Ovicidal and larvicidal effect of bifenthrin and malathion on leafroller Amorbia sp. (Lepidoptera: Tortricidae) Alma M. Espino1, Ana M. Martínez1, José I. Figueroa1, Ángel Rebollar2, José L. Morales3, Javier Valle4, Juan M. Chavarrieta1 y Samuel Pineda1 1 Instituto de Investigaciones Agropecuarias y Forestales, Universidad Michoacana de San Nicolás de Hidalgo, Km. 9.5 Carr. Morelia-Zinapécuaro. 58880 Tarímbaro, Michoacán México. 2 spineda_us@yahoo.com. Universidad Autónoma Chapingo, Periférico Paseo de la República No. 3 1000. 58170 Morelia, Michoacán, México. Facultad de Agrobiología, Universidad Michoacana de San Nicolás de Hidalgo, Paseo Lázaro Cárdenas esquina Berlín, Colonia Viveros, Uruapan, 4 Michoacán, México. ECOSUR, Apdo. Postal 36, Km. 2.5 Carr. Antiguo Aeropuerto, CP. 30700 Tapachula, Chiapas, México. The toxicity of bifenthrin (Talstar®) and malathion (Malphus®) was tested against eggs of two different age classes (48 h and 6 d old) of two populations of the leafroller, Amorbia sp. (Lepidoptera: Tortricidae) collected in conventional and organic crops of blackberries (Rubus sp.) at Los Reyes and Tocumbo, Michoacán, Mexico, respectively. High density polyethylene papers strips containing egg masses were cut in small circles (15 mm diam) and dipped for 5 s in seven different concentrations for each insecticide (0, 0.1, 1, 10, 50, 100, 200, and 500 mg [AI]/liter). Concentrations were diluted in water plus the surfactant Tween at 0.01%. After drying, the polyethylene circles papers containing treated egg masses were transferred individually to ventilated plastic cups (4 cm x 6 cm). Each treatment was replicated four times (a repetition = a mass eggs). Egg mortality was assessed 5 days after hatching. 80 larvae from each treatment were selected randomly from larvae that emerged on the first day of hatching, placed on semisynthetic diet, kept in four plastic cups, and observed daily during five days to determinate larval mortality. Bifenthrin and malathion caused significant differences in egg mortality in the two age classes (48-h- [F = 8.44, P = 0.000] and 6-d-old [F = 2.22, P=0.03] for organic population; and 48-h- [F=2.90, P=0.007] and 6-d-old [F=2.65, P=0.01] for conventional population). Median lethal concentration (LC50) obtained for organic (27.95 and 32.48 mg a.i/liter, for larvae that hatched from 48-h- and 6-d-old eggs, respectively) and conventional population (29.74 and 25.48 mg a.i/liter for larvae that hatched from 48-h- and 6-d-old eggs, respectively) were not significantly different. Mortality caused by malathion was between 4947% and 21-17% for larvae hatched from eggs of two ages bioassayed of organic and conventional populations, respectively. Key words: Amorbia sp., chemical insecticides, Rubus sp. Support: To PIFI 2013, CIC-UMSNH, and CONACYT for the scholarship to A. M. Espino.