Microsporidian pathogens in biological control agents of hemlock woolly adelgid [poster]

Latent or cryptic pathogens such as submicroscopic viruses and microsporidia may go undetected in quarantined and laboratory reared invertebrate hosts collected for biological control programs. Although most pathogens persist at low enzootic levels in field populations of their hosts, the laboratory setting provides a highly favorable environment for epizootics, and disease can quickly compromise expensive, long-term efforts to mass-rear and establish biological control agents. At least five microsporidian species have been recovered from four species of coleopteran predators of Adelges tsugae Annand, the hemlock woolly adelgid (HWA), the Asian imports Sasajiscymnus tsugae (Sasaji & McClure) and Scymnus sinuanodulus Yu & Yao, and Laricobius nigrinus Fender and Scymnus coniferarum Crotch collected in western U.S. Three beetle colonies infected with different species of microsporidia were compromised by the pathogens. Regular screening for one microsporidian species in a laboratory colony of S. tsugae showed an increase in prevalence from 12% to 50% in one rearing season, and high winter mortality was recorded among infected beetles in a preliminary semi-field experiment. This Tubilinosema sp. was infective to L. nigrinus, S. sinuanodulus and Laricobius osakensis Montgomery & Shiyake in laboratory host specificity testing. Predatory beetle species being collected or reared for release to control HWA are relatively host specific to hemlock and pine adelgids, increasing the risk that infected beetles will inoculate the feeding niche of the adelgids, thereby exposing conspecific individuals and other predatory species to the pathogens. Current studies will determine if the microsporidia from released mass reared hosts persist in the field.;