Citrus Huanglongbing (Greening) Disease

Abstract

Abstract Huanglongbing disease (HLB), also known as citrus greening disease, is the most important and damaging disease of citrus fruits worldwide. The disease is caused by three closely related bacteria belonging to the genus Candidatus Liberibacter . The bacteria are spread over short distances by sucking insects known as psyllids and by the movement of infected (yet often undetected) planting material between countries and continents. Citrus is a general category of fruits which includes oranges, lemons, grapefruits and tangerines. All types are susceptible to infection and researchers have yet to develop resistant or tolerant varieties. The leading growers of citrus fruits are China, Brazil and India, which collectively produced 75 million tonnes in 2021. All three are affected by the disease; in total around 65 countries have confirmed the disease. HLB is not present in Europe, where Spain and Italy are leading citrus producers. Climate change poses a significant threat to the expansion of the disease. The arrival of HLB in the USA in the early 2000s, at around the same time as Brazil, marked a significant stage in the continuing battle to manage the disease. The USA is a major producer of citrus fruits, which was primarily from Florida before the arrival of HLB. Research efforts were intensified and over $100 million was allocated in the USA from 2007 to 2016 to develop effective ways to reduce damaging losses. Despite major advances in knowledge of the pathogen and insect vector, and how they interact with citrus hosts, it is clear that much more needs to be done to achieve long-lasting success in managing a challenging disease. Information © The Author 2023