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Longan witches’ broom (LgWB) syndrome was observed in all longan-growing provinces of Vietnam. Key symptoms include: small, stunted shoots with curved, rolled up margins, deformed leaves with blisters and hairy patches on the underside; abnormal development of flower structures, flower abortion, failure to produce fruits or developing small fruits. During 2012–2015, field surveys and study of the relationship between LgWB symptoms and Eriophyes dimocarpi mites presence were carried out. Moreover, molecular analysis, electron microscopy observations, E. dimocarpi inoculations, pruning of affected spikelets and miticide experiments were performed. An average of 36.58% of longan seedlings inoculated with E. dimocarpi mites showed typical symptoms of LgWB at about 27.5 days after inoculation. The use of several pesticides in different combinations showed high efficacy on E. dimocarpi mites elimination and of symptomatology incidence reduction. These results suggest a significant association of E. dimocarpi with LgWB syndrome in Vietnam.

Longan witches’ broom syndrome is one of the most devastating epidemic in the majority of longan-growing areas of Vietnam. Main symptoms are small and roll upwards leaves, shortened internodes, and witches’ broom. Diverse etiology is reported for this syndrome enclosing viruses and eriophyoid mites. In this work, using a DNA approach based on 16S rDNA gene, phytoplasmas belonging to 16SrII and 16SrI groups were associated with longan witches’ broom syndrome, corroborating previous findings in Vietnam and in other longan-growing countries of other phytoplasmas associated with the same syndrome.