Technical Abstract: There are many pathogens with excellent potential for insect pest control and many situations where the control produced by innundative (pesticidal) or inoculative (classical control) release of pathogens or by naturally occurring epizootics is sufficient to limit or avoid economic damage. Rangeland and pasture systems are particularly amenable to biological controls due to a relatively high economic threshold and because they are ecologically complex systems with naturally occurring control agents that are more likely to be present and undisturbed. This chapter reviews the most important pathogens for each of the significant insect pests of forage and rangeland.