Environ Monit Assess (2012) 184:4267–4270 DOI 10.1007/s10661-011-2261-x
Assessment of flubendiamide residues in pigeon pea in different agro-climatic zones of India V. D. Kale & A. R. Walunj & R. S. Battu & Sanjay K. Sahoo & Balwinder Singh & M. Paramasivam & Sankhajit Roy & Tirthankar Banerjee & Hemanta Banerjee & Cherukuri Sreenivasa Rao & D. Jagdishwar Reddy & K. Narasimha Reddy & C. Narendra Reddy & Vandana Tripathy & Maisnam Jaya & Shashi Pant & Monika Gupta & Geeta Singh & K. K. Sharma
Received: 10 November 2010 / Accepted: 15 July 2011 / Published online: 3 August 2011 # Springer Science+Business Media B.V. 2011
Abstract Supervised field trials were conducted at the research farms of four agricultural universities located at different agro-climatic zones of India to find out the harvest time residues of flubendiamide and its des-iodo metabolite on pigeon pea (Cajanus cajan) during the year 2006–2007. Two spray applications of flubendiamide 20 WDG at 50 g (T1) and 100 g (T2) a.i./ha were given to the crop at 15-days interval. The foliage samples at different time intervals were drawn at only one location, however, the harvest time samples of pigeon pea grain, shell, and straw were drawn at all the four locations. The residues were estimated by HPLC coupled with UV-VIS variable detector. No residues of flubendiamide and its des-iodo metabolite were found at harvest of the crop at or above the LOQ level of 0.05 μg/g. On the basis of the data generated, a preharvest interval (PHI) of 28 days has been recommended and the flubendiamide 20 WDG has been registered for use on pigeon pea by Central Insecticide Board and Registration Committee, Ministry of Agriculture, Government of India and the MRL has been V. D. Kale : A. R. Walunj : R. S. Battu : S. K. Sahoo : B. Singh : M. Paramasivam : S. Roy : T. Banerjee : H. Banerjee : C. S. Rao : D. J. Reddy : K. N. Reddy : C. N. Reddy : V. Tripathy : M. Jaya : S. Pant : M. Gupta : G. Singh : K. K. Sharma (*) All India Network Project on Pesticide Residues, Division of Agricultural Chemicals, IARI, New Delhi 110 012, India e-mail:
[email protected]
fixed by Ministry of Health and Family Welfare, Government of India under Prevention of Food and Adulteration as 0.05 μg/g on pigeon pea grains. Keywords Flubendiamide . Des-iodo flubendiamide . Pigeon pea . Persistence . Half-life
Introduction Pigeon pea (Cajanus cajan) is the second most important grain legume crop in India. It accounts for about 11.8% of the total pulse area and 17% of total pulse production of the country. It is a rich source of protein and supplies a major share of the protein requirement of the vegetarian population of the country. Pigeon pea is usually grown in rainfed areas prone to drought. There are several insects which are found to attack the crop like pod borers, plume moth, hairy caterpillar, leaf hopper, bean fly, etc.; however, the lepidopterous pod borer has been found to cause a considerable loss to the crop. Flubendiamide, N2-(1,1dimethyl-2-methyl sulphonyl ethyl)-3-iodo-N1-[2-methyl-4-{1,2,2,2-tetrafluoro-1-(trifluoromethyl) ethyl} phenyl] 1,2–benzene dicarboxamide, a phthalic acid diamide (Diaz de Toranzo and Brieux 1967) insecticide, shows extremely strong insecticidal activity especially against lepidopterous pests including resistant strains in rice, cotton, corn, grapes, fruits, and vegetables (Pessah 1989; Tohnishi et al. 2005) due to its unique mode of
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action (Hall et al. 1995). Flubendiamide has a favorable ecological, ecotoxicological, and environmental profile with low mammalian toxicity and no genotoxic, mutagenic, or oncogenic properties (Shane 2006). It is the insecticide being recently introduced in India and there is little information available on its persistence in pigeon pea under Indian condition. Therefore, multi location supervised field trials were undertaken in different agro-climatic zones of India to generate the data on the persistence of flubendiamide in pigeon pea and harvest time residue in soil. The information generated in the present study has been utilized by the Government of India for the registration and safety evaluation of flubendiamide on pigeon pea.
