Dissipation of residues of mancozeb and metalaxyl in tomato (Solanum lycopersicum L.).

Dissipation of mancozeb and metalaxyl in tomato was estimated following four applications of a combination formulation Ridomil MZ (mancozeb 64% + metalaxyl 8%) at 0.25 and 0.50% at 10 days interval by carbon disulphide evolution method and gas liquid chromatography with nitrogen phosphorous detector, respectively. Half-life periods for mancozeb were 3.76 and 4.14 days, whereas for metalaxyl these values were 1.29 and 0.41 days at single and double the application rates, respectively. Residues of mancozeb dissipated below limit of quantification (LOQ) of 0.25 mg kg(-1) after 10 and 15 days at single and double the application dosage, respectively. Similarly, residues of metalaxyl took 3 and 5 days to reach LOQ of 0.02 mg kg(-1), at single and double dosages, respectively.

Dissipation kinetics of metalaxyl in cucumber.

Residues of metalaxyl were estimated in cucumber fruits using Gas Liquid Chromatography (GLC) with Nitrogen phosphorus detector (NPD). Following three applications of Ridomil-MZ @ 0.3% and 0.6%, the average initial deposits of metalaxyl were observed to be 0.19 and 0.24 mg kg(-1), respectively. The residues dissipated below the limit of quantification (LOQ) of 0.02 mg kg(-1) after 10 days at both the dosages. The half-life values (T(1/2)) of metalaxyl was worked out to be 3.5 and 3.0 days, respectively at 0.3% and 0.6% concentration. Thus, a waiting period of 1 day was suggested for the safe consumption of metalaxyl treated cucumber.