Dahlia Sap Stain on Clothing?

I do hope someone will be able to help me! I got dahlia sap (a black stain) on the front of a new red t-shirt (polyester/cotton). I suppose I could "recycle" it to wear in the garden, but, as it is new, I do not want to do that. I've tried everything: Spot-out pre-wash, hairspray, vinegar, hydrogen peroxide but it SITS for all it's worth. I am willing to try any legal tip as I become more stubborn and determined to remove the stain the longer it sits.