Residues of malathion and pirimephos-methyl insecticides on some medicinal plants and their elimination through technological process.

Abstract

The present data emphasized the role of insecticide type, medicinal plant species and intervals after treatment in determining the initial deposits and degradation pattern of the two tested insecticides on medicinal plants grown under greenhouse conditions. The organophosphate malathion (2.5 ml/litre) showed the highest initial deposit in comparison with pirimiphos-methyl (3.0 ml/litre). This was pronounced with Atropa belladonna compared with Digitalis lanata in the case of the two sprayed insecticides. The residue half-life (t1/2's) of the tested compounds showed in general, a relatively rapid degradation pattern on the treated plants. Pirimiphos-methyl showed relatively slower degradation compared with malathion. The corresponding calculated t1/2's were (7.62 and 7.45 days) for pirimiphos-methyl and (6.24 and 6.54 days) for malathion on A. belladona and D. lanata plants, respectively. Data also indicate that soaking of pesticide-contaminated plants for 5 minutes in tap water achieved a moderate decontamination of the existing insecticide residues. A great efficiency in decontamination process was noticed when washing-dryness processes were combined. Neither malathion nor pirimiphos-methyl residues were detected after washing the contaminated plants for 5 minutes followed by dryness as well as alkaloid and glycoside extraction.