The annual leatheijacket survey in Northern Ireland, 1965–82, and some factors affecting populations

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Abstract
An annual leatherjacket survey was made each winter in Northern Ireland from 1965 to 1982. Over this period the mean population was 520,130/ha and showed less annual variation than in some parts of Britain. This appears to be due to the regulation of populations by rainfall in July, August and November rather than in September and October as has been shown elsewhere.It is concluded that in Northern Ireland 18,096 ha of grassland would benefit from an insecticide treatment each year. Grassland with leatheijacket populations of 1 × 106/ha or more may suffer damage and up to 100,000 ha are at risk each year. Leatherjackets are therefore considered to be serious pests of grassland in Northern Ireland.