Guild Wars 2

I killed a Toxic krait and it dropped a pristine spore for me, achievement didn’t increase.
I finished a Toxic Offshoot event, got 3 pristine spores, achievement increased by one.

Do we need to do 20 offshoot events in a day?

EDIT: Achievement is called Toxic Field Researcher

I don’t even have this as a daily. I have a daily called Toxic Spore Researcher. Take a look at this page http://dulfy.net/2013/10/30/gw2-tower-of-nightmares-achievement-guide/

you will find the dailies on top while all other achievements are on the bottom. If we follow the guide then you have to collect the spores from the seeds that spawn after the offshoot event and around the map (nodes may vary every day)

Hope that helps, if not ignore my post

Successfully gather a pristine spore sample 20 times. Spores spawned after events are guaranteed (to harvest pristine samples) while the ones found around the world are not. Getting a mushed sample doesn’t count.

Getting a mushed sample does count. It’s essentially ‘Daily Gatherer’, but only for Toxic Seedlings. Whatever you get per gather, it increases by one each time. If you manage to gather a single node twice, the count goes up twice.

I know where there are a ton of Toxic Seedlings in Sparkfly on BG, but you’ll have to look around on your own world. Or just do 20 offshoot events.