American walnut problems, page-2

Good pick up bongo
I noticed it affects Black Walnuts - from the net
The Black Walnut and Butternut walnut are natives of North America. These two varieties have thicker shells than the standard European walnuts. For walnut production, Black Walnut (Juglans niger) seeds or seedlings are often used as the rootstock from which commercial walnut varieties are grafted. J.regia is often used as rootstock for well drained soils while J. niger is sometimes preferred for wetter soils. http://www.austnuts.com.au/walnuts.html