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Mr. Smarty Plants - Webbing on oak leaves and fuzzy yellow growths on leaf veins

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Tuesday - November 09, 2010

From: Dallas, TX
Region: Southwest
Topic: Trees
Title: Webbing on oak leaves and fuzzy yellow growths on leaf veins
Answered by: Nan Hampton and Eric Beckers

QUESTION:

I have a large red oak(?) and live oak that appear to have the same problem. Clumps of leaves all over the trees are covered by fine webbing and the leaves appear to be curling up and dying in the webs. I have not seen any worms in the webbing and the individual webs do not seem to cover as large an area as web worms that I have seen on other trees in the past. The leaves at the ends of the branches on the red oak are almost entirely covered by the clumps of leaves and webs. The same leaves have another issue on both trees. On the underside of the leaves there are rounded, fuzzy yellow growths on the leaf veins. Is it possible that I have 2 different diseases/insects at the same time? I thought about some sort of leaf galls and spider mites.

ANSWER:

I consulted Eric Beckers with the Texas Forest Service about the fine webbing on your oak trees and he said that he can't imagine anything other than webworm.  The size of the web might have been kept to a minimum by a late hatch after the September rains followed by a very dry October.  Lack of caterpillars could have been a sign of good predator activity (we had a bumper crop of wasps this fall!).

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.  There is no evidence that your two problems are linked since these tiny wasps that produce the galls are not likely to be predators of the webworms.

You might like to contact your Dallas County AgriLife Extension Agency to see if there have been other reports of webworms in your area.

 


 

 

 

 

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