A model for the Colorado potato beetle (CPB), potato plant and mycorrhiza mutual interactions is presented, accounting for the symbiotic and predator-prey features of this system. The study is performed to determine if arbuscular mycorrhizal fungi (AMF) increase potato tolerance to CPB. To this end, data collected by biological experiments are used. The system exhibits several possible equilibria that are related to each other via bi-furcations. The latter are investigated both analytically and through simulations. The results indicate that the use of mycorrhiza is effective in keeping the pest population at low levels.