Materials and methods Analytical grade flubendiamide (purity 96.7%) and its metabolite des-iodo-flubendiamide (purity 99.3%) were supplied by M/s Rallis India Ltd. The reagents used were analytical grade and the solvents were of high-performance liquid chromatography (HPLC) grade where required. The field trials were laid out with pigeon pea in randomized block design (RBD) with three replications during the year 2006–2007 at the university research farms of four agricultural universities viz. Bidhan Chandra Krishi Viswavidyalaya, Kalyani; Punjab Agricultural University, Ludhiana; Acharya N. G. Ranga Agricultural University, Hyderabad and Mahatma Phule Krishi Viswavidyalaya (MPKV), Rahuri which are located at four different agro-climatic regions of India. The cultivated varieties of pigeon pea were IR-8, AL-15, ICPL87119, ICPL-87, respectively, and plot sizes were 30, 100, 50, and 12 m2, respectively. The first application of flubendiamide 20 WDG was made at 50 g (T1) and 100 g (T2) a.i/ha at pre-flowering stage of the crop using Knapsack sprayer and the subsequent application was made at 15-days interval. In control plot, only water was sprayed (T0). The persistence study of flubendiamide and its des-iodo metabolite was conducted only at MPKV, Rahuri. The foliage samples were collected at 0 (1 h), 3, 5, 7, 10, 15, 21, and 28 days after the last application of flubendiamide 20% WDG. Pigeon pea grain, shell, straw, and soil samples were collected randomly
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from each plot at harvest for the estimation of harvest residue of flubendiamide and des-iodo flubendiamide at all the four locations. The extraction and cleanup procedure for pigeon pea foliage, grain, shell, straw, and soil samples were followed as per the methodology adopted by Battu et al. (2008). A representative 50-g sample of finely ground pigeon pea foliage/grain/shell/straw/soil was dipped overnight into 100 mL acetonitrile in an erlenmayer flask. The extract was filtered into 1-L separatory funnel along with rinsings of acetonitrile. The filtrate in the separatory funnel was diluted with 600 mL brine solution and the contents were partitioned three times with 100, 50, and 50 mL chloroform. The chloroform fractions were combined, dried over anhydrous sodium sulfate and treated with 500-mg activated charcoal for about 2–3 h at room temperature. The clear extract so obtained was filtered through Whatman filter paper no.1, concentrated to near dryness. To the dried residue, about 20 mL HPLC grade acetonitrile was added and concentrated using rotary vacuum evaporator at 30°C. The process was repeated to completely evaporate chloroform and the final volume was reconstituted to about 5 mL using HPLC grade acetonitrile. The estimation of flubendiamide and its des-iodo metabolite in the cleaned extracts was carried out on HPLC equipped with UV-VIS detector using reversed phase C-18 column (25×4.6 mm i.d.) and acetonitrile: water (6:4 v/v) as the mobile phase with a flow rate of 2 mL min−1 at 230 nm. Recovery studies were carried out by spiking the pigeon pea foliage, grain, shell, straw, and soil samples at 0.05 μg/g (limit of quantification (LOQ) level), 0.25 μg/g (five times LOQ level) and 0.50 μg/g (ten times LOQ level) with analytical standard of flubendiamide and its des-iodo metabolite. The spiked samples were analyzed as per the method described above. Quantification of flubendiamide and des-iodo flubendiamide in samples were made by comparing the detector response (area) for the samples to that measured for the calibration standard within the linear range. Estimation of the method's sensitivity, the limit of detection and LOQ were performed for all the pigeon pea substrates in accordance with the method of Their and Zeumer (1987). The method's LOQ value for both the compounds under these conditions was 0.05 μg/g.
