ABSTRACT
Field experiments carried out by Helbig (2002b) did not reveal any supporting effect of carbohydrate sources when added to antagonistic yeasts or bacteria. The mixtures were tested in two experimental years with quite different weather conditions and with different yeasts and bacteria. The nutrients may have been used by pathogens and saprophytes (Blakeman and Fokkema, 1982; Lukezic et al., 1990). This could have hindered establishment of antagonist population or supported infection by the pathogen. A third reason for failure of nutrient addition might be the mode of action involved. Results from Janisiewicz (1988) showed that addition of nutrients might reduce efficacy of antagonists if competition for nutrients is the mode of action and if the pathogen requires external nutrients for conidial germination. It could, therefore, be concluded that addition of nutrients might support antagonists and that these nutrients should carefully be selected and quantified in order to avoid possible negative effects.
