Effect of the presence of a floral resource on higher trophic level omnivores and herbivore prey
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Jørgensen, Nina1, Forfatter
Langer, Vibeke1, Vejleder
Wratten, Stephen D.1, Vejleder
1Det Biovidenskabelige Fakultet, København, Danmark
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 Abstract: It is increasingly recognized that the use of floral resources targeted towards natural enemies can be a powerful habitat management tool in conservation biological control to enhance the effectiveness of omnivorous predators and parasitoids in the agricultural landscape. The use of floral resources can contribute to the management of pests in agricultural systems by attracting natural enemies to the site and by enhancing their performance. The use of floral resources is however no guarantee of pest suppression, as the flowers may also attract insects which can interfere with the natural enemies’ ability to control pest populations. Such an unwanted interference could be imposed by the presence of a fourth-trophic-level antagonist preying on natural enemies. In order to improve the success of conservation biological control of pests in agricultural systems, it is important to understand mechanism which may have an adverse effect on the activity of natural enemies. The present experiment set out to test how the presence of a floral resource (buckwheat) would affect a natural enemy’s ability to suppress pest populations in the presence and absence of a fourth-trophic-level antagonist. The components of the study system consisted of lucerne, pea aphids, the predatory lacewing Micromus tasmaniae (Neuroptera:Hemerobiidae) and the parasitoid Anacharis zealandica (Hymenoptera: Figitidae). M. tasmaniae is a polyphagous predator, which is considered to be of high value as a natural enemy of aphids in New Zealand. It could be a potential target of future habitat management strategies as the adult lacewing feed on plant-provided food in addition to animal prey. The larva of the lacewing is parasitized by the hymenopteran parasitoid A. zealandica which also has omnivorous traits. The experiment was carried out as a semi-field experiment in field cages at Lincoln University’s experimental field sites in Canterbury, New Zealand. The results from the experiment did not reveal any effect of the presence of a fourth-trophic-level antagonist on the components of the study system, as the parasitoid A. zealandica had poor success in establishing and reproducing on populations of lacewing in the field cages. Lacewing densities were found to be linked to the densities of their prey and the presence of a floral resource. The presence of buckwheat significantly increased densities of adult lacewings in buckwheat treatments compared to lacewing densities in treatments without buckwheat. The positive effect of buckwheat on densities of adult lacewings was associated with an increased longevity of the adult lacewings; the densities of aphids were too low for the lacewings to maintain reproduction. These results suggest that the presence of buckwheat as a floral resource can benefit adult lacewings when prey numbers are scarce.
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 Type: Speciale
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Sprog: English - eng
 Datoer: 2007
 Sider: 52 pages
 Publiceringsinfo: København, Danmark : Institut for Jordbrugsvidenskab
 Indholdsfortegnelse: -
 Note: Agricultural Science, Agronom
 Type: Speciale
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