Biological efficacy of some biorational and conventional insecticides in the control of different stages of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

摘要

The biological efficacy of some biorational and conventional insecticides against different stages of Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) was evaluated under laboratory and semi-field conditions. Seven different commercial products were tested, including the biorational insecticides: Spinosad, Mectin, Fitoverm, Match, Neemix in addition to two conventional insecticides: Actara and Actellic. Data indicated that all tested insecticides showed low toxic effects to L. decemlineata eggs, but most hatching neonates died shortly after hatching. All tested insecticides at their field rates showed high toxicity to larvae of L. decemlineata. The highest mortality was obtained in earlier instars, as compared to older ones, and mortality increased with the time of exposure. Moreover, the lower concentrations (up to 25% of the field rate) of Actara, Mectin, Spinosad, and Fitoverm showed high efficacy against L. decemlineata third instar larvae. Also, Actara caused the highest mortality in L. decemlineata adults, followed by Spinosad, Mectin, and Fitoverm as compared to Actellic, Match, and Neemix. In pupal bioassay, Fitoverm caused the greatest reduction in L. decemlineata adult emergence followed by Mectin, Actara, Actellic and Spinosad. In translocation bioassays, Actara caused the highest mortality in L. decemlineata 3rd instar larvae or adults followed by Spinosad and Mectin. The residual activity of tested insecticides against third instar larvae was also evaluated. Actara, Spinosad, and Mectin were more persistent under field conditions, consequently the mortality rates after 30 days of application were 46.67%, 44.44%, and 35.56%, respectively.