Blue Point Juniper Unique to the Las Vegas Area and Probably Has Mites

Q. My 9-foot tall cone-shaped blue point juniper has a huge area that is turning brown. What can I do to restore the burnt-like brown to a normal green? I looked at the brown area closely and found whitish cobwebs with little white dots on the area.  What mites are inhibiting the juniper and what is the best way to get rid of them?

Click here to see a Blue Point Juniper

A. Junipers are notorious for two things and uprights possibly a third; spider mites which are frequently associated with webbing, root rot when they are planted in heavy soil or if they are watered too frequently or both and possibly borer damage. Damage from overwatering usually appears at first as single branch dieback.

            Blue Point Juniper is a small to medium sized upright very small tree or shrub that is cone shaped with a bluish green color. This is a very pretty plant in the right landscape. I have not seen very many of them growing here in our landscapes.

Webbing from spider mites

            Spider mite damage can cause browning but normally the surrounding foliage of the juniper appears to be dusty looking. Most of this dustiness appears, to me, to be dead mites. Spider mites are extremely small, about the size of the period at the end of this sentence.

            The webbing may not mean anything. Just because there is webbing does not mean it has a problem with spider mites. Spider mites can be of a type that creates webbing or it may be of a type which does not. Secondly, there are good mites and bad mites. The good mites help to control the bad mites so spraying a chemical aimed at controlling mites may just backfire.

            The best way to determine if spider mites are an issue is the paper test. Take a white sheet of paper and a branch of the juniper and slap the branch or foliage against the white paper. Hold the white paper still and look at the dust or debris on the paper. If spider mites are present you will see a number of tiny dots the size of a period moving on the paper.

            Usually spider mite problems begin developing during the heat of the summer, not when it is cool. Soap and water sprays once a month during the summer is a common way to try and keep spider mites from becoming a problem. If the problem is severe than that may require a miticide or insecticide for controlling mites.

Scanning electromicrograph of spider mite the size of a
pencil dot.

            Since you have had this juniper for quite a while it is probably not root rot due to overwatering unless you have recently changed the irrigation pattern or if there has been a release of water near the plant in the past few months. This might be from a leaky irrigation valve or broken pipe.

            Borers in major limbs or branches are a problem on some upright junipers such as the Hollywood twisted juniper. It might be on this plant as well. Boring insects that tunnel into these branches cause these limbs to die while the surrounding area stays green. Pull the canopy of this juniper apart and look at the limbs inside of it to see if there is sap coming from a limb or limbs. The damaged limb is pruned out just below the sappy area.

            Once a branch is damaged and it has turned brown it is difficult to get it to come back to green again. If the damage is not severe it might come back over time if the problem that caused the browning is corrected. If the damage is severe it may be permanent like the toothless gap of a smile and never repair itself.

            The nurseries to carry a green paint that can be used to help the plant cosmetically. This is a problem with plants that grow beautiful, perfect cones of canopy.

Response

Thank your very much for your detailed response.  My two blue point junipers are doing quite well now after I sprayed them with insecticide.  I live in Sun City Anthem and you are right--nobody else has these trees.  Mine are now six years old, eight feet tall and trimmed to a conical shape.