Endophytic fungi affect the host selection behavior of two key hemipteran plant pests, Lygus hesperus (Miridae) and Nezara viridula (Pentatomidae)

Hemipteran sucking bugs have emerged as major pests across the US cotton belt, reducing yields directly by feeding on squares and bolls and indirectly by vectoring plant pathogens.  All plants including cotton host a wide range of microorganisms as endophytes. Increasing evidence suggests that many members of the plant microbiome may be beneficial mutualists that confer protection to the plant from a variety of abiotic and abiotic stressors including herbivorous insects, nematodes and pathogens.  We used choice and no-choice assays to examine the host selection behavior of western tarnished plant bugs (Lygus hesperus) and southern green stink bugs (Nezara viridula) in response to cotton squares and bolls from plants endophytically-colonized by one of two candidate beneficial fungal isolates. Both species exhibited strong negative responses to squares (L. hesperus) and bolls (N. viridula) from plants that had been colonized by candidate endophytic fungi relative to control plants under both no-choice and choice conditions.  Behavioral responses of both species indicated that the insects were deterred prior to contact with plant tissues from endophyte-colonized plants, suggesting a possible underlying role for volatile compounds in mediating the negative response. Our results highlight the role of fungal endophytes as plant mutualists that can have positive effects on resistance to pests, plant performance, fitness and corresponding yields in the field.