Reduction of Huanglongbing Due to the 'Appropriate Techniques Expansion for the Cultivation of King Mandarin' Project in Southern Vietnam

Our project was the expansion of appropriate cultivation techniques of King mandarin (Citrus nobilis Loureiro) to growers who have average-sized farms of 1,000 to 10,000 m 2 in southern Vietnam. In this region, most citrus trees are infected by huanglongbing (HLB) within two years of planting. The HLB management techniques implemented consisted principally of Nippa palm (Nypa fruticans) or Banana (Musa spp.) windbreaks on all sides of the orchards, planting of guavas (Psidium guajava) one to two months prior to planting disease-free King mandarin trees, and insecticide applications. Insecticide applications were scheduled as follows: 1) soil-drenching with neonicotinoid around King mandarin trees 10 days before planting and every two months for one year thereafter; and 2) leaf-spraying every month from the second year on. In seven of the eleven orchards included in the project, 0.3 to 2.6% of King mandarin trees were infected by HLB in the first year and 3.0 to 21.9% in the second year. However, the infection rate in the first year reached at 21.1 to 39.3% in four orchards where the insecticide was not correctly applied. The results indicate that the appropriate use of neonicotinoid curtailed the infection of King mandarin trees by HLB. The success of our project thus depends on how precisely the techniques are transferred and incorporated by the growers.