Increasing Bt maize in Germany will consequently lead to a high risk concerning adaptation of the European corn borer, Ostrinia nubilalis (Hübner), populations for Bacillus thuringiensis endotoxins.  Obligatory growing of susceptible maize cultivars by farmers as refuge close to Bt fields will sustainably face this development.  The high efficiency of such strategy has been documented by robust data gathered in the USA where pest populations being resistant for B. thuringiensis have not been detected after utilization of Bt maize and cotton on Million of hectares for over 10 years.  For supporting decision making on farm scale in planning refuges in Germany, a GIS based software tool is being developed in close collaboration with three experienced Bt maize growing farms located in north-east Germany (region Oderbruch).  (Please note, article text is in German.)