hard with small little bumps on them. When the warm spring rains begin, the small bumps develop small reddish-orange arms that resemble tentacles. When completely active, these armed galls look like a soft gelatinous mass. It is at this time that the spores are released. If you are familiar with our region, you will know that the spring season brings with it many windy days to transport these sporing bodies. These will move to any of the other host species in which they cause damage. This transfer usually happens during the time that the trees begin to bloom. It is at this point that they enter both the fruit and the leaf structures and even the stems. Repeated annual infection will eventually cause the tree to go into stress ultimately resulting in death if it goes untreated. Keep in mind the fungus cannot be transported from apple tree to apple tree or from juniper to juniper. It moves from one species to another.


Often people think that the cedar or juniper is the problem, but they are affected by the galls also as wherever that attaches to the stem, the branch eventually dies beyond that point. I had a ‘Skyrocket’ juniper in the backyard once that I adored, but it got these galls and started to die back. Given I already had a large apple tree, a crabapple and a hawthorn, I eventually had to dig it out and get rid of it. I no longer had the problem after that removal.

As with any challenge, there is always a solution to amend the issue. The first form of combat is to select species that are not susceptible to the cedar apple rust. In apple trees, these may include Red Delicious, Freedom and Liberty. If you are concerned about crabapples you might seek out Royalty, Prairiefire, Candymint, Dolgo and Special Radiant, to name a few. Keep in mind that resistance means that they are less susceptible to the problem but they still have the ability to fall prey.

There are numerous fungicides out there you can pursue for early spring application also. Always apply these fungicides before the symptoms begin to show. This is usually when the tree begins to bud out and starts to bloom. Application will need to be done every 7–10 days with up to four applications. The most effective fungicides happen to be Copper Fungicide and Spectricide’s Immunox. Along with spraying your apple trees, eliminate the sporing bodies from your junipers when you notice them in spring to eliminate the amount of spores in your vicinity. When removing these galls from your juniper species, cut the stem 4–6” back from the gall formation and dip your pruner in a bleach solution each time to avoid spreading the fungus.

Cedar apple rust may not affect everyone, but for those who have the problem, these suggestions may just assist you towards a more problem-free environment. If you noticed this fungus in your garden this season, attack it right away in the spring when things begin to bud out and you will find great success in the process with maybe a little less worry through the growing season.

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