Effects of insecticide application to winter wheat and subsequent tillage on groundbeetle communities (Coleoptera : Carabidae)

Four plots of about 5 hectares' size each were marked off in a large wheat field near Magdeburg, Germany, for a simple comparison of variants. Two plo ts (IP, IK) were treated with the insecticide Karate (lambda-cyhalothrin) o nce at growth stage BBCH 69, while the other two (CK, CP) served as untreat ed controls. Several surveys were performed, including pitfall trapping (n= 10) to elucidate groundbeetle activity and diversity. Plots IP and CP were ploughed in autumn, whereas plots IK and CK were conservatively tilled. Pit fall trapping was again performed in the succeeding crop (sugar beets) on a ll four plots exactly one year after insecticide application. The plots varied significantly with respect to activity densities (sums, do minant species) within three weeks of treatment, that is, activity was high er in the controls (SAS, t-test, P <0.05). These differences vanished later on and in autumn. Surveys in the succeeding crop (sugar beets) showed no i ndication that ploughing might be an additional stress factor in the treate d plots, because the number of Groundbeetles trapped in the treated and plo ughed plot (IP) was the same as in the untreated and unploughed plot (CK). Most beetles were found in the untreated and ploughed plot (CP), which diff ered significantly from IP and CK. The results did not indicate any sustain ed or synergistic effects of insecticide treatment or tillage. They are dis cussed relative to species and other study findings.