Multitrophic interaction between the ryegrass Lolium perenne, its endophyte Neotyphodium lolii, the weevil pest Listronotus bonariensis, and its parasitoid Microctonus hyperodae

Abstract Field experiments in Canterbury, New Zealand, investigated four levels of interaction involving the clavicipitaceous endophytic fungi Neotyphodium lolii measured as ppm of the alkaloid peramine in bulked samples of Lolium perenne, the weevil pest Listronotus bonariensis, and its braconid parasitoid Microctonus hyperodae. Weevil numbers were unusually low and the expected inverse relationship between ground densities and peramine concentration was not observed. There was, however, a highly significant tritrophic interaction whereby percent parasitism was inversely related to ppm of peramine. Possible mechanisms for this interaction are discussed and it is suggested that it may have been the result of reduced feeding intensity of L. bonariensis that led to a corresponding reduction in opportunity for the parasitoid to attack.