There is nothing quite as alarming as when you see your deep emerald juniper trees starting to turn brown. The Emerald Sentinel juniper, also known as the eastern red cedar, is highly resistant to disease and easily tolerates pests, drought, harsh weather and conditions that other trees could not survive. Its tolerance of harsh conditions is what makes the tree so long-lived and also why it is so shocking to see it dying.
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Types of Juniper Fungi
Three types of fungi attack juniper trees and cause blight, or the browning of branches that subsequently fall off and die. Cercospora, phomopsis and kabatina blights all cause the needles of the juniper tree to turn brown and then die. Cercospora blight makes all of the needles of the juniper tree turn brown from the bottom up and then fall off, with the exception of the tip ends of each branch. The tip ends remain green, which is the opposite of the phomopsis tip blight. Phomopsis only affects new growth, so only the tip ends of the tree branches turn brown and fall off. Kabatina blight is unable to attack new growth, so it only affects areas that are 1 year old. Quite often, this means that whole branches fall off until the tree dies.
How the Fungi Attack
The fungi infect the plant through a wound caused by animals, insects or weather damage. Spores infect the tree and spread through areas that are warm and wet. Prolonged periods of wetness can make the tree more susceptible to infection, especially if the tree is young or if blight fungi have attacked it in previous years. Once the tree's needles fall off, the fungus remains attached and can live for over a year waiting for a new host. Spores are released from the infected needles and can spread to other juniper trees.
Damage to Junipers
Blight damage to junipers can be severe, even leading to the death of the tree. Although young trees are more susceptible to death and have more difficulty recovering, even large, healthy trees can fall prey to blight. This is especially true if the trees have become reinfected with blight in subsequent years or if they were exposed to more than one type of blight at a time. Cercospora blight is slightly less deadly than the other two blights, simply because it usually takes three years to kill a tree, while phomopsis and kabatina blights can kill a tree in a single season.
Prevention and Treatment
You can take proactive steps to prevent the juniper tree from falling prey to blight. Make sure that the tree has adequate sun and space to spread its branches. When branches are hindered, such as by a fence near the tree, they can prevent the branches from drying out and cause warm conditions that spread the growth of fungus and bacteria. Prune trees only with cutting tools that have been disinfected between each tree. Do not use old juniper needles as mulch, and take care to use a fungicide as directed to prevent reinfection. Using resistant varieties of juniper from reputable nurseries also prevents many infections.
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