Residual behavior of quizalofop ethyl on onion(Allium cepa L.)

S. K. Sahoo & Kousik Mandal & Gurmail Singh &

Rajinder Kumar & G. S. Chahil & R. S. Battu &

Balwinder Singh

Received: 28 September 2011 /Accepted: 23 April 2012 /Published online: 11 May 2012# Springer Science+Business Media B.V. 2012

Abstract Quizalofop ethyl, a phenoxy propionateherbicide, is used for postemergence control of annualand perennial grass weeds in broad-leaved crops inIndia. The experiments were designed to study thedissipation kinetics of quizalofop ethyl on onionfor two seasons. A simple, rapid, and sensitivemethod for estimation of quizalofop ethyl residuesin onion and soil was developed and validated.The recoveries of quizalofop ethyl residues fromonion and soil at different spiking level range from84.81 to 92.68 %. The limit of quantification ofthis method was found to be 0.01 μg g−1. The riskassessment through consumption of the onion incomparison to its acceptable daily intake which isan important parameter for the safety of the con-sumer was also evaluated. Standardized methodol-ogy supported by recovery studies was adopted toestimate residues of quizalofop ethyl on onion and soil.The average initial deposits of quizalofop ethyl on onionwere observed to be 0.25 and 0.33 mg kg−1, followingsingle application of the herbicide at 50 g activeingredient (a.i.) ha−1 during 2009 and 2010, re-spectively. The half-life values (T1/2) of quizalofopethyl on onion crop were worked out to be 0.85 and

0.79 days, respectively, during 2009 and 2010. At har-vest time, the residues of quizalofop ethyl on onion andsoil were found to be below the determination limit of0.01 mg kg−1 following single application of the herbi-cide at 50 and 100 g a.i. ha−1 for both the periods.

Keywords Quizalofop ethyl . Onion . Residues .

Dissipation . ADI

Introduction

Onion (Allium cepa L.) is a major bulbous crop amongvegetables and is of global importance. Out of 15vegetables listed by the Food and AgriculturalOrganization, onion falls second only to tomato interms of total annual world production. Onion is usedas an ingredient in many dishes and is consumed byboth poor and rich people. Onion production might beincreased by increasing the growing area with goodvariety and changing existing management practices(Ashrafuzzaman et al. 2009). However, the lack ofweed control can result in the total loss of marketableonions (Wicks et al. 1973). Onions do not competewell with weeds due to their slow growth rate (Wickset al. 1973; Umeda et al. 1998; Bell and Boutwell2001), short height (Singh et al. 1992), nonbranchingplant structure (Singh et al. 1992), low leaf area(Dunan et al. 1996; Bell and Boutwell 2001), andshallow root system (Singh et al. 1992).

Environ Monit Assess (2013) 185:1711–1718DOI 10.1007/s10661-012-2662-5

S. K. Sahoo :K. Mandal (*) :G. Singh : R. Kumar :G. S. Chahil :R. S. Battu : B. SinghPesticide Residue Analysis Laboratory, Department ofEntomology, Punjab Agricultural University,Ludhiana-141004 Punjab, Indiae-mail: kousik11@gmail.com

Although mechanical weed control through cul-tivation is useful for controlling weeds betweenrows, it is ineffective for controlling weeds be-tween plants within rows. Chemical weed controlis an alternative to hoeing or hand removal ofweeds from within the crop row. Potential chemi-cal weed control options including conventional syn-thetic herbicides such as quizalofop ethyl play a greatrole in grassy weed control.

Quizalofop ethyl, ethyl (2RS)-2-[4-(6-chloroqui-noxalin-2-yloxy)phenoxy]propionate (Fig. 1) is usedfor postemergence control of annual and perennialgrass weeds in broad-leaved crops, particularly sugarbeet, fodder beet, oilseed, rape, sunflower, soybean,cotton, peanut, flax, alfalfa, and some vegetables. It isa selective and systemic herbicide absorbed by theleaves with translocation throughout the plant. As asystemic herbicide to inhibit acetyl CoA carboxylase,quizalofop ethyl was absorbed from the leaf surfaceand translocated throughout the plant, moved in bothxylem and phloem from the treated foliage to the rootsystem, and accumulated in the meristematic tissue,and thus it inhibits the biosynthesis of fatty acid.Quizalofop ethyl, the active ingredient in ASSUREherbicide, is a registered product of DuPont in theUSA (Koeppe et al. 1990). Quizalofop ethyl, a newgeneration herbicide Targa Super 5 % EC developedby Nissan Chemicals, Japan and Dhanuka Group ofCompanies, is used for grassy weed control in soybean(Singh 2002).

