Can plants use entomopathogens as bodyguards?

For 20 years, ecologists have been gathering evidence in support of the hyp othesis chat plants can use insect natural enemies such as Predators and pa rasitoids as bodyguards to protect themselves from herbivory, but entomopat hogens have escaped this consideration. We extend the bodyguard hypothesis to ask whether plants can use entomopathogens as bodyguards. We first discu ss the evolutionary context of such tritrophic interactions and then catego rize possible mechanisms as: (1) maintaining a population of bodyguards on the plant surface, (2) increasing contact rates between insect host and pat hogen and (3) increasing the susceptibility of the host. We explore these m echanisms further, examining published studies for evidence for the hypothe sis. We then discuss potential costs to the plant of promoting pathogens as bodyguards which may include a reduction in the efficiency of other "bodyg uard" species, the incidental promotion of plant pathogens and the risk of entomopathogens developing phytopathogenicity. Aside from our intention to stimulate the resting of the bodyguard hypothesis with entompathogens and t o provide a conceptual framework for this, we hope to bring evolutionary ec ology and insect pathology closer together.