Abstract:
In a field study, potential adverse effects of Bt maize on
plant-dwelling spiders (Araneae) were assessed in 2001 in Bavaria,
South Germany. Spider assemblages were recorded in Bt maize fields
and conventional maize fields, with and without (pyrethroid)
insecticide application. In addition, the efficacy of several
sampling techniques to collect plant-dwelling spiders was tested
(beating sheets, suction sampling, plant removal, stem eclectors).
A total of 29 species and 14 families were identified. Juvenile
spiders of the families Theridiidae, Linyphiidae, Tetragnathidae
and Araneidae dominated the catch. The sampling methods differed in
their capture efficiency with regard to abundance, family
composition, species richness and power to detect effects. Suction
samplers performed best, and are recommended for monitoring
plant-dwelling spiders in maize. Bt maize had no substantial
effects on species richness and abundance of spiders, whereas
insecticide application reduced spider densities.
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