**2.1 Incidence of Huanglongbing**

HLB (also known as Yellow Dragon/shoot disease) was first identified as an unknown disease in citrus trees by citrus farmers in Guangdong Province, China, at the end of the nineteenth century [19], but studies suggest that HLB most likely originated in Taiwan in 1870 where it was known as Likubin ("Drooping disease") [20, 21]. Later, the HLB spread to other parts of China; by 1935, it had become a severe disease of citrus species [21]. Like HLB, dieback was first described in the central parts of India in the middle of the eighteenth century [22]. At that time, it might have been limited, but HLB was recorded in Assam in the eighteenth century and, by 1912, was a devastating disease in Bombay, India. However, the Citrus tristeza virus might cause this disease. Raychaudhuri [23] exhibited that dieback was the same as HLB. African greening disease was first identified in a sweet orange orchard in parts of South Africa in 1929 [24]. Outside of China, HLB was known as the "Greening" disease in South Africa, where extensive research was conducted in the 1950s. In Indonesia, the HLB disease was first noticed in the 1940s and is called the "citrus phloem degeneration" disease [25]. Reinking, in 1919, first described this disease in English as yellowing and leaf mottle of citrus noticed in China. According to International nomenclature rules, the name "Huanglongbing" was considered the official name by citrus pathologists at the 13th conference of the International Organization of Citrus Virologists in China [26]. "Huanglong" means yellowing of the shoot, as well as the yellow dragon (the symptom appears almost like a yellow dragon over the infected trees) and "bing," which means disease in Chinese [10]. Since the discovery of HLB, it has been named differently worldwide [27]. HLB was known outside under the name "citrus dieback" in India [23], "mottle leaf disease" in the Philippines [28], "vein phloem degeneration disease" in Indonesia [25], "yellow branch," "blotchy mottle," or "greening" disease in South Africa [29].
