A mixture of dry olive wastes, sugar beet wastes, and rock phosphate was treated with Phanerochaete chrisosporium. Optimizing the solid-state fermentation parameters, the fungus was able to simultaneously produce 1100U/l manganese peroxidase and solubilize rock phosphate (26 mg/flask soluble P) after a 21-day process. The final fermentation product was found to significantly improve growth and N and P uptake of mycorrhized plants. Combined application of arbuscular mycorrhizal fungus and microbially treated agro-wastes and partially solubilized rock phosphate exerted biocontrol functions on Fusarium oxysporum inoculated in a typical Mediterranean soil. The described biotechnological scheme offers an environmentally safe alternative to chemical fungicide application.