We have a large old elm tree in our back yard. It is close to and shades much of our house and some of our neighbor's garage. Increasingly, we are seeing evidence each year of what we believe to be aphids. The evidence is gooey thick sticky sap (probably what is referred to as "honey doo"). Last year it drenched one of our vehicles on the parking pad (also shaded by this tree), and it is nearly impossible to remove. We need to remove our shoes after being outside to avoid messing the floor and carpet. Last year also saw a dramatic increase in this sap from the 5 other elms around our home (corner lot), and in many parts of Bismarck as well. We have researched internet for prevention, control, etc. and most of the treatments applauded by one source are nixed as useless by others. We are not very encouraged. So, in your expert opinion, (1) is there any prevention for aphids in large elm trees, and, (2) if not, how do we get rid of them? Incidentally, we also have one type of tall yellow fall flower that each year is loaded with red aphids that also produce this sap; no other flowering plants seem to be affected. And yes, we have some pretty protective ants on our property - and now I know why. (But they are not in our house.)

We would be truly thankful to learn about effective prevention and control. 

J in Bismarck