Title: On a mission Authors
Submitted to: Florida Grower
Publication Type: Popular Publication
Publication Acceptance Date: April 20, 2011
Publication Date: June 1, 2011
Citation: Hall, D.G., Lapointe, S.L., Shatters, R.G., Hunter, W.B., Ammar, E., Robbins, P.S., Morgan, J.K., Richardson, M.L., Walter, A.J. 2011. On a mission. Florida Grower. 104(6):22-23. Technical Abstract: Scientists at USDA-ARS in Fort Pierce are actively pursuing improved IPM strategies for the Asian citrus psyllid and searching for solutions to citrus greening disease. A review is presented of some specific research activities. One project focuses on components of an area-wide management program including the role of urban plants on infestations of the psyllid in commercial citrus, biological control of the psyllid in these urban plantings, and seasonal flight activity of the psyllid distant from citrus. Research on acquisition and transmission of the greening pathogen by psyllids gives clues on how fast the disease can be spread, whether all psyllid individuals are capable of transmitting the disease, whether there are seasonal trends in transmission, and other important information. One USDA-ARS project focuses on the transmission mechanism and distribution of the pathogen in the body of an infected psyllid. Results of research suggest that just because a psyllid is infected doesn’t mean it can transmit the pathogen. This is because the pathogen, once ingested, moves into the psyllid’s alimentary canal, but is not always able to pass through the gut wall into the body cavity and ultimately into the salivary glands. In order for the pathogen to be transmitted by an infected psyllid, the pathogen must reach the salivary glands. Of interest is why some psyllids have the pathogen in their gut and other tissues, but not in their salivary glands. USDA-ARS is assessing the mechanism of this transmission barrier in hopes of finding a way to block transmission by the psyllids. Another interesting research project concerns finding antibiotics or antimicrobial compounds that could be used to control the greening pathogen in infected trees. With respect to finding new chemicals that could be used for psyllid control, USDA-ARS discovered that, in order for a psyllid to successfully feed on citrus, a psyllid must generate a sheath that envelopes their sucking mouthparts. Research is being conducted to determine the molecular characterization of these sheaths and to identify a way to block the formation of feeding sheaths. Research has already confirmed that specific chemicals such as EDTA, a divalent cation chelating agent, can block the psyllid feeding process. Semiochemicals is a term that refers to chemical odors that play a role in the relationships between insects and the plants they feed on, or between the insects themselves. USDA-ARS, in collaboration with the University of Florida, is searching for semiochemicals that could be used to detect, monitor or control the Asian citrus psyllid. The goal of this research is to develop new traps or other innovative means of control. USDA-ARS interest in host plant resistance prompted a project to search for and indentify plant resistance to the psyllid in citrus and related germplasm. The research has shown that there is germplasm variability in susceptibility to psyllid infestations. It is possible that commercial citrus with natural resistance to the psyllid (and consequently to greening disease) might be developed. Plant volatiles associated with susceptible and resistant genotypes are being investigated in search of attractants and repellents for the psyllid. On the molecular front, USDA-ARS is studying RNA interference (RNAi) as a psyllid management strategy. The research is concentrating on RNAi strategies to disrupt and thereby suppress the biological needs of psyllids. USDA-ARS has just completed the sequencing the Asian citrus psyllid genome, and is in the process of assembly, annotation, and release into the public domain. Projected benefits from sequencing the genome includes identifying enzymatic and metabolic pathways to identify critical interdiction points; identifying gene targets for RNA interference; and expanding our understanding of the interaction between the bacterium and psyllid physiologies. All this new information will enable researchers to forge ahead in the development of improved psyllid population management strategies.