Because of his appearance and very tall frame (6 feet, 6 inches), Dierkes enjoyed a long career as a character actor, often portraying villains or soldiers. In the 1953 film Shane, Dierkes portrays villain Morgan Ryker, who is the last man shot by the title character, Shane, in the final bar room shootout. One of his more memorable scenes is in the 1960 film, The Alamo. Dierkes portrays a Tennessean named Jocko, who is torn between leaving before the attack to care for his blind wife, or staying to support the Texans' cause. Understanding that if Jocko stays to fight she will likely be widowed, Jocko's wife coaxes him to stay and defend the fort, despite her disability.
Dierkes died in 1975 of emphesyma and was survived by his wife Cynthia, two sons, and two daughters.