The threat of Citrus Greening Disease (Huanglongbing) to the citrus industry in Sarawak

The citrus industry is an important fruit industry in Sarawak, providing a livelihood to many growers and supplying mainly to the domestic market. In 1988, the Citrus Greening Disease (CGD) or ‘Huanglongbing’ was first detected in Sarawak in the Samarahan Division. By 1991, the disease managed to destroy a total of 1143 ha of citrus trees in the Samarahan Division, resulting in an estimated economic loss of RM 6.5 million. This disease is also present in Indonesia, Thailand, Vietnam, the Philippines, Bangladesh, India, Papua New Guinea, Taiwan, China, Japan (Okinawa), Florida and South Africa. The disease, which is caused by the bacterium “Candidatus Liberibacter asiaticus”, causes dieback of the citrus trees. After the decline of the citrus industry in the Samarahan Division in the early 1990’s, the Department of Agriculture produced disease-free planting material for replanting by farmers in the Samarahan Division. The disease became severe again around 2001-2002. The use of CGD-free planting material and good field surveillance are key factors in the prevention and management of the citrus greening disease. Citrus production is a good income generator. The citrus fruit, especially the honey mandarin, is a good import substitute for oranges and mandarins. It also has good potential as an export crop with its comparatively long shelf life and easy handling and transportation characteristics. This paper discusses CGD, how it spreads and its effects on the citrus trees in particular, with a case study, and the citrus industry as a whole. It also highlights some important management issues that are paramount to ensuring a healthy orchard.