Dave... Be MOST careful... If you have lots of seedlings, you no doubt have some older vines growing up the trees. They will look a lot like the woody, fibrous stems of Virginia Creeper. Whatever you do, DO NOT cut them with a chain saw! You will have poison ivy in your eyes and on every other conceivable part of your body, and maybe even in your lungs! We managed to take a machete and slice off ours near the root, but even at that, the branches were still toxic 2 years later, and we had good cases of poison ivy getting rid of it. I understand poison ivy can remain toxic (root and stem) for many years after it has supposedly 'died'.
The seedlings respond well to a specific Round-Up product just for poison ivy.oak, available at Lowe's, and although I hate using toxins, I'd rather that than an annual case of poison ivy. After 3 years, we are slowly eradicating it... winning by maybe 55-45. It's a bear! (And it makes such pretty red leaves in the Fall!)
Dave, I just came across an article with a recipe for a homemade remedy to eradicate poison ivy:
3 pounds of salt dissolved in a gallon bucket of soapy water. Spray/brush it on the leaves and/or pour it around the base of the plant.
I have no idea if this works, but it might be worth a shot as a side-by-side test with the Roundup. If you try it and it works, let us know, okay? I've got some in the back of our property that I think got killed back last year, but I'm keeping my eye on the apparently dead stem just in case.