Bioefficacy and persistence of acaricides applied against two spotted spider mite (Tetranychus urticae Koch) in cucumber (Cucumis sativus Linnaeus) under protected cultivation system

DOI: https://doi.org/10.21203/rs.3.rs-1756121/v1

Abstract

The two-spotted spider mite (Tetranychus urticae Koch) is the most pronounced polyphagous non-insect pest, wreaking havoc on agricultural and horticultural crops. In cucumber, the infestation by various pests jeopardises effective cultivation, with two spotted spider mites causing great harm to the crop. Six different chemical acaricides were tested for their effectiveness against T. urticae in cucumber cultivated under protected cultivation system at the farmer’s field.  The results revealed that none of the acaricides exhibited a tangible decrease over the control, but spiromesifen (59.50 %) recorded a rather excellent reduction over the other investigated chemicals (40 to 54.47 %). The experimental bioassays were performed to determine the effective dosage, which resulted in a significant mite population reduction and the results revealed that tested chemical acaricides were found to be effective at their higher dose, ranging nearly from 3X to 4X of recommended by CIB&RC. The pot culture and field study was conducted to determine the effectiveness of fixed doses from bioassay investigations. A good reduction in mite population was observed for all tested chemicals with spiromesifen recorded a 100 per cent reduction in mite population. Residue analysis of harvest time samples of cucumber after spiromesifen application revealed residues below quantification limit of 0.025 µg/kg. 

1. Introduction

The cultivation of vegetables in protected conditions such as polyhouse or greenhouse provides promising yield and consent to the farmers to cultivate them throughout the year irrespective of seasonal requirements. Production of good quality fruit and vegetables has been attained through protected cultivation systems compared to the open field condition due to the adaptation of specialized techniques and high-yielding varieties (Dhooria, 1999). The polyhouse/greenhouse fashions an environment that helps in the growth and development of plants likewise, also bolstering the prevalence of many insects and non-insect pests.

The two-spotted spider mite (Tetranychus urticae Koch) is the major polyphagous non-insect pest, threatening both agricultural and horticulture crops (Reddy & Latha, 2013). It is the most influential pest species in Tetranychidae family (Smith, 1996), attacking around 1200 plant species, 150 of them are commercially valuable crops (Zhang, 2003). The high temperature and warm weather circumstances promotes the development of two-spotted spider mite swiftly and live retentive under protected cultivation (Vashisth et al., 2013). This notorious pest has caused crop loss in both sheltered and open fields.

Cucumber (Cucumis sativus Linnaeus) is now widely cultivated in India and is progressively used in protected farming as an important table vegetable. Nevertheless, a significant number of pests endanger its effective cultivation. In recent days, T. urticae achieved key pest status and caused devastating effects on the crops (Park & Lee, 2002). It usually thrives on the abaxial side of the plant and feeds on the plant juice by penetrating the leaf tissues with its piercing and sucking mouthparts. T. urticae possess a precipitous population growth rate, a short developmental time, high fecundity, and a long lifespan (Clotuche et al., 2011). The egg-to-adult lifecycle of female T. urticae takes around 6.5 days at 30°C, while the male completes just before female (Clotuche et al., 2013).

As cucumbers are commercially grown under controlled conditions, farmers are necessitated to apply huge quantity of synthetic acaricides on a consistent basis to maintain pest populations below the economic threshold level. Mites have evolved resistance to most of these chemicals at a certain level, which were previously proven fatal, resulting in a fifty percent mortality rate. Resistance development in T. urticae has led to the failure of many acaricides such as hexythiazox (Herron et al., 1993), fenpyroximate (Sato et al., 2004) and abamectin (Beers et al., 1998). Indiscriminate use of acaricides was reported to be a factor for the development of resistance to a number of acaricides, thereby making mite control very difficult (Ganjisaffar et al., 2011; Lee, 2007).The symptoms of damage caused by mites includes leaves turn into small yellowish patch initially and later on coalesce to form typical yellowish white large area as the mite persists to drain the fluid content from the plant parts (Abdel-Wali et al., 2012). Mites are observed both on the abaxial and adaxial sides of the leaves, later converge on the tip of the plants to disperse to nearby plants (Clotuche et al., 2011).

