Various Problems Cause Damage to Large Trees Growing in the Desert

Ash decline disease hits younger ash trees if they are water stressed. Hits older ash trees for simply no reason at all

Sooty canker disease in Chinaberry. It hits many different trees including Mulberry.Frequently associated with stress. The stress can come from drought.

 

Aleppo pine blight usually happens in the winter months and associated with a lack of water.

Q. I have noticed that many trees including elm, pine, ash and mulberrry have dead and dying branches.  I am a native of Las Vegas and have never seen this before.  It is not the lack of water.  The branch suddenly dies and then eventually the whole tree in the case of one pine.  Thought it was a lightning strike but not so sure now.  I am speaking of the northwest  area  of town near Texas Station.

A. There isn't a life-threatening disease that is spreading community-wide among all of those different plant species that your mentioning. Ash trees do get a disease called ash decline that causes branch die back. I've mentioned that several times in my blog. It hits younger ash trees when they are water stressed. Older ash trees seem to come down with it.

Mulberries seem to get hit fairly hard with a different disease called sooty canker and I've mentioned that in my blog. It's often times associated with trees that are stressed. 

Possible sooty canker of Mulberry

Aleppo pine is hit in the winter time with a disease called Aleppo pine blight which causes tip die back and branch die back when the disease is extreme. It is usually associated with drought.

And Siberian Elm, well, good riddance. It's a horrible tree, trashy, soft wood that breaks in the wind. Not to be confused with Chinese Elm which is a beautiful large tree with very few problems.But Siberian Elm's usual problems are related to water and dieback.

Chinese elm not to be confused with Siberian Elm is a wonderful tree

I think a lot of what you're seeing is related to water. I moved here in 1984 when water was abundant, cheap and everyone watered with abundance. In the late 1980s and into the early 1990s there was a campaign in town to get rid of all the lawns. 

The campaign was called "Cash for Grass" program where water utilities were offering people money if they converted their landscapes from grassy landscapes to rock landscapes. Those big trees that survived for years on water given the lawns were suddenly put on small drip emitters and surrounded by rock. 90% of the time these large trees either died or had severe setback because they were not getting enough water. You see this kind of problem less often where these large trees are growing surrounded by lawns. Now you have my $.02 worth.