Evidence of the role of honey bees (Apis mellifera) as vectors of the bacterial plant pathogen Pseudomonas syringae

Abstract

Honey bees (Apis mellifera) have been implicated in the spread of the fire blight pathogen (Erwinia amylovora), and may transmit other bacterial plant pathogens in the process of pollinating crops. Furthermore, the movement of hives from one orchard to another could spread plant diseases over large distances. We investigated whether honey bees might play a role in the transmission of different pathovars of Pseudomonas syringae. We detected live P. syringae pv. actinidiae (Psa), a pathogen of kiwifruit (Actinidia spp.), on caged bees in hives 6 days after the bees were inoculated with Psa, and recorded up to 1.8×10 4 colony forming units of Psa on honey bees foraging naturally on flowers of Psa-infected vines. P. syringae pv. syringae (PssSmr), a pathogen with a wide host range, was spread to untreated bees in a hive within 24 h following the introduction of foragers doused in PssSmr-contaminated pollen and was still detected on bees 9 days later. PssSmr was found on caged bees in hives 6 d after they were inoculated and PssSmr survived in hives for at least 14 days. These results demonstrate that P. syringae can survive in beehives and spread within a hive, which broadens the applicability of results from studies of E. amylovora and supports recommendations for a stand down period before moving beehives from a contaminated to a noncontaminated orchard.

Survival and probability of transmission of plant pathogenic fungi through the digestive tract of honey bee workers

“…Movement of honey bee hives may pose a potential pathway for the spread of myrtle rust against the prevailing wind direction and beyond its current distribution along the eastern seaboard and the North Territory of Australia. As noted by Pattemore et al (2014), little can be done to manage the transport of plant pathogens within the foraging range of a hive, but quarantine restrictions associated with movement of bee hives from currently infected to uninfected areas should be considered.…”

“…The concentration of fungal spores administrated to the bees was based on the amount of colony forming units (CFU) of plant pathogens found on bees foraging on infected flowers, which commonly ranges from 10 3 to 10 6 CFU per bee (Dedej et al 2004;Pattemore et al 2014).…”

“…Honey bees (Apis mellifera L.) have been implicated as vectors of plant pathogens by several authors (Alexandrova et al 2002a;Dedej et al 2004;Gasparoto et al 2017;Pattemore et al 2014;Shaw 1999). Honey bees are known to disperse pathogens, such as the bacterium Erwinia amylovora (the causal agent of fire blight of apple and pear trees), from inoculum placed in hives to flowers, leading to the establishment of the bacteria on the surface of the stigmas and, consequently, infection (Johnson et al 1993).…”

Bacterial Diseases of Crops

“…Phytopathogenic bacteria have evolved to harness insects as vectors to affect their dissemination and delivery directly on or into their preferred plant hosts (Nadarasah and Stavrinides, 2011). The role of insects as vectors of phytopathogenic bacteria has been demonstrated in kiwifruit, P. syringae; grapevine, Xylella fastidiosa; corn, Pantoea stewartii; cucurbits, Serratia marcescens; cucurbits, Erwinia tracheiphila; pome, E. amylovora; citrus, Candidatus liberibacter, and potato, P. carotovorum pathosystems (Nadarasah and Stavrinides, 2011;Pattemore et al, 2014).…”

Plant pathogenic bacteria in open irrigation systems: what risk for crop health?

“…Most recent examples include citrus greening caused by bacteria of the genus 'Candidatus Liberibacter' that are transmitted by psyllids (Stokstad, 2012) and bacterial canker of kiwifruit and horse chestnut bleeding canker caused by the bacterium Pseudomonas syringae (reviewed by Lamichhane et al, 2014b). For kiwifruit canker, a large number of epidemiological studies on the disease suggested the role of latently infected propagation materials (Scortichini et al, 2012), insect vectors (Pattemore et al, 2014) or contaminated pollen (Gallelli et al, 2011;Stefani & Giovanardi, 2011). However, to the knowledge of the authors, no study has yet investigated the possible role of irrigation water as a source of pathogen inoculum.…”