Fusarium oxysporum f.sp. orthoceras, a potential biocontrol agent against the parasitic weed Orobanche cumana Wallr., has proven to be efficacous under greenhouse conditions when formulated as wheat-kaolin granules. To help minimize the loss of viable fungal propagules during the formulation process, the addition of a commercial fertilizer containing the iron chelate of EDDHA to the formulation was investigated. The proportion of surviving propagules was significantly increased after adding the fertilizer. However, growing conidia in fertilizer-amended liquid medium did not reduce losses in viability during formulation. The efficacy of the formulated fungus and the storability at room temperature for the first 3 months was not affected by the iron fertilizer. The protective effect could neither be obtained with the chelator EDDHA alone nor with FeEDTA or FeSO4.