The importance of monitoring the Ceutorhynchus pallidactylus female fly activity for the timing of insecticidal treatment

The effects of two pyrethroids and one combination of organophosphate and pyrethroid (alpha-cypermethrin, etofenprox, chlorpyrifos + cypermethrin) on Ceutorhynchus pallidactylus (Marsham, 1802) (Coleoptera: Curculionidae) were tested under field conditions in the Czech Republic in 2006 – 2008. Significant differences in the effects of the compared insecticides on C. pallidactylus were recorded in the years (2006, 2007, 2008). It was less important and somewhat less complicated to establish the most suitable time for spraying in the case of the chlorpyrifos + cypermethrin combination in comparison with the pyrethroids applied separately. The effectiveness of the tested insecticides was markedly influenced by the time of spraying. The effects of the pyrethroids applied singly achieved results comparable to that of the chlorpyrifos + cypermethrin combination only at the optimal spraying time.