Predator mortality depends on whether its prey feeds on organic or conventionally fertilised plants

[Display omitted] ► Coccinellid mortality on plants in organic and synthetic fertilisers was tested. ► Mortality increased by 10% when eating aphids on plants in synthetic fertiliser. ► Two aphid prey species (Brevicoryne brassicae, Myzus persicae) gave same result. ► Sequestration of plant defences...

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Bibliographic Details
Published in:Biological control 2012-10, Vol.63 (1), p.56-61
Main Authors: Banfield-Zanin, J.A., Rossiter, J.T., Wright, D.J., Leather, S.R., Staley, J.T.
Format: Article
Language:English
Subjects:
Abundance
Adalia bipunctata
Aphididae
Aphidoidea
Biological control
biological control agents
Brassica
Brevicoryne brassicae
conventional farming
Feeding
feeds
food chain
Food chains
Food plants
Glucosinolate
Glucosinolates
Herbivores
Host plants
larvae
Mortality
Myzus persicae
Natural enemies
organic fertilizers
Parasitism
Pest control
Predation
Predators
Prey
Sustainable agriculture
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Summary:[Display omitted] ► Coccinellid mortality on plants in organic and synthetic fertilisers was tested. ► Mortality increased by 10% when eating aphids on plants in synthetic fertiliser. ► Two aphid prey species (Brevicoryne brassicae, Myzus persicae) gave same result. ► Sequestration of plant defences did not explain differential mortality. ► Predator efficacy for biocontrol may differ between conventional and organic farms. Natural enemy abundance and diversity can be increased under sustainable farming systems, but this has not been shown to consistently increase predation and parasitism rates or decrease herbivore abundance. ‘Top-down’ regulation of herbivore populations may depend on ‘bottom-up’ factors such as plant quality, and not solely on predator diversity or abundance. Specialised herbivore species can sequester secondary chemicals from plants to use in a defensive system against predators which mimics that of their host plants, but this herbivore defence may vary with the concentration of plant defences. We investigated whether fertiliser type and concentration alter the mortality of coccinellids feeding on two aphid species from Brassica plants growing in fertilisers typical of organic and conventional farming systems, due to differences in concentrations of defensive glucosinolate compounds cascading up the food chain. Coccinellid larval mortality was 10% higher when feeding on aphids from synthetically fertilised plants compared with those in organic fertilisers, regardless of the aphid species. Concentrations of both constitutive foliar glucosinolates, and those induced by aphids, varied with fertiliser type but this did not affect the glucosinolate concentrations sequestered by the aphids. The efficacy of predators as biological control agents may thus differ between conventional and sustainable farming systems.
ISSN:1049-9644
1090-2112
DOI:10.1016/j.biocontrol.2012.05.008