18.104.22.168. Active ingredient and chemical formulation
An AI is a molecule able to bind on specific receptors of target organisms and produce adverse effects (Hodgson, 2004). Generally the chemical formula is only mentioned, without respect of the spatial arrangements. However, pyrethroids have isomers with varying levels of toxicity (Soderlund and Bloomquist, 1989). The same findings are true for some enantiomers, which have identical physical-chemical properties, but different biological activities (Konwick et al., 2005).
To be used in laboratory conditions, the AI should be formulated as simply as possible, generally with one solvent. The commercial formulation spread in field conditions is more complex because surfactants, stabilizing agents, dispersants, sometimes synergists (Bernard and Philogène, 1993) are added after dilution of the AI. The commercial formulation is targeted at the improvement of the AI activity in time and/or in toxicity. Certain mixtures of AI have synergistic effects, i.e. insecticide and fungicide at sub-lethal doses (Colin and Belzunces, 1992). Some AIs are converted under biological or environmental conditions into products (metabolites) that are often higher in toxicity than the parent compound (Ramade, 1992; Nauen et al., 1998; Suchail et al., 2001; Tingle et al., 2003).