Strategy for combating citrus greening disease

Huanglongbing (HLB) or citrus greening disease is considered the most destructive citrus disease in the world. Now, a new strategy for combating the vector that transmits the disease has been identified in the shape of an essential oil that repels the insect. When infected by the disease symptoms include progressive yellowing of the canopy, premature defoliation, and extensive twig dieback. Fruit are small, irregularly shaped and bitter tasting, with a peel that remains green at the bottom. Brazilian researchers affiliated with the Federal University of S?o Carlos (UFSCar), funded by the National Council for Scientific & Technological Development (CNPq) and the by FAPESP S?o Paulo Research Foundation, analyzed the chemical composition of the essential oils produced by 22 species of the genus?Citrus, including oranges, limes and tangerines. Their purpose was to understand the effects of these substances on organisms that interact with the plants, particularly?D. citri. The research published in the journal?Molecules?showed that that the insect prefers to lay eggs on certain citrus species rather than others. Two in particular were found to be repellent:?Citrus reticulata, known as the Murcott mandarin, and the Swingle citrumelo, a hybrid of?C. paradisi?grapefruit with?Poncirus trifoliata, the trifoliate orange. "We now know the substance produced by the plant responsible for attracting the insect, as well as the oils produced by the citrus genotypes that also attract it, facilitating contamination," said Maria F?tima das Gra?as Fernandes da Silva, a researcher at UFSCar's Center for Exact Sciences & Technology (CCET) and corresponding author of the study. "In the absence of a plant that strongly resists HLB, it might be possible to produce grafts with plants that we now know to be repellent to its vector," suggests Fernandes da Silva.