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A preliminary comparison of some management options for reducing grass losses caused by leatherjackets in Northern Ireland
Author(s) -
BLACKSHAW R. P.
Publication year - 1985
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1985.tb01571.x
Subject(s) - revenue , biology , dry matter , yield (engineering) , population , toxicology , agronomy , agricultural economics , demography , economics , materials science , accounting , sociology , metallurgy
SUMMARY Leatherjackets can cause serious yield reductions in Northern Ireland grass. This paper considers the distribution of field population sizes derived from 19 years' data in conjuction with calculated damage functions to estimate average expected losses. Six management options were compared. These were ‘No action’, routine insecticide application in September or March, insecticide application in March in high risk years only and the use of monitoring and economic thresholds in September or March. The annual expected revenues for each of these options was calculated for herbage dry‐matter values of £0.01–0.07 kg ‐1 . It was concluded that action against leatherjackets in September would give better returns than action in March and that the use of monitoring and spraying of only those field populations above an economic threshold gave rise to greatest revenue. An annual loss to leatherjackets in Northern Ireland of over £15 million was calculated from an assumed herbage value of £0.035 kg ‐1 dry matter.