Weevils in pasture a comparison of sampling techniques

Abstract

This study compared four methods to quantitatively sample adult Listronotus bonariensis and Sitona lepidus (both Coleoptera Curculionidae) in dairy pasture with a view of determining an appropriate sampling method for accurate population estimation in terms of weevils/m² Collections were made by one of three vacuum methods a vacuum cleaner to take 12 02 m² quadrats a Vortis (24 16 cm diameter 002 m²) or blowervac (30 m ca 11 cm diameter 327 m2) to suck the weevils from the soil surface; or by taking turf cores (48 10 cm diameter 000785 m²) with extraction of weevils using a Berlesse funnel The sampling was carried out on three occasions and the four methods compared for each occasion Overall for both weevil species coring or the vacuum cleaner generally indicated significantly higher densities compared to the Vortis or blower vac and are concluded to be the most accurate methods for measuring adult density However the blowervac is a convenient tool for mass collection of weevils and parasitoids while the Vortis is useful for monitoring more fragile insects such as Hymenoptera