Persistence of trifloxystrobin and tebuconazole on grape leaves, grape berries and soil.

Following four foliar applications of Nativo 75 WG (trifloxystrobin 25% + tebuconazole 50%) on grapes @ 175 and 350 g/ha, resulting in active applications of trifloxystrobin @ 43.75 and 87.5 g a.i./ha and that of tebuconazole @ 87.5 and 175 g a.i./ha, the average initial deposits of trifloxystrobin were observed to be 7.76 and 15.53 mg/kg, respectively, at single and double the application rates. These residue levels dissipated to >85% after 10 days of its application at both the dosages. Similarly, the average initial deposits of tebuconazole were observed to be 13.84 and 26.55 mg/kg at single and double the application rate, respectively. These residue levels dissipated to >90% after 10 days of application at both the dosages. The half-life (t(1/2)) periods of trifloxystrobin on grape leaves were observed to be 2.92 and 3.48 days at single and double application rates, respectively, whereas these values were 2.68 and 3.96 days for tebuconazole. Ripe grape berries and soil samples collected at harvest which happened to be 34 days after the last application, did not show the presence of residues of trifloxystrobin and tebuconazole at their determination limit of 0.01 and 0.02 mg/kg, respectively.

Persistence of imidacloprid on grape leaves, grape berries and soil.

Residues of imidacloprid were estimated in grape leaves, grape berries and soil following four applications of Confidor 200SL at 400 and 800 mL ha(-1) using 1,000 L water. The average initial deposits of imidacloprid on grape leaves were found to be 10.01 and 16.97 mg kg(-1) at single and double dosages, respectively. These residues of imidacloprid dissipated to be the extract of 98.8% and 97.0%, respectively, at single and double dosages in 15 days, with half-life period of 2.35 and 2.97 days. Residues of imidacloprid in grape berries at harvest time were observed to below determination limit of 0.05 mg kg(-1) at single dose and 0.06 mg kg(-1) at double dose. However, acceptable daily intake (ADI) of imidacloprid is 0.06 mg kg(-1) body weight day(-1), which means an adult of 60 kg and a child of 10 kg can safely tolerate intake of 3,600 and 600 microg imidacloprid, respectively, without any appreciable risk to their life. Assuming consumption of 200 g grape berries contaminated at 0.06 mg kg(-1), it will lead to an intake of only 12 microg of imidacloprid, which is quite safe for a child as well as for an adult. Hence, the use of imidacloprid on grape crop seems to be toxicologically acceptable.