Bulletin of Entomological Research (2006) 96, 637-645

W.O.C. Symondson, S. Cesarini, P.W. Dodd, G.L. Harper, M.W. Bruford, D.M. Glen, C.W. Wiltshire and J.D. Harwood (2006)
Biodiversity vs. biocontrol: positive and negative effects of alternative prey on control of slugs by carabid beetles
Bulletin of Entomological Research 96 (6), 637-645
Abstract: Environment-friendly farming techniques seek to increase invertebrate biodiversity in part with the intention of encouraging greater numbers of predators that will help to control crop pests. However, in theory, this effect may be negated if the availability of a greater abundance and diversity of alternative prey diverts predators away from feeding on pests. The hypothesis that access to alternative prey can lead to reduced pest suppression under semi-field conditions was tested. Alternative prey type and diversity were manipulated in 70 mesocosms over 7+ weeks in the presence of the carabid Pterostichus melanarius (Illiger), a known predator of slugs, and reproducing populations of the slug Deroceras reticulatum (Müller). Significantly fewer slugs survived where no alternative prey were provided. Maximum slug numbers and biomass were found in treatments containing either carabids plus a high diversity of alternative prey (many species of earthworm and three of Diptera larvae) or a single additional prey (blowfly larvae, Calliphora vomitoria Linnaeus). In these treatments slug numbers and biomass were as high as in plots lacking predators. The effects of alternative prey were taxon-specific. Alternative prey strongly affected carabid fitness in terms of biomass and egg load. The fittest predators (those with access to high alternative prey diversity or C. vomitoria larvae) reduced slug numbers the least. The mean individual slug weights were greater in treatments with alternative prey than where no alternative prey were provided to the carabids. These results suggest that pests may survive and reproduce more rapidly in patches where predators have access to alternative prey.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): William O.C. Symondson, James D. Harwood, David M. Glen

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Deroceras reticulatum
Pterostichus melanarius (predator)	Deroceras reticulatum