Can You Eat Mouldy Pesto?
No, don't ever eat pesto that shows signs of mould, it's simply not worth the risk.
Unlike blue cheeses and cured meats where certain moulds are perfectly safe to eat, any sauce, including pesto, should be discarded if it shows any signs of mould. For what is a reasonably low-ticket item, it's simply not worth the risk of getting sick.
Regardless of your thoughts on food waste, don’t be tempted to scoop away the mouldy bits on top of your jar of pesto and continue eating the rest of the batch. There's a high chance that threads of the mould will have already penetrated deep into the sauce, thereby contaminating even the parts that look and smell perfectly fine.
The toxic substances that mould produces – mycotoxins in particular – can make even a fully healthy person seriously ill, so if you spot even the smallest amount of mould, we recommend binning the whole batch without a second thought.