Cotton (Gossypium hirsutum L.) is the one of the most important commercial crops of the world, which belongs to the family Malvaceae. India is the largest cotton growing country in the world with an area of around 12.35 M ha followed by United States and China with production of 36.1 M bales and productivity of 524 kg lint/ha. Cotton crop is known to suffer from number of fungal, bacterial and viral diseases. Cotton is under constant threat of foliar diseases viz., grey mildew, Alternaria leaf spot, Myrothecium leaf spot, bacterial leaf blight, rust etc. Among them, Alternaria leaf spot caused by Alternaria spp. is predominant in causing economic losses to the cotton crop in the country. Evaluation of systemic, non-systemic and combined fungicides under in vitro conditions revealed that the among eight fungicides evaluated against Alternaria macrospora (N2A isolate), Propiconazole, Hexaconazole and Tebuconazole @ 500 and 1000 ppm recorded maximum inhibition with 100 per cent inhibition and no radial growth of mycelium was observed. Pyraclostrobin and Azoxystrobin @1000 ppm showed 91.0 and 87.2 per cent inhibition respectively. Carbendazim+Mancozeb (SAAF) @ 1500 ppm and 2000 ppm showed 96.1 and 96.9 per cent inhibition respectively.
Aim :
Methodology :Results :
Interpretation :Keeping in view the use of hexaconazole on apple in Kashmir, the dissipation behaviour at two dosages on two cultivars were studied to ascertain the residues at different time intervals, waiting period and theoretical maximum residue contribution (TMRC), so that its use may not pose any danger to the consumers and is acceptable in domestic and international markets. processed by QuEChERS method for the estimation of hexaconazole residues in apple fruit and the final extract was analysed on gas chromatograph (GLC) coupled with an electron capture detector (ECD).The average initial deposits were found to be 2.60 and 4.01 μg g on Golden Delicious and 2.43 respectively.-1The residues of hexaconazole dissipated below quantification level of 0.008 μg g and waiting periods of 8. 13 and 7.45 concentration of SKUAST-K, T ) and 50 g a.i. ha (double the 1 recommended, T ). For studying dissipation of hexaconazole 2 residues in apple, representative samples 1.5 kg (0.5 kg from each replicate) were collected at time 0 day (1 hour post application when the spray mixture had dried up) and 3, 6, 9, 12 days after application, and at the time of harvest that correspond to 30 day post treatment. Control trees were only sprayed with water.Samples were placed in plastic bags and transported in iceboxes to laboratory for subsequent refrigeration at -4°C till further processing. Minimum and maximum daily temperatures ranged from 11.0 to 18.0 and from 22.5 to 29.5°C, respectively and average relative humidity and rainfall ranged between 52-88% and 0-1.9 mm during the experimental period (from spraying to last sampling).
Preparation of standard solution :The standard stock solution of −1 hexaconazole (1mg ml ) was prepared in HPLC grade hexane: acetone in 1:1 ratio. The standard solutions required for constructing −1 a calibration curve (20, 40, 60, 80 and 100 ng ml ) were prepared from stock solution by serial dilution with hexane: acetone in 1:1 ratio. All the standard solutions were stored at -2°C before use.
Chromatographic analysis :The final extracts were analysed on a Varian 450 (Walnut Creek, CA, USA) gas chromatograph 63 (GLC) coupled with an electron capture detector (ECD Ni ). The capillary column used was CP SIL 8 CB (30 m× 0.25 μm ID × 0.25 μm film thickness of 5% diphenyl and 95% dimethylpolysiloxane), injector port temperature 280°C and detector temperature 300°C. Column oven temperatures 60°C hold for 5 min then then 5°C min to 230°C (ramp II). Carrier gas nitrogen was used −1 with flow of 1 ml min through the column and detector make-up −1 of 30 ml min . Under these operating conditions, the retention time of hexaconazole was 16.45 min. Total run time was 26 min. Galaxy chromatography data system version 1.9.302.530 was used for the instrument control and data processing.
Processing of samples :Samples were processed by QuEChERS method as described by Lehotay et al. (2010) for the estimation of hexaconazole residues in apple fruit with slight modification. Samples...
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