Neonicotinoid insecticides have adverse effects not only on bees but also on freshwater invertebrates. Exposure to low but constant concentrations of these substances -- which are highly soluble in water -- has lethal effects on these aquatic organisms.
At the end of April, the EU imposed a 2-year ban on the use of neurotoxic agents belonging to the neonicotinoid group. In Switzerland, the Federal Office for Agriculture (FOAG) has followed suit, suspending the authorizations of three insecticides used on oilseed rape and maize fields. These measures have been taken in response to evidence that neonicotinoids are toxic to honeybees and are contributing to the decline of bee colonies.
An Eawag study published today in the journal PLOS ONE (Public Library of Science) now shows that at least one of the insecticides in this class also has toxic effects on freshwater invertebrates. In this study, native freshwater shrimps (gammarids) were exposed to pulsed high and to constant low concentrations of imidacloprid. Peak concentrations typically occur when rain falls on farmland during or shortly after the application of insecticides; these soluble but persistent substances can then enter surface waters via runoff. Interestingly, pulses lasting...