Hannah Kendall and Jade Garza, both 14 years old and from Sterling, were killed July 25 when they came into contact with a field irrigator while working near Tampico.
About 72 people were de-tasseling corn for St. Louis-based Monsanto at the time.
In a lawsuit filed this week, Kendall's father, Brian, says Monsanto knew about problems with the field's irrigation equipment and did nothing to fix them.
In a statement, Monsanto denied those claims, saying crews wouldn't have been allowed to work in the cornfield if the company knew there was an electrical hazard.
Brian Kendall's suit also names the cornfield's owners and an electric company.