neem based integrated approaches for the management of tea thrips scirtothrips dorsalis hood...

RESEARCH ARTICLE

Neem based Integrated Approaches for the Management of TeaThrips Scirtothrips dorsalis Hood (Thripidae: Thysanoptera)in Tea

Somnath Roy • Guruswami Gurusubramanian •

Senthil Kumar Nachimuthu

Received: 5 January 2011 / Revised: 21 August 2011 / Accepted: 24 October 2011 / Published online: 29 November 2011

� Zoological Society, Kolkata, India 2011

Abstract Tea thrips, Scirtothrips dorsalis Hood (Thripi-

dae: Thysanoptera), has been the most destructive pest of

tea in North East India since last few decades. In order to

reduce the load of the synthetic chemicals in tea vis-a-vis

their deleterious effect, integration of biopesticides, syn-

thetic pesticides along with effective spraying strategies,

have been attempted. The anti-insect property of ‘‘neem’’,

Azadirachta indica A. Juss. (Meliaceae) has been used to

solve many pest problems. Two field trials were conducted

between May and June 2008 at Red Bank Tea Estate,

Jalpaiguri, West Bengal, India following randomized block

design against tea thrips, S. dorsalis. In one experiment,

different azadirachtin concentrations (300, 1,500, 3,000,

10,000 and 50,000 ppm) at different doses (1:200, 1:300,

1:500, 1:1,000 and 1:1,500) were evaluated to find out the

relationship between azadirachtin concentration and its

bioactivity against S. dorsalis. At 50,000 ppm azadirachtin

concentration 82% control of reduction in thrips population

could be attained, whereas at 3,000 and 10,000 ppm, gave

60–73% reduction and 300 and 1,500 ppm \60% control

was possible. Therefore, azadirachtin concentration and its

dilutions are the major criteria to determine the bioactivity

against tea thrips. In another field experiment, a neem

formulation alone and in combination with Tea Research

Association recommended and reduced dose of endosulfan

and monocrotophos were tested. Treatments with com-

bined formulations (neem ? insecticide) recorded signifi-

cant reduction in S. dorsalis incidence even at reduced

doses (1:600 and 1:800), as compared to sole application

of neem or synthetic insecticide at recommended doses.

Azadirachtin concentrations and their bioactivity, effective

combinations and dose of the insecticides along with their

formulations in controlling S. dorsalis have been presented

and discussed.

Keywords Azadirachtin � Neem formulation �Azadirachtin-synthetic insecticide combinations �Bioactivity � Tea thrips � Scirtothrips dorsalis

Introduction

The tea thrips, Scirtothrips dorsalis Hood (Thripidae:

Thysanoptera) which is previously considered as minor

pest or occasionally as serious in particular localized areas

of tea plantations (Das 1965), are now established as

serious and regular pests in tea plantation (Camellia sin-

ensis), causing a substantial loss in crop in North east India

(Sarmah et al. 2006a; Roy et al. 2009, 2010). Climate

change, deforestation and over reliance of chemical pesti-

cides during last five decades are supposed to have a sig-

nificant impact on incidence and abundance of the pest

scenario in tea (Mukhopadhyay and Roy 2009).

Greater awareness of consumers and planters regarding

the residue of synthetic insecticide in tea forced the plant

S. Roy

Entomology Research Unit, Department of Zoology, University

of North Bengal, Siliguri, Darjeeling 734013, India

e-mail: [email protected]

G. Gurusubramanian (&)

Department of Zoology, Mizoram University, Tanhril,

Aizawl 796004, Mizoram, India

e-mail: [email protected]; [email protected]

S. K. Nachimuthu

Department of Biotechnology, Mizoram University,

Tanhril, Aizawl 796004, Mizoram, India

e-mail: [email protected]

123

Proc Zool Soc (July-Dec 2011) 64(2):72–77

DOI 10.1007/s12595-011-0015-y

TH

EZ

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OLOGICAL SOC

IET

YKO LK ATA

protectionists to look for safer alternatives and reduce the

load of pesticides by all possible means. The maximum

residue limit for most of the chemicals in EU has been

fixed at 0.1 mg kg-1 and below, which has become the

major constraint to tea exporting countries like India

(Anonymous 2005).

