Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662938
Title: Behavioural and physiological responses of the seven-spotted ladybird, Coccinella septempunctata, to insecticides
Author: Thornham, D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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Abstract:
Laboratory-based behavioural bioassays were used to examine the locomotor activity and feeding behaviour of C. septempunctata in response to residues and odours of five commercial insecticides, whose active ingredients were chlorpyrifos (an OP), cypermethrin (a pyrethroid), l-cyhalothrin (a pyrethroid), dimethoate (an OP), and pirimicarb (a carbamate). The greatest behavioural changes were observed in response to the pyrethroids, which reduced locomotor activity, but did not significantly affect mortality. The OPs also affected locomotor behaviour, albeit to a much smaller degree, and significantly increased mortality. The carbamate did not lead to changes in any of the variables tested throughout the study. The same patterns were observed regardless of application rate or spray pattern. Only limited responses were observed to the active ingredients of the products. Pyrethroid-contaminated prey significantly reduced feeding levels, but did not kill the predators. OP-contaminated prey altered feeding rates to a lesser extent, but caused significant levels of mortality. C. septempunctata did not respond behaviourally to odours of the test compounds. Scanning electron microscopy revealed that the greatest numbers of chemically responsive sensilla were located on the maxillary palps, and electrophysiological examination confirmed their sensitivity to both the dimethoate-based product and to the carrier formulation. This may act to reduce insecticide exposure in the field, and preserve the coccinellids in crop strata receiving lower doses, allowing greater aphid control in the days following insecticide application. The mechanism for detection involves contact chemoreception of the carrier formulation, and not olfaction. The use of pyrethroid-based insecticides in IPM requires further study to determine the full impact and potential of these chemicals.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.662938  DOI: Not available
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