Dissipation kinetics of trifloxystrobin and tebuconazole on apple (Malus domestica) and soil--a multi location study from north western Himalayan region.

A new combinational fungicide formulation trifloxystrobin 25%+tebuconazole 50% (Nativo 75WG), introduced as a part of resistance management strategy, was studied for dissipation behaviour on apple fruits. Nativo 75WG was sprayed twice at the rate of 400 g and 800 g a.i. ha(-1) equal to trifloxystrobin application rate of 100 and 200 g a.i. ha(-1) and tebuconazole at application rate of 200 and 400 g a.i. ha(-1) at four different locations in the Northwest Himalayan region of India. The fruit samples collected at 10d interval and soil samples taken at harvest time were analyzed after second spray. The residual concentrations of trifloxystrobin, its acid metabolite CGA 321113 and tebuconazole were measured. Residues of both fungicides were determined by using gas chromatograph, Agilent 6890N having electron capture detector. The mean initial deposits of trifloxystrobin at four locations were found to be in the range of 0.333-0.387 mg kg(-1) and 0.512-0.714 mg kg(-1) at the application rate of 100 and 200 g a.i. ha(-1), and half-life were found between 19.38-24.93 d and 19.84-28.86 d at the respective doses. The Σ-trifloxystrobin and tebuconazole residues were below determination limit in 40 d apple fruits and soil samples. Initial deposits of trifloxystrobin and tebuconazole were below their Codex MRLs at the respective single doses. The half life value of the tebuconazole deposits ranged between 19.38-25.99 d and 19.84-28.86 d at the respective single and double dose. The study thus suggests 1d pre harvest interval for safe consumption of apple fruit after the application of Nativo 75 WG at single dose.