Enhancement of non-target insects: indications about dimensions of unsprayed crop edges

Published source details de Snoo G.R. (1996) Enhancement of non-target insects: indications about dimensions of unsprayed crop edges. Pages 209-219 in: K. Booij & L.d. Nijs (eds.) Arthropod Natural Enemies in Arable Land II - Survival, Reproduction and Enhancement: Acta Jutlandica 71:2, Natural Science Series, 10. Aarhus University Press, Aarhus, Denmark.
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This study is summarised as evidence for the following.

	Action	Category
	Leave headlands in fields unsprayed (conservation headlands) Action Link
	Leave headlands in fields unsprayed (conservation headlands) Action Link

Leave headlands in fields unsprayed (conservation headlands)

A replicated, paired, controlled study in 1990–1992 of arable field edges in the Netherlands (de Snoo 1996, same experimental set up as de Snoo et al. 1998) found that unsprayed field margins had greater butterfly abundance than sprayed margins. In unsprayed margins, the abundance of butterflies (6–7 individuals/300 m²) was higher than in sprayed margins (1–2 individuals/300 m²). Abundance did not differ between 3-m-wide (6 individuals/300 m²) and 6-m-wide (7 individuals/300 m²) unsprayed margins. Numbers on adjacent ditch banks were also higher for unsprayed (18–20 individuals/100 m) than sprayed margins (9–11 individuals/100 m). From January 1990 and 1992, margins 3 × 100 m (in 1990) and 6 × 400 m (in 1992) were left unsprayed by herbicides and insecticides and compared to sprayed edges in the same field. From mid-May–July 1992, butterflies were sampled 11 times on 3 m (eight farms) and 6 m (six farms) margins.

(Summarised by: Andrew Bladon, edited from Farmland synopsis)
Leave headlands in fields unsprayed (conservation headlands)

A replicated, controlled, paired study of arable field edges from 1990 to 1992 in the Netherlands (de Snoo 1996) found that unsprayed field margins had greater plant cover, broad-leaved species, butterfly (Lepidoptera) abundance and insect groups than sprayed margins. Plant cover was significantly higher in 6 m (outer 3 m: 35%, inner 3 m: 26%) and 3 m unsprayed margins (36%) than sprayed margins (outer 3 m: 6%, inner 3 m: 3%). Numbers of broad-leaved species were also higher in 6 m (outer 3 m: 13 species, inner 3 m: 11) and 3 m (12) unsprayed strips than sprayed edges (outer 3 m: 3, inner 3 m: 2). Grass species did not differ (2-3). Numbers of butterfly species were significantly higher in unsprayed margins (6-7/300 m²) compared to sprayed margins (1-2/300 m²). Density did not differ between 3 m (6/300 m²) and 6 m (7/300 m²) unsprayed margins. Numbers on adjacent ditch banks were also higher for unsprayed (18-20) than sprayed margins (9-11). The number of insect groups in the upper vegetation was higher in the unsprayed (12-14) than sprayed margins (8-11). The predominant groups were flower-visiting insects, such as hoverflies (Syrphidae) and ladybirds (Coccinellidae). Insect density was also significantly higher in unsprayed (3 m: 53/100 m, 6 m: 31/100m) compared to sprayed margins (3 m: 20/100m, 6 m: 12/100m). Margins 3 m x 100 m and 6 m x 400 m were left unsprayed by herbicides and insecticides and compared to sprayed edges in the same field. Plant species were sampled in 75 m² plots within margins in June. Butterflies were sampled on 3 m (eight farms) and 6 m (six farms) margins 11 times between mid-May-July. Insects in the upper parts of plants were sampled twice/plot at the end of June with a sweep net. This study was part of the same experimental set-up as (de Snoo et al. 1994, de Snoo & de Leeuw 1996, de Snoo 1997, de Snoo et al. 1998, de Snoo 1999).