2. Materials And Method

2.1. Chemical and reagents

The acaricides, spiromesifen (Bayer crop science, 3-mesityl-2-oxo-1-oxaspiro[4.4]non-3-en-4-yl 3,3-dimethylbutyrate), Fenazaquin (Dupont, 4-tert-butylphenethyl quinazolin-4-yl ether), Fenpyroximate (Tata Rallis, tert-butyl4-[[(E)-(1,3-dimethyl-5-phenoxypyrazol-4-yl)methylideneamino]oxmethyl]benzoate), Hexythiazox (Biostadt, trans-5-(4-Chlorophenyl)-N-cyclohexyl-4-methyl-2-oxo-3-thiazolidine carboxamide) Abamectin (Abacin, 1'R,2R,3S,4'S,6S,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-2-[(2S)-butan-2-yl]-21',24'-dihydroxy-12'-[(2R,4S,5S,6S)-5-[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy-4-methoxy-6-methyloxan-2-yl]oxy-3,11',13',22'-tetramethylspiro[2,3-dihydropyran-6,6'-3,7,19-trioxatetracyclopentacosa-10,14,16,22-tetraene]-2'-one) and Propargite (, 2-(4-(tert-Butyl) phenoxy) cyclohexyl prop-2-yn-1-yl sulfite) were obtained from local pesticide market.

For residue analysis study, mass-spectrometry grade acetonitrile, magnesium sulphate, formic acid, and anhydrous sodium chloride (analytical grade) were purchased from Merch.India Ltd. Graphitised carbon black and primary secondary amine were supplied by Agilent technologies India Private Ltd. Ultrapure water from the Q3 Merch Millipore unit was utilized for analysis. Certified raw material of spiromesifen was purchased from Sigma Alderich.

2.2. Field experiment 

The trial was conducted at a farmers’ field in Coimbatore to evaluate the efficacy of different acaricides against T. urticae, as per the recommendations given by CIBRC (Central Insecticide Board and Registration Committee). Multi star R1 variety was purchased and primarily was sown in protrays and subsequently at their two-leaf stage it was transplanted in the bounds of the polyhouse. Seed rate, spacing and agronomic practices were followed as per the recommendation suggested by Tamil Nadu Agricultural University (TNAU AGRITECH PORTAL). Six different acaricides (Table 1) were selected and sprayed on cucumber under protected conditions. The field trial was laid out using RBD (Randomized Block Design) with replicated thrice during first fortnight of November. Spraying was done in three rounds at fortnightly intervals, commencing at 30 DAS, 45 DAS, and 60 DAS (days after sowing). On 0, 3, 5, 7, 10, and 14 days after each spraying, the population of nymph and adults of T. urticae were counted from the top, middle, and bottom leaves of 10 randomly selected plant from each treatment.

Table 1 Treatment and their concentration 

Treatments

Formulation

Dose

Manufacturer

T1- Fenazaquin

10% EC

2.0 ml/ lit

Dupont

T2-Fenpyroximate

5% SC

0.8 ml/ lit

Tata Rallis

T3- Spiromesifen

22.90 % SC

0.8 ml/ lit

Bayer crop science

T4- Hexythiazox

5.45% EC

0.8 ml/ lit

Biostadt

T5- Abamectin

1.9% EC

0.5 ml/ lit

Crystal

T6- Propargite

57% EC

2.5 ml/ lit

Dhanuka Agritech Limited

T7- Control

-

-

-

 2.3. Bioassay studies on field population of T. urticae

A bioassay was carried out to appraise the median lethal dose that causes 50 per cent mortality of mite. To this study, populations were collected from the polyhouses located at kannam palaiyam, Coimbatore, Tamil Nadu. The collected mites were cultured in the laboratory at a temperature of 30± 1°C and a relative humidity of 65-70 percent. In laboratory experiments, leaf dip bioassay was performed. Filter paper was laid over an adsorbent cotton in a petridish, which was maintained wet by adding water. Acaricidal solutions were made at various concentrations such as spiromesifen (4 ppm to 8 ppm), fenazaquin (5 ppm to 9 ppm), fenpyroximate (1.5 ppm to 3ppm), hexythiazox (1.00 ppm to 2.25 ppm), abamectin (0.90 ppm to 1.30 ppm) and propargite (28 ppm to 52 ppm). Mulberry leaves taken from plants that was maintained deprived of spraying any chemical in the Insectary, Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, were used for the bioassay. The collected leaves were cut into a 75 mm leaf disc, immersed in the acaricidal solution, and kept upside down on the filter paper, which was then moistened to keep the leaves fresh until an observation was over. The cultured mite was transferred at the rate of 30 mites per Petridish. The treatments were implemented in CRD design with three replications.  Mortality count of mite was taken at 6, 12, 24 and 48 hours intervals, by observing under stereo microscope (CETI).

