The Q&A Archives: Unhealthy Red Oak

Question: I have two red oaks. One is about 15' and was transplanted in Sept. 08. It leafed out this spring and looked good for about a month, then almost overnight, its leaves turned brown. The other smaller one, about 10', has leaves that are turning brown and speckled. Could this be drought related and should I start watering more or could it be the dreaded oak wilt? How can I tell for sure? Thanks!

Answer: In dry years, the appearance of trees with oak wilt may be confused with that of trees with drought symptoms.

Symptoms of wilt in red oak occur as early as May. The leaves turn dull green or bronze, appear water-soaked, wilt, and then turn yellow or brown. Damage occurs from the tip and outer edges toward the midrib and base. Wilting leaves typically curl around the midrib and the line between the bronze and green tissues in individual leaves is very distinct. These symptoms quickly appear throughout the crown, often within a few weeks, and leaves at the ends of branches are shed. Heavy defoliation accompanies leaf wilting and discoloration. Leaves fall in all stages of discoloration. Even entirely green leaves may fall from affected branches. Some affected branches hold green leaves longer than others~sometimes until autumn. Therefore, the crowns of trees with oak wilt are seldom as uniformly brown as those of nondiseased trees that have been poisoned, girdled, or damaged by drought.
The disease progresses rapidly, and some trees die within 1 or 2 months after the onset of symptoms. Most trees die within a year.

If your trees don't exactly match the above symptoms, the browning is probably drought related and you should water your trees regularly to help them recover. I hope the symptoms are drought related!

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