Journal of Applied Entomology - Zeitschrift für angewandte Entomologie (1999) 123, 407-411

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T.-W. Schröder, T. Basedow and T. Mangali (1999)
Population density of Theridion impressum L. Koch (Araneae, Theridiidae) in sugar beet fields in Germany, and its possible effects on numbers of Myzus persicae (Sulzer) (Hom., Aphididae)
Journal of Applied Entomology - Zeitschrift für angewandte Entomologie 123 (7), 407-411
Abstract: Theridion impressum was found in summer with an average of 1.6 females per m2 in fields of sugar beets near Frankfurt/Main (Germany). No significant differences between insecticidal treatments occurred, while no synthetic pyrethroids were used. In the laboratory, female T. impressum exerted a significant effect on the growth rate of colonies of Myzus persicae. On average, one female spider eliminated 10.4 aphids per day initially, and 14.4 when the spiderlings had hatched. But although significant, the reduction (9.5 to 20.5%) of aphid density by T. impressum is not to be regarded as sufficient for the natural control of aphids in fields of sugar beets. In the fields, where there might be alternative prey, the percentage of aphids preyed upon might even be lower than in the laboratory exeriments presented here. Suggestions about the annual life cycle of T. impressum, which has not been described exactly before (hibernation as juveniles in field margins and other undisturbed areas), are given.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Thies Basedow

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
health/environmental effects of pesticides
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology
resistance to pesticides

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.


Myzus persicae Beet/sugarbeet (Beta vulgaris) Germany
Phylloneta impressa (predator) Myzus persicae Beet/sugarbeet (Beta vulgaris) Germany
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