Q.Black walnut dropping twiglets in june
I have two very old black walnuts. Some have estimated well over 150 yrs. Have appeared relatively healthy. Last year practically no walnuts, the year before bumper crop. This year 2017, they were very slow to leaf out, and now have started to drop twiglets with 7 leaves each, and lots of very immature tiny walnuts the size of olives. The leaves are green, don’t look diseased, but the end od bcc each twiglet is black. Looks powdery but doesn’t come off on your hand when rubbed. Any idea what I may be and how to treat. I don’t want to loose them. Thx Annie Withers

Though a Black Walnut Tree can live to 200 years, your tree is certainly getting up there in it's life span.
There are some diseases to these trees. Thousands Cankers Disease is talked about in the links below.
You can take leaf samples to your County Extension Office for inspection.
https://www.gardeningknowhow.com/extension-search
http://msue.anr.msu.edu/news/black_walnut_trees_threatened_by_thousand_cankers_disease
http://msue.anr.msu.edu/news/tiny_insects_pose_huge_risk_for_black_walnut_trees