How do I Remove Rendered Halo Effect around PNG Leaves?

Hello. I went through a lot of trouble to figure out how to get rid of halos around transparent png images. I got that issue solved in photoshop but now I'm getting halos around my leaves when I render. I tried playing around with the edge outline options but every time I click on apply, it goes back to default instantly (not even sure if that has anything to do with it). I'm trying to make some nice renders of trees and shrubs. How do I get rid of the halo affect around the leaves? (Note: this is not a Photoshop issue as I already got rid of the halo in that program, it appears when rendering.)

This is a test scene I quickly made in Sketchup. If you look closely at the tree, you can see the white halo effect around the leaves.

Tree Test

I got help by Massimo over at SU. Turns out I needed to use an unbiased method. I used MLT and it worked. Baffled as to why though.

[Fletch]

the AA method is likely the culprit.