Are there smaller diameter dead limbs throughout the canopy of your live oak?
In a drought, the live oaks, as with most trees are also experiencing stress. The good news is that live oaks are extremely drought tolerant. They are resilient and can handle long periods with very little water. Very few diseases affect live oaks, and those that do (oak wit aside) are often not fatal.
It is important to note that live oaks form dead wood in the inner canopy naturally over time. This ‘interior’ dead wood is normal and forms because the interior limbs get less sunlight as the outer canopy grows and thickens over time, causing them to drop their leaves and ‘shed’ these branches. The scientific name for this branch shedding is cladoptosis.
Occasionally, live oaks lose previously healthy limbs in the canopy. These can be caused by physical damage such as wind damage or vehicle damage, or in rare occasions they can be disease related.
When trees are weak from stress, they are more susceptible to disease. One of the diseases that live oaks get more frequently during drought years is a fungus called twig blight, Cryptocline cinerescens. It is not widespread in theAustin area, but when it does happen, it can be scary to the homeowner. Since most local arborists are not familiar with this disease, it is often misdiagnosed.
I was first introduced to this disease 20 years ago inNorthern California, where it is much more prevalent. The disease is characterized by many dead and dying limbs of smaller diameter, scattered throughout the live oak canopy, usually but not always fairly evenly distributed.
This disease is rarely fatal. Most of the time, it is just responsible for the death of specific smaller limbs throughout the canopy which then can be pruned out past the transition zone into the healthy wood. After that, we usually spray the tree with a fungicide to address re-infestation. As with all diseases, initial and correct diagnosis is the key.