Neem and neem products have been widely used in tea

ecosystem and that are effective on several tea pests

(Gurusubramanian et al. 2008; Sarmah et al. 2006a). Neem

is widely used in several tea producing countries around

the world today either singly in organic farming or in

conjunction with synthetic pesticides in integrated pest

management (Sarmah et al. 2006b; Rahman et al. 2007).

Different neem formulations are available in India from

commercially, ranging 300 ppm (0.03% azadirachtin) to

50,000 ppm (5.0% azadirachtin). Isman et al. (1990)

envisaged that as azadirachtin concentration of neem oil

varies widely it is highly correlated to bioactivity against

pest species.

In view of this, reducing dependence on chemical pes-

ticides in favour of combinations and newer formulations

would be a good pest control strategy for the planters.

Hence in this study an attempt has been made to explore

the potential utilities of neem by quantifying the bioactivity

of different azadirachtin concentrations (300, 1,500, 3,000,

10,000 and 50,000 ppm) against the S. dorsalis; and

moreover, to ascertain the efficacy of neem formulations

(Neemazhal F) combined with insecticides (endosulfan and

monocrotophos) at Tea Research Association (TRA), India

recommended and reduced doses on population level of

this pest.

Materials and Methods

Azadirachtin Concentrations and Dilutions

Samples of different azadirachtin concentrations (300,

1,500, 3,000, 10,000 and 50,000 ppm) were obtained from

Entomology Research Institute, Loyola College, Chennai,

India. The samples were analyzed on HPLC to check the

azadirachtin concentrations. From each such concentrate

five dilutions were prepared (1:200, 1:300, 1:500, 1:1,000

and 1:1,500) and tested against S. dorsalis along with

untreated control (water spray).

Neem Formulation and Insecticides Concentrations

and Dilutions

Neem formulation (Neemazal F 5 EC, EID Parry, India;

azadirachtin–5,000 ppm; at TRA recommended dose of

0.0625%) alone and in combination with recommended

TRA dose (0.25%) and reduced dose of endosulfan and

deltamethrin (0.16 and 0.125%) were used in a field

experiment along with untreated control (water spray).

Field Evaluation of Bioactivity of Azadirachtin

Concentration Against S. dorsalis

A field experiment was conducted from the fourth week of

May, 2008 (21.05.2008) to second week of June 2008

(11.06.2008) at Red Bank Tea Estate, Jalpaiguri, West

Bengal, India following a randomized block design (RBD)

to evaluate the efficacy of different azadirachtin concen-

trations (300, 1,500, 3,000, 10,000, and 50,000 ppm) at

different dilutions (1:200, 1:300, 1:500, 1:1,000, and

1:1,500) against S. dorsalis along with untreated control.

The young tea bushes of Tocklai varieties i.e., TV1 and

TV9 clones of about 10 years of age, growing under the

shade trees, Albizia chinensis and Albizia lebbek were used

for the experimental trials. The pattern of plantation used

was single hedge type i.e., distance between the tea bushes

was maintained at 65 cm and distance between two parallel

rows of bushes was maintained at 100 cm. Spray treat-

ments were given using randomized block design. Each

block (6.5 9 9.0 m) comprised one hundred bushes. Each

treated block in the experiment was separated by two

buffer rows or guard row (1.3 m) to avoid the cross

contamination.

Plots with heavy infestation of S. dorsalis (90–95%)

were chosen for this study. Before applying the test sub-

stance, infestation of S. dorsalis was observed in each

treatment at random as pretreatment observation

(14.05.2008) in the respective plots and two rounds of

foliar spray were given at 15 days interval (I spray–

14.05.2008 and II spray–28.05.2008) with hand operated

calibrated knapsak sprayer at 400 l ha-1 (hollow cone

NMD 60450 nozzle, droplet diameter 1.6 mm, droplet size

140 lm, discharge 450 ml min-1 at 40 psi pressure, dis-

tance between nozzle and target 30–45 cm). Post treatment

observations were taken in four consecutive weeks (21 and

28 May 2008 and 04 and 11 June 2008). Each treatment

with the respective dilution of the concentrate of azadi-

rachtin was replicated thrice.

