Question
I have several oaks, Sand live oak  (Quercus geminata) I am pretty sure. I just
notices a lot of pure white, flossy material on the cupped underside of the
leaves and in small spaces where twigs leave the trunk. Some leaves are full
to overflowing and the fluff moves easily in the breese.  I did not see any
insects when gently removing bit of this material, which is slightly sticky
when rubbed between fingers where is disappears. One nearby tree has the
same affliction, but several others do not, though they have small, closed
galls on the tops of the leaves. Can you tell me the cause of these and the
preferred treatment, if necessary.

Answer
Hi Bill,

Give me a day or two to do some initial research on this.  There are several things that could be the problem.  Even in the most serious of fungal infestations, I have not seen so much pure white flossy material that it could been seen in a breeze.  It is more likely of insect or spider derivation.  The galls that you mention are also associated with many insect infestations.  

I am not an entomologist, so I am going to refer this to one of my colleagues.

If you would like, you can e-mail me at [email protected] with any photos that you may have.  

Thanks,

John