However, considerable concern is being expressedover the magnitude of pest control chemicals leftin foodstuffs following their use on crops. It isimportant to ensure that the levels of harvest timeresidues of pesticides on foodstuffs do not poseany hazard to consumers and are admissible indomestic as well as international trade. Therefore, thepresent studies were undertaken to know the persistenceof quizalofop ethyl on onion crop under subtropicalconditions of Ludhiana, Punjab, India.

Materials and methods

Chemicals and reagents

Solvents like acetone and toluene were obtained fromE. Merck (India) Limited, Mumbai. Sodium chloridewas also obtained from E. Merck (India) Limited,Mumbai. Sodium sulfate anhydrous was from S. D.Fine Chemicals, Mumbai. Activated charcoal decolor-izing powder was obtained from Qualigens FineChemials, Mumbai. All common solvents were redis-tilled in all-glass apparatus before use. The suitabilityof the solvents and other chemicals was ensured byrunning reagent blanks before actual analysis. Thecertified reference standard of quizalofop ethyl (purity100.0 %) was supplied by M/s Dhanuka AgritechLimited. Targa Super 5EC (quizalofop ethyl) usedfor application of the crop was obtained from M/sDhanuka Agritech Limited, India. Analysis of acetoneextract of the formulation showed only quizalofopethyl, and no interfering peak was observed near theretention time of the compound estimated. Moreover,quizalofop ethyl was found to be accurate with respectto its purity as claimed by the manufacturers.

Crop planting for the field experiment

Onion (var. PRO-6) was raised during Rabi 2009 and2010 at Punjab Agricultural University, Seed FarmLadhowal, Ludhiana Punjab, India, and the crop wasraised according to recommended agronomic practices(Anonymous 2008). Three replications were selectedfor each treatment, i.e., control, recommended, anddouble the recommended dosages. There were threereplications for each treatment arranged in a random-ized block design, and size of the each plot was140 m2. The soil under crop was of light texture withlow content of organic matter. Other relevant proper-ties of the soil were organic carbon00.30 %, pH08.0,sand078.0 %, silt010.2, and clay011.8 %.

Application of insecticide

Single application of quizalofop ethyl (Targa Super5EC) at 50 and 100 g active ingredient (a.i.) ha−1

was made at 30 days after sowing as postemergenceof herbicides in onion. In control plots, only water wassprayed. Pesticide was sprayed as foliar application inthree replications with the help of a Knapsack sprayer

3

23

Fig. 1 Structure of quizalofop ethyl

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fitted with a flat fan nozzle. In control plots, onlywater was sprayed.

Sampling procedure

Onion

About 1 kg of onion whole plants was collected ran-domly from control and treated plots of each treatmentat 0 (2 h), 1, 3, 5, 7, and 10 days after application ofthe insecticide. Onion bulbs were also collected at thetime of harvest (preharvest interval090 days). Thesamples from each treatment plot were pooled andmixed thoroughly on a sheet of polyethylene in thefield. A subsample of about 250 g was taken fromeach pooled sample from each treatment plot andtransported to the laboratory, and a representative50 g was processed immediately after the subsamplereached the laboratory.

Soil

In onion, soil samples (1 kg) were collected 10 daysafter application of the insecticide. Soil samples werecollected separately from 10 to 15 sites of each treatedplot with the help of tube auger at a depth of about 10–15 cm; the soil from the 10–15 sites were pooled andsieved, and extraneous matter, including stones/peb-bles, were removed. After thorough mixing, a subsam-ple of about 1 kg was taken from each pooled samplefrom each treatment plot and transported to the laboratory;

a representative 50 g was processed immediately afterbringing the samples in the laboratory.

Weather conditions

The meteorological data, comprising temperature, rel-ative humidity, rainy days, number of bright sunshinehours, and wind speed, from the first spray to finalsampling (2009 and 2010) are presented in Table 1.

