"Wet or damp grain in storage will do the same thing, unless stirred or run through a grain blower. Enough heat buildup, and the grain will explode."
In the book "The Day of St. Anthony's Fire" a situation was described in France in 1951 where some kind of grainbin had a spontaneous generation of LSD.
It was then used in bread baking, and other food preparation, causing horrific, and sometimes deadly reactions.
Ergot (fungus) I believe - while not exactly LSD I think it has essentially the same effect.