On A Mission

Areawide management of the Asian citrus psyllid (ACP) is a hot topic among many citrus growers and researchers. USDA-ARS has been working with Indian River citrus growers to implement an areawide management program for the psyllid in Martin, St. Lucie, and Indian River counties. Of interest is the influence of psyllid host plants grown in urban areas on populations of the psyllid in commercial citrus. Orange jasmine is a favored host plant of the psyllid and is widely grown as an ornamental landscape plant. No information was available on biological control agents attacking the psyllid in urban plantings of jasmine.

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USDA-ARS is particularly interested in biological control by the parasitoid Tamarixia radiata and has been surveying different plantings from Ft. Pierce to West Palm Beach for psyllid infestations and Tamarixia. Results of the project show the psyllid is common in urban plantings of orange jasmine and that Tamarixia commonly attacks the psyllid in these urban plantings. The parasitoid persists in orange jasmine under regular management practices and contributes to area-wide suppression of the psyllid.

Going The Distance

Hard To Resist
Interest in host plant resistance prompted a USDA-ARS project to search for and identify plant resistance to the psyllid in citrus and related germplasm. A planting of 87 genotypes of citrus and citrus relatives was established, and these genotypes were surveyed during 2010 for infestation levels of psyllid eggs, nymphs, and adults. Among the 87 genotypes, the following were found to be most susceptible to colonization by the psyllid: Tien Chieh mandarin, curry tree, orange jasmine, Mato Buntan pummel, Diamante citron, alemow, Swingle citrumelo, and Nansho Daidai sour orange. In free choice situations, the following genotypes were colonized least by the psyllid: Japanese prickly-ash, white sapote, Simmons trifoliate, orangeberry/gin berry, Clausena harmandiana, Chinese box orange (brachytic form), and Australian finger lime var. sanguinea. No-choice experiments are being conducted with these apparently resistant genotypes, and plant volatiles associated with susceptible and resistant genotypes are being investigated in search of attractants and repellents for the psyllid.
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.

Body Of Evidence

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A Shot In The Arm

Another interesting research project being conducted by USDA-ARS concerns finding antibiotics or antimicrobial compounds that could be used to control the greening pathogen in infected trees. Should effective chemicals be found, a way to treat infected trees with these chemicals would be needed. USDA-ARS is therefore evaluating methods of infusing chemicals into the phloem tissues of trees. Research is being directed toward finding a phloem infusion method that allows low-volume treatment of citrus. It is possible chemicals that control psyllids or deter their feeding might also be infused into citrus.
This research project also is studying the infusion of natural plant products as possible antimicrobial agents or psyllid antifeedants. The ultimate goal of this research is to develop a cost-effective and sustainable grove treatment strategy that will prevent HLB symptom development and reduce the amount of psyllid feeding on treated plants.

On The Molecular Level

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