A person who studies crop circles. Also: cerealogist.
They appeared like magic in the middle of the night hundreds of huge geometrical patterns in the middle of English wheat fields. To some, the mysterious circles that first made headlines in 1980 were proof of alien visitors. Self-styled crop-circle experts claimed the precise shapes were the result of energy from spaceships that flattened the wheat as they hovered. "cereologists" devoted books to the wheat-field wonders, and curious tourists flocked to see them until September 1991, when two 60-something artists came forward to show how they had created the circles at night with lengths of rope and flat boards. The con that baffled the world for more than a decade had been cooked up over a pint in a local pub.
Andrew Curry et al., "Hoaxes of the ages," U.S. News & World Report, July 24, 2000
As the last of 1991's 160 or more British corn circles are mown down and the serious debate is shelved for another year, the small, back-biting, intensely jealous world of 'cereologists' has been struck dumb by the claims made this week of two elderly men.
Doug Bower and Dave Chorley claimed in Today newspaper and subsequently on world television that they were responsible for the lot. . . . The few British, American and Japanese scientists who are trying to research the phenomenon are distraught. Doug and Dave, said one this week, have set research back years. In fact they may have done the opposite. Fewer photographs will appear in the press from now on but the publicity may attract more money for proper investigation. The growing number of amateur and professional cereologists may have the last laugh.
John Vidal, "Cereal Killers," The Guardian, September 13, 1991
Today's word is based on the name Ceres, the Roman goddess of agriculture. (The word cereal also comes from Ceres, but the cerealogist variant of today's word strikes me as hilarious: it sounds more like some kind of Froot Loops expert.) Strangely, although I came across dozens of sightings for the term cereologist, I couldn't find a single instance of cereologism. Insert shoulder shrug here.
A magazine called The Cereologist ("The Journal for Crop Circle Studies") was founded in 1990 and it provides all the early citations for cereologist. Here's the first one I could find that wasn't a reference to the magazine: