Researchers of the University Koblenz-Landau studied the sensitivity of midges, central food resources of wetlands in a standardised laboratory design against the biocide Bti used in mosquito control. The young larval stages were up to 100 times more sensitive than the older stages and are more than 200 times below the environmental concentrations used in the Upper Rhine Valley, Germany. The data indicate the crossing of a risk threshold factor used in biocide regulation by three orders of magnitude. A potential risk for other animal groups via food web effects in treated conservation areas cannot be excluded.