If you have noticed an increase in the price of citrus over the past few years, you have an invasive insect from Asia to blame. The Asian citrus psyllid, which appeared in Florida in 1998, carries a bacterium that causes trees to produce bitter, misshapen, inedible fruit. The disease caused by the bacterium — known as citrus greening, Huanglongbing (HLB) or yellow dragon disease — has infected as much as 70 percent of Florida's citrus over the past few years. It reached California in 2008.
Until now, there was no known cure for citrus greening other than cutting down infected trees to keep the bacterium from spreading to healthy trees. But last week a team of scientists from the University of Florida announced a possible solution. It seems the chemical benzbromarone — which is normally used to treat gout in humans — was extremely effective in halting the spread of the bacteria in infected tree shoots. The chemical binds to a protein called LdtR in the bacterium. The protein is then deactivated, which disrupts a key process that the bacterium needs to survive inside the tree.
The researchers also tested two other chemicals which had some efficacy toward stopping the spread of citrus greening: hexestrol, which is a carcinogenic synthetic estrogen compound; and phloretin, which presents the absorption of glucose into the small intestine. Neither was as effective as the gout medication.
The chemicals have only been tested in the lab so far, so there's no word on how they will work in the field. But as researcher Claudio Gonzalez told Florida Today, "We are getting closer and closer." The team hopes to start field experiments later this year which will determine how effective the treatment is in a natural setting, as well as it if effects the taste of any fruits that the trees later generate. The U.S. Department of Agriculture (USDA) needs to approve the testing, and then later would also need to approve widespread use of the chemical. The entire process could take another five to seven years.
This isn't the only work being done to potentially save Florida's $9 billion citrus industry, or similar industries in other states. Last month the USDA approved the expansion of already ongoing efforts to release tiny parasitic wasps in California, which would target and hopefully control the Asian citrus psyllid. The wasps, Tamarixia radiate, come from Vietnam and experts say they pose no threat to the environment. Meanwhile, a team of scientists — also from the University of Florida — is working on a new way to detect citrus greening earlier. It seems that infected trees give off a smell which attracts even more of the psyllids. The researchers think the smell could also be used to attract wasps, which could then eat the invasive insects before the infections get any worse.
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