I lived in a house with lots of pine trees and always used the needles for mulch. I never had an issue with scorpions.

I have both and I also have not had issues with scorpions. Scorpions like to hide under things, like logs, lumber and rocks, and pine straw, for me at least, mattes too quick to make for a very likely place for scorpions to hide. If anything, I would think they would prefer the pine nuggets since there is space between them. The pine straw does break down much faster though.

Edit: Not that I've bothered thinking about it much for my roses, but I think I would actually alternate with the two. Lay down a layer of pine straw and then top with the bark. That way you get both a quick and then a slow infusion of organic matter. It might be something worth experimenting with... perhaps I'll try that, just to see what happens.

This post was edited by Leekle2ManE on Sat, Jun 15, 13 at 10:11

Thank you both for your feedback, experience is always the best teacher.
Don