2.4. Pot culture and field experiment 

The pot culture and field experiment were conducted in cucumber under protected conditions to evaluate the efficacy of selected six acaricides against two spotted spider mite (T. urticae) in the Insectary polyhouse (latitude: 11.0162913˚N and longitude: 76.9286577˚E), Department of Agricultural Entomology, Centre for Plant Protection Studies, Tamil Nadu Agricultural University, Coimbatore. Cucumber variety of Multistar Rizwan F1 was employed for the field and pot culture experiment and the plants of 25 days old were inoculated artificially by the mite culture, which was collected from polyhouse and cultured in the laboratory. As the preliminary laboratory bioassay studies shown resistance of mite to the dose recommended by the CIB&RC (Central Insecticide Board and Registration Committee), the effective dose obtained from the bioassay study was selected sprayed (Table 2) and the efficacy of the dose was observed in both pot culture and field experiment. Two rounds of chemicals spray were given at fortnightly intervals. During second fortnight of February, the trial was conducted in a CRD and RBD design with three replications for field and pot culture experiment respectively. The population count of nymph and adult of T. urticae was recorded on the top, middle, and bottom leaves of both potted and field plants in each treatment at 0,3, 5, 7, 10, and 14 days after each spray.

Table 2 Treatment with resulted concentration

Treatments

Concentration

Fenazaquin 10EC

2.99ml/lit

Fenpyroximate 5EC

3.3 ml/lit

Spiromesifen 22.90SC

2.93 ml/lit

Hexythiazox 5.45SC

3.90 ml/lit

Abamectin 1.9EC

1.4 ml/lit

Propargite 57EC

3.1 ml/lit

control

-

 2.5.  Harvest time residues in cucumber

2.5.1. Sampling of fruits

      The acaricide, spiromesifen was applied at the dose of 2.93 ml/lit against two spotted spider mites in cucumber under poly house condition. Fruit sample from treated plants were collected during first three harvest and subjected for residue studies. Sample of 1 kg were collected and stored at -4˚C for residues analysis.

2.5.2. Sample extraction

      A 50 mL Polypropylene centrifuge tube was filled with approximately 10 g of homogenised cucumber fruits sample. The solution was then vortexed for 10 minutes with 10 ml ultrapure water and 20 ml of acetonitrile in a vortex mixer. The homogenised solution was then mixed with 4 g of anhydrous MgSO4 and 1 g of NaCl in a vortexer and centrifuged for 10 minutes at 6000 rpm. A six ml of the supernatant extract was then placed in a 15 ml centrifuge tube containing 100 mg florisil, 100 mg PSA, 25 mg GCB, and 600 mg anhydrous Magnesium sulphate (MgSO4). It was vortexed for 1 minute and then centrifuged for 10 minutes at 3000 rpm. A four ml of extract of the supernatant was transferred to a glass tube and dried in a turbovap LV at 40°C using nitrogen gas. Following optimal settings, the dried extract was redissolved in 1 ml acetonitrile and placed into an autosampler vial for Liquid Chromatography-Mass Spectrometry-Mass Spectrometry (LC-MS/MS) analysis. 

2.4.3. Instrument conditions for chromatography optimization

        A Waters Alliance 2695 Separations Module and an ACQUITY tandem triple quadrupole mass spectrometer with electrospray ionisation interface in positive mode constitutes the LC-MS/MS system. The LC analysis was carried out on a 5µm (4.8 250 mm) Xterra analytical column C18 (Waters, Milford, MA, USA). The temperature of the column was fixed at 30℃. Water with 0.1 percent formic acid (A) and acetonitrile with 0.1 percent formic acid (B) (70:30 ratio) were used as mobile phases, with a flow rate of 0.5 ml min-1. The injection volume was 10 µl, and the analyte was eluted in 7.05 minutes using an isocratic mode. The optimal MS/MS settings were set to be 3.5 kV voltage, 150°C ion source temperature, and 500°C desolvation temperature. The cone gas and desolvation gas flow rates were 50 and 1100 l h-1, respectively. Working standard solutions of spiromesifen at 0.5 µg ml-1 in acetonitrile containing 0.1 percent (v/v) formic acid was directly fed into the mass spectrometer and chromatogram was acquired in the full scan mode to identify the parent and daughter ions.

