Bacterial endosymbionts of the psyllid Cacopsylla pyricola in the Pacific Northwestern United States (Hemiptera: Psyllidae)

Authors: Cooper, William - Rodney; Garczynski, Stephen; Horton, David; Unruh, Thomas; BEERS, ELIZABETH - Washington State University; SHEARER, PETER - Oregon State University; HILTON, RICHARD - Oregon State University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2017
Publication Date: 3/3/2017
Citation: Cooper, W.R., Garczynski, S.F., Horton, D.R., Unruh, T.R., Beers, E., Shearer, P., Hilton, R. 2017. Bacterial endosymbionts of the psyllid Cacopsylla pyricola in the Pacific Northwestern United States (Hemiptera: Psyllidae). Environmental Entomology. 46:393-402.

Interpretive Summary: Psyllids are often associated with bacterial endosymbionts that can alter the insects' susceptibility to parasitism, insect pathogens, and insecticides. Scientists at the USDA-ARS laboratory in Wapato, WA screened pear psylla populations in the Pacific Northwest (Wenatchee, WA, Yakima, WA, Hood River, OR, and Medford, OR) for bacterial endosymbionts. They found that nearly all pear psylla carry the endosymbiont Arsenophonus, which provides another psyllid pest with protection against parasitism. They also found that psyllids collected nearly Yakima, WA were more likely to care Phytoplasma pyri, the pathogen associated with pear decline disease, than were psyllids collected from other regions. Bacteria associated with other psyllid pests including Profftella, Liberibacter, and Wolbachia were not present in pear psylla. Our study is the first characterize the diversity of endosymbionts of pear psylla in North America and provides a foundation for further study on how these bacteria influence psyllid behavior and management.

Technical Abstract: Insects often have facultative associations with bacterial endosymbionts, which can alter the insects' susceptibility to parasitism, pathogens, plant defenses, and certain classes of insecticides. We collected pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), from pear orchards in Washington and Oregon, and surveyed them for the presence of bacterial endosymbionts. Adult psyllids were collected on multiple dates to allow us to assay specimens of both the summer (“summerform”) and the overwintering morphotypes (“winterform”). Two endosymbionts, Arsenophonus and Phytoplasma pyri, were detected in psyllids of both morphotypes in both states. A separate survey revealed these associations have been stable for at least three decades. Arsenophonus was present in 80-100% of psyllids in all growing regions. A slightly lower proportion of summerform than winterform psyllids harbored the bacterium. Arsenophonus was present in the bacteriomes and developing oocytes of most psyllids indicating that this endosymbiont is transovarially transmitted. This bacterium was also observed in the salivary glands and midguts of some psyllids. Phytoplasma pyri was present in a greater proportion of pear psylla from orchards near Yakima, WA than from other locations, and was present in a higher proportion of winterforms than summerforms. We did not detect Wolbachia, Profftella, or Liberibacter europaeus, which are associated with other psyllid pests including other species of Cacopsylla. Our study is the first to survey North American populations of C. pyricola for endosymbionts, and provides a foundation for further research on how bacterial associations may influence the ecology and management of this pest.