Evaluation of floral-derived volatile blend for attracting aphid parasitoids and lady beetles in the tobacco fields

• The mixture of synthetic floral-derived compounds was optimized to efficiently attract aphid parasitoids and ladybeetles. • The synthetic blend obtained in the study was β-pinene, methyl salicylate, linalool and limonene(6:6:2:20 mg). • 3-layer film lure has been developed to be applied in the field as a stable and slow-release carrier of volatile blend. • The blend has been demonstrated to increase the population of natural enemies and control aphids in tobacco field. • Combined with other measures, it can be applied for practicing conservative biological control. In tobacco planting in China, the artificial release of aphid parasitoids Aphidius gifuensis has been applied to control aphids for a decade. However, due to seasonal effects and crop rotation, the sustainability of releasing parasitoids and the aphid control efficacy have not been properly evaluated. In this study, effective semiochemical-based attractants were further screened and optimized in the tobacco fields. Film lures were developed to release the synthetic attractant blends. In tobacco planting fields, the synthetic mixture of β-pinene, methyl salicylate, linalool, and limonene(6:6:2:20 mg) significantly increased the population of natural enemies, including A. gifuensis and ladybeetles ( Coccinella septempunctata , Harmonia axyridis and Hippodamia variegate ) monitored using using malaise traps. The increase in the natural enemy population was related to the season and the lure placement density in the tobacco fields, as well as the distribution of surrounding habitats and flowering plants. A density of 135 lures per hectare significantly increased the number of parasitoids, reduced the population of aphids, elevated the rate of parasitized aphids by 42%, and effectively suppressed the aphid population in the tobacco fields. Combined with the protection of flowering plants around tobacco fields, synthetic lures may provide a technical measure for conservative biological control.