2.4.4. Data analysis

The following formula was used to calculate insecticide residue levels using data from the LC-MS/MS chromatogram.

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2.5. Data aanalysis

The data recorded from pot culture and field experiment was analysed using IBM SPSS software. Finney's (1971) approach was used to compute LC50 and LC95 values of bioassay studies with help of IBM SPSS software.

3. Results

3.1. Bioefficacy of different acaricides tested in cucumber at the farmer’s field

The results of the field trial under protected cultivation revealed that the mite have evolved resistance to all the acaricides tested. Among the six chemicals sprayed, spiromesifen (59.53 %) resulted in a considerable reduction compared to the control plot, which was kept unsprayed (tables 3, 4, and 5). This was followed by, hexythiazox (54.80 %) and fenpyroximate (50.58 %) which shown slight reduction in mite population compared to control, while abamectin and fenazaquin (44.28 %) showed on pair on mite reduction. Propargite (40.16 %) on the other hand, showed the least reduction compared to control, which could be attributed to overuse of chemicals and ongoing exposure rather than a different chemical usage pattern. The mean population of mites and their corresponding reduction were presented in the figure 1.

Table 3 Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population after first spraying)

Treatment

PTC

3 DAS

5 DAS

7 DAS

10 DAS

14 DAS

MEAN

PROC

T1

22.59

(4.81)

19.17

(4.44)e

14.36

(3.85)e

15.51

(4.00)e

17.50

(4.24)de

18.26

(4.33)cd

16.96

(4.18)d

43.82

T2

24.37

(4.99)

16.62

(4.14)c

11.65

(3.49)c

13.18

(3.70)c

15.68

(4.02)c

18.59

(4.37)d

15.14

(3.95)c

49.84

T3

22.19

(4.70)

13.81

(3.78) a

9.45

(3.15)a

10.82

(3.36)a

12.39

(3.59)a

14.66

(3.89)a

12.23

(3.57)a

59.50

T4

22.50

(4.80)

15.57

(4.01)b

10.14

(3.26)b

12.67

(3.63)b

14.23

(3.84)b

15.97

(4.06)b

13.72

(3.77)b

54.57

T5

23.12

(4.86)

18.28

(4.33)d

12.51

(3.61)d

14.26

(3.84)d

16.75

(4.15)d

17.21

(4.21)bc

15.80

(4.00)c

47.66

T6

23.71

(4.92)

20.15

(4.54)f

15.43

(3.99)f

16.39

(4.11)f

18.26

(4.33)e

20.14

(4.54)e

18.07

(4.31)e

40.13

T7

23.26

(4.87)

24.69

(5.02)g

27.23

(5.27)g

30.15 
(5.54)g

33.27

(5.81)f

35.61

(6.01)f

30.19

(5.54)f

0.00

CD (p=0.05)

-

0.6477

0.6252

0.4765

0.9152

1.2467

0.8705

 

CV (%)

-

1.99

2.44

1.66

2.81

3.49

2.81

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, DAS: Days After Spraying, PROC: Percentage reduction over control, PTC: Pre-Treatment Count.

Table 4  Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population after second spraying)

Treatment

PTC

3 DAS

5 DAS

7 DAS

10 DAS

14 DAS

MEAN

PROC

T1

18.26

(4.33)

16.47

(4.12)e

14.35

(3.85)e

17.57

(4.25)e

19.67

(4.49)e

22.18

(4.76)d

18.05

(4.31)e

59.15

T2

18.59

(4.37)

13.28

(3.71)c

10.43

(3.31)c

13.74

(3.77)c

15.35

(3.98)c

17.52

(4.24)b

14.06

(3.82)c

68.17

T3

14.66

(3.89)

