Generalist predators in organically and conventionally managed grass-clover fields: implications for conservation biological control

Published source details Birkhofer K., Fliessbach A., Wise D.H. & Scheu S. (2008) Generalist predators in organically and conventionally managed grass-clover fields: implications for conservation biological control. Annals of Applied Biology, 153, 271-280.
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This study is summarised as evidence for the following.

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	Use organic rather than mineral fertilizers Action Link

Use organic rather than mineral fertilizers

A replicated, controlled study in 2004 of grass/clover Trifolium spp. fields in Switzerland (Birkhofer et al. 2008) found that spider (Araneae), but not ground beetle (Carabidae) or rove beetle (Staphylinidae), abundance was significantly greater in plots with organic fertilizers compared to those with synthetic fertilizers. Spider activity density was 80% greater in organic plots in April and October (1.1/m²) than conventional plots (0.9/m²). Spider diversity did not differ significantly with treatment. Ground-running spider abundance (78% Pardosa spp.) was significantly greater in organic compared to conventional plots in April (1.0 vs 0.6/m²), August (1.2 vs 1.0/m²) and October (1.2 vs 0.9/m²). In contrast, foliage-running spiders were more abundant in conventional plots in May (0.5 vs 0/m²). There was no effect of treatment on potential prey (aphids (Aphididae), leafhoppers (Auchenorrhyncha), and globular (Sminthuridae) and slender (Entomobryidae) springtails (Collembola)). Treatments were replicated in a 12 x 4 Latin square design of 10 x 20 m plots. Half of each plot received high levels of manure or synthetic fertilizers. No pesticides were applied. Five pitfall traps were placed within a fenced enclosure (1.8 m²) established within each plot before each of the five annual cuts (April-November 2004). After 14 days invertebrates were identified to group and activity densities calculated. Potential prey taxa were sampled by suction sampling (2 m² area) and a soil core (20 cm diameter) in each subplot in October.