First record of Asian Citrus Psyllid (ACP) (Diaphorina citri) vector of Huanglongbing (HLB) disease (Candidatus Liberibacter asiaticus) in Tonga

The Asian Citrus Psyllid (ACP) is the primary vector responsible for transmitting Huanglongbing (HLB) disease, a highly destructive bacterial infection that threatens citrus production worldwide. While HLB disease has not yet been detected in Tonga, the presence of ACP significantly increases the likelihood of an outbreak, which could severely impact the country's citrus industry. Until now, ACP had not been recorded in Tonga or most Pacific Island nations, except Papua New Guinea and Samoa. Given its serious biosecurity implications, implementing proactive preventive measures and protective strategies is crucial to safeguarding Tonga’s citrus sector. This study aims to evaluate the risk of HLB disease in Tonga based on ACP’s presence. A delimiting survey was conducted across major citrus farms and areas near international ports and airports—potential entry points for the pest. Surveys were carried out on all six main islands of Tonga (Tongatapu, ‘Eua, Ha’apai, Vava’u, Niuatoputapu, and Niuafo’ou) using three methods: yellow sticky traps; visual inspections; and sweep net collections. A total of 1,487 plants were identified, mapped, and examined, including 1,419 citrus plants and 68 jasmine orange (Murraya paniculata). Of this sample, 226 citrus and all 68 jasmine orange plants were surveyed specifically for ACP across all islands. The results confirmed the presence of ACP on each Island, highlighting the urgent need for biosecurity interventions. Further research is currently underway to determine whether HLB is also present in Tonga, ensuring early detection and mitigation efforts.