Neonicotinoids have become the most widely used class of insecticides in the US. The neonicotinoids are water soluble and systemic. Plants take up the neonicotinoids in their roots and distribute them throughout the plant, providing protection to leaves and other vulnerable tissues. Neonicotiniods are used in place of organophosphorous insecticides that are far more toxic to humans. Neonicotinoids are orders of magnitude more toxic to insects than the organophosphorous insecticides. This means they can be applied in smaller amounts with even greater safety. However, this also means that very low levels of neonicotinoid contamination in the environment can cause problems.
Insecticides not only kill pest insects but also kill non-target insects. Neonicotinoids have been implicated in massive bee kills. Neonicotinoids can contaminate ground water and surface water. Studies* have found levels of neonicotinoids in water that could have negative impact on mayflies, caddisflies and other aquatic insects that are important in aquatic food webs. As little as 0.1 ppb chronic exposure can have negative effects on aquatic insects. Greater than seventy percent of the surface water near sites where neoncotinoids are used contain levels higher than 0.1 ppb.
Neonicotinoids can affect insect behaviors such as feeding, mating and predator avoidance. Other animals such as fish, crustaceans and shellfish are more tolerant of neonicotinoids. However, they may be indirectly affected by effects on more susceptible species.
Studying the effects of neonicotinoids on non-target aquatic insects is necessary to set contamination levels low enough that aquatic ecosystems will be protected. Efforts to monitor the presences and levels of neonicotinoids in our surface water tell us how well we are minimizing contamination and whether or not we need to alter current practices.
*Christy A. Morrissey, Pierre Mineau, James H. Devries, Francisco Sanchez-Bayo, Matthias Liess, Michael C. Cavallaro, Karsten Liber. Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates: A review. Environment International, Volume 74, January 2015, pp 291-303.