Help identifying citrus problem

[FrankDrebinOfFruits]

I have this die off on several of my citrus trees. I cannot see anything except ants. The first thing that happens is the branch looses its leaves then the branch dies. The other branches are still alive. 


This particular one is a clementine mandarine


I need some hints!

Thanks in advance.

[jcaldeira]

Ants often suggest mealy bugs, aphids or some other pest that they feed on.

I don't know the answer, but suggest trimming off the dead/dying wood and carefully observe the remaining tree. 

[Millet]

Periodically, twig dieback is a problem on citrus trees in most growing districts. Causes include a poor root system, a mild scion-rootstock incompatibility, water stress and weather related stress.  Sudden twig dieback sometimes occurs in the spring.  Terminal leaves turn brown, die and remain attached to the twig, or drop from the tree. Roots are mostly inactive at this time because the soil is cool.  However, increasing daytime temperatures increase the tree's water loss and the canopy's water demand, resulting in water deficit or stress even when there is ample soil moisture. Gum may form in the conducting tissue of twigs further inhibiting water transport. As a result, leaves and twigs may die immediately or become more likely to die some weeks later, often during another hot period.  On navel orange trees, this type of dieback often occurs after fruit have been harvested. Twig dieback can also occur in late summer. This type of dieback typically occurs after hot temperatures and may be related to moisture stress, or poor root health. Lastly, your tree looks to be undernourished.  A young tree the size of yours needs (requires) to be fertilized 4 times a year, using a complete fertilizer containing micro nutrients.  I would also remove all the wild vegetation from around the tree, and keep the trees root zone vegetation free. The very first duty when growing a young citrus tree - by far the most important item -  is developing a strong root system. - Millet