Field efficacy and economics of some new insecticide molecules against lepidopteran caterpillars in chickpea

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1 Field efficacy and economics of some new insecticide molecules against lepidopteran caterpillars in chickpea G. V. Suneel Kumar* and O. Sarada** *Agricultural Research Station, Darsi , Prakasam District, A. P., India **District Agricultural Advisory and Transfer of Technology Centre, Ongole , Prakasam District, A. P., India * suneelkumar.gonam@gmail.com ABSTRACT Field studies were carried out to evaluate the efficacy and economics of some new insecticides against lepidopteran caterpillars viz., Spodoptera exigua and Helicpa armigera (Hubner) during Rabi season of 2012 and 2013 in chickpea. The pooled mean of two years showed that the number of S. exigua and H. armigera larvae per 10 plants were lowest in plots treated with chlorantraniliprole 20 (0.33 and 0.50), spinosad 45 (0.34 and 0.67) and flubendiamide 20 WG (0.50 and 0.84) as against untreated control plot (16.67 and 8.17 larvae/10 plants) with 98.0, 97.9 and 97.0 per cent reduction of S. exigua population and 93.9, 91.8 and 89.7 per cent reduction of H. armigera population, respectively. Pod damage due to pod borer, H. armigera was lowest in plots treated with spinosad 45 (1.53), flubendiamide 20 WG (2.46), chlorantraniliprole 20 (2.60) and emamectin benzoate 5 SG (2.85) with 88.8, 81.9, 80.9 and 79.1 per cent reduction control, respectively. Highest seed yield was recorded in spinosad 45 treated plots ( kg/ha) with per cent increase control, followed by chlorantraniliprole 20 ( kg/ha), flubendiamide 20 WG ( kg/ha) and emamectin benzoate 5 SG ( kg/ha) with 110.4, and 92.2 per cent increase control, respectively as against the minimum yield of kg/ha in the untreated control. The cost effectiveness of flubendiamide 20 WG was high with cost-benefit ratio of 1: 4.08 followed by emamectin benzoate 5 SG (1:3.75), chlorantraniliprole 20 and spinosad 45 (1:3.57) KEY WORDS: Chickpea, Helicpa armigera, insecticides, Spodoptera exigua INTRODUCTION Chickpea is the second largest pulse crop produced in the world and play important role in human nutrition as source of protein. Area occupied by chickpea is about 7.29 million ha with production of 5.77 million tones which accounts for 30 and 38 of the national pulse acreage and production, respectively. Among the several constraints in its successful cultivation, insect pests pose greater threat to chickpea production that result in poor yields. Though its yield potential is 2.5 to 3.0 t/ha, the average yields have remained stagnant with only 0.8 t/ha. The extent of losses caused by Helicpa armigera (Hub) varies from region to region and depends upon climate and crop intensity. Its preference for flowering and fruiting parts results in heavy monetary loss of 203 crore rupees annually under subsistence agriculture in the tropics. Spodoptera exigua F. became a serious pest of chickpea (vegetative stage) in the latter part of the 20 th century. Management of these lepidopteran caterpillars relies heavily on insecticides, often to the exclusion of other methods of management. Large scale and misuse of insecticides has led to problems like development of resistance, resurgence besides posing problems to humans. Hence, judicious use of safer and effective insecticides in management of these lepidopteran caterpillars that pose lesser residues and lower environmental threat are warranted. New molecular structures with novel mode of action are recently been introduced to control 153

2 lepidopteran pests. Hence, the present study is aimed at evaluating the efficacy of certain newer insecticides against the lepidopteran caterpillars in chickpea ecosystem. MATERIAL AND METHODS Two field experiments were laid out in Randomized Block Design with twelve treatments including control replicated thrice in 3.0 m x 5.0 m plot size maintaining the spacing of 30 cm between rows and 10 cm from plant to plant during Rabi seasons of 2012 and 2013 at Agricultural Research Station, Darsi, Prakasam district, Andhra Pradesh. The chickpea variety NBeG 3 was raised as per recommended package of practices except plant protection measures. The crop received two sprays in each season, the first during vegetative stage (30 days after sowing) and second given after pod formation (50 days after sowing) with hand operated knapsack sprayer