BioControl (2007) 52, 775-788

B. Freier, H. Triltsch, M. Möwes and E. Moll (2007)
The potential of predators in natural control of aphids in wheat: Results of a ten-year field study in two German landscapes
BioControl 52 (6), 775-788
Abstract: In the present study, we investigated the natural control of aphids by predators in wheat fields in a low (L) and high-input cropping region (H) of Germany during a 10-year period. Data for the statistical analyses were obtained from weekly after the start of aphid emergence. The mean annual aphid indices, calculated as the sum of Sitobion avenae (Fabr.), Rhopalosiphum padi (L.), Metopolophium dirhodum (Walk.)(Homoptera: Aphididae), were 30.4 and 81.5 × 10³ aphid days per m², for L and H, respectively. Nine predator fractions were analysed: Coccinella septempunctata L., adults (1) and larvae (2), Propylea quatuordecimpunctata (L.) (Coleoptera: Coccinellidae) adults (3) and larvae (4), syrphid larvae (mostly Episyrphus balteatus [De Geer] (Diptera: Syrphidae)) (5), Chrysoperla carnea Steph. (Neuroptera: Chrysopidae) larvae (6), and adult carabids (7), staphylinids (8) and spiders (9). The two sites were comparable in terms of the mean size of the overall predator community, expressed in predator units (PU): 4.9 PU/m² (L) vs. 5.4 PU/m² (H). Most predator fractions responded numerically to increasing aphid densities. The numerical response was strongest in syrphid larvae, scarcely detectable in adult coccinellids, and virtually non-existent in epigeic arthropods. Multiple regression models revealed indirect relationships between the weekly overall predator community densities (PU/m²) and individual predator fractions (individuals/m²) and absolute rates of aphid density increase (individuals/m²) one or two weeks after baseline. A site-independent reduction of the aphid density increase to nil (y = 0) was observed at 3.9 to 4.2 PU/m². Consequently, the 2.7 times higher aphid density at H cannot be attributed to the presence of fewer predators or lower effects of the overall predator community or of any individual predator fraction.
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Link to article at publishers website
Database assignments for author(s): Bernd Freier

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

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sitobion avenae	Wheat (Triticum)	Germany
	Rhopalosiphum padi	Wheat (Triticum)	Germany
	Metopolophium dirhodum	Wheat (Triticum)	Germany
Coccinella septempunctata (predator)			Germany
Chrysoperla carnea (predator)			Germany
Propylea quatuordecimpunctata (predator)			Germany
Episyrphus balteatus (predator)			Germany