Reduced numbers of generalist arthropod predators after crop management

  • Published source details Thorbek P. & Bilde T. (2004) Reduced numbers of generalist arthropod predators after crop management. Journal of Applied Ecology, 41, 526-538.


This study is summarised as evidence for the following.

Action Category

Reduce tillage

Action Link
Farmland Conservation
  1. Reduce tillage

    A randomized, replicated controlled trial in spring 1999 and 2000 at the Rugballegaard Institute of Agricultural Sciences, Denmark (Thorbek & Bilde 2004) found that both soil loosening and non-inversion tillage have adverse effects on ground beetles (Carabidae) and spiders (Araneae), but for non-inversion tillage these are not quite as severe as the effects of ploughing. There were around 20 ground beetles/m2 immediately after non-inversion tillage, compared to around 12 ground beetles/m2 after ploughing and around 18 in untreated control plots. There was no difference between ploughing and non-inversion tillage plots in numbers of spiders or rove beetles (Staphylinidae), or in any of the three arthropod groups 26 days after the treatment. Overall, neither ploughing nor non-inversion tillage immediately reduced the numbers of predatory arthropods significantly, relative to untreated control plots, but all three groups had lower numbers in ploughed or non-inversion tilled plots 26 days later than in untreated control plots (for example <5 spiders and <20 ground beetles/m2 in both ploughed and non-inversion tillage plots, compared to around 25 spiders and 130 ground beetles/m2 in control plots). In a separate experiment, soil-loosening to 8 cm depth with a tined hoe immediately reduced spider numbers by 25% (around 120 spiders/m2 in control plots and 90 spiders/m2 in treated plots) and ground beetle numbers by 51% (around 70 ground beetles/m2 in control plots, 35 ground beetles/m2 in treated plots) but not rove beetle numbers. These differences were statistically significant and persisted in a second sample 18 days later. The treatments were replicated between four and eight times, on 12 x 40 m plots. Predatory arthropods were sampled using emergence traps.


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