The importance of monitoring the Ceutorhynchus pallidactylus female flight 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 particular 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 those of the chlorpyrifos + cypermethrin combination only at the optimal spraying time. The most suitable time for spraying varied from the point when the first females appeared in yellow water traps in somewhat higher quantities to the time when a substantial proportion of caught females was able to lay eggs.