Change in abundance of three phytophagous mite species (Acari: Eriophyidae, Tetranychidae) on quackgrass in the presence of choke disease.

Phytophagous mites and endophytic fungi may interact when sharing a host plant, potentially influencing one another's growth or population dynamics; however, interactions between them are poorly known and remain largely unexplored. In this study, quantitative associations between three species of phytophagous mites and the endophytic fungus Epichloë bromicola Leuchtm. & Schardl (Clavicipitaceae, Ascomycotina) on quackgrass, Elymus repens (L.) Gould are reported. The mites' abundance was assessed on field-collected grass shoots that were either exhibiting choke disease symptoms or without the fungus. Overall, the abundance of Tetranychus urticae and Aculodes mckenziei was significantly lower on quackgrass plants infected by E. bromicola compared to plants without the fungus. Conversely, populations of Abacarus hystrix were significantly larger on plants colonised by the fungus than on uninfected plants. Thus, the presence of this endophytic fungus may have divergent effects on different phytophagous mite species although the basis of these effects is not yet known.