A person who sprayed pesticides on a mango can still enter onto a blockchain system that the mangoes were organic.
Blockchain is not only crappy technology but a bad vision for the future
Kai Stinchcombe

Indeed. I think the relevant point is that once they enter that on the blockchain they cannot take it back. Once proven that the fruits from a a batch are not organic, whoever entered that into the blockchain is proven guilty. IMO the problem (or rather more difficult aspect) is that unless you have a tamper proof physical packaging as well (e.g. sealed container) it’s difficult to implement in practice. Any tamper proof packaging has a relatively high cost, etc.