Main Research and Focus Currently, my main research is yellow leaf disease (YLD) , an destructive disease of betel palm caused by phytoplasma, and bacterial leaf spot of arecanut (Areca catechu L.). YLD was first reported in India in 1949 and it was discovered in Tunchang, a county of Hainan Province in China, in 1981. To date, diseased areca has arrived at about 51 000 ha, with an incidence of 10 to 30%; in the severely infected areas, the incidence was as high as approximately 90%. As a result, reduction in yield was up to 50 to 80% even 100%, and a lot of early infected gardens have been thoroughly destroyed. To date, it has spread to most regions where betel palm is an economically important crop in Hainan.