During World War II Riecke was the State Secretary (Staatssekretär) to Herbert Backe, the Reichsminister of Food and Agriculture.
Riecke headed the agricultural section of the Economic Staff East of the Four Year Plan, whose guidelines appeared on 23 May 1941 and acknowledged that mass starvation would occur among the Slavic civilian populations under German occupation by directing all food supplies to the German home front and the Wehrmacht deployed on the Eastern Front.
[6] In denazification proceedings, Riecke was classified as "Group II" (Offenders) and on 30 October 1950 was sentenced to 2 years imprisonment but was released on the basis of time served.
An appeal was denied on 16 November 1952, but a request for clemency to the state of Hesse resulted in his reclassification as "Group IV" (Followers) after payment of a 500 Reichsmark fine, effective 1 July 1954.
[7] From 1952 to 1970 Riecke was an official and head of the Economics Department of the Alfred C. Toepfer Company, which operated, among other areas, in global trade in agricultural products, particularly grain.