There is a great requirement for cultivation of grain legumes (e.g. peas) in organic farming systems (protein supply for animals, biological nitrogen fixation, previous crop effects). The occurrence of pests and diseases, e.g. Acyrthosiphon pisum, leads to strong yield losses and yield fluctuations. In organic farming systems the use of plant protection products is strongly limited. Plant strengthening products are compatible to this kind of land use and enhance the resistance of plants to harmful organisms. Field trials with some selected plant strengthening products achieve small yield growth under North-German site and climatic conditions, but rarely it is possible to produce statistical evidence. At low up to medium level of disease attack they show good results, meanwhile strong disease attacks lead to unsatisfied results
