Impact Magazine - Spring 2008 - (Page 12)

Jim Graham evaluates the susceptibility of sweet orange varieties to citrus canker after seedlings have been inoculated with the pathogen. uf/ifas file photo “For instance, we saw parasitism that averaged 70 percent — reaching nearly 100 percent — in Puerto Rico, but less than 20 percent during spring and summer in Florida,” Stansly said. “This indicates a need for species or biotypes of parasitic wasps that are better adapted to Florida conditions.” Stansly, Hall and Eric Rohrig, an entomology graduate student in UF’s College of Agricultural and Life Sciences, are working with a beneficial wasp from China, a biotype of Diaphorencyrtus aligarhensis. Field releases of the parasitoid have started in southwest Florida. Jim Graham, a professor of soil microbiology at the Lake Alfred center, said groves should be carefully checked at least four times a year, particularly during fall and winter months when greening symptoms are most prevalent. Groves should be sprayed at least five times a year with a pesticide to control the psyllid population. However, research needs to be conducted to determine how compatible these products are with natural enemies. When greening is confirmed, immediately remove the infected tree to prevent the disease from spreading, he said. Biotechnology Dean Gabriel, a professor of plant pathology and plant molecular and cell biology, said his work on citrus greening includes detection of reservoir hosts, other than citrus, where greening may be harbored and accidentally shipped to citrus growing areas that are currently greening-free. His research, performed in collaboration with DPI, showed that the orange jasmine plant can be a carrier host for citrus greening in Florida. In a second collaborative effort with DPI, he is working to determine if heat treatment of budded citrus can be used to cure greening. If heat can be used to cure greening, it would help ensure the safety of Florida’s nursery stock at low added cost, Gabriel said. In a third research project, funded by USDA’s Animal and Plant Health Inspection Service, Gabriel is attempting to obtain the DNA sequence of the citrus greening bacterium. “If the genome of the greening organism could be determined, it would reveal all of the genes that the greening bacterium possesses and enable prediction of the organism’s weaknesses and strengths,” Gabriel said. “This allows more rational design of control strategies and also provides potential molecular targets for chemical controls.” With support from USDA-APHIS, Gabriel is also working to improve detection of greening. “We are attempting to determine if Florida has a new and previously unknown strain of the citrus greening bacterium, in addition to the known Asiatic strain of greening currently confirmed,” Gabriel said. continues to reproduce on citrus or on the orange jasmine plant (Murraya paniculata). “Unfortunately, the orange jasmine plant has been shown to be a host for greening disease, so encouraging populations of psyllids to develop on this common landscape ornamental plant during the winter is not an appropriate strategy for increasing populations of host-specific natural enemies of the psyllid,” Hoy said. She said biological control agents can reduce psyllid populations if the natural enemies are not killed by pesticides, but no biological control agent can eliminate all psyllids and the possibility of transmission of greening disease. Unfortunately, this is also true of pesticides, she said. The effectiveness of the Tamarixia radiata wasp in controlling the psyllid is being evaluated by Phil Stansly, a professor of entomology at UF’s Southwest Florida Research and Education Center, in cooperation with Michael Rogers at Lake Alfred and David Hall, an entomologist at USDA’s Horticultural Research Laboratory in Fort Pierce. “With the help of participating growers, the study determined that the beneficial wasp is present in most Florida citrus groves, but does not provide the level of control observed in other countries with warmer winter climates,” Stansly said. 12 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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