Preparation of analytical sample

The samples from each treatment plot were pooled andmixed thoroughly on a sheet of polyethylene in thelaboratory. From the field sample, a subsample of 1 kglaboratory sample was drawn by dividing the wholesample in four parts and randomly rejecting the threeparts. Onion plants were mixed in a high-speed Waringblender (Blixer 6 V.V. by robot coupe, France), and arepresentative 50 g of chopped and macerated sampleswas drawn for further analysis.

Extraction and cleanup

The samples were processed and analyzed at PesticideResidueAnalysis Laboratory, Department of Entomology,Punjab Agricultural University, Ludhiana. A representa-tive 50 g sample of chopped andmacerated onion and soilwas dipped separately overnight into 100 mL acetone inan Erlenmayer flask for 24 h. The extract was filtered intoa 1-L separatory funnel along with rinsings of acetone.The filtrate in the separatory funnel was diluted with

Table 1 Meteorological data during the experimental period for onion

Month Temperature (°C) Relative humidity (%) Rainfall (mm) Sunshine (h) Wind speed(km h−1)

Maximum Minimum Morning Evening

2009

January 19.6 7.7 97.1 60.9 0.6 5.9 3.8

February 23.3 9.1 96.2 52.0 1.6 9.4 4.9

March 28.9 13.0 90.7 39.5 0.5 8.6 3.8

April 35.2 17.6 59.3 22.7 0.8 10.2 5.6

2010

February 22.5 9.0 94.0 50.0 25.0 7.3 3.6

March 31.0 14.8 92.0 38.0 1.0 9.4 3.1

April 38.7 20.1 63.0 28.0 4.4 8.8 4.6

May 40.2 24.4 54.0 33.0 3.8 7.7 7.3

Environ Monit Assess (2013) 185:1711–1718 1713

600 mL brine solution (almost saturated sodium chloridesolution), and the contents were partitioned three timesinto 100, 75, and 50 mL toluene. The combined organiclayers were collected into a 500-mL beaker through a 1.5-in. layer of anhydrous sodium sulfate supported on aprewashed glass wool in a funnel. Toluene fractions weretreated with 500 mg activated charcoal powder for about2–3 h at room temperature. The clear extract so obtainedwas filtered through a Whatman filter paper No.1, con-centrated to near dryness, and again added with about20 mL acetone and concentrated using a rotary vacuumevaporator at 40 °C. The final volumewas reconstituted toabout 5 mL using acetone.

Gas chromatographic analysis

Analysis of the quizalofop ethyl insecticide was car-ried out on a gas liquid chromatograph (GLC)(Shimadzu Model GC-2010) equipped with an elec-tron capture detector 63Ni supplied by M/S ShimadzuCorporation, Kyoto, Japan. A capillary column DB-1(30 m×0.25 mm i.d. × 0.25-μm film thickness) withsplit ratio 1:10 was used for estimation of quizalofopethyl pesticide. GC operating parameters were as fol-lows: carrier gas flow rate, 30 mL min−1; temperatureof the injection port, 290 °C; temperature of the de-tector, 300 °C; and column temperature, 270 °C.Under these operating conditions, the retention timeof quizalofop ethyl was found to be 7.262 min.

Results and discussion

Validation of the method

As the quantitative determination of quizalofop ethyl indifferent agricultural commodities is directly related tothe evaluation and interpretation of data, a reliable andreproducible determination of different commodities isessential. The method was fully validated according tobioanalytical method recommendations described in theFood and Drug Administration guidelines in terms ofselectivity, linearity, and repeatability (Food and DrugAdministration 2001; Viswanathan et al. 2007).

Selectivity

Selectivity of the method was assessed by comparingthe GLC chromatograms of a set of six blank samples

with that of six samples spiked at the limit of quanti-fication (LOQ) level (0.01 μg/mL for GLC detection).No peak was detectable at the retention times of qui-zalofop ethyl.

Linearity

The linearity of a method is a measure of range withinwhich the results are directly, or by a well definedmathematical transformation, proportional to the con-centration of analyte in samples within a given range(Francotte et al. 1996). The calibration curves withrespect to quizalofop ethyl produces a linear relationshipbetween detector response (y) and analyte concentration(x). The parameters obtained by the selected chromato-graphic conditions for quizalofop ethyl calibration cor-respond to y063.05x+2,036 and R200.996 where y0peak area, x0quizalofop ethyl concentration (in milli-grams per liter), and R0correlation coefficient (Fig. 2).

