If Your Cedar Tree Is Looking Sickly, These Diseases Might Be To Blame

There's nothing quite as majestic and imposing as a fully-grown cedar tree with its broad horizontal branches and fragrant evergreen needles in delightful shades of green and blue. Thanks to its almost graceful growth habit, the cedar makes an excellent shade tree. It's also one of the fruit and berry trees to grow in your yard that birds love — it's especially beneficial to nesting birds, and it provides a food source for small mammals such as squirrels. Plus, when grown close together and regularly trimmed, these evergreen trees can give you privacy all year round. As cedars can take a while to reach maturity, it can be somewhat concerning if you notice that your prize specimen is starting to look a little sickly. This might be caused by a number of diseases that can infect your cedar, including rust, sooty mold, root or crown rot, and twig blight.

Carefully inspect your tree so you can correctly identify the disease and take the necessary steps to save it, where possible. The most common diseases that affect cedar trees are fungal and can be treated if you notice them early enough. The exceptions are root or crown rots such as those caused by the Phytophthora or Heterobasidion annosum fungi. The best treatment for these fungal conditions is prevention. Ensure the tree is growing in well-draining soil, and don't overwater it. Some pesticides can help to control the diseases, but if the trees are large, these problems can be very difficult to combat. 

Twig or needle blight is most common amongst seedlings and young trees growing close to each other. Blight can also be prevalent during periods of wet weather. It causes the smaller branches and needles to turn brown and slowly die back. You might also find small black or brown spots on the infected tree parts. If you notice evidence of this disease, it's best to prune out the affected sections and destroy them. Spraying your cedar with a recommended fungicide is also a good idea, especially during wet weather.

Rust is another common fungal disease you should look out for. Evidence of this can be seen by the presence of galls or growths that are green to reddish-brown and corky. These can usually be found on smaller branches and needles in the fall. Once spring comes around, the galls will produce spores in the form of orange gum-like tentacles or horns. You may also see new shoot growth, which is bunched and commonly referred to as witches' brooms. While most rusts won't kill your tree, it's advisable to cut out the infected parts and dispose of them. You also want to avoid making a common mistake when growing Taylor juniper trees and other cedars, and that is planting these species anywhere near your apple trees. One type of rust disease known as cedar apple rust can also infect your fruit trees and spoil your harvest. You can apply a fungicide in the spring if your cedar is prone to rust disease. 

Sooty mold is another common cedar disease that is treatable because it's actually the result of an insect infestation from aphids, white flies, or scale. When these insects suck the sap, usually from young growth, they excrete a sticky substance known as honeydew. This results in the growth of the unsightly mold that will appear as black or brown blotches on the branches and needles. While the fungus will not harm your cedar, it's quite unattractive and might limit the tree's photosynthesis capabilities due to shading. Getting rid of the insects will stop the mold from developing. If the insect infestation is severe or you need to treat a large tree, often the best solution is to inject a systemic insecticide into the trunk. Ideally, it's advisable to call in a professional to do this effectively.

If you suspect your cedar tree has been infected with a disease but you lack the confidence to diagnose it correctly, this might be one of those times that you need a professional tree inspection. In most cases, a qualified arborist should be able to identify the disease affecting your cedar quite easily and give you the right information on how to treat it so that you can bring your tree back to full health. Of course, not all cedar trees that aren't thriving will be infected by a disease. You may also want to consider that the cedar isn't getting the care it requires because this could also cause browning foliage or stunted growth.