How to Diagnose Cedar Tree Pests & Diseases


Part of the pine tree family, cedars (Cedrus spp.) are large trees that can grow up to 100 feet in height and have needlelike leaves. Cedars are evergreen coniferous trees that usually have few disease or insect problems, although they can be susceptible to the same pests and diseases that attack other tree species in the pine family. Common cedar tree species include the incense cedar, American arborvitae, Eastern red cedar and red cedar. The most common problems for cedar trees are bark beetle infestations and injuries from droughts.

Cedar Tree Pests

Step 1

Identify a bark beetle infestation by looking for sap-flowing "pitch tubes" on the bark of your cedar tree, accompanied by sawdustlike deposits in the bark crevices. You'll also see holes in the bark and dead branch tips.

Step 2

Look for small insects feeding in groups on the leaves or stems of your cedar tree to spot an infestation of the giant conifer aphid. With heavy aphid infestations, you'll see stunted shoots, yellowing leaves and a sticky liquid covering the leaves that the aphid secretes, called honeydew.

Step 3

Diagnose infestations of armored scales, such as the Latania and pine needle scales, on your cedar tree by looking for wilted, yellowed and dropping leaves. The armored scale insects have plated, flattened coverings on their bodies that are about 1/8-inch wide.

Step 4

Spot an infestation of nematodes, particularly the root knot and pinewood nematodes, on your cedar tree by looking for branch dieback and the presence of longhorned beetles or roundheaded borers, to which the nematodes attach themselves. Nematodes are eel-like worms that are so miniscule you cannot see them well with the naked eye.

Cedar Tree Diseases

Step 1

Diagnose canker diseases in your cedar tree by looking for discolored, dead tissue on a branch, stem or trunk that is at first sunken in appearance and then becomes surrounded by callus tissues. The infected bark sometimes oozes a resinlike substance and the foliage on the diseased branch will turn yellow or brown and wilt.

Step 2

Look for yellow, orange or reddish spots on the underside of the leaves on your cedar tree to identify rust fungal diseases. You may also see gel-like orange masses, as well as galls or swelling tissues on the infected branches and stems.

Step 3

Spot crown, collar or root rots in your cedar tree by discolored, stunted and prematurely dropping leaves with branch dieback. Cedar trees that are infected with the Phytophthora fungus will often have a vertical cankerlike stain on the trunk.

Step 4

Look for pink or tan discoloration of the needles and new shoots on your cedar tree to diagnose needle blight. Needle blight is usually caused by a fungal disease and can cause twig dieback.

Tips and Warnings

  • Don't confuse armored scales with the Monterey cypress scales, which can also infest cedar trees. Monterey cypress scales create waxy white threads on the bark, underneath which are the tiny, immobile scale insects.


  • UC IPM Online: How to Manage Pests -- Cedar, Cedrus spp.

Who Can Help

  • Cedar Trees
Keywords: cedar tree pests, cedar tree diseases, cedar tree insects

About this Author

Sarah Terry brings 10 years of experience writing novels, business-to-business newsletters, and a plethora of how-to articles. Terry has written articles and publications for a wide range of markets and subject matters, including Medicine & Health, Eli Financial, Dartnell Publications and Eli Journals.