Kh. Talebi,
Volume 5, Issue 4 (1-2002)
Abstract
In this research, the presence of metalaxyl residues was studied in field-grown cucumber. Two different formulations of metalaxyl were used in the experiments. In the first experiment, cucumber plants were sprayed once and repeatedly by Ridomil-MZ 72 WP at 2.5 g/litre. In the second experiment, single and double applications of metalaxyl granule 5G were carried out at 5 g/m2. Leaves and fruits were sampled at different times after each treatment and analyzed for metalaxyl residues by HPLC.
In leaf samples from single sprayed plots, metalaxyl residues declined rapidly following the treatment and more than 50% of the residues disappeared in the first two days, whereas in the leaf from single granule-applied plants, the residues increased during the first three weeks and then declined. Metalaxyl residues in cucumber sampled from single sprayed-plots were at a high level during the first three days after the spray and declined below the MRL (0.5 mg/kg) on the 7th day. In granule-applied plots, the residues increased during the first 7 days and the level below the limit was recorded 20 days after application. Residual values for plants sprayed with suspension showed a faster dissipation rate than granulated treatment. Metalaxyl recovered after three times of spraying and two times of granular application did not show any toxic accumulation of residues in fruit.
J. Keramat, Kh. Talebi, L. Mosaffa,
Volume 9, Issue 1 (4-2005)
Abstract
Vegetable crops are exposed to repeated spraying against the pests and diseases during the growing sessions. Crops such as greenhouse cucumber are usually harvested a short time after spraying, bearing a high level of pesticides with them. This fact justifies a research on this problem. This research was carried out to determine the effects of metalaxyl (a fungicide commonly used in greenhouse) residue in cucumbers grown under traditional and modern greenhouse conditions. Cucumber plants were sprayed with two different doses: 1/1 000 and 2/1000 metalaxyl in modern and traditional greenhouses. Samples were collected 1, 2, 4, 7, 10, 14, 21 and 28 days after spraying with metalaxyl. The fungicide residue was extracted, cleaned up by TLC and the final solution was analyzed by HPLC. Data were analyzed statistically by t-test (paired observations) and Duncans multiple range test.
The results revealed that the amount of metalaxyl residues increased in the first four days following spraying. This amount of the residue was 10 times higher than MRL (0.5 mg/kg), while a lower level of MRL (0.5 mg/kg) was detected 21 days after the application. Results also showed that a lower dose of application left a higher residual level than the higher one. On the other hand, no significant differences (p<0.05) were found between the amounts of residues in peeled and unpeeled cucumbers. Thus, fruit peeling does not reduce the fungicide residue in cucumber. Also, there were no significant differences (p<0.05) between the results obtained from modern and traditional greenhouses. Therefore, cucumber must either be harvested before or at least 14 days after spraying with metalaxyl.
