The people inhabiting our planet are expected to touch the nine million mark within the next 40 years. Feeding the world population adequately is a problem which has been faced for a long time, and although considerable efforts have been made in tackling global food security, further solutions are needed to increase the supply of basic staples in the coming decades. Generally, there are two major strategies to approach this goal for food production: firstly, to grow more crop plants on newly reclaimed land or to increase yields on existing farm land by using improved cultivars; and secondly, to diminish the actual losses in crop yield arising due to pests, diseases or from the competition for nutrients with weeds. In view of the size of the challenge it is reasonable to assume that only a combination of different approaches can achieve global food security. However, implementation of the first strategy may have negative ecological impacts on existing ecosystems, and a higher input of fertilizer or water, both of which are expensive or limited, will be a consequence. The second strategy, by contrast, displays an attractive alternative because it deals with the conservation of already produced biomass. Thus, in principle, would not need any further input of resources for crop growth. It was estimated in 1994 that the actual losses due to insects, microbes and weeds reduced the theoretically achievable global crop yield by 42% (Oerke et al., 1994). Reducing this depletion would be a valuable contribution to ensure food security. This chapter will deal with soybean as one of the world’s major staple crops and strategies will be presented to combat yield losses caused by a prominent foliar pathogen known as Asian soybean rust caused by the fungus Phakopsora pachyrhizi (Fig. 1). Generally, all parts of soybean plants are targeted by different pathogens and pests during the growing season, e.g. roots by cyst nematodes, young seedling by different Pythium, Rhizoctonia or Phytophthora species and leaves e.g. by Phakopsora pachyrhizi. Asian soybean rust (ASR) affects yield because of premature leaf drop and reduced green leaf area which affects the photosynthetic capacity of the plant. Generally, agronomists try to keep plant diseases in check by breeding resistant cultivars or, more recently, by using biotechnological tools. However, it must be noted that the latter approach which includes the generation and release of genetically modified plants into nature are discussed controversially in public debates. Unlike for some other important plant diseases, neither breeding for resistant cultivars nor the biotechnological approach have so far led to novel soybean genotypes that could withstand all isolates of the ASR fungus.