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Quantification of the Impact of Hoverflies (Diptera: Syrphidae) On Cereal Aphids in Winter Wheat: An Analysis of Field Populations

R. J. Chambers and T. H. L. Adams
Journal of Applied Ecology
Vol. 23, No. 3 (Dec., 1986), pp. 895-904
DOI: 10.2307/2403942
Stable URL: http://www.jstor.org/stable/2403942
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Quantification of the Impact of Hoverflies (Diptera: Syrphidae) On Cereal Aphids in Winter Wheat: An Analysis of Field Populations
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Abstract

(1) An analysis of predation of cereal aphids by syrphid larvae is described. The analysis uses field data on the absolute densities of predator and prey in winter wheat crops in Sussex in 1981 and 1982. The method calculates and compares two quantities: the estimated kill rate by syrphid larvae, and the kill required to provide the degree of control observed in the aphid population. (2) This approach provides a separate analysis for each weekly sampling interval to identify when predation was most effective, and permits an initial appraisal of the impact of other antagonists acting concurrently. The method indicates clearly if syrphids were sufficiently numerous to achieve control alone or, alternatively, if they were too few to have had any significant effect on the aphid population. (3) Syrphid larvae had the potential to halt the aphid increase in four of the six field populations analysed.

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