The performance of each test substance against S. dor-

salis was assessed by recording the number of thrips pop-

ulation (both larvae and adults) on abaxial surface of 30

randomly collected young tea leaves (two and a bud)

50 bushes-1 in each plot of the treatment during morning

hours (9.00–10.00 h) and carried in muslin cloth bags

(800 9 1200) to the laboratory (Rahman et al. 2007). Mean

population reduction of thrips (TPR) per treatment was

calculated using the following formula:

Proc Zool Soc (July-Dec 2011) 64(2):72–77 73

123

Control Efficacy of Neem Formulations in Combination

with Reduced Dose of Insecticides

An another field trial was conducted simultaneously at Red

Bank Tea Estate, Jalpaiguri, West Bengal, India using a

neem formulation, Neemazal F 5 EC (Azadirachtin–

5,000 ppm) alone and in combination with endosulfan and

deltamethrin at different dilutions was evaluated using

similar randomized block design methods as mentioned

earlier. The control plot was treated with water spray. The

treatments were applied at fortnightly interval with Knapsak

sprayer at 400 l ha-1. Pre and post treatment observations

were made at weekly interval as mentioned in the above

azadirachtin field trial. Populations of thrips have been

assessed at weekly intervals by collecting 30 tea leaves

50 bushes-1 at random from each treatment and counting

the number of adult and larval thrips (Rahman et al. 2007).

TPR was assessed on the basis of pre- and post treatment

counts from each replicate of the treatment and averaged.

Statistical Analysis

The data thus obtained were subjected to Analysis of

Variance (ANOVA) following RBD and critical difference

(CD; P = 0.05) and critical variation (CV%) were calcu-

lated (Snedecor and Cochran 1989) for taking statistical

decisions.

Results and Discussion

Azadirachtin Concentrations and Their Relative

Insecticidal Value

The bioactivity of different azadirachtin concentrations

(300, 1,500, 3,000, 10,000 and 50,000 ppm) at different

dilutions (1:200, 1:300, 1:500, 1:1,000 and 1:1,500) under

field conditions against S. dorsalis was noted and sum-

marized in Table 1. During first and second weeks after

first spraying of different azadirachtin concentration the

mean reduction of S. dorsalis was recorded at a minimum

of 18.5% to the maximum of 63.8% at the respective

dilutions as against untreated control (1.8–3.8%). However,

after the second round of spray the TPR was reduced by

22.0–81.9% in all the dilutions during third and fourth

weeks (Table 1).

After completion of two rounds of foliar spraying of

different azadirachtin concentrations percent reduction

ranged from 30.7 to 47.6, 44.4 to 59.1, 59.6 to 72.9, 60.4 to

73.3, and 66.4 to 81.9% at 1:1,500, 1:1,000, 1:500, 1:300

and 1:200 dilutions, respectively. Significant difference

(P \ 0.05) was noticed between dilutions, azadirachtin

concentration and their interactions (Table 1). The percent

reduction in S. dorsalis infestation was in ascending trend

with respect to azadirachtin concentration as well as dilu-

tions. At higher dilutions (1:1,500), i.e. 300 and 1,500 ppm

azadirachtin concentration gave\45% reduction; and[59–

\66% reduction was registered at 3,000, 1,0000, and

50,000 ppm of azadirachtin concentration, whereas [48–

\81% reduction was observed at a lower dilution (1:200)

(Table 1).

All the tested azadirachtin concentrations and their

dilutions affected the population of tea thrips and were

significantly (P \ 0.05) varying from each other. Statisti-

cally significant differences in mean TPR between azadi-

rachtin content (CD-8.10–14.05; CV-17.74–34.52%),

tested dose (CD-6.40–14.17; CV-11.95–42.39%) and their

interactions (CD-5.64–16.32; CV-12.87–22.14%) were

found from first to fourth week observations after post

application, respectively (Table 1). Further, lower CV

values were observed during fourth week observation of

post application in comparison with first week observation

in the field trials.

