Individual study: The foraging ecology of hoverflies and the potential for manipulating their distribution on farmland.
Cowgill S.E. (1991) The foraging ecology of hoverflies and the potential for manipulating their distribution on farmland.
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Leave headlands in fields unsprayed (conservation headlands)
A replicated, controlled study of two headlands over two years 1989-1990 in England (Cowgill 1991) found that in 1990, there were significantly higher proportions of some species of hoverfly (Syrphidae) adults (marmalade hoverfly Episyrphus balteatus, Metasyrphus spp.) in conservation headlands (20-24%) compared to fully sprayed headlands (9-12%). There were also higher proportions of E. balteatus adults feeding and lower proportions inactive in conservation (feeding: 15-90%, inactive: 0-85%) compared to fully sprayed headlands (feeding: 0-35%, inactive: 0-100%). Behaviour of Metasyrphus corollae did not differ with treatment. There were no significant differences in 1989. Weed density and floral area tended to be higher in conservation compared to sprayed plots. Headlands were divided into three or five replicate plots of 75-100 m x 12 m wide, each containing the two pesticide treatments. A set route was walked to record hoverflies encountered during a fixed time period. Weekly counts of weeds and hoverfly eggs on wheat were made in 15-21 quadrats/plot from May-July. Aphids (Aphidoidea) were also recorded but results are not included here.