The impact of dimethoate on the spatial distribution of beneficial arthropods in winter wheat

Published source details Holland J.M., Winder L. & Perry J.N. (2000) The impact of dimethoate on the spatial distribution of beneficial arthropods in winter wheat. Annals of Applied Biology, 136, 93-105.
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This study is summarised as evidence for the following.

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	Leave headlands in fields unsprayed (conservation headlands) Action Link

Leave headlands in fields unsprayed (conservation headlands)

A before-and-after study of two winter wheat fields over one year in Dorset, UK (Holland et al. 2000) found that some arthropod taxa survived within the unsprayed headland and appeared to recolonize the mid-field surrounded by the headland more extensively compared to when there was no headland. Ground beetle (Carabidae) species (Pterostichus melanarius, P. madidus), spiders (Araneae: money spiders (Linyphiidae), wolf spiders (Lycosidae)), parasitic wasps (Aphidius spp.) and total predatory arthropods showed the greatest decline immediately after application of the insecticide dimethoate; rove beetles in the sub-family Aleocharinae did not decline. Numbers of the ground beetle P. madidus, money spiders and parasitic wasps Aphidius spp. decreased within the field and unsprayed headland. Numbers of P. madidus recovered faster within the field edge than mid-field and particularly within the unsprayed buffer zone and the mid-field area it enclosed. Money spiders were present across most areas of both fields 19 days after spraying, although in lower numbers than pre-spraying, parasitic wasps Aphidius spp. had not recovered 20 days after spraying. A grid of 75 and 29 pitfall traps were used in each field, over two days on five occasions May-July 1997 and then 6, 20 and 34 days after spraying with the pesticide dimethoate (0.86 l/ha). A 6 m headland around half of one field was unsprayed. A D-Vac suction sampler was also used three times pre-spraying and at 6 and 20 days after treatment.