Control Efficacy of Neem Formulations

in Combinations with Monocrotophos and Endosulfan

First spray of TRA recommended dose, i.e. 1:1,600 of neem

formulations (Neemazal F 5 EC) gave 39.8–45.6% reduc-

tion in S. dorsalis population in first and second weeks,

respectively, which later increased to 59.3–66.4% in third

and fourth weeks, respectively after second spray. The fol-

lowing spray with endosulfan at recommended doses

(1:400) brought in a reduction of 54.4–66% in first and

second weeks and 82.3–85.0% in third and fourth weeks;

monocrotophos at recommended doses (1:400) resulted in

reduction of S. dorsalis population by 54.8–66.6% in first

and second weeks and 85.4–87.3% in third and fourth weeks

(Table 2). The treatment solely with insecticides had shown

a better performance by causing a reduction in S. dorsalis

population as compared to neem formulations.

Combination of Neemazal ? monocrotophos at

1:1,600 ? 1:800 and at 1:1,600 ? 1:600 doses caused

Thrips population reduction TPRð Þ ¼ Pretreatment population count � Post treatment population count

Pretreatment population count� 100:

74 Proc Zool Soc (July-Dec 2011) 64(2):72–77

123

reduction of S. dorsalis populations by 52.3–57.2% and

58.6–63.4 in first and second weeks and by 69.0–82.3%

and 73.6–86.1% in third and fourth weeks, respectively.

When Neemazal was combined with endosulfan at

1:1,600 ? 1:800 and at 1:1,600 ? 1:600 doses and

applied, the S. dorsalis infestation was reduced to the tune

Table 1 Influence of azadirachtin concentrations on the mean population reduction of Scirtothrips dorsalis on tea

Parent concentration

of azadirachtin (ppm)

Dilution of different

azadirachtin contentaMean thrips population reduction (TPR %) in different weekb

First week

(21.05.2008)

Second week

(28.05.2008)

Third week

(04.06.2008)

Fourth week

(11.06.2008)

300 1:1,500 18.5 (25.47) 19.7 (26.35) 22.0 (27.97) 30.7 (33.65)

1:1,000 25.0 (30.00) 22.1 (28.04) 27.1 (31.37) 33.2 (35.18)

1:500 30.1 (33.27) 24.3 (29.53) 32.6 (34.82) 40.3 (39.41)

1:300 34.7 (36.09) 30.7 (33.65) 35.7 (36.69) 45.3 (42.30)

1:200 39.8 (39.11) 32.9 (35.00) 36.8 (37.35) 47.6 (43.62)

Control Water spray 3.4 (10.63) 1.8 (7.71) -12.8 (20.96) -9.8 (18.24)

1,500 1:1,500 32.6 (34.82) 24.3 (29.53) 38.9 (38.59) 44.4 (41.78)

1:1,000 33.7 (35.49) 31.6 (34.20) 40.8 (39.70) 46.4 (42.94)

1:500 39.1 (38.70) 37.0 (37.46) 44.2 (41.67) 54.7 (47.70)

1:300 47.6 (43.62) 41.7 (40.22) 43.0 (40.98) 57.8 (49.49)

1:200 51.2 (45.69) 43.1 (41.03) 43.3 (41.15) 59.1 (50.24)

Control Water spray 2.6 (9.28) 3.8 (11.24) -5.5(13.56) -9.7 (18.15)

3,000 1:1,500 39.7 (39.06) 32.5 (34.76) 50.8 (45.46) 59.6 (50.53)

1:1,000 41.2 (39.93) 35.5 (36.57) 53.0 (46.72) 61.0 (51.35)

1:500 47.0 (43.28) 38.0 (38.06) 56.5 (48.73) 62.2 (52.06)

1:300 56.4 (48.68) 48.5 (44.14) 60.0 (50.77) 66.1 (54.39)

1:200 59.4 (50.42) 51.3 (45.74) 69.4 (56.42) 72.9 (58.63)


