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Q. Who is Mr. Smarty Plants?

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Sunday - April 03, 2011

From: Wimberley , TX
Region: Southwest
Topic: Diseases and Disorders
Title: Browned foliage on Juniperus ashei in Wimberley TX
Answered by: Barbara Medford

QUESTION:

We are in Central Texas and have native "cedar" juniper trees. One with foliage that looked brown, on close inspection, is covered with white webs. The foliage looks like it is dying. No worms are visible. It is about 15 ft tall and close to oak and other cedars as well as other native landscape plants. Should it be treated? With what, or must it be removed and burned? Guess we need an answer very quickly before it spreads further. Thanks very much.

ANSWER:

Following the "cedar fever" season we have just had, most Central Texans would say "burn it" and use descriptive adjectives we can't repeat in a family website. However, a tree is a tree and Juniperus ashei (Ashe juniper) is native to Central Texas, so we will see what we can find to help you make a decision. Just about this same time last year, we had a similar question from San Antonio. We never came up with an actual answer, but had several links that we think should be helpful. We are just going to copy portions of that answer for you.

Note from Mr. Smarty Plants: After this answer was published, we heard from Eric Beckers, a forestry specialist and got some better information. We are always grateful for technical help from the professionals in the field, and Eric has been especially valuable to the Wildflower Center and to Mr. Smarty Plants.

"I was reading Barbara Medford's March 19 Mr. Smarty Plants response concerning browning junipers in the Wimberley area and I can confirm the cause to be mites (not sure of the species).  I've been hearing about it from Hays County Master Naturalists over the past couple weeks and saw it first hand earlier this week.  You might consider modifying your response and lean even harder towards a diagnostic of mites.  I also saw something like a thrip, but the webbing and mites were obvious.  Barbara's reference to the New Mexico State University site was a good one and NMSU is right on with our own similar issue.  Until it rains we will probably continue hearing about this problem."

You don't ordinarily think of this plant as having problems. More people want to get rid of it than take care of it. Because we are not plant pathologists and, of course, can't see the tree in question, we went hunting on the Internet to see if we could find clues for you. Some of these have pictures, and we will give you a link to a couple of Google Images sites to compare with your tree. The two from New Mexico State University and West Virginia State University were the only mentions of spider mites. One was written three years ago and mentions that the weather had been dry, which helped contribute to spider mite infestation.

If you get the impression that we really don't know what is causing the die-back on your tree, you are absolutely right. After you have read these sites, and compared the symptoms with your tree, we suggest you contact the Texas A&M AgriLife Extension Office for Hays County. They are more likely to be familiar with this problem than we are

Morton Arboretum Juniper Tip Blight "Common disease of junpers in most states east of the Mississippi River."

University of Illinois Integrated Pest Management Phomopsis "This disease could be confused with cold injury or spider mites." Images of Juniper Twig Blight from Google.

USDA Forest Insects & Disease Leaflet Phomopsis Blight of Junipers

New Mexico State University Juniper branches turning brown Blames spider mites.

Washington State University The Trouble with Juniper mentions that too much humidity and moisture can cause this browning, as well as aphids. Images of aphids on junipers from Google.

Of all these, we are most likely to go with spider mites in your case. See this article on Spider Mites from Colorado State University Extension in which whitish webs are observed.

 

 

 

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