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Saturday - November 20, 2010

From: Georgetown, TX
Region: Southwest
Topic: Trees
Title: Black spots and fuzzy circles on live oak leaves
Answered by: Nan Hampton

QUESTION:

We live in Georgetown Texas and have many Live Oaks on our property. Lately some leaves have fallen off which have fuzzy round circles on the back along with some little raised black dots. Should we be alarmed?

ANSWER:

The fuzzy yellow growths on the underside of the leaves are most likely galls caused by a tiny wasp. Acraspis erinacei, Andricus quercusflocci, Andricus quercuslanigera, Andricus laniger, Andricus fullawayi and Andricus ignotus are all gall wasps that produce fuzzy galls on oaks. The galls aren't likely to affect the health of your trees at all so there is really no need to do anything about them.

The black spots are probably caused by a fungus. There are several that affect Quercus virginiana (Coastal live oak) and Quercus fusiformis (Escarpment live oak); but, like those with the insect galls, unless they are heavily infested there is no need to treat them. Here is some information from Florida Department of Agriculture about tar spot caused by the fungus, Trabutia quercina. You can read about common diseases of oaks from the Neighborhood Association of Southwestern Williamson County and here is Dr. Jerry Parsons', the Bexar County Extension Agent, take on problems with live oaks in Texas. If your infestation is severe enough that you think treatment is necessary, contact your Williamson County AgriLife Extension office to ask for their advice on treatment.