The plants become more tolerant to disease and pests. You can think of the mechanism as similar to a vaccine: when a plant comes into contact with the mycorrhizal fungus, the defence mechanisms of the plant are driven into action. This process has a positive effect on the plant’s vitality. Additionally, potential entry points for harmful organisms in the roots of the plant are already occupied by the mycorrhiza fungus. However, mycorrhiza cannot be considered a protective substance for plants, and does not foster resistance to disease or pests in the plant.