Limit of detection and quantification

In general, residues of quizalofop ethyl were determinedby comparison of peak areas of the reference standardswith that of the unknown or spiked samples run underidentical working conditions of the instrumentsemployed. The limit of detection (LOD, in milligramsper kilogram) of each analyte was determined as thelowest concentration giving response of three times thestandard dilution of the baseline noise defined from theanalysis of the three control samples andworked out to be0.003 mg kg−1. LOQ for the compound was worked outon the basis of the response of the nanogram of standardworking solution injected as well as the sample weight inmilligram injected so that the base line of the instrumentremains stable and no noise is observed. Half-scale de-flection was obtained for 0.5 ng quizalofop ethyl whichcould be easily identified from the baseline. As 0.1 ng ofthe compound produced 10 %, full-scale deflection canbe measured. When 50 g of sample was extracted andcleanup and final volume made to 5 mL, 1 μL(10 mg) of the sample when injected did not produceany background interference. Thus, LOQ was found tobe 0.01 mg kg−1 and LOD being 0.003 mg kg−1.

Repeatability

The precision of the method was determined by re-peatability studies of the method and expressed by

1714 Environ Monit Assess (2013) 185:1711–1718

relative standard deviation values. The RSDr (relativestandard deviation for repeatability) was measured bycomparing the SD values of the recoveries fromspiked samples analyzed the same day. The RSDr

values, which ranged from 1.27 to 4.38 % quizalofopethyl for the spiking levels, were shown in Table 2.

Efficiency of the method

The selected method provided good recoveries of qui-zalofop ethyl residues, 87.36–89.22 % from onion in theconcentration range of 0.01–0.10 μg g−1. In the case ofsoil samples, 84.81–92.68 % recovery was found forquizalofop ethyl at 0.01–0.10-μg g−1 fortification level(Table 2). So the percent recoveries of quizalofop ethylin onion and soil were found to be consistent and morethan 85 %. Therefore, the results have been presented assuch without applying any correction factor.

Residues on green onion field samples

The overall results of the analysis of onion bulbsfollowing application of quizalofop ethyl (TargaSuper 5EC) at 50 and 100 g a.i. ha−1 are presented inTable 3. The mean initial deposits of quizalofop ethylwere observed to be 0.25 and 0.46 mg kg−1 during 2009and 0.33 and 0.54 mg kg−1 during 2010 on the onionfollowing the application of quizalofop ethyl at singleand double dosages, respectively. These deposits dissi-pated to 0.11 and 0.19 mg kg−1 after 1 day, respectively,during 2009 and 2010 thereby showing a loss of about56.00 and 42.42 % following the application of quiza-lofop ethyl at 50 g a.i. ha−1. The residues reached belowthe detectable limit of 0.01mg kg−1 in 7 and 10 days, forsingle and double dose, respectively, for both seasons.

These results are in agreement with those of Sondhia(2006) who reported that following application of halox-yfop (10 EC) at 100 gha−1, the concentration of halox-yfop in green onion was found to be 0.0045 μg g−1,which dissipated to 0.0035 in mature onion bulbs(129 days). The initial deposit of propineb in green onionleaves was 5.34 and 11.72 mg kg−1 following applicationof propineb at 1,225 and 2,450 g a.i. ha−1 applied thrice ata 10-day interval. Popineb residues were below the LOQlevel (0.2 mg kg−1) 15 days after the last application ofthe pesticide (Ganguly et al. 2009).

Koeppe et al. (1990) reported the metabolism of[phenyl-U-14C]quizalofop-ethyl or [quinoxaline-14C]quizalofop-ethyl in soybean and cotton plants. [14C]Quizalofop-ethy1 was applied to soybean or cotton

Fig. 2 Calibration curve ofdifferent concentrations ofquizalofop ethyl

Table 2 Recovery studies of quizalofop ethyl on onion and soil

Substrate Level of fortification(mg kg−1)

% Recoverya % RSDr

Onion 0.01 87.82 3.46

0.05 87.36 3.17

0.10 89.22 4.38

Soil 0.01 88.88 2.34

0.05 92.68 5.10

0.10 84.81 1.27

a Each value is the mean of three replicate determinations

Environ Monit Assess (2013) 185:1711–1718 1715

plants at 4 oz of AI/acre as a postemergence spray, andplant samples were harvested initially (day 0) and at 3, 6,and 13.5 (maturity) weeks after treatment. No de-tectable 14C residues (<0.01 ppm) were found inmature beans or pods, whereas the mature fiber andseeds from the cotton contained 0.08 and 0.09 ppmtotal 14C residues, respectively.