ND
ND
21
28
ND
ND
ND
ND
ND
ND
ND
ND
R2
ND
ND
ND
ND
ND
ND
ND
ND
R3
ND
ND
ND
ND
ND
ND
ND
ND
Mean ± S.D.
BDL
0.05
0.17
0.24
0.42
0.49
0.87
0.98
R2
BDL
0.06
0.22
0.22
0.42
0.63
0.71
1.26
R3
Y=3.067−0.063×(r2 =0.98) 4.77
BDL
0.05
0.15
0.21
0.33
0.62
0.91
1.21
R1
Flubendiamide
BDL
ND
ND
ND
ND
ND
ND
5
7
10
15
21
28
ND
ND
ND
ND
ND
ND
ND
ND
R2
ND
ND
ND
ND
ND
ND
ND
ND
R3
ND
ND
ND
ND
ND
ND
ND
ND
Mean ± S.D.
BDL below determination limit, ND not detected
Limit of quantification (LOQ): 0.05 ppm
Regression equation Half-life (t½), days
ND
ND
0
R1
Control
Residues of pigeon pea foliage, μg/g
3
Sampling interval (days)
BDL
0.11
0.51
0.57
0.90
1.22
1.57
1.73
R2
BDL
0.11
0.55
0.52
0.98
1.23
1.72
1.83
R3
Y=3.358−0.057×(r2 =0.93) 5.28
BDL
0.09
0.47
0.61
0.82
1.15
1.90
1.89
R1
Flubendiamide
0.05±0.01
0.18±0.04
0.22±0.02
0.39±0.05
0.58±0.08
0.83±0.11
1.15±0.15
Mean ± S.D.
BDL
0.10±0.01
0.51±0.04
0.57±0.05
0.90±0.08
1.20±0.04
1.73±0.17
1.82±0.08
Mean ± S.D.
Table 2 Residues of flubendiamide and des-iodo in pigeon pea foliage at 100 g a.i./ha
BDL below determination limit, ND not detected
Limit of quantification (LOQ): 0.05 ppm
Regression equation Half-life (t½), days
ND
ND
10
15
ND
ND
5
7
ND
ND
0
R1
Control
Residues of pigeon pea foliage, μg/g
3
Sampling interval (days)
Table 1 Residues of flubendiamide & des-iodo in pigeon pea foliage at 50 g a.i./ha
1.01
BDL
BDL
BDL
0.50
0.90
1.75
1.68
0.82
R1
Des-iodo
BDL
BDL
BDL
0.25
0.75
BDL
BDL
BDL
0.41
1.12
2.00
1.81
0.71
R2
BDL
BDL
BDL
0.26
0.54
0.78
0.93
–
– 0.81
R2
R1
Des-iodo
BDL
BDL
BDL
0.22
0.99
1.68
1.20
0.50
R3
BDL
BDL
BDL
0.27
0.32
1.00
0.99
–
R3
BDL
BDL
BDL
0.38±0.14
1.00±0.11
1.81±0.17
1.56±0.32
0.68±0.16
Mean ± S.D.
BDL
BDL
BDL
0.26±0.01
0.54±0.22
0.93±0.13
0.91±0.09
–
Mean ± S.D.
BDL
0.05
0.22
0.24
0.96
1.27
1.80
0.98
R2
BDL
0.06
0.18
0.75
0.74
1.63
1.70
1.26
R3
BDL
0.05±0.01
0.18±0.04
0.48±0.02
0.93±0.17
1.51±0.21
1.74±0.05
1.15±0.15
Mean ± S.D.
BDL
0.09
0.47
1.11
1.72
2.90
3.58
2.71
R1
BDL
0.11
0.51
0.98
2.02
3.22
3.38
2.44
R2
BDL
0.11
0.55
0.74
1.97
2.91
2.92
2.33
R3
BDL
0.10±0.01
0.51±0.04
0.94±0.19
1.90±0.16
3.01±0.18
3.29±0.34
2.49±0.20
Mean ± S.D.
