August F. Schimmack, 89, a retired Agriculture Department auditor who had served in both world wars, died of pneumonia Saturday at Walter Reed Army Hospital. He lived in Silver Spring.

Mr. Schimmack was born in Washington, Pa., and earned a degree in education from Washington and Jefferson College there. He worked with the YMCA there until World War I, when he was commissioned in the Army and helped handle training at Fort George Meade, Md.

After the war, Mr. Schimmack joined the Agriculture Department here. He remained in the Army Reserves and helped to establish Civilian Conservation Corps camps during the 1930s. He was recalled to active duty in World War II and was post adjutant with the rank of major at Indiantown Gap, Pa., during the war.

Mr. Schimmack returned to the Agriculture Department after the war. He retired from both his government job and from the Army Reserves in 1953. He then worked for Garfinckel's store in shipping and receiving and internal security until a second retirement in 1965.

He had been a member of Petworth Lodge No. 47 of the Masons for more than 50 years.

His wife, the former Ruth Hull, died in 1960. A daughter, Lillian Shea, died in 1976.

Survivors include a son, Harold of Crofton, Md.; two sisters, Lillian Seik of Eighty Four, Pa., and Clara Rush of Washington, Pa., and four grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to Grace Lutheran Church in Washington.