Question
When do I know that my hackberry trees this fall have stopped their sap from falling? I want to pay a firm to clean my roof, deck and concrete drive, etc from the black tar sap and aphids, but I do not want to do bear this expense until I know the sap and aphids are over for this winter.Thank you for addressing this question.

Cordially,

Mike Bates
cell# (24x7)&

Answer
Not knowing where on the US you are I would generally say when the leaves fall off the tree is dormant and will out produce any more sap flow until Spring.  I would treat the tree with Bayer Advanced Tree and Shrub insect Control next Spring . This will keep the aphids under control for the whole growing season and stop the dripping from the aphids. Check with your local garden type store for the Bayer produce.