Question of the Week Number 2: May 31, 2018

“Neil, sections of my Arizona cypress are turning brown and sap is running down the trunk. What is it, and what can I do about it?”

Facebook friend Carolynn Dolan posted this photo and question recently. As you’ll read, I was really sad to see it.

Since I was a young horticulturist of 12 or 13 years of age I’ve always loved Arizona cypress and their soft texture, especially the selections with steely blue needles.

That’s why I hated to see this photo and question when they came to my Facebook page a few days ago. This is almost assuredly Seiridium canker, the same fatal fungal disease that has ravaged Leyland cypress and Italian cypress plantings across Texas.

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It hit Leyland cypress plants horrifically six years ago and probably three-fourths of the plants where I live and work (DFW) were lost in one year. In many cases they were big trees that had been used as screens for entire neighborhoods, and large equipment had to be brought in to remove them.

These plants all share the common name “cypress,” and they are all somewhat related. However, this disease didn’t hit all of them at the same time. Italian cypress were hit by the canker and other diseases two years ago and last spring, and now this on Arizona cypress as well.

And it’s obviously been going on for a while. Although a web search for key words “university Seiridium canker Arizona cypress” turned up primarily matches for Leyland cypress, Oklahoma State has ventured forth to say that all three species are susceptible. Here is a link to their information.

This is a sad problem for these plants as it appears there isn’t much we can do to prevent or cure it. At this point it’s probably best just not to plant any more. But at least you know.

Posted by Neil Sperry
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