Comparative Effects of Individual and Combined Plant-Derived Essential Oils Against the Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a destructive insect pest of citrus crop due to direct feeding damage and indirect role in transmitting Huanglongbing disease, which infects the citrus production globally. However, limited studies were carried out on the efficacy of natural resources such as botanicals as a safe method for controlling this insect pest. We investigated the effects of three plant-based essential oils (EOs), mint, eucalyptus, and lemongrass, individually and in combination, against adult D. citri using toxicity and repellent bioassays. At 7.0% concentration and 48 hours of exposure, mint oil caused 72.8% mortality, with an LC50 of 3.17%, the lowest among all other treatments. In case of combinations of EOs, the mint+eucalyptus showed 88.9% adult mortality at 48 hours. No synergistic or antagonistic effect was recorded in all combination treatments against D. citri adult mortality. Repellency tests also revealed the strongest repellent activity of mint oil, with up to 75.6% repellency at 7.0% concentration. The repellency was further enhanced with EO combinations, where the mint + eucalyptus showed the highest repellent effect (80.6%) at 4 hours. Our findings indicate that mint oil, especially in combination with eucalyptus oil, is an effective EO to control the population of D. citri, offering a promising alternative approach in eco-friendly pest control in citrus orchards.