with a spray volume of 500 lts per ha. Ten plants in each plot from the each replication were selected randomly from the middle eight rows for the observations on larval population of S. exigua and H. armigera. At maturity, 100 pods were picked up randomly from ten plants in each plot for H. armigera pod damage assessment and expressed as a percentage of the total number of pods. Seed yield recorded from each plot was converted into Kg/ha. Data on larval population of lepidopteran caterpillars, pod damage and yield corresponding to each treatment was subjected to statistical analysis after suitable transformation (Gomez and Gomez, 1984). Cost-benefit ratio (CBR) was also assessed by dividing the net return by the total additional cost due to treatments. RESULTS AND DIUSSION The all mean efficacy of different test insecticides given in two sprays against S. exigua and H. armigera (Table 1) revealed that all the treatments were found to be significantly superior to untreated check in suppressing the larval population. During 2012, chlorantraniliprole 20 was found to be significantly superior to all other insecticides with 0.33 and 0.67 S. exigua and H. armigera larval population/10 plants. Spinosad 45 and Flubendiamide 20 WG recorded identical population of 0.67 and 0.90 S. exigua and H. armigera larvae/10 plants without any significant difference among them and these two treatments were statistically at par with that of chlorantraniliprole. The S. exigua and H. armigera larval population in other treatments ranged from 1.00 to 3.33 and 1.00 to 4.67 larvae/10 plants as against control which had the population abundance of and 6.67 larvae/10 plants, respectively. During 2013, Spinosad registered nil incidence of S. exigua and was significantly superior to all other insecticides. Chlorantraniliprole and Flubendiamide were at par with statistically identical population of 0.33 S. exigua larvae/10 plants. Both Spinosad and Chlorantraniliprole recorded significantly lower identical population of 0.33 H. armigera larvae/10 plants and were at par with Flubendiamide, which recorded 0.67 larvae/10 plants. In other treatments S. exigua and H. armigera abundance ranged from 0.67 to 2.33 and 1.00 to 4.00 larvae/10 plants compared to and 9.67 larvae/10 plants, respectively in untreated control. This significant reduction of S. exigua and H. armigera larval population was due to their new broad spectrum and high insecticidal activity with novel mode of action against lepidopteran caterpillars. The pooled mean of 2012 and 2013 Rabi seasons showed that chlorantraniliprole, spinosad and flubendiamide have recorded 0.33, 0.34 and 0.50 S. exigua and 0.50, 0.67 and 0.84 H. armigera larvae/10 plants with 98.0, 97.9, and 97.0 per cent reduction of S. exigua population and 93.9, 91.8 and 89.7 per cent reduction of H. armigera population control, respectively and were found to be significantly superior to all other treatments including untreated control (16.67 and 8.17 larvae/10 plants). Similar findings were reported wherein chlorantraniliprole was highly effective against H. armigera in okra (Chowdary et al., 2010), cotton (Ma et al., 2000) and higher efficacy of flubendiamide against H. armigera in tomato (Kuttalam et al., 2008 and Vinoth Kumar et al., 2010), blackgram (Patil et al., 2008 and Ashok Kumar and Shivaraju, 2009), redgram (Meena et al., 2006; Dodia et al., 2009 and Srikanth et al., 2014) and greengram (Yadav and Singh, 2013)

3 The results also showed that all the treatments significantly reduced the pod damage caused by H. armigera. During Rabi 2012, per cent pod damage by H. armigera was significantly less with spinosad 45 which recorded 2.43 damage followed by indoxacarb 15.8 EC (3.60) which was at par with flubendiamide (3.64).Chlorantraniliprole and emamectin benzoate 5 SG treated plots are also at par with pod damage of 3.90 and 4.40, respectively. The pod damage was significantly high (15.97) in untreated control plots. During Rabi 2013, the pod damage was significantly reduced in plots treated with spinosad (0.63) and flubendiamide (1.29) which were at par with Chlorantraniliprole (1.30) and emamectin benzoate (1.30). Rest of the insecticides recorded 2.73 to 4.30 pod damage compared to damage in untreated control (Table 1). The pooled mean of two years showed that pod damage was significantly low in plots treated with spinosad (1.53) and was superior rest