10.34

(3.30)a

7.16

(2.77)a

9.84

(3.22)a

12.61

(3.62)a

15.23

(3.97)a

11.06

(3.40)a

75.02

T4

15.97

(4.06)

11.19

(3.42)b

8.26

(2.96)b

11.29

(4.34)b

13.84

(3.79)b

16.68

(4.14)b

12.25

(3.57)b

72.27

T5

17.21

(4.21)

14.65

(3.89)d

13.54

(3.75)d

15.31

(3.98)d

17.29

(4.22)d

20.74

(4.61)c

16.31

(4.10)d

63.09

T6

20.14

(4.54)

17.31

(4.22)f

15.66

(4.02)f

18.25

(4.33)e

21.14

(4.65)f

24.61

(5.01)e

19.39

(4.46)f

56.10

T7

35.61

(6.01)

38.49

(6.24)g

41.28

(6.46)g

44.65

(6.72)f

46.32

(6.84)g

50.17

(7.12)f

44.18

(6.68)g

0.00

CD (p=0.05)

 

0.7680

0.4608

0.6837

0.8048

1.3170

1.0971

 

CV (%)

 

2.48

1.64

2.06

2.17

3.10

3.19

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, DAS: Days After Spraying, PROC: Percentage reduction over control, PTC: Pre-Treatment Count.

Table 5   Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population after third spraying)

Treatment

PTC

3 DAS

5 DAS

7 DAS

10 DAS

14 DAS

MEAN

PROC

T1

22.18

(4.76)

17.38

(4.23)c

15.27

(3.97)e

17.43

(4.23)d

19.65

(4.49)d

23.34

(4.87)e

18.61

(4.37)d

67.71

T2

17.52

(4.24)

14.36

(3.85)b

12.73

(3.64)c

15.48

(4.00)c

18.56

(4.37)c

21.39

(4.68)c

16.50

(4.12)c

71.37

T3

15.23

(3.97)

11.51

(3.45)a

9.44

(3.15)a

12.82

(3.65)a

16.31

(4.10)a

18.09

(4.36)a

13.63

(3.76)a

76.35

T4

16.68

(4.14)

13.54

(3.75)b

10.52

(3.32)b

14.25

(3.84)b

17.08

(4.19)b

19.15

(4.43)b

14.91

(3.93)b

74.14

T5

20.74

(4.61)

16.25

(4.09)c

14.32

(3.85)d

18.21

(4.33)d

20.24

(4.55)d

22.47

(4.79)d

18.30

(4.34)d

68.26

T6

24.61

(5.01)

19.20

(4.44)d

16.55

(4.13)f

19.64

(4.49)e

22.78

(4.82)e

25.61

(5.11)f

20.76

(4.61)e

64.00

T7

50.17

(7.12)

52.39

(7.27)e

55.14

(7.46)g

58.12

(7.66)f

60.23

(7.79)f

62.39

(7.93)g

57.65

(7.63)f

0.00

CD (p=0.05)

 

1.3627

0.5626

1.2142

0.6874

0.7792

0.7966

 

CV (%)

 

3.71

1.65

3.06

1.55

1.59

1.96

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, DAS: Days After Spraying, PROC: Percentage reduction over control, PTC: Pre-Treatment Count.

3.2. Laboratory bioassay on efficacy of acaricides against two spotted spider mites

          The results revealed that the mite has evolved resistance to the CIB&RC recommended dose (ppqs.gov.in). To date, constant exposure to the chemical has resulted in the development of resistance to the sprayed chemical showing that the mite was resistant to all the chemicals tested, and the lethal dose found to be efficient was laid nearly from 2X to 4X of CIB&RC recommended dosage. The results of bioassay investigation were presented in the table 6.

