Junipers often have brown growths that look a little like human brains on their needles. These are one stage of cedar-apple rust, which is a fungus. After the spring rains, the fungus will be covered in orange tentacle-like growths that release spores. The spores are released from these growths called spore horns, and then infect apple trees causing brown or orange spots on the leaves later in the summer. Cedar-apple rust rarely does much damage to junipers and is simply unsightly, although some twig dieback may occur.

This disease is much more damaging to the apple trees that are the alternate host. Crabapples that are very susceptible to the disease may even drop their leaves after infection. Planting resistant varieties is the first step to preventing the disease. Also, avoid planting cedars and crabapples or apple trees close together if possible. For desirable trees that are susceptible, a fungicide can be sprayed on both crabapples and apple trees when the gelatinous tendrils first appear on the galls. Spray again every 7 to 10 days as long as the gelatinous galls are present on the junipers.  We recommend Fertilome’s F-Stop Lawn & Garden Fungicide. Junipers are generally not treated.

Cedar-apple rust on crabapples