Black Walnut Tree Enemies?

A lot of information is posted about how many plants are juglone intolerant, and how many plants cannot live near a Black Walnut tree (and, to a lesser degree, other Walnut trees).

I am wondering if a similar process works the other way around: are there any plants that walnut trees don't like being around?
For example, I've read that the resin washed off pine and spruce trees inhibits some plants from growing under them.
Would a walnut tree planted near pine or spruce trees have their growth negatively effected by these trees?

What plants do walnut trees not like being around?

Interesting question! Walnuts definitely seem to be sensitive to certain allelopathic plants. Squirrels plant huge quantities of black walnuts around here, and they come up pretty much everywhere they can. Black walnut seedlings don't mind growing in the shade of most trees, but I almost never see them sprouting under oak, eucalyptus, pine, privet, cottonwood, or locust.

I'm not sure which allelopathic understory plants might affect walnut in a guild. Elderberry can be allelopathic, but walnuts and elderberry get along fine. I guess a competitive understory plant might get discouraged by the juglone before it has a chance to discourage the walnut. I'm not sure I've ever seen a black walnut above a certain size struggling to thrive, except when dying of old age -- they're pretty tough trees!

It's possible, though I can't think of any.  Maybe bush honeysuckle, but it'd probably create more problems than it solves.  Pines and spruces can grow pretty quickly compared to walnut, and it may be inhibition by competition for light, nutrients, and other resources- not necessarily allelopathy.  

Site conditions are usually limiting for black walnut- they like well-drained sandy loam, and suffer in areas with high water tables.  Pines (at least the local species) are more adapted to sandier soils and drier conditions, more frequent occurrence of fire.  In my part of the world black walnuts can be buried by a squirrel in loam or duff and germinate just fine, but those pine seeds need to find bare mineral soil in which to root.