Okay. So. If we're not doing poison ivy, which, fair enough, maybe we want to avoid literal biological warfare (as hilarious as it is) then we need something biodegradable but still as infuriating as glitter. Qualities of glitter that drive people to insanity: it is so small that it is easily attracted to skin, clothes, and generally everything you own, so it is extremely difficult to get rid of if it coats you, AND it sparkles and comes in bright colors so it's impossible to ignore.. I don't think that holes cut out of leaves would have exactly the same effect - they simply would be heavier, not to mention they aren't sparkly so might just look like, well, a speck of leaf, which just isn't as annoying.

Starting with the first problem - getting the biodegradable material to coat and stick to our enemy - is there a way to charge the leaf confetti with static electricity somehow?