Persistence of Dimethoate Residues in Olive Fruits under Field Conditions

M. Maher Khaznawi, M. Jamal Hajjar, Marwan Dimashki


This study was carried out at Abou Jarash farm, Faculty of Agriculture, Damascus University, to study the stability of dimethoate residues and its oxygen–analogue metabolites (omethoate) in olives at the recommended application rate of 100 ml/100 liter water of dimethoate 40% EC on olive trees. Samples were collected after application which extended to 25 days, then transferred to the laboratory after putting them in polyethylene bags, and the whole preparation procedures were applied to conduct the analysis by gas chromatography. Dimethoate residues in olive fruits was 9.264 mg/kg after one–hour post treatment, and then decreased to 0.723 mg/kg after 25 days of application. The results showed that the pesticide dissipation has gone through two main stages. The first is the relative sharp dissipation stage during the first 10 days after application. In the second stage, the dissipation was relatively slow. The line regression of dimethoate degradation in olives took a first- order reaction, also the remaining deposit of 0.723 mg/kg after 25 days was above the recommended MRL=0.5 mg/kg on olives. The dimethoate half-life on olives was 8.4 days and the calculated pre-harvest interval (PHI) was 53.7 days, whereas the PHI as stated by the manufacturing company was 21 days. This study also showed that the persistence of omethoate in olives was observed at the beginning of application until the end of the sampling period 25 days post treatment. The residue quantities ranged from 0.84 to 0.36 mg/kg in olives.

Full Text:



  • There are currently no refbacks.