Among the many rumors that abound about the Radley family and particularly the reclusive Boo, the pecan tree on their property adjacent to the school is also considered a dangerous temptation to passersby and children. According to local legend, Boo has poisoned the pecans that fall from the tree: They await unsuspecting children who may choose to partake of the free nuts, only to face sickness or even death. Few people take advantage of the fruit from the trees, however, because everyone in Maycomb has already heard the story.
... the nuts lay untouched by the children: Radley pecans would kill you. (Chapter 1)
Probably because he lives in rural Old Sarum and didn't know better, Walter Cunningham Jr. even claims to have eaten them and survived.
"Almost died first year I come to school and et them pecans.--folks say he pizened 'em and put 'em over on the school side of the fence." (Chapter 3)