Q.golden willow tree leaves turn yellow, drop off
My golden willow is about 4 yrs old, branches appear healthy but leaves are turning yellow and fall off in the middle of branch. Leaves at end or near base of branches tend to stay green longer and stay on. Also, my tree is about 100 ft from septic system. Will roots interfere with my system? I have included a picture. Hopefully, you can zoom in to see leaves.

this is not an answer but wanted to add to my above question, Oklahoma had a wetter than usual summer and then the heat came back with no rain. Also there is no sign of insects, mold, etc on bark, limbs or leaves.