Leave headlands in fields unsprayed (conservation headlands)

Supporting evidence from individual studies

1. A replicated, paired, controlled study in 1984–1987 on an arable farm in Hampshire, UK (Dover et al. 1990, same experimental set up as Dover 1997), found that the abundance and species richness of butterflies was greater on unsprayed conservation headlands than on conventional sprayed headlands. On unsprayed headlands, the abundance of butterflies (222–472 individuals/km) was higher than on conventional headlands (80–259 individuals/km) in all four years. In total, 29 species of butterfly were recorded, of which 13–21 were found on unsprayed headlands and 13–17 on conventional headlands each year (statistical significance not assessed). On half of 14 fields, a 6-m strip around the edge (headland) was left unsprayed, while the remainder received conventional broadleaved herbicide applications. Spring and summer applications of insecticide were not used anywhere on the farm. From 1984–1987, butterflies were sampled along a transect at least once a week from 14 May to 19 August. Sprayed and unsprayed headlands were paired with similar adjacent habitats.

   Study and other actions tested

   Referenced paper

   Dover J., Sotherton N. & Gobbett K.A.Y. (1990) Reduced pesticide inputs on cereal field margins: the effects on butterfly abundance. Ecological Entomology, 15, 17-24.

2. 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.

   Study and other actions tested

   Referenced paper

   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.

3. A replicated, paired, controlled study in 1985–1987 on an arable farm in Hampshire, UK (Dover 1997, same experimental set-up as Dover et al. 1990) found mixed effects of unsprayed conservation headlands on the behaviour of butterflies. In fields with unsprayed headlands, white butterflies (Pieridae) spent more time in the headland (57–220 seconds) than the adjacent hedgerow (4–40 seconds), whilst in fields with sprayed headlands they spent less time in the headland (5–40 seconds) than the hedgerow (18–72 seconds). However, gatekeepers Pyronia tithonus spent more time in the hedgerow (145–900 seconds) than the headland (15–375 seconds) in all fields. Flight and transit speeds of male white butterflies and transits of female green-veined white Pieris napi in unsprayed headlands (male flight: 0.56–1.35; male transit: 0.74–0.98; female transit: 0.14 m/s) were slower than in sprayed headlands (male flight: 0.21–1.75; male transit: 1.19–1.66; female transit: 0.57 m/s). However, gatekeeper males (in 1986) moved faster in the unsprayed (flight: 0.70; transit: 0.43 m/s) than the sprayed headlands (flight: 0.51; transit: 0.22 m/s).  In unsprayed headlands, male large white P. brassicae and small white P. rapae spent more time feeding (47–60%) and interacting (20–65%) than in sprayed headlands (feeding: 4–8%; interacting: 23–33%), whereas male gatekeeper spent less time feeding (32%) and interacting (36%) in unsprayed headlands than in sprayed headlands (feeding: 67%; interacting: 71%). Sample sizes were too small for other species and females. On half of 4–8 fields each year, a 6-m strip around the edge (headland) was left unsprayed, while the remainder received conventional broadleaved herbicide applications. Insecticide was not used in spring and summer anywhere on the farm. The behaviour and location (hedgerow or headland) of five butterfly species were observed. Flight speed (distance travelled/time spent in flight) and transit speed (distance travelled/time observed) were calculated.

   Study and other actions tested

   Referenced paper

   Dover J.W. (1997) Conservation headlands: effects on butterfly distribution and behaviour. Agriculture, Ecosystems & Environment, 63, 31-49.

4. A replicated, paired, controlled study in 1990–1992 in arable field edges on 12 farms in the Netherlands (de Snoo et al. 1998, same experimental set-up as de Snoo 1996) found that unsprayed field margins had a higher abundance and species richness of butterflies than sprayed margins. Butterfly abundance was higher in unsprayed edges of winter wheat in both years (10–12 individuals/100 m²) and potatoes in 1992 (5 individuals/100 m²) compared to sprayed edges (wheat: 2–3, potato: 1 individuals/100 m²). Species richness was also higher in unsprayed winter wheat in both years (3–4 species/100 m²) and potatoes in 1992 (3 species/100 m²) compared to sprayed edges (wheat: 1–2, potato: 1 species/100 m²). All six of the most common species (Meadow brown Maniola jurtina, Wall Lasiommata megera, Small heath Coenonympha pamphilus, Small white Pieris rapae, Green-veined white Pieris napi, Essex skipper Thymelicus lineola) had higher abundance in unsprayed than sprayed edges in one or both years and crops (see paper for data). Strips 6 × 100 m or 400 m along field edges were left unsprayed by herbicides and insecticides and were compared to sprayed edges in the same field. Butterflies were sampled once/week on the crop edges and adjacent ditch banks nine times from mid-May to July in 1990 and 1992.

   Study and other actions tested

   Referenced paper

   de Snoo G.R., van der Poll R.J. & Bertels J. (1998) Butterflies in sprayed and unsprayed field margins. Journal of Applied Entomology (formerly Zeitschrift für angewandte Entomologie), 122, 157-161.

5. A replicated, randomized, controlled study in 1989–1991 on an arable farm on the Hampshire–Dorset border, UK (Moreby & Southway 1999) found that caterpillar abundance was similar in unsprayed headlands and in headlands receiving autumn herbicide applications. The number of caterpillars was similar in unsprayed (0.1–0.3 individuals/0.5 m²) and sprayed (0.1–0.4 individuals/0.5 m²) plots. Two field headlands were divided into 6–8 plots (6 × 100 m), and half were randomly assigned to each treatment each year: sprayed with herbicides in autumn or left unsprayed. No insecticides or fungicides were applied. Caterpillars were surveyed in five samples/plot using a D-Vac insect sampler on five occasions from May–July 1989–1991, in one field each year.

   Study and other actions tested

   Referenced paper

   Moreby S.J. & Southway S.E. (1999) Influence of autumn applied herbicides on summer and autumn food available to birds in winter wheat fields in southern England. Agriculture, Ecosystems & Environment, 72, 285-297.

6. A replicated, randomized, controlled study in 1997–1998 on permanent pasture at three sites in Dumfries and Galloway, UK (Haysom et al. 2000) found that leaving field headlands unsprayed increased the abundance of caterpillars. Field headlands which were not sprayed with herbicide in spring had more caterpillars the following summer than headlands which were sprayed once with herbicide, but numbers were similar one year later (data not presented). From spring 1997, four treatments were carried out in adjacent plots (10 × 50 m long) on the boundaries of seven pasture fields: unsprayed unfenced, unsprayed fenced (May–September), sprayed unfenced, and sprayed fenced (May–September). In sprayed plots, herbicide (6 l glyphosate/ha) was applied in April 1997 to clear strips to trial a method for increasing foraging access for birds. Unfenced plots were grazed by cattle and sheep during summer, and all plots were intermittently grazed by sheep during winter. Insects were sweep net sampled in June and July 1997 and 1998.

   Study and other actions tested

   Referenced paper

   Haysom K.A., McCracken D.I., Roberts D.J. & Sotherton N.W. (2000) Grassland conservation headlands: a new approach to enhancing biodiversity on grazing land. Grazing Management: the Principles and Practice of Grazing, for Profit and Environmental Gain, within Temperate Grassland Systems: Proceedings of the British Grassland Society Conference, 29 February-2 March, 2000, Harrogate, UK, 159-160.