Table 6  LC50  values of different chemicals tested against T. urticae in laboratory

Treatment 

χ2

Regression equation

LC50

(ppm)

50% fiducial limit

LC95

(ppm)

 

95% Fiducial limit

 

LL

UL

LL

UL

Fenazaquin

2.48

y = 4.3636x + 2.9243

2.99

2.77

3.22

7.12

5.61

9.03

Fenpyroximate

5.65

y = 4.046x + 4.1146

1.65

1.52

1.81

4.22

3.35

5.32

Spiromesifen 

5.69

y = 3.0684x + 2.452

6.76

6.22

7.35

14.29

11.94

17.08

Hexythiazox 

2.73

y = 1.8764x + 4.3828

2.13

1.75

2.59

16.05

4.75

54.24

Abamectin

4.70

y = 2.5091x + 3.8862
 

2.77

2.47

3.13

12.57

6.75

23.40

Propargite 

4.98

y = 2.9032x + 1.3413

18.20

16.35

20.26

67.14

42.87

105.05

 3.3. Bioefficacy of acaricides in the pot and field experiment under protected cultivation system

         The results of the pot culture and field experiment under protected cultivation (table 7, 8, and 9) revealed that spiromesifen provided a much better reduction than the control. Followed by the treatments such as hexythiazox, fenpyroximate, abamectin, and fenazaquin were also exhibited effective control over mite population in comparison to chceck. Propargite, on the other hand, have a lower reduction over control than the other treatments. This was most likely related to the built resistance in mites and the field experiment revealed that spiromesifen given significant reduction in mite population compared to other synthetic chemicals under protected cultivation system.

Table 7   Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population after first spraying)

Treatment

PTC

3 DAS

5 DAS

7 DAS

10 DAS

14 DAS

MEAN

PROC

T1

22.42

(4.79)

9.23(3.12) d

6.22

(2.59)e

5.37

(2.42)d

7.25

(2.78)e

9.14

(3.10)e

7.44 

(2.82)e

72.38 

T2

20.87

(4.62) 

7.18

(2.77) b

4.78

(2.30)c

3.64

(2.03)C

5.51

(2.45)C

6.36

(2.62)c

5.49 

(2.45)c

79.61 

T3

22.71

(4.82)

5.09

(2.36) a

1.95

(1.56) a

0.98

(1.22) a

2.84

(1.83) a

3.93

(2.10) a

2.96 

(1.83) a

89.02 

T4

23.02

(4.85)

6.76

(2.69) b

3.31

(1.95) b

2.53

(1.74)b

4.16

(2.16)b

5.59

(2.47)b

4.47 

(2.23)b

83.41 

T5

19.64

(4.49)

8.56

(3.01) c

5.36

(2.42)d

4.21

(2.17)C

6.38

(2.62)d

7.52

(2.83)d

6.41 

(2.63)d

76.22 

T6

20.25

(4.55)

10.64

(3.34) e

7.94

(2.91)f

6.42

(2.63)e

8.49

(3.00)f

10.87

(3.37)f

8.87 

(3.06)f

67.07 

T7

21.62

(4.70)

23.81

(4.93) f

25.41

(5.09)g

26.97

(5.24)f

28.36

(5.37)g

30.15

(5.54)g

26.94

(5.24)g

0

CD (p=0.05)

 

0.5549

0.2246

0.7433

0.2400

0.5379

0.4433

 

CV (%)

 

3.06

1.61

5.84

1.50

2.88

2.79

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, DAS: Days After Spraying, PROC: Percentage reduction over control, PTC: Pre-Treatment Count.

Table 8   Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population after second spraying)

Treatment

PTC

3 DAS

5 DAS

7 DAS

10 DAS

14 DAS

MEAN

PROC

T1

9.14

(3.10)

3.36

(1.96)d

1.65

(1.47)c

0

(0.71)a

0

(0.71)a

0

(0.71)a

1.00 

(1.22)d

97.19 

T2

6.36

(2.62)

1.49

(1.41)c

0

(0.71)a

0

(0.71)a

0

(0.71)a

0

(0.71)a

0.30 

(0.89)bc

99.16 

T3

3.93

(2.10) 

0

(0.71)a

0

(0.71)a

0

(0.71)a

0

(0.71)a

0

(0.71)a

0.00 

(0.71)a

100.00 

T4

5.59

(2.47)

0.65

(1.07)b

0

(0.71)a

0

(0.71)a

0

(0.71)a

0

(0.71)a

0.13 

(0.79)a

99.63 

T5

7.52

(2.83)

2.09

(1.61)c

0.27

(0.88)b

0

(0.71)a

0

(0.71)a

0

(0.71)a

0.47 

(0.98)c

98.67 

T6

10.87

(3.37)

4.51

(2.24)e

2.18

(1.64)d

0

(0.71)a

(0

0.71)a

0

(0.71)a

1.34 

(1.36)e

96.24 

T7

30.15

(5.54)

32.54

(5.75)f

33.38

(5.82)e

35.42

(5.99)b

36.94

(6.12)b

39.75

(6.34)b

35.61

(6.01)

0

CD (p=0.05)

 

0.6337

0.0994

0.1904

0.6061

0.4364

0.1781

 

CV (%)

 

5.59

1.04

2.15

6.46

4.32

1.80

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, DAS: Days After Spraying, PROC: Percentage reduction over control, PTC: Pre-Treatment Count.

