Question
I have a lilac bush that gets this white long- not powdery fungus on it.  Last year the main stalk had it on there & I sprayed it with soap & water but it did not work.  The fungus ended up killing the main stalk, now it is on another.  Please help me with what will kill this fungus & possibly what is causing it, I don't want to lose my lilac to it.  Thank you

Answer
You may be seeing a white powdery substance, but it is associated with an insect rather than a fungus itself.  Dig around in the white stuff and see if you find small oval shaped bugs.  They will be closely appressed to the stem and will not move when disturbed.  If you find these, this would be scale insects, which can kill your plant if left untreated.  I would treat the plant with Bayer Advanced Tree and Shrub Insecticide.  This product is mixed with water and poured on the soil around the base of the plant.  It is taken up systemically and will kill the bugs within a week or so.  It also provides protection from reinfestation for up to a year.  I hope this fixes the problem.  Good Luck.