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New Zealand Plant Protection 64 (2011): 284

Weevils in pasture: a comparison of sampling techniques

M.R. McNeill and C. van Koten

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 0.2 m2 quadrats, a Vortis (24 16 cm diameter, 0.02 m2) or blower-vac (30 m ca 11 cm diameter, 3.27 m2) to suck the weevils from the soil surface; or by taking turf cores (48 10 cm diameter, 0.00785 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 blower-vac is a convenient tool for mass collection of weevils and parasitoids, while the Vortis is useful for monitoring more fragile insects such as Hymenoptera.

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pdfAbundance and parasitism of clover root weevil (Sitona lepidus) and Argentine stem weevil (Listronotus bonariensis) in pastures
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New Zealand Plant Protection 65: 180-185

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