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Tuesday, December 26, 2017

Borers in Italian Cypress and What to Do

Q. Good day, Bob. I had 9 mature Italian Cyprus that have all died. Upon inspection by me, I discovered a borer in the trunks. I think it is the flat head borer. Other Italian Cyprus in my north Las Vegas neighborhood are dying as well. Have you heard of anything like this happening in the valley? And any preventive measures? Or is the insect destined to kill all the Italian Cyprus in the valley doomed the insect fate?
This was the picture sent to me several years ago when I asked for help identifying borers in Italian cypress. Flatheaded borer damage confirmed.

A.  Years ago I thought borers was not a problem for Italian cypress. There are many reports from reputable organizations that many of our borers, flat headed apple tree borer and Pacific borer, are primarily attracted to trees damaged by intense sunlight or sunburn. I didn't think this was a problem for Italian cypress so I thought that Italian cypress was not bothered by these insects. Plus the outside of the trunk is covered with evergreen foliage which should prevent egg laying on the trunks by these insects.
Borers in Arizona cypress were well known as a problem.

There were many reports of dieback in Italian cypress. 


I asked for help from my readers because I wasn't sure. A few years ago a reader sent me a picture of Italian cypress with damage suspected by flat headed borers. I am now convinced that flat headed board does occur in Italian cypress. Live and learn. 
The active ingredient is Imidicloprid and a widely used insecticide for many crops. I has been implicated in honeybee colony collapse but has not been proven but has been banned in several countries primarily for this reason. Use of it as a soil drench for killing insects on nonflowering trees is perhaps a good use for it because it has a minimum impact on bees when used this way.
The best protection is a soil applied liquid insecticide called a soil drench. One of the manufacturers of this insecticide is Bayer and it is called Tree and Shrub Insect control . Follow the label directions and the manufacturer claims up to twelve months protection with one application.

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