[phaker]

From what i can find, the difference is that ergot is parasitic and rare but the fungus growing on darnel is symbiotic and common.

Polish wikipedia says up to 86% of seeds carry it but without source. This paper [1] says 70% of 'wild populations' of related L. perenne, implies infection in darnel (L. temulentum) is also prevalent, but notes most populations have low frequency of infected individuals and then tries to explain that.

[1]: https://mivegec.ird.fr/images/stories/PDF_files/0250.pdf

[eyelidlessness]

This seems similar enough to the allergy commonly associated with peanuts to be worth mentioning too.