Abstract
Pesticides are applied for the better protection of vegetable crops against unpredictable losses caused by pests. The detection and monitoring of pesticide residues in vegetable crops is being done for the safe guard of consumers and environment. Considering this issue, three experiments were carried out in the field of Horticulture Farm, Bangladesh Agricultural University, Mymensingh within the time frame of January, 2014 to March, 2018 covering situation of pesticide consumption in Bangladesh; effectiveness of diazinon, chlorpyrifos and fenitrothion on fruit infestation and yield of tomato and detection of their residues in tomato fruit at different days after spraying (DAS). The study revealed that during the last thirteen years (2005-2017), pesticide consumption in Bangladesh was increased by 102.09% in the year 2008 (48688.02 metric tons) compared to the year 2005 (24092.18 metric tons). Afterwards, it was gradually decreased up to the year 2014 (35801.68 metric tons). From the year 2015, consumption was again increased and finally, it was 37627.10 metric tons in 2017, which was 56.18% more compared to the year 2005. In study area, 83% farmers stated that fruit worm was the major damaging insect of tomato. Only 40% farmers viewed that the control of insects was effective during pesticide application and 33% farmers did not take any protective measure. Diazinon (Sabion 60 EC), chlorpyrifos (Dursban 20 EC) and fenitrothion (Sumithion 50 EC) were applied twice viz., at 10 days interval during fruiting stage of tomato. In case of pesticide spraying, the dose of each pesticide was fixed on the basis of national standard/recommended dose (RD) as 1.0 ml L-1 for diazinon as well as fenitrothion and 1.5 ml L-1 for chlorpyrifos, respectively. Recommended doses (RD), half of recommended doses (HRD) and double of recommended doses (DRD) of diazinon, chlorpyrifos and fenitrothion were treated on tomato including control one. Recommended doses of diazinon, chlorpyrifos and fenitrothion showed the best performance for marketable yield of tomato as estimated to 37.64, 40.62 and 35.97 t ha-1, respectively. In case of fruit infestation, recommended doses of those pesticides indicated the values of 6.45% for diazinon, 5.19% for chlorpyrifos and 8.78% for fenitrothion. The double of recommended doses of chlorpyrifos and fenitrothion numerically showed the least infestation than that of recommended doses, but differences was not significant having the less yield than that of recommended doses. The residues of three pesticides under recommended doses were detected within the spraying intervals of 0, 1, 3, 5, 6 and 7 days. The quantity of diazinon remained 9.56 ppm at 0 DAS, which was above maximum residue limit (MRL) of 0.50 ppm in tomato fruit. Residue was detected above MRL upto 5 DAS (0.842 ppm), but lower at 6 DAS (0.395 ppm) and at last in 7 DAS (0.048 ppm). The detected residue of chlorpyrifos was 11.031 ppm at 0 DAS, which was above maximum residue limit (MRL) up to 6 DAS (0.617 ppm) and finally at 7 DAS (0.279 ppm) which was below MRL (0.50 ppm) in tomato. In case of fenitrothion, initial (0 DAS) detected residue was 8.341 ppm and it was 0.617 ppm at 5 DAS, which was above MRL (0.50 ppm). So, this residue oriented research agreed that upto the certain period i.e., before 5 DAS for diazinon and fenitrothion and 6 DAS for chlorpyrifos sprayed tomato consumption was strictly and entirely prohibited.