Table 9 Efficacy of acaricides on the occurrence of mites in cucumber under protected cultivation (assessment of mite population during first and second spraying)

First spraying

Second spraying

 

 

Treatment

PTC

mean

PROC

PTC

mean

PROC

Polled mean

PROC

T1

15.42

(3.92)

 

 

(3.92)

3.14

(1.77)c

81.87

3.14

(1.77)

0.56

(0.74) c

97.26

1.85

(1.36)

90.20

T2

14.36

(3.79)

3.56

(1.88)d

79.44

3.56

(1.88)

0.13

(0.36) a b

99.36

1.845

(1.35)

90.23

T3

15.89

(3.98)

2.25

(1.50)a

87.01

2.25

(1.50)

0.00

(0.71) a

100.00

1.125

(1.06)

94.04

T4

13.57

(3.68)

2.41

(1.55) a

86.08

2.41

(1.55) 

0.00

(0.71) a

100.00

1.205

(1.09)

93.61

T5

14.24

(4.77)

2.68

(1.63)b

84.52

2.68

(1.63)

0.37

(0.60) b c

98.19

1.525

(1.23)

91.92

T6

16.63

(4.07)

 

3.97

(1.99)e

77.07

3.97

(1.99)

0.24

(0.49) a b c

98.82

2.105

(1.45)

88.85

T7

14.15

(3.76)

17.32

(4.16)f

0.00

17.32

(4.16)

20.45

(4.52)d

0.00

18.885

(4.34)

0.00

CD (p=0.05)

 

0.2294

 

 

0.3554

 

 

 

CV (%)

 

2.56

 

 

6.43

 

 

 

Means (separated by Duncan’s test) within a column followed by the same letter are not significantly different. Figures in parentheses indicate √x+0.5 transformations, PROC: Percentage reduction over control, PTC: Pre-Treatment Count

3.4. Harvest time residues of spiromesifen in cucumber fruits

Cucumber fruit samples were subjected to residue analysis using LC-MS/MS. Spiromesifen was found at below quantification limit (0.025 µg/g) in the fruits which indicated the safety of fruits to consumers (Figure 2).

4. Discussion

Due to conservancy and consumption of vegetables during the offseason. To meet the demand, producing them under protected condition is necessary and increasing now a days. The crop has its unique seasonal requirements and thrives best under ideal environmental circumstances. Crops might be grown in particular season, but they are consumed throughout the year. Vegetable cultivation is achievable during the off-season by adopting better varieties growing under protected condition. Cultivation of cucumber under protected conditions is imperiled by an infestation of the non-insect pest T. urticae. Pest T. urticae, which is having the ability to develop swiftly in a protected environment due to regulated environmental conditions such as temperature and relative humidity. Many researchers have developed management tools for mite control in polyhouses in various crops (Eswara Reddy, 2005; Jhansi Rani & Sridhar, 2005; Reddy, Urvashi, et al., 2014; Sato et al., 2005)

