In the density sampling of Otiorhynchus ligustici (L.) in the soil, double-depth sampling provided equally precise estimates at lower total costs than conventional sampling in which all sampling units are processed to the same depth.
In five test plots, double-depth sampling with 30 cm first sample depths and 60 cm second depths appeared the most efficient for estimating the number of O. ligustici larvae per 30 cm. These samplings average 72% of the total cost of conventional single-depth sampling.