Total (flubendiamide + des-iodo)
BDL
0.05
0.17
0.46
1.08
1.63
1.72
1.21
R1
Total (Flubendiamide + Des-iodo)
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Results and discussion Average recovery from spiked samples of flubendiamide in pigeon pea foliage, grain, shell, straw, and soil ranged from 87.7% to 90.2%, 89.4% to 96.0%, 89.6% to 90.1%, 87.1% to 89.2%, and 87.7% to 89.9% respectively. The corresponding recoveries for des-iodo flubendiamide were 79.9% to 83.0%, 91.9% to 99.3%, 91.5% to 94.3%, 89.2% to 90.3%, and 88.0% to 94.7%. The control samples were found free of flubendiamide residues. The results of persistence of flubendiamide and its metabolite in/on pigeon pea foliage at MPKV, Rahuri location are summarized in Tables 1 and 2. The application of flubendiamide 20% WG at 50 and 100 g a.i./ha resulted in total initial deposits of 1.15 and 2.49 μg/g, respectively. The residue progressively declined with time and reduced to the level of 0.18 and 0.51 μg/g, respectively on the 15th day. The dissipation was very fast and reached below detection limit within 28 days after application at both the tested doses. The dissipation followed the first order kinetics and the calculated half-life periods for the parent compound were found to be in the range of 4.77–5.28 days. No residues of flubendiamide and des-iodo flubendiamide were detected in pigeon pea grain, shell, and straw samples at harvest time at the detection limit of 0.05 μg/g. Soil samples at recommended and double the recommended dosages did not show the presence of flubendiamide or des-iodo flubendiamide at their detection limit of 0.05 μg/g. Interestingly, pigeon pea grain, shell, straw, and soil samples did not show the presence of des-iodo flubendiamide at detection limit of 0.05 μg/g. Thus, it may be inferred that spray application of Flubendiamide 20 WDG on pigeon pea at 50 and 100 g a.i./ha at pre-flowering stage and 15 days later,
Environ Monit Assess (2012) 184:4267–4270
results in no residues, at the time of harvest in pigeon pea grains, shell, and straw. Hence, it may be concluded that flubendiamide 20 WDG can be safely introduced in the plant protection schedule of pigeon pea and pre-harvest interval of 28 days can be suggested.
Acknowledgments We thank M/s Rallis India Limited for supplying the analytical standards and financial assistance.
References Battu, R. S., Singh, B., Kooner, R., & Singh, B. (2008). Simple and efficient method for the estimation of residues of flubendiamide and its metabolite desiodo flubendiamide. Journal of Agricultural and Food Chemistry, 56(7), 2299– 2302. Diaz de Toranzo, E. G., & Brieux, J. A. (1967). Synthesis of unsymmetric o-phthalic acid diamides. Journal of Medicinal Chemistry, 10, 982–983. Hall, L. M., Ren, D., Feng, G., Eberl, D. F., Dubald, M., Yang, M., et al. (1995). Calcium channel as a new potential target for insecticides. ACS Symposium Series, 59, 162– 172. Pessah, I. N. (1989). Recent advances in the chemistry of insect control. In L. Crombie (Ed.), Royal society of chemistry, special publication, vol 79 (pp. 278–296). Cambridge: RSC. Shane, H. (2006). Flubendiamide: the next generation in Lepidopteran pest management. Paper presented at the Annual Meeting of the Entomological Society of America (ESA), December 10–13, Research Triangle Park, NC2006. Their, H. P., & Zeumer, H. (Eds.) (1987). Introduction and instructions in manual of pesticide residue analysis; DFG, Dt Forchungsgemeinschaft, Pesticides committee; VCH: New York, Vol.1. Tohnishi, M., Nakao, H., Furuya, T., Seo, A., Kodama, H., Tsubata, K., et al. (2005). Flubendiamide, a novel insecticide highly active against lepidopterous insect pests. Journal of Pesticide Science, 30, 354–360.