10,000 1:1,500 41.8 (40.28) 35.2 (36.39) 52.9 (46.66) 60.4 (51.00)

1:1,000 44.0 (41.55) 37.8 (37.94) 55.1 (47.93) 63.3 (52.71)

1:500 43.2 (41.09) 34.0 (35.67) 57.8 (49.49) 59.7 (50.59)

1:300 43.4 (41.21) 33.1 (35.12) 62.1 (52.00) 69.5 (56.48)

1:200 50.6 (45.34) 43.8 (41.44) 68.4 (55.80) 73.3 (58.89)


50,000 1:1,500 51.0 (45.57) 41.2 (39.93) 61.2 (51.47) 66.4 (54.57)

1:1,000 42.5 (40.69) 32.1 (34.51) 64.5 (53.43) 72.4 (58.31)

1:500 55.7 (48.27) 47.6 (43.62) 68.9 (56.10) 77.0 (61.34)

1:300 63.1 (52.59) 9.4 (17.85) 70.8 (57.29) 81.5 (64.53)

1:200 63.8 (53.01) 39.5 (38.94) 73.8 (59.21) 81.9 (64.82)


ANOVA–Two way

Factor I week II week III week IV week

SEM (±) CD (0.05) CV (%) SEM (±) CD (0.05) CV (%) SEM (±) CD (0.05) CV (%) SEM (±) CD (0.05) CV (%)

A 2.45 13.49 34.52 1.44 8.10 27.03 1.56 8.61 18.10 2.14 14.05 17.74

B 1.97 7.26 21.20 1.28 11.13 42.39 1.88 6.40 15.35 2.02 14.17 11.95

A 9 B 1.49 9.67 18.97 1.67 15.47 22.14 1.24 5.64 14.22 2.56 16.32 12.87

Data within the parentheses are angular transformed values, which were used for analysis

A Azadirachtin concentration, B dilution of different azadirachtin content, SEM standard error mean, CD critical difference (P \ 0.05),

CV coefficient of variationa Two rounds of foliar spray at 15 days interval-I spray–14.05.2008 and II spray–28.05.2008b Mean value of three observations (30 leaves per observation)


123

of 52.3–57.2% and 58.6–63.4% in first and second weeks

and 69.0–82.2% and 75.5–83.9% in third and fourth weeks,

respectively (Table 2). The combination treatments,

therefore recorded a statistically significant control of

S. dorsalis incidence and at reduced dose compared to that

of neem alone. It was also noted that with the reduced dose

of insecticides in combination with neem formulations

gave statistically significant control of S. dorsalis popula-

tion (Table 2).

Roy et al. (2010) confirmed that azadirachtin concen-

tration and its dilutions are the major criteria which

determine bioactivity against tea mosquito bug, Helopeltis

theivora. The present study hints at a possible relationship

between bioactivity of different azadirachtin concentra-

tions and S. dorsalis damage. Among five different con-

centrations of azadirachtin only 50,000 ppm resulted in the

maximum (82%) control of S. dorsalis at higher dilutions

(1:200). In this study, a maximum control of 70–80%

S. dorsalis population was accomplished at 3,000 ppm and

above of azadirachtin concentrations. As S. dorsalis has

sucking type of mouth parts, a chance of ingesting toxi-

cologically active neem (azadirachtin) from leaf surface is

much less. This may be the principal reason for a limited

control of S. dorsalis with neem formulations alone. Such

observations are validated by the findings of Lowery and

Isman (1995).

