“…The availability of data on the toxicity of coumaphos to mites from untreated populations (Milani and Della Vedova, 1996) has made it possible to detect resistance to this organophosphorous acaricide (Spreafico et al, 2000), before bee losses were reported. On the other hand, little is known of the mode of action of oxalic acid, in particular, why a solution of oxalic acid and sucrose, applied by tricking (Mutinelli et al, 1997), is more effective than a solution of the acid alone, used in the same way.…”