The fumigant ethyl formate exposure induces metabolic changes in the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae)

Ethyl formate (EF), a fumigant as an alternative to methyl bromide, is highly valued for its efficacy and low environmental risk of destroying the ozone layer. In this study, comparative metabolomics and lipidomic analyses were conducted to investigate the physiological and biochemical effects of EF exposure on adults of Planococcus citri. EF was exposed at lethal concentrations (LCt₁₀ and LCt₅₀), and metabolic changes were analyzed by liquid chromatography tandem quadrupole time-of-flight mass spectrometry. EF-inducing metabolic changes contained central carbon metabolism, amino acid metabolism, and nucleotide metabolism. Notably, EF exposure activated energy mobilization pathways, including glycolysis/gluconeogenesis and the tricarboxylic acid cycle, and promoted the up-regulation of detoxification-related pathways, such as cytochrome P450 and glucuronate interconversion. EF-inducing lipidomics further exhibited the inhibition of glycerolipid, glycerophospholipid, and sphingolipid metabolism, highlighting the disruption of cell membrane integrity and redox homeostasis. This study demonstrates that EF exposure induces physiological and biochemical disruptions in P. citri by activating energy metabolism and detoxification pathways while suppressing lipid metabolism.