         The effectiveness of six different acaricides was evaluated in the field under protected cultivation. All the tested chemicals exhibited significant reduction in the mite population, with spiromesifen revealed the best reduction among the six sprayed acaricides. Similarly Al-Antary (2010) reported that spiromesifen proved to be the best in reducing in mite population and achieved an excellent reduction of two spotted spider mites (T. urticae) under polyhouse condition with an extended period of toxicity of 9 days (Al-Antary et al., 2012). Similar chemicals were also studied by Chauhan (2014), who also reported that the chemicals were effective against T. uticae with 99% reduction (Reddy, Chauhan, et al., 2014). According to the results of the present field study, mites have developed resistance to the tested compounds, which might be attributed to constant exposure to chemical pesticides and similarly resistance status of mites to the synthetic acaricides were also reported by (Sato et al., 2005). Previously, abamectin was reported to be significantly effective against T. urticae in capsicum and eggplant (Eswara Reddy, 2005), but the present study revealed that abamectin was not effective at a dose reported to be effective and higher dose was observed to be given significant reduction.  Bhardwaj and Sharma (2010) experimented to test efficacy of seven different acaricides against T. urticae, of which abamectin @ 0.01%, hexythiazox @ 0.0025%, propargite @ 0.05%, and fenazaquin @ 0.001% recorded excellent reduction on mite population, while fenpyroximate (96.10%) and hexythiazox (55.73-100%) recorded the highest reduction resulted by longer residual action (Bharadwaj & Sharma, 2010). Previously, propargite and spiromesifen were observed to be effective against two spotted spider mite and remained effective for an extended period after spray (Tomar & Singh, 2011). But the present study revealed that mites have developed resistance to the tested chemicals and resulted in less effectiveness in reducing mite population. Wu (2019) reported that mites possess ability to develop resistance to the sprayed synthetic acaricides quickly and investigated acaricides such as etoxazole and fenpyroximate were not yielded good reduction against T. urticae. The increase in activities of detoxifying enzyme attributed the developed resistance in mites (Wu et al., 2019). The efficacy study was conducted by Wang (2018) disclosed that all of synthetic acaricides tested against two spotted spider mites were recorded good reduction under greenhouse condition with  fenpyroximate and hexythiazox recorded excellent reduction on mite population without any residues at their recommended dose, while propargite even showed a better reduction, also resulted residues on sprayed strawberries under greenhouse cultivation (Wang et al., 2018)

         The efficacy of six selected acaricides was tested against T. urticae in the laboratory to find the effective dosage that gives a 50 per cent reduction in mite population. All the six tested chemicals have provided a good result at their least doses previously, but mites have developed resistance and these chemicals were not effective at a dose recommended by the CIB&RC. Abamectin 1.9EC and fenazaquin 10EC recorded the highest mortality under laboratory conditions, but our studies revealed that these two chemicals were yielded the lowest reduction at the recommended dose, and laboratory bioassay studies indicated that double the recommended dose was found to be effective. Abamectin is reported to be effective at their lower concentration(Croft et al., 1987), but nowadays efficiency of this chemical have lasted at their lower concentration and higher dosage is given satisfactory results. Wang (2015) reported that the laboratory bioassay studies were conducted against T. urticae showed resistance to all six tested acaricides, of which abamectin shown more resistance, while other recorded moderate resistance (Wang et al., 2015).

         In the pot culture experiment, an effective dosage determined by the laboratory bioassay was tested. The same cucumber variety was purchased from the seller and planted in a pot inside the polyhouse. During the first spray, spiromesifen provided a considerable decrease over the control, however during the second spray, all the tested chemicals provided an excellent reduction over the control, with spiromesifen providing 100% percentage mortality compared to the other five tested chemicals. Efficacy of spiromesifen was also checked by Marcic (2010), who reported that gross fertility and female surviving ability was reduced up to 99% at the concentration of 180 µl of spiromesifen(Marcic et al., 2010).

        Cucumber is a major perishable table crop that is harvested and immediately sold in the market. The persistent level of chemicals sprayed was tested thrice followed by chemical spraying in field experiment. LCMS/MS analysis was performed to determine the durability of the best treatment observed in the field experiment, and the findings revealed that all the three samples yielded negative results.

5. Conclusion

This study provided information on the efficacy of various acaricides available on the market, and observations revealed that the mite has evolved resistance to the dose advised by the CIB&RC. The newly identified dose in this study significantly reduced T. urticae population to considerable level. Their effectiveness against mites was also tested in a pot experiment, as was their durability in fruit to ensure residual free fruits.

Declarations

Acknowledgement 

The author sincerely thanks to the farmer Mr. Manivasagam for permit us to perform acaricide evaluation inside the polyhouse. They are grateful gratitude to Dr. S. V. Krishnamoorthy, the Professor and Head, Department of Agricultural Entomology, Centre for Plant protection studies, Coimbatore for successful conduct of the pot culture experiment under polyhouse at the insectary, Department of Agricultural Entomology, TNAU, Coimbatore.

Disclosure statement

The authors report there are no competing interests to declare.

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