Research progress on integrated control techniques for Diaphorina citri

Citrus, belonging to the Rutaceae, is the most extensively cultivated and highest- yielding fruit crop in China, leading the world in both planting area and production. However, Citrus Huanglongbing (HLB), a devastating bacterial disease caused by Candidatus Liberibacter spp., poses a severe global threat to the citrus industry. HLB causes tree decline, stunted growth, and symptoms including leaf yellowing and mottling, as well as small, misshapen, and unevenly colored fruits. Infected young trees typically die within 2-3 years, while mature trees succumb within 5-8 years. The primary insect vector of this disease, the Asian citrus psyllid (ACP), Diaphorina citri, is native to Asia but has now spread to major citrus-producing regions worldwide, including the Americas and Africa. Currently, 13 provinces in China have found this pest. Influenced by factors such as warmer and more humid winter conditions, the psyllid is exhibiting a northward migration trend, with its suitable habitat continuously expanding. This significantly increases the risk of further HLB spread within China. As there is currently no effective cure for HLB, controlling its insect vector, the Asian citrus psyllid, has become the most critical strategy for disease management. This review systematically summarizes recent advances in various control strategies against the Asian citrus psyllid, focusing on four main aspects: (1) Agricultural control, centering on integrated orchard management. This involves scientific orchard planning, intercropping, and the rational use of adjuvants like mineral oils to create field environments unfavorable for psyllid establishment and dispersal; (2) Chemical control, which remains predominant challenges of insecticide resistance. Commonly used insecticides primarily belong to six major classes, including neonicotinoids and pyrethroids. However, prolonged and repetitive use of single modes of action has led to varying degrees of resistance in psyllid populations to many conventional insecticides. Therefore, imple- menting science-based pesticide application practices is crucial. Key measures include targeted application, rotation of chemicals with different modes of action, rational use of adjuvants, and prioritizing highly effective, low-toxicity, and environmentally friendly agents to delay resistance development; (3) Biological control utilizing natural enemies and entomopathogens. Entomopathogenic fungi represent highly promising biocontrol agents. Researchers have found that Lecanicillium psalliotae ZJLP09 and Purpureocillium lilacinum GDIZM-2 exhibit considerable efficacy against the Asian citrus psyllid and hold potential for field application. Concurrently, the mass rearing and release of parasitoid wasps such as Tamarixia radiata and Diaphorencyrtus aligarhensis have achieved successful field control both domestically and internationally, serving as exemplary models of biological control. Predatory natural enemies, including ladybugs, lacewings, thrips, and spiders, also contribute effectively to suppressing adult psyllids and eggs; (4) Physical control methods, such as using insect-proof nets as barriers, and employing yellow sticky traps or light traps of specific wavelengths to monitor and mass-trap psyllids by exploiting their tropisms, effectively reducing pest population densities. Furthermore, the integration of unmanned aerial vehicle (UAV)- based remote sensing and sprayer technology is emerging as a new trend to enhance orchard monitoring efficiency and application precision. The article also explores the current status and potential of emerging molecular technologies like RNA interference (RNAi) and gene editing. Studies showed that the CsTPS21 gene encodes a jasmonic acid- responsive monoterpene synthase that produces β-ocimene in citrus, which exhibits significant repellent effects against the psyllid. Psyllid control can be enhanced through metabolic engineering to modulate CsTPS21 expression or via the direct application of β-ocimene. Additionally, developing plant-derived or synthetic high-efficacy attractants or repellents based on insect allelochemical mechanisms, integrated with a“push-pull”strategy to divert psyllids from citrus trees to trap plants for concentrated control, represents a highly promising green pest management direction. RNAi has become an important tool in insect functional genomics. Research has found that the Asian citrus psyllid is highly sensitive to double- stranded RNA (dsRNA), and effective gene silencing can be achieved through oral delivery or topical contact. However, significant challenges remain for its practical field application. Issues such as the cost of dsRNA, its stability under field conditions, and the development of efficient delivery systems currently hinder the translation of RNAi technology from laboratory research to field implementation. In conclusion, every individual control method has its inherent limitations. Future management directions must inevitably evolve towards establishing an Integrated Pest Management (IPM) system grounded in ecological regulation and involving the synergistic application of multiple technologies. This review aims to systematically consolidate existing research findings, analyze current challenges, and outline future research priorities, thereby providing a theoretical foundation for the scientific management of the Asian citrus psyllid and for promoting the sustainable development of the citrus industry.