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Chicago Urban Gardening

The day to day experiences of a University of Illinois Extension Urban Horticulture Educator in Chicago, Illinois
evergreen needles browning

Evergreen Dieback Problems

Posted by Ron Wolford -

Many evergreen trees are experiencing needle dieback this year. According to Rhonda Ferree, extension educator in horticulture, the cold, wet spring has brought out many tree diseases that are causing significant damage on evergreens throughout central Illinois.

In particular, spruce and pine trees show needle browning and dieback. Spruce trees have small needles arranged along the stem. Pine trees have needles in bundles of two, three, or five along the stem.

Spruce trees are experiencing three different diseases, each with slightly different symptoms and treatment. First is Rhizosphaera needle cast. Spruce trees with purple/brown one- and two-year-old needles are suspect. The newest growth will appear green. Affected needles are cast (dropped). Since evergreens do not re-foliate along the branches, the disease will cause bare areas scattered throughout the tree. Norway spruces are considered resistant to this needle cast while Colorado blue spruce is a common host.

The second disease we see regularly on spruce in Illinois is Cytospora canker. That disease causes entire branches to turn purple/brown. Cytospora affects all needles from the tip of the branch to the base. Often lower branches are affected first. The disease may progress up the tree slowly, killing branches over a number of years. The fungus is known as a stress pathogen, meaning it invades spruce trees growing in less than ideal sites or environmental conditions.

Third, the University of Illinois Plant Clinic recently confirmed a new spruce disease in Illinois called Sudden Needle Drop (SNEED). SNEED has been found on Norway, white and Colorado blue spruce trees. Symptoms of SNEED are yellowing and eventual browning of older needles. Typically, by the end of summer, all of the needles on affected branches fall off except the newest needles on the tips of the branches.

Pines are prone to several diseases as well, including diplodia blight, pine wilt, and Dothistroma blight. All three diseases will cause needles to turn brown. The pattern of symptoms will help with diagnosis in each case.

The main disease that Rhonda has seen this year is diplodia on Austrian Pine. Diplodia tip blight causes entire needles to turn brown, not just tips of needles as might occur with Dothistroma blight, scorch, salt injury, or transplant shock. Diplodia blight causes all of the needles at the tip of a branch to turn brown.

Several practices can help reduce the amount of damage caused by these diseases. When the foliage is dry, remove dead branches and dead stem tips. Because the fungus survives on cones, rake and remove fallen cones throughout the season. Stressed trees are typically more susceptible to infection, so follow proper watering and fertilization to keep trees healthy. Chemical options are available for some diseases, but sprays this late in the season are not beneficial.

For more information on these diseases and more, read the Home, Yard, and Garden Newsletter from University of Illinois Extension at http://hyg.ipm.illinois.edu/index.php. You can also find out more information on this or other horticultural issues by contacting your local Extension office at www.extension.illinois.edu. You can also post questions on Rhonda's facebook page at www.facebook.com/ferree.horticulture.

Source: Rhonda J. Ferree, Associate Regional Director, ferreer@illinois.edu



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