Discovery of Paraherquamide E as an Eco-Friendly Insecticide against Asian Citrus Psyllid from the Endophyte <i>Aspergillus aculeatus</i> GC-147-5 and Its Mode of Action

The Asian citrus psyllid (ACP) is the primary vector of huanglongbing (HLB), a severe citrus disease. This study identified three insecticidal paraherquamide alkaloids (paraherquamide E, SB200437, and paraherquamide B) that were effective against the ACP from the strain <i>Aspergillus aculeatus</i> GC-147-5 using a bioactivity-guided isolation method. The median lethal doses (LD₅₀) of paraherquamide E were 19.93 μg/mL (24 h) and 29.08 μg/mL (12 h), comparable to those of imidacloprid. Investigations into the insecticidal mechanism revealed that paraherquamide E disrupts fatty acid synthesis, inhibits vitellogenin production, and alters metabolic homeostasis, ultimately leading to ACP mortality. Microscopic analysis confirmed ovarian abnormalities in treated females. Additionally, paraherquamide E exhibited negligible toxicity to the nontarget species, the ladybug, indicating its high selectivity and favorable environmental safety profile. The findings of this study could lead to the development of new, environmentally friendly, and effective insecticidal agents for managing ACP.