Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2011
Publication Date: 1/9/2012
Citation: Esquivel, J.F., Medrano, E.G. 2012. Localization of selected pathogens of cotton within the southern green stink bug. Entomologia Experimentalis et Applicata. 142:114-120. Interpretive Summary: Southern green stink bugs are pests of cotton that transmit disease pathogens that can cause boll rot in cotton bolls, while also reducing yield quality and quantity. However, information is needed on where these disease-causing pathogens reside after ingestion by stink bugs. In this study, adult stink bugs reared in a laboratory were fed sterile green beans soaked in water (untreated) or beans treated with one of three bacterial pathogens (Pantoea agglomerans, P. ananatis, or Klebsiella pneumoniae) or yeast (Nematospora coryli). Overall, after feeding, the gut contained significantly higher concentrations of pathogens than the head and mouthparts, but concentrations were similar between the head and mouthparts. All four pathogens were detected in the gut, but only P. agglomerans and N. coryli were detected in the mouthparts and head. The distribution pattern of tested bacteria and yeast explains the increased likelihood for transmission of P. agglomerans and N. coryli, two key pathogens of cotton transmitted by southern green stink bug.
Technical Abstract: Southern green stink bugs, Nezara viridula (L.) (Hemiptera: Pentatomidae), are pests of cotton recently shown to ingest and retain disease pathogens of cotton, and selectively inoculate these pathogens into bolls. The objective of this study was to determine where pathogen colonization occurs in N. viridula after ingestion. Laboratory-reared adult N. viridula were fed sterile green beans soaked in water (control) or beans previously soaked in a suspension of one of three opportunistic bacterial pathogens (Pantoea agglomerans, P. ananatis, or Klebsiella pneumoniae) or a yeast (Nematospora coryli). The insect rostrum, head, and alimentary canal were subsequently processed to determine the presence of pathogenic organisms. Overall, the alimentary canal exhibited significantly higher mean (± SEM) concentrations of colony forming units per g tissue (4,806.25 ± 397.23) than the head (443.37 ± 397.23) and rostrum (46.04 ± 397.23); differences were not observed between the head and rostrum. All four pathogens were detected in the alimentary canals, but only P. agglomerans and N. coryli were also detected in the rostrum and head. Although P. ananatis and K. pneumoniae were only detected in the alimentary canal, their ranges of concentrations were similar to those of P. agglomerans and N. coryli in this tissue. Non-selective media indicated other bacterial fauna were also detected in all study insects but this is not unusual given that the insect colony was not maintained in a sterile environment. Thus, N. viridula does not discriminate with regard to ingestion of pathogens. The observed distribution pattern of tested bacteria and yeast in certain tissues of N. viridula clarifies the propensity for transmission of P. agglomerans and N. coryli. Results are discussed in relation to future research avenues examining selective colonization of certain pathogens and frequency of host infection by adults harboring the pathogenic organisms.