Experiments were carried out to study the effect of treated schefflera plants Schefflera arboricola fam: Araliaceae by triacontanol hormone (TRIA) in different concentrations on the infestation by Macrosiphum euphorbia under glasshouses conditions. Experiments were done in two locations International Garden, Cairo Governorate and El-Orman Garden, Giza Governorate throughout 2017 season under glasshouses conditions. Three treatments (concentrations) of triacontanol hormone were done in both two locations, small concentration (35ppm), medium concentration (50ppm) and high concentration (65ppm), beside fourth treatment which did not treat with any hormone (control). The infestation by Macrosiphum euphorbia in both two locations was the same trend. But Schefflera plants which treated with small and medium concentration of (TRIA) (35ppm, 50ppm) respectively were lower infestation by Macrosiphum euphorbia comparing to control. On the other hand Schefflera plants which treated with high concentration of (TRIA) (65ppm) were higher infestation by the same insect comparing to control. Also, experiments were done to study the effect of different concentrations of (TRIA) on the morphological and physiological adjectivesoftreated Schefflera plants. Small and medium concentrations of (TRIA) improved morphological and physiological adjectives of treated Schefflera plants. On the other hand, the high concentration of (TRIA) jaeal morphological and physiological adjectives of Schefflera plants worse than control.