title: Spider web survey or whole plant visual sampling? Impact assessment of Bt corn on non-target predatory insects with two concurrent methods.
abstract: Impact assessment studies rely on relevant sampling methods. Correct evaluation of methods can be done by their concurrent use in the same sampling site and period. Collecting webs of Theridion impressum L. Koch (Araneae: Theridiidae) may serve as an arthropod sampling method: empty cuticles of prey items remain attached to the back side of the leaves with adhesive silk. Our study aimed to compare the applicability of the two methods concurrently (spider web survey and whole plant visual sampling) in a risk assessment study. The spider web survey recorded more predatory insect families than the whole plant visual sampling. Both methods were able to detect significant differences in the quantity of predatory insects in Bt vs. isogenic plots, but not in the same taxa (Nabidae: spider-web, 2001, Bt > Iso; Coccinellidae: plant sampling, 2001, Iso > Bt; Welsh-test, P < 0.05); thus, they could not confirm each other. The lack of confirmation can be explained by differences in the sensitivity and selectivity of the two methods. A web survey of T. impressum has the practical advantage that although we concentrate only on the one species during field sampling, we gain additional information on a wide range of foliage-dwelling arthropods. Due to several biological uncertainties, interpretation and explanation of the results remain problematic. Thus, additional research--based on in-situ observation and recording of T. impressum-prey interactions--is necessary before we could propose web survey method as a complementary tool in ecological impact assessment.
authors: Szent István University, Faculty of Agricultural and Environmental Sciences, Department of Plant Protection, H-2103 Gödöllö, Páter K. u. 1, Hungary. toth.ferenc@mkk.szie.hu
authors: Ferenc
authors: F
authors: Tóth
authors: Krisztina
authors: K
authors: Arpás
authors: Dóra
authors: D
authors: Szekeres
authors: Ferenc
authors: F
authors: Kádár
authors: Ferenc
authors: F
authors: Szentkirályi
authors: Agnes
authors: A
authors: Szénási
authors: József
authors: J
authors: Kiss
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000472:pathogenicity*; D003625:Data Collection; D004784:Environmental Monitoring / Q000379:methods; D020387:Food Chain; D018515:Plant Leaves; D030821:Plants, Genetically Modified; D011157:Population Dynamics; D011235:Predatory Behavior; D018570:Risk Assessment; D013112:Spiders; D003313:Zea mays / Q000737:chemistry* / Q000382:microbiology*