Pre‐Bloom Application of Petroleum Spray Oil for the Control of Green Apple Aphid, <i>Aphis pomi</i> De Geer in Apple Orchards

ABSTRACT The green apple aphid ( Aphis pomi De Geer) is a major early‐season pest in apple orchards. While petroleum spray oils (PSOs) are commonly applied at the delayed dormant stage to control San José scale and European red mite, their effect on A. pomi remains unclear. This study assessed the ovicidal and larvicidal efficacy of 2% PSO applications at the delayed dormant/green tip stage. Laboratory and field assays demonstrated substantial suppression of egg hatch, with cumulative hatch reduced to 9.90% ± 0.57% (laboratory assay) and 9.62% ± 0.71% (field evaluation) in treated shoots. Survival analyses revealed significantly higher mortality risk for treated eggs. Direct toxicity trials on nymphs showed mortality rates of 69.9% ± 1.95% in field conditions and &gt; 99% in lab dip assays by 5 days after treatment. Residual toxicity assays indicated cumulative mortality reaching 64.07% ± 2.74% by 2 days post‐exposure, confirming efficacy even after drying. Field trials further revealed that PSO significantly reduced bud infestation by A. pomi (5.22% ± 0.54%) compared to the untreated control (19.04% ± 2.34%), with enhanced suppression observed when combined with imidacloprid (0.29% ± 0.14%). These findings underscore the potential of PSO as both a standalone and synergistic agent in aphid management. This is the first detailed report on the ovicidal and larvicidal activity of PSOs against A. pomi , supporting its inclusion in sustainable, early‐season integrated pest management programmes.