Question
We have 5 mature raywood ash trees in our back yard.  Some large branches on each tree didn't bloom this spring and have turned almost black and are brittle when they are cut.  The rest of the tree appears healthy but I have noticed alot of ants on the trees.  Is this a sign of some type of disease or just something older trees do?  We live in Southern California.

Answer
Sounds like a scale. Scales are insects that resemble a turtle but are attached to the twigs and do not move. They are inside a protective cover so it is difficult to get a insecticide spray to the insect. Scales suck the plant juices from the tree and secrete a substance called honeydew. This is high in sugar content and sticky. A sooty mold will grow on the honeydew. This is the black you are seeing. Treat the tree with an insecticide called Bayer Advanced Tree and Shrub Insect Control. This is applied to the soil and the roots take it up to the twigs and leaves and when the scale sucks the plant juices they are killed. It will take a couple of weeks for the insecticide to reach the top of the tree. The time depends on the height of the tree nd the weather conditions. The black will go away  after the scales are killed.  Check with your local garden type store for this product. It will last the season so I would plan on treating again next Spring for the 2014 season.