Creation of 'island' habitats in farmland to manipulate populations of beneficial arthropods: predator densities and emigration

  • Published source details Thomas M.B., Wratten S.D. & Sotherton N.W. (1991) Creation of 'island' habitats in farmland to manipulate populations of beneficial arthropods: predator densities and emigration. Journal of Applied Ecology, 28, 906-917.


This study is summarised as evidence for the following.

Action Category

Create beetle banks

Action Link
Farmland Conservation

Create beetle banks

Action Link
Natural Pest Control
  1. Create beetle banks

    A replicated, randomized and controlled study in the two winters of 1987-1989 at a mixed/arable farm in north Hampshire, UK (Thomas et al. 1991) found that two beetle banks sown with four different grass species (creeping bent Agrostis stolonifera, cock’s-foot Dactylis glomerata, Yorkshire fog Holcus lanatus and perennial rye grass Lolium perenne) produced densities of polyphagous invertebrate predators (invertebrates that feed on many different food sources) of up to 150 individuals/m2 in the first winter and over 1,500/m2 in the second winter. In the first winter, on bank 1 (in a 7 ha field) creeping bent held fewer predators (39/m2) than the other three grass species (66-102/m2), and similar numbers to bare ground (30/m2). In the second winter, Yorkshire fog held more predatory invertebrates (648-1,398/m2) than creeping bent (273-488/m2) and perennial ryegrass (276-394/m2) on both banks as well as cock’s-foot (218/m2) on bank 2 (in a 20 ha field) but not on bank 1 (cock’s-foot: 1,488/m2). In comparison, densities in the field were much lower (26-29/m2). In the second winter the two most abundant species were the ground beetle (Carabidae) Demetrias atriacapillus and the rove beetle (Staphylinidae) Tachyporus hypnorum. In spring 1989 D. atriacapillus occurred in higher numbers on or immediately adjacent to the banks up until 3 May (average density 12/m2 at 0-3m). After this date the distribution of this beetle throughout the field was more even (0.4/m2 at 0-60m). Significantly higher abundances of T. hypnorum occurred at 0 and 60 m into the field up until 18 April 1989 after which there were no consistent spatial patterns for this species, although there were lower numbers on the banks than in the field at the end of the study (22 May). The beetle banks were created in cereal fields on chalky-flint soil in autumn 1986 and treated with a broad-spectrum herbicide prior to hand-sowing in spring 1987. Six replicates of each treatment (four single grass species, two mixes of three or four of the grass species, and bare ground) were created. Predator communities were studied (November-February) through ground-zone searching in quadrats and destructive sampling (digging up turf samples) in the banks as well as mid-field. Crop penetration by emigrating predators was studied (once a week April-late May 1989) through transects of vacuum-net sampling at 0, 3 10, 30 and 60 m distance perpendicular to the cock’s-foot treatments on bank 1. This study was part of the same experimental set-up as (Thomas 1991, Thomas et al. 1992, MacLeod 1994, MacLeod et al. 2004).


  2. Create beetle banks

    A randomised, replicated, controlled study in winter 1987-1988 and 1988-1989 on two beetle banks in two cereal fields on a farm in Hampshire, UK (Thomas et al. 1991) found total invertebrate predator numbers collected from turf samples and ground searching were higher on beetle banks (218-1,488 individuals/m² in turf samples, 39-188 individuals/m² in surface searches) than the surrounding crop (26-29 individuals/m² in turf samples, 16-49 individuals/m² in surface searches). Invertebrate predators included ground beetles (Carabidae), rove beetles (Staphylinidae) and spiders (Araneae). In 1989, emigration patterns of the rove beetle Tachyporus hypnorum and the ground beetle Demetrias atricapillus showed movement of individuals from the bank into the field from 14 April-22 May. From 14 April-3 May, there were 12.2 individuals/m² of D. atricapillus at 0-3 m from the bank, after which the average density was 0.4 individuals/m² at 0-60 m from the bank. By the end of the study there were significantly fewer T. hypnorum on the bank than the crop. Establishment costs were estimated at £85 in year one and £30 in following years for a 20 ha field (1990 prices). Maintaining aphid (Aphidoidea) populations below a spray threshold was valued at £300/year and £660/year if an aphid-induced yield loss of 5% was prevented. This study was part of the same experimental set-up as Thomas 1991, Thomas et al. 1992, MacLeod 1994 and MacLeod et al. 2004.

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