The effect of a siliconate coadjuvant + poliether (Break) at 50, 75, and 100 mL•hL-1 , along with standard insecticides, was studied during the 2005-2006 growing season on Pseudococcus viburni mealybug control in two commercial vineyards in the central valley of the Metropolitan Region of Chile. These vineyards were naturally infested with mealybugs the previous season. A control program included three insecticide sprays, chlorpyrifos at post-harvest (autumn), and before cluster filling (summer), and diazinon when shoots were 10-15 cm long in the spring. A standard diazinon treatment without surfactant and a control treatment without spray were included. Levels of uninfested and infested clusters were determined at harvest on 100 clusters per experiment unit. Results were transformed by arcosen√% and subjected to analysis of variance. Means were separated according to Tukey’s test. On the basis of the results obtained, the application of trisiloxane in combination with polyether (Break) did not improve the effectiveness of chemical control in areas with a moderate to high infestation of P. viburni. Se estudió durante la temporada 2005-2006 el efecto del coadyuvante siliconado trisiloxano en combinación con poliéter (Break) en concentraciones de 50, 75 y 100 mL·hL-1 junto con insecticidas en el control de chanchito blanco de la vid (Pseudococcus viburni) en dos viñedos comerciales de la Región Metropolitana de Chile, infestados naturalmente la temporada precedente. Como parte de un programa normal de control, con clorpirifos en postcosecha y previo al cierre del racimo (verano), y diazinon en brote de 10-15 cm en primavera. Se incluyó un tratamiento estándar de diazinon sin surfactante y un testigo sin aplicación. En cosecha, se determinaron los racimos sanos y con diversos grados de infestación, sobre 100 racimos por unidad experimental. Los resultados se transformaron por arcoseno y sometieron a análisis de varianza y prueba Tukey para separar promedios. Bajo las condiciones del ensayo, las concentraciones de Break no afectaron la efi cacia de los tratamientos, expresada en porcentaje de racimos sanos.