We received a question on oak tree care from New Jersey so we took that as a prompt to discuss oak trees, a species that isn’t as common in Colorado. The caller who asked the question had an extremely large oak that was beginning to die back.
Because oaks require a great deal of water and because over 60% of the US is in a drought, it would make sense that lack of water could be a stressor on the tree. He agreed that it could be an issue because it has been dry in comparison to other seasons but went on to say that all the oak trees in the neighborhood are growing fine.
The tree had other symptoms that seemed to point to it being diseased. He said there was brown leaves along the center margins of the leaves. The lower leaves were much worse and many of the branches were dead already. After some deliberation and research we came to the conclusion that the oak was infected with “bacterial leaf scorch”.
However, being in New Jersey, we advised the customer to have a local arborist inspect it.
Bacterial leaf scorch is spread by insects that transport the disease from tree to tree. We recommended an injection from an arborist with a formula that contains Oxytetracyclin, such as Phospho-jet from ArborJet.
This will need to be injected every few years to keep the disease at bay.
Oaks aren’t drought tolerant which is why they aren’t popular in Denver. Although New Jersey is far away, Colorado has its own variety of oak trees that are susceptible to similar diseases. To defend against disease the most important thing you can do is make the tree as healthy and vibrant as possible.
Some actions you can take to make your tree more healthy:
- Location – For example some trees need full sun while others can be planted in the shade. Go to Colorado Tree Coalition and find the right tree for your location.
- Soil – Trees require unique soils, most needing soil that soaks up moisture while others prefer sandy soils.
- Prune – Prune your tree every year or two to make it storm resistant and to allow sun light to penetrate through the branches.