Volume 76, September 2014, Pages 19–27
Highlights
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- Wildflower plants can attract and nourish natural enemies of pest species.
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- Cornflowers in cabbage fields increased parasitation of Mamestra larvae.
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- Cornflowers increased parasitation and predation of Mamestra eggs.
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- Cornflowers reduced crop damage and increase yield.
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- Egg parasitoids may be more efficient that larval parasitoids for biocontrol.
Abstract
Monocultures
typical of intensive agriculture offer ideal conditions to specialized
herbivores while depriving their natural enemies of habitat and
nutritional resources. The resulting release of herbivores from both
bottom-up and top-down control causes pest outbreaks in economically
important crops. Boosting locally occurring natural enemy populations
through species-specific habitat management to restore natural herbivore
control has been much advocated but remains rarely tested in the field.
Here, we investigated whether adding specifically selected flowering
plants to monocultures increases parasitation rates of herbivores and
crop yield. We performed replicated field experiments in 2 years and
found that adding cornflowers (Centaurea cyanus) into cabbage (Brassica oleracea)
fields significantly increased larval and egg parasitation and egg
predation of the herbivore, reduced herbivory rates, and increased crop
biomass in at least 1 year. These findings show that addition of a
single, well-chosen flowering plant species can significantly increase
natural top-down pest control in monocultures but success is variable.
This is relevant on two applied levels. First, well chosen companion
plants may partially substitute pesticides in agriculture if the
approach is optimized, reducing negative effects such as unspecific
killing of non-target organisms, residues in food, contamination of
soils and water-bodies and increasing pesticide resistances. Our results
suggest that, from an agro-economical point of view, egg parasitoids or
predators may be the best targets for habitat management because strong
natural selection acts on larval parasitoids to keep their hosts alive
for their own development. Second, the addition of non-crop vegetation
to monocultures benefits biodiversity conservation directly through
resource diversification and indirectly through the reduction of
pesticide application that increased natural control makes possible.
Graphical abstract
Keywords
- Trophic interaction;
- Parasitoid;
- Floral subsidy;
- Wildflower strip;
- Microplitis;
- Mamestra
Copyright © 2014 Elsevier Inc. All rights reserved.
