Endophytic Fungi in Elymus canadensis Affects Insect Abundance and Reduces Plant Damage from Sucking Insects

Endophytes are microbial species, often bacteria or fungi, which live within a plant asymptomatically. Some fungal endophytes have developed a symbiotic relationship with cool-season grasses. It has been suggested that these symbiotic fungi act in a defensive mutualism with their host grasses. Endophytes can produce alkaloids that deter various types of herbivores. We examined the effect these endophytic fungi have on insect abundance, insect herbivory, and plant growth in Canada Wild Rye (Elymus canadensis), a native grass of North America. Grasses that were naturally uninfected, naturally infected with Epichloë canadensis, and artificially disinfected were studied in outdoor and laboratory trials. Bird-cherry Oat Aphids (Rhopalosiphum padi) were used as a bioassay. Our field experiment showed that endophyte infection resulted in a reduction in plant damage due to sucking insects. Our laboratory experiment corroborated this result, showing fewer apterous aphids on grasses with endophyte presence