Question
There is white (not powdery) "stuff" spread all over the underside of the leaves on my lilac bush.  Very hard to wipe off - I tried the natural soap and water treatment but it didn't work.  I'm hoping you would know what it is.  I don't actually see "bugs" of any kind but a lot of the tops of the leaves have that dried out look as if something is sucking all the juices out of them.  Help! What to use???  Thanks!!

Answer
Sounds like scale or powdery mildew.  Most soaps will do nothing.  This is one of the most difficult insects to get rid of. They attach themselves to the bottom of the leaf because this area typically is more vulnerable and does not have the protective cuticle layer that the top does.   

If you go to Crowleynursery.net Kathy sells Neem oil and Atomic Grow.  The Neem oil may work by smothering the insects and eventually cause suffocation.  But the Neem does nothing for the health of the tree.  The other product called Atomic Grow will really do a great job of cleaning everything off the leaves and stimulating the plant at the same time.  Insects hate Atomic Grow.  Both of these products are all natural and pesticide free.  

Good luck Carol