INTERACTIVE EFFECTS OF PROCHLORAZ AND MALATHION IN PIGEON, STARLING AND HYBRID RED-LEGGED PARTRIDGE

Recent laboratory studies with hybrid red-legged partridges have shown that the interaction of certain combinations of agricultural pesticid es can lead to an enhancement of toxicity. In view of this finding, ca ptive feral pigeons (Columba livia) and European starlings (Sturnus vu lgaris), in addition to hybrid red-legged partridges (Alectoris rufa c ross), were used in a laboratory study to extend investigations of the enhancement of toxicity of the organophosphorus (OP) insecticide mala thion in birds predosed with the ergosterol-biosynthesis-inhibiting (E BI) fungicide, prochloraz. Following pretreatment with either 90 or 18 0 mg/kg prochloraz, both pigeons and partridges showed significantly g reater inhibition of serum butyrylcholinesterase (BuChE) activity (1.4 - to 2. 1-fold increase for pigeons and 1.3- to 3.8-fold increase for partridges) when dosed with malathion than control birds; this differe nce was evident at some or all of the blood-sampling time points. On t he other hand, starlings given either 180 or 300 mg/kg prochloraz show ed no difference from controls in serum BuChE inhibition after dosing with malathion. The enhanced inhibition of serum BuChE in the pigeon a nd the partridge after malathion dosing was attributed to the increase d activation of malathion to malaoxon following induction of the hepat ic monooxygenase system by prochloraz. Serum BuChE inhibition may be u seful in studying the interactive effects of OPs and EBI fungicides in the field.