Residues on mature onion bulb samples

No quizalofop ethyl residues were detected in matureonion bulbs at the time of harvest (90 days after applica-tion) in both the seasons. Sondhia and Dubey (2006)reported the terminal residues of butachlor (50 EC) andpendimethalin (30 EC) following their application at1.0 kg ha−1 in direct seeded onion crop as preemergenceherbicides. The mature onion bulb samples collected at

harvest time (129 days) showed 0.002 μg g−1 residues ofbutachlor, but pendimethalin residues were not detected.

Residues on soil samples

Any residues of quizalofop ethyl for both the dosageswere not found in the soil samples collected from onionfield at 10 days of application (Table 3). Sondhia (2006)who reported that soil samples of onion field collected atharvest (125 days) had a residue of 0.091 μg g−1 fol-lowing application of haloxyfop (10 EC) at 100 gha−1.Butachlor (50 EC) and pendimethalin (30 EC) wereapplied at 1.0 kg ha−1 in direct seeded onion crop aspreemergence herbicides. The soil samples collectedfrom the onion field at harvest time (129 days) showed0.015 μg g−1 residues of butachlor; however, pendime-thalin residues were not detected (Sondhia and Dubey

Table 3 Residues of quizalofop ethyl (in milligrams per kilogram) on onion and soil at harvest time after the application of Targa Super5 % EC (quizalofop ethyl 5 EC) at 1 and 2 L/ha during 2009 and 2010

Interval (days) Quizalofop ethyl residue in milligrams per kilogram ± standard deviation

2009 2010

T1 T2 T1 T2

0 (1 h after spray) 0.25±0.02 (0.00) 0.46±0.04 (0.00) 0.33±0.03 (0.00) 0.54±0.03 (0.00)

1 0.11±0.01 (56.00) 0.29±0.04 (36.96) 0.19±0.02 (42.42) 0.36±0.02 (33.33)

3 0.07±0.01 (72.00) 0.15±0.03 (67.39) 0.10±0.01 (69.70) 0.15±0.02 (72.22)

5 0.02±0.01 (92.00) 0.07±0.01 (84.78) 0.03±0.01 (90.91) 0.07±0.01 (87.04)

7 BDL 0.02±0.01 (95.65) BDL 0.02±0.01 (96.30)

10 BDL BDL BDL BDL

Harvest time(PHI090 days)

BDL BDL BDL BDL

Soil (10 days) BDL BDL BDL BDL

T½ (days) 0.85 0.87 0.79 0.83

Values enclosed in parentheses indicate the percentage dissipation after spraying

T1 quizalofop ethyl at 50 g a.i. ha−1 , T2 quizalofop ethyl at 100 g a.i. ha−1 , BDL below the determination limit of 0.01 mg kg−1 , PHIpreharvest interval, T½ half-life

Fig. 3 Semi-logarithmicgraph showing dissipationkinetics of quizalofop ethylon onion during 2009

1716 Environ Monit Assess (2013) 185:1711–1718

2006). In the case of cropped soil, no residues weredetected after third and fifth day respectively, followingapplication of mancozeb at 750 and 1,500 g a.i. ha−1 forall the three seasons (Sarkar et al. 2005). No residueswere detected 7 days after application in the soil follow-ing application of propineb at 1,225 and 2,450 g a.i. ha−1

(Ganguly et al. 2009).

Half-life values of quizalofop ethyl on green onion

The persistence of quizalofop ethyl in two seasons isgenerally expressed in terms of half-life (T1/2) or DT50,i.e., time for disappearance of pesticide to 50%of its initialconcentration. T1/2 values are often obtained by fittingfirst-order kinetics to observed degradation patterns as

C ¼ C0e�k=t

where C is the chemical concentration (in milligrams perkilogram) at time t (in hour), C0 is the initial concentration(in milligrams per kilogram), and k1 is the first-order rateconstant (in per hour) independent of C and C0. The T1/2of quizalofop ethyl was calculated using Hoskins for-mula (1961) for each seasons separately. The half-life(T1/2) of quizalofop ethyl on onion was observed to be0.85 and 0.87 days, respectively, when applied at 50 and

