Ingredient for the fungicide brewing still

Hello community,

Small post for a call for help. I discovered everything except the second ingredient to put in the fungicide brewing still. The first is a terracotta pot and the third is (potato, mushroom or carrot) but the second I have the image in black so I only see the outlines but after exploring a huge amount of islands I don't discover anything more.

Thank you for your help, I would like to succeed in finishing.