Diseases in Junipers

Junipers (Juniperus spp.) are a family of woody, cone-bearing, evergreen plants. Ranging in size from 4 inches to over 50 feet in height, these plants are popular in the home landscape as ground covers, screens, hedges and windbreaks, among other uses. They grow best in full sunlight and well-drained soil and are tolerant of a wide range of soil types. Junipers are susceptible to a number of diseases that may detract from their beauty or cause plant death.

Cedar Rust

Fungal infections sometimes occur when junipers and members of the rose family such as apple, hawthorn and quince are grown in close proximity. Junipers infected with cedar-apple rust develop rounded, smooth brown galls on their twigs that can grow as large as 2 inches in diameter. As the fungus matures, it sends out gelatinous, orange, tentacle-like, spore-containing structures that infect apple and crab apple plantings. Cedar-hawthorn rust produces similar symptoms, only with slightly smaller galls, while cedar-quince rust produces rounded galls covered by unremarkable mats of orange fungal growth.

Twig and Needle Blights

Cercospora needle blight, Kabatina twig blight and Phomopsis blight commonly damage juniper plantings. The Cercospora sequoiae var. juniperi fungus causes Cercospora needle blight. The needles at the bottom of the tree turn brown. The discoloration begins close to the base and extends outward, gradually moving up the trunk, killing the older shoot tips until only the current year's shoots remain. Diseased branches fall from the tree, leaving unattractive open spots in the canopy. This disease is most evident during the summer months. Symptoms of Kabatina blight usually appear during the earliest part of spring when the weather is still cool. The previous year's shoots lose their color and change to red, yellow, and finally brown, but they remain on the shrub for a long time after they have died. Grayish areas of diseased bark called cankers also appear on the stems. Phomopsis blight usually shows up in late spring or early summer. The Phomopsis juniperovora fungus attacks the new, immature shoot tips, which turn brown and die. Nancy Doubrava and J. McLeod Scott, information specialists from Clemson University, note that Phomopsis and Kabatina blights have very similar symptoms, but the main difference is that Phomopsis kills off that year's growth, while the Kabatina fungus attacks year-old shoots.

Root Rot

Phytophthora root rot occurs when junipers are planted in areas where the soil is warm and poorly drained. It can also occur after a period of prolonged flooding. The fungus attacks the roots, which change from a healthy white to a soggy brown. The outer part of the root sometimes peels away from the inner core. Sick plants may appear discolored or stunted. Left untreated, the disease continues to weaken the plant until it finally wilts and dies.

Other Disorders

The Botryosphaeria stevensii fungus that causes Botryosphaeria canker attacks trees that are stressed from weather-related causes such as prolonged drought or hard freezes. The foliage on juniper branches becomes discolored, and dark, diseased areas of bark, or cankers, appear near the base of shoots. Nematodes, which are tiny roundworms that live in the soil, sometimes feed on juniper roots, which allows bacteria and fungi to enter the plant and may lead to secondary diseases. Diseased plants may become discolored, their growth is often stunted, and they may lose their needles or leaves.

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