Schmutterer (1990) concluded that a foliar spray appli-

cation of most commercial neem formulations persist

5–7 days under field conditions. The present findings cor-

roborate the foregoing observation, indicated by a reduc-

tion in incidence of S. dorsalis after about a week of the

first spray. Even though breakdown of azadirachtin occurs

in UV light, its metabolites may still remain bioactive for

some time (Ascher 1993). Dihydroazadirachtin, a com-

pound obtained by hydrogenation of the C-22, 23 double

bond of the hydroxy-furan fragment of azadirachtin, cur-

rently shows promise as a more stable compound for better

field persistence (Mordue and Blackwell 1993). In this

study, different azadirachtin concentrations were tested

against S. dorsalis and significant variations in their control

efficacy was recorded. Azadirachtin concentrations in the

neem oils (0.2–0.4%) tested by Isman et al. (1990) showed

sufficient bioactivity for their utilization in the preparation

of neem based insecticides. The present study, however,

revealed the fact that azadirachtin concentration is the

determining factor in terms of its bioactivity, i.e., in con-

trolling the pest. The bioactivity of azadirachtin concen-

trations may vary from insect to insect but in tea, using of

5% azadirachtin is ideal for getting desired control of

66–82% of S. dorsalis at 1:200. The CIB (Central Insec-

ticide Board), India and Tea board, Kolkata have also

approved only 5% azadirachtin formulations (50,000 ppm)

as pesticide. Hopefully the market for neem-based pesti-

cides will increase, as the farmers become aware of its

benefits as an ecofriendly botanical pesticide with no res-

idue problem in tea.

Combining botanical with synthetic pesticides often

help minimizing the dose and application of the pesticides,

often with an enhanced control efficacy. Recent studies by

Sarmah et al. (2006a) and (b), Rahman et al. (2007)and

Roy et al. (2010) reported that neem formulations com-

bined with reduced dosages of acaricides and insecticides

are found effective against tea red spider mite (Oligony-

chus coffeae) tea mosquito bug (H. theivora) and S.

Table 2 Effect of insecticide formulations and combinations on mean population reduction of Scirtothrips dorsalis on tea

Treatmenta Dilution Mean thrips population reduction (TPR %) in different weekb

First week

(21.05.2008)

Second week

(28.05.2008)

Third week

(04.06.2008)

Fourth week

(11.06.2008)

Neemazal 1:1,600 39.8 (39.11) 45.6 (42.48) 59.3 (50.36) 66.4 (54.57)

Monocrotophos 1:400 54.8 (47.75) 66.6 (54.70) 85.4 (67.54) 87.3 (69.12)

Endosulfan 1:400 54.4 (47.52) 66.0 (54.33) 82.3 (65.12) 85.0 (67.21)

Neemazal ? Monocrotophos 1:1,600 ? 1:600 58.6 (49.95) 63.4 (52.77) 73.6 (59.08) 86.1 (68.11)

Neemazal ? Monocrotophos 1:1,600 ? 1:800 52.3 (46.32) 57.2 (49.14) 69.0 (56.17) 82.3 (65.12)

Neemazal ? Endosulfan 1:1,600 ? 1:600 58.6 (49.95) 63.4 (52.77) 75.5 (60.33) 83.9 (66.34)

Neemazal ? Endosulfan 1:1,600 ? 1:800 52.3 (46.32) 57.2 (49.14) 69.0 (56.17) 82.2 (65.05)

Control Water spray -12.5 (20.70) -6.9 (15.23) -5.8 (13.94) -14.7 (22.54)

CD (P = 0.05) 2.55 3.25 2.76 3.08

CV (%) 7.88 5.12 4.37 3.86

Data within the parentheses are angular transformed values, which were used for analysis

CD Critical difference (P \ 0.05), CV coefficient of variationa Two rounds of foliar spray at 15 days interval-I spray–14.05.2008 and II spray–28.05.2008b Mean value of three observations (30 leaves per observation)

76 Proc Zool Soc (July-Dec 2011) 64(2):72–77

123

dorsalis, respectively. Further, applications of neem with

reduced dose of monocrotophos and endosulfan gave sig-

nificant reduction in thrips population (82–86%) than neem

formulation alone (66%). These studies illustrated that

biorational insecticides especially neem, alone or at

reduced doses in combination with synthetic insecticides,

had the potential to play a vital role in a tea pest man-

agement program. The suggestion if implemented in letters

and spirit would possible reduced the load of chemical

insecticide on the crop and also the environment, all the

same inculcate region-wise practice of integrated man-

agement of the pest, the necessity of the hour.

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