100 g a.i. ha−1 during 2009 (Table 3, Fig. 3). During2010, the half-life (T1/2) values were observed to be 0.79and 0.83 days, respectively, at single and double doses(Table 3, Fig. 4).The half-life values of propineb ongreen onion were 2.30 days following application of1,225 g a.i. ha−1, and the correlation coefficient (r00.95–0.97) indicated a statistical conformity of the dis-sipation data to first-order kinetics (Ganguly et al.2009). Sarkar et al. (2005) reported that the half-lifevalues of mancozeb in onion bulb and leaf rangedbetween 0.97 and 1.16 days for three seasons followingapplication of mancozeb at 750 g a.i. ha−1.

Risk assessment of quizalofop ethyl on green onion

The use of pesticides on food crops leads to unwantedresidues, which may constitute barriers to exportersand domestic consumptions when they exceed maxi-mum residue limits (MRLs). MRL for quizalofop ethylon onion is not available for comparison. However,acceptable daily intake (ADI) for quizalofop ethyl hasbeen observed to be 0.099mg kg−1 bodyweight per day.The ADI of quizalofop ethyl has been reported as99 μg kg−1 body weight per day, which means an adultof 55 kg can safely tolerate intake of 5,445 μg of

Fig. 4 Semi-logarithmicgraph showing dissipationkinetics of quizalofop ethylon onion during 2010

Table 4 Theoretical maximum residue contribution (TMRC) in green onion

Days 2009 2010

Maximum residuesin onion(mg kg−1) in T1

TMRC(μg person−1

day−1)

Maximum residuesin onion(mg kg−1) in T2

TMRC(μg person−1

day−1)

Maximum residuesin onion(mg kg−1)in T1

TMRC(μg person−1

day−1)

Maximum residuesin onion(mg kg−1) in T2

TMRC(μg person−1

day-−1)

0 0.27 21.6 0.49 39.2 0.35 28.0 0.56 44.8

1 0.12 9.6 0.33 26.4 0.21 16.8 0.38 30.4

3 0.08 6.4 0.18 14.4 0.11 8.8 0.17 13.6

5 0.03 2.4 0.08 6.4 0.04 3.2 0.07 5.6

7 BDL – 0.03 2.4 BDL – 0.03 2.4

10 – – BDL – – – BDL –

BDL below determination limit (<0.01 mg kg−1 ), T1 quizalofop ethyl at 50 g a.i. ha−1 , T2 quizalofop ethyl at 100 g a.i. ha−1

Environ Monit Assess (2013) 185:1711–1718 1717

quizalofop ethyl residues without any appreciable risk totheir life (Mukherjee and Gopal 2000). The theoreticalmaximum residue contribution has been calculated at aconsidering recommended consumption of vegetable as80 g in Indian context (Anonymous 1999). An assess-ment of the intake of quizalofop ethyl residues 0 dayafter application at the recommended dosage based onaverage consumption of 80 g onion leaf by an adult of55 kg reveals an intake of 21.6 and 28.0 μg of quizalo-fop ethyl, which is quite safe when compared to its ADI(Table 4). These studies therefore suggest that the use ofquizalofop ethyl at the recommended dosages does notseem to pose any hazards to the consumers and a wait-ing period of one day is suggested to reduce the riskbefore consumption of green onion.

Conclusions

Half-life values for quizalofop ethyl following single ap-plication at recommended dose on green onion was ob-served to be 0.85 and 0.79 days during 2009 and 2010,respectively. Residues of quizalofop ethyl were below thedetectable limit of 0.01 mg kg−1 at harvest. Residue datashowed that theoretical maximum residues contributionfor quizalofop ethyl were found to be well below theacceptable daily intake of 5,445 μg quizalofop ethyl whencompared with an average 80-g consumption of greenonions at 0 day (1 h after spraying) for the both thedosages. Therefore, application of quizalofop ethyl at therecommended dose on green onion is quite safe from cropprotection and environmental contamination point of view.

Acknowledgments The authors are thankful to the IndianCouncil of Agricultural Research, New Delhi India for sponsor-ing the project and also to the head of the Department ofEntomology, PAU, Ludhiana and the director of the Seed FarmLadhowal, Punjab Agricultural University, Ludhiana Punjab,India, for providing the necessary research facilities.

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