Impact Magazine - Spring 2008 - (Page 10)

Transmitted by the Asian citrus psyllid (Diaphorina citri) now widely distributed throughout Florida, citrus greening has been found in 27 counties, including most major commercial citrus areas. Browning said it’s not practical to eradicate citrus greening, but the spread of the disease can be slowed with an effective integrated pest management program that includes limited use of insecticides, beneficial insects that attack the psyllid and other improved grove management practices. “What complicates control of citrus greening is the fact that symptoms don’t begin to show up in trees until several months after the trees are infected by the psyllid insects,” said Ron Brlansky, a professor of plant pathology at UF’s Lake Alfred center. “Lack of early detection of the systemic bacterial disease is a major problem for the citrus industry — once the symptoms show up, it’s too late to save the tree.” He said early symptoms such as leaf mottling and yellow discoloration may be mistaken for other problems such as nutritional deficiencies, and improved laboratory tests are needed to determine if greening is the problem. The disease can also be identified by cutting open small and poorly colored fruit and looking for aborted seeds. Brlansky is working with Michael Rogers, an assistant professor of entomology at the Lake Alfred center, to investigate the interaction between the Asian citrus psyllid and the citrus greening pathogen (Candidatus Liberibacter asiaticus). They are also determining if the transmission of the greening pathogen can be reduced through the use of insecticides, particularly systemic insecticides. Unlike broad-spectrum insecticides that are applied to the foliage of citrus trees, soil-applied systemic insecticides are less likely to impact other beneficial insects that control citrus pests in existing biological control programs, Rogers said. “Recent results in our field trials have demonstrated that soil-applied systemic insecticides can reduce psyllid populations on mature citrus trees and provide a significantly longer period of control than foliar applications,” Rogers said. “These research projects will allow us to manage psyllids with fewer pesticide applications than growers use in other regions of the world where greening is a problem.” Brlansky said other projects are also underway to learn more about the transmission of the greening pathogen by the psyllids. Researchers are looking for answers to questions such as: how long must a psyllid feed to acquire the pathogen from an infected plant, how long must an infected psyllid feed on a healthy plant before it transmits the pathogen to the plant, can the pathogen be passed from mother to offspring, can the psyllid acquire the pathogen from plants that are infected but not yet showing disease symptoms, and what is the percentage of psyllids likely to be infected with the greening pathogen at different times of the year? Meanwhile, a new collaborative diagnostic laboratory operated by U.S. Sugar Corp. and UF in Clewiston is helping growers improve their ability to detect the disease, and state funds have been allocated for a new diagnostic laboratory at UF’s Southwest Florida Research and Education Center in Immokalee. The Immokalee lab, part of the Florida Extension Plant Disease Clinic, is being managed by Pamela cover story Adult Asian citrus psyillid Immature stages of psyllid feeding on citrus leaves Chlorosis on citrus leaves infected with citrus greening Small, lopsided fruit from greening-infected citrus tree Citrus canker lesions on leaves Citrus canker lesions on fruit photos by michael rogers 10 IMPACT | Spring 2008

Table of Contents Feed for the Digital Edition of Impact Magazine - Spring 2008

Impact Magazine - Spring 2008 Contents A Big Boost for Biofuels Top Priority Partnerships for Sustainable Agriculture Eliminating the Evil Weevil Invasive Pest Defeating Resistant Roaches Biodiesel Boon User-Friendly Updates for FAWN Flat-Out Great for the Grill! Laser Labeling Cashing in on Caviar Saving Water with Soil-Moisture Sensors Spotlight IFAS Development News

Impact Magazine - Spring 2008

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