Individual study: Impact of different meadow mowing techniques on field invertebrates
Humbert J.Y., Ghazoul J., Sauter G.J. & Walter T. (2010) Impact of different meadow mowing techniques on field invertebrates. Journal of Applied Entomology, 134, 592-599
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Use mowing techniques to reduce mortality
A randomized replicated trial in 2007 and 2008 in Switzerland (Humbert et al. 2010) found that harvesting meadow plots using a hand-pushed bar mower killed or injured on average 20% of caterpillars (Lepidoptera) added to plots before mowing, compared to 37% when using a tractor-pulled rotary drum mower, and 69% if a conditioner was attached to the rotary mower. Using a conditioner also increased the proportion of damaged wax invertebrate models from on average 11% (bar mower, no conditioner) to 30% (rotary mower with conditioner). Large (4 cm) invertebrate models were damaged more often than small (2 cm) models. Caterpillars and models placed on the ground or in vegetation (30 cm high) before mowing were affected differently by mowing treatments. Organisms on the ground were strongly impacted by tractor wheels, whilst those in vegetation were damaged by the mower/conditioner. Cutting height did not affect mortality in this study, but the authors note it is likely to be important for larger animals. Nine meadows were studied, with four 2.5 m-long plots each. There were four mowing treatments: hand-pushed bar mower (cutting height 6 cm, 1.7 m-wide), tractor-pulled rotary drum mower (2.5 m-wide) with two cutting heights 9 cm and 6 cm (one with, one without conditioner). Before mowing, 50 small and 50 larger wax invertebrate models were placed either on the ground or tied to vegetation 30 cm high. In 2008 on five meadows, large white butterfly caterpillars, Pieris brassicae, were placed on the ground (50 caterpillars) and in the vegetation (50 caterpillars). After mowing, both wax models and caterpillars that survived mowing were checked for injuries.