The battle to save citrus

Huanglongbing (HLB), also known as citrus greening, has devastated Florida's citrus farms. Although some producers in China and Brazil have been able to control the problem, California groves are now under threat, according to an article in News in chemistry and engineering (C & EN), the weekly magazine of the American Chemical Society. Chemists and biologists strive to develop strategies to contain the disease and hopefully find an antidote.

HLB-infected trees develop green fruit, yellow shoots, and mottled, premature and unbalanced leaves, which significantly reduces citrus yields. Originally from China in the early 1900s, the disease is related to the microbe. Candidatus Liberibacter asiaticus (CLas). This bacterium is transmitted by the Asian citrus psyllid (Diaphorina citri), a flying insect that feeds on the phloem of infected trees and transmits the microbe to other trees. The CLas are poorly known because the experts are still not able to cultivate them in the laboratory for research. Although 90% of lemon trees in Florida have been infected, there is still hope for California if producers and scientists quickly find a cure, writes freelance journalist Cici Zhang.

Researchers are studying different strategies for controlling the disease, such as creating resistant cultures with the CRISPR gene editing tool, delivering anti-CLs peptides directly into the phloem and using them. Interferences of RNA to exterminate the psyllids. However, with many of these solutions in years, producers need immediate action for existing trees. Chinese producers have created the "three-axis" approach to HLB prevention, which includes three steps: planting seedlings without bacteria, eliminating infected trees, and monitoring and removing psyllids. Although the disease is still present in citrus plantations in China, the percentage of infected trees has decreased. In Brazil, the "10 Commandments" for HLB management encompbad the same basic ideas of tree and pest management. Meanwhile, in California, the use of a Pakistani parasitic wasp has made progress in controlling the psyllid population. Overcoming HLB will likely involve a combination of approaches, experts say.