When I was very young my family lived in a neighborhood with a lot of pre-adolescent boys who liked to trick me. One time they convinced me that because I picked up a rotted old branch that fell off the tree, that I was going to get a disease and die. They called it "disease wood", though technically I guess you'd call it diseased wood. Anytime I see a dried out, withered branch I remember that incident.
A childhood belief about plants

others believed things like this
- I used to think that Alzheimers disease was called Old Timers Disease.— Justin
- I used to believe that all old people got the disease "OLD TIMERS DISEASE" Instead of alzheimers disease :D— MollyJohnson
- That Alzheimer's Disease was Old Timer's Disease.— Todd K
- I used to think tree-nuts (especially almonds) were made of wood. — Josh
- I used to believe that Haggis grew on trees, cause my dad tied one to a branch in the garden— Lynne
- When I was 10, I thought that nausea was called Lack-O-Candy Disease. My mom made it up— Teddybearhaha