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Tuesday - September 04, 2007

From: Kyle, TX
Region: Southwest
Topic: Trees
Title: Possibility of oak wilt or iron deficiency
Answered by: Joe Marcus

QUESTION:

This spring my two oak trees, 4" and 7" in diameter, in my yard in Kyle started showing very light green leaves with green veins. I've been told this is chlorosis, so I treated them with a couple of granular products containing iron, purchased locally. Also, I started watering them weekly. This treatment seems to be successful. The appearance of light green leaves has decreased, and growth on both trees has greatly increased in terms of new leaves and branches. My question: The new growth shows the light green leaf color, and on one of the trees the new leaves seem to start out with a brownish color. These new leaves then change color from light brown to to light green, and finally change in color to be pretty much like the mature leaves. Should I regard the color of the new leaves as indicating chlorosis, or are new leaves supposed to start out light green or brownish color? Should I continue the iron treatments, and if so how often? Another question: The 4" diameter tree has black dots on the leaves. I've been told this is a fungus and not to worry about it. Should I treat this tree for fungus? Thanks for your help. or

ANSWER:

We don't want to unduly alarm you, but you should consider the possibility that your trees may be infected with Oak Wilt Disease. Some of the symptoms you describe could indicate Oak Wilt Disease. The Texas Oak Wilt Information Partnership website provides a tremendous amount of information about diagnosing and treating trees infected with the Oak Wilt fungus as well as preventing its occurence and spread.

However, since adding iron seemed to help your trees, chances are they are suffering from iron deficiency. New oak growth is often a bronze color which changes to green as the new stem and leaves mature. This is a normal condition and is, in fact, often very attractive.

The black dots on the leaves of your tree may or may not be a fungus. To find out for sure, it is a good idea to contact the state Cooperative Extension Service agent in your county for a diagnosis.