of the new insecticide molecules with 88.8 per cent reduction in pod damage untreated control. Mittal and Ujagir (2005) also recorded lower numbers of H. armigera and lower pod damage with different concentrations of spinosad in pigeonpea. Flubendiamide (2.46), chlorantraniliprole (2.60), emamectin benzoate (2.85) were next best treatments and at par with indoxacarb (3.18) with 81.9, 80.9, 79.1 and 76.7 per cent reduction in pod damage control, respectively. The untreated plot has maximum pod damage of Singh et al. (2009) reported that indoxacarb was the best treatment for the management of H. armigera in chickpea. Superior performance of indoxacarb against H. armigera was also reported by Gunning and Devonshire (2002). Effectiveness of emamectin benzoate in minimizing yield losses through reduction in H. armigera incidence in pigeonpea was reported by Sharma et al. (2011) which support the present findings. Significantly highest seed yield of kg/ha was obtained in plots treated with spinosad followed by chlorantraniliprole ( kg/ha), flubendiamide ( kg/ha) which were at par with indoxacarb ( kg/ha) as against the lowest seed yield of kg/ha in untreated control during Rabi 2012 (Table 2). Spinosad maintained its superiority during Rabi 2013 too, with a maximum seed yield of kg/ha followed by chlorantraniliprole ( kg/ha), flubendiamide ( kg/ha), emamectin benzoate ( kg/ha) and novaluron ( kg/ha) as against kg/ha in untreated control. Two years pooled data revealed that highest seed yield was recorded in spinosad treated plots ( kg/ha) with per cent increase control, followed by chlorantraniliprole ( kg/ha), flubendiamide ( kg/ha) and emamectin benzoate ( kg/ha) with 110.4, and 92.2 per cent increase control, respectively as against the minimum yield of kg/ha in the untreated control. The economics of treatments was calculated on the basis of net profit obtained in terms of additional yield control and cost of treatment applications to get cost-benefit ratio. The cost effectiveness of flubendiamide was high among all the treatments with costbenefit ratio of 1: 4.08 followed by emamectin benzoate (1:3.75), chlorantraniliprole (1:3.57), spinosad (1:3.57), and indoxacarb (1: 3.19). Lowest cost-benefit ratio of 1:1.53 was obtained with Chlorfenapyr and proved less favorable (Table 2). CONCLUSION The present findings conclude that the new generation insecticides like flubendiamide chlorantraniliprole, and spinosad were found effective against lepidopteran caterpillars viz., S. exigua and H. armigera along with an additional yield level in chickpea. Further, it was observed that the cost- benefit ratio was also high with flubendiamide, emamectin benzoate, chlorantraniliprole and spinosad. Hence, it is suggested that the effective insecticides may be alternated in harmony with existing Integrated Pest Management programs in order to avoid the problems associated with insecticide usage like development of insecticidal resistance, pest resurgence, etc

4 Table 1: Efficacy of new insecticides against the lepidopteran caterpillar pests viz., Spodoptera exigua and Helicpa armigera in chickpea Treatments Dose /ha Mean larval population of Spodoptera exigua / 10 plants* Reduction Mean larval population of Helicpa armigera / 10 plants* Reduction Pod damage by H. armigera** Reduction Mean control Mean control Mean control Thiodicarb 75 WP bc 1.00 bcd 1.67 bcd bc 2.00 cd 2.67 b b 3.23 bc 5.56 b 59.3 gm (1.68) (1.23) (1.47) (1.95) (1.58 ) (1.77) (16.31) (10.35) (13.64) Indoxacarb bcd 1.00 bcd 1.17 bcde cdef 1.00 def 1.34 cde g 2.77 c 3.18 ef 76.7 EC ml (1.27) (1.23) (1.27) (1.44) (1.23) (1.36) (10.93) ( 9.50) (10.27) Spinosad cd 0.00 e 0.34 e ef 0.33 f 0.67 e h 0.63 e 1.53 g 88.8 ml (1.05) (0.70) (0.90) (1.18) (0.88) (1.04) (8.73) (4.37) (6.94) Chlorfenapyr b 1.67 bc 2.50 b bcd 2.33 cd 2.67 bc bc 3.59 bc 5.25 bc 61.5 ml (1.94) (1.46) (1.72) (1.86) (1.64) (1.77) (15.24) (10.90) (13.25) Thiacloprid bc 2.33 b 2.50 b bcde 4.00 b 3.34 b b 4.30 b 5.93 b 56.6 ml (1.76) (1.65) (1.71) (1.76) (2.11) (1.96) (15.98) (11.93) (14.10) Flubendiamide cd 0.33 de 0.50 de ef 0.67 ef 0.84 e fg 1.29 de 2.46 f 81.9 WG gm (1.05) (0.88) (0.97) (1.18) (1.05) (1.13) (10.99) (6.33) (9.03) Chlorantraniliprole d 0.33 de 0.33 e f 0.33 f 0.50 e efg 1.30 d 2.60 f ml (0.88) (0.88) (0.88) (1.05) (0.88) (0.97) (11.39) (6.47) (9.27) Pyridalyl 10 EC bcd 1.00 bcd 1.34 bcde ab 2.33 c 3.50 b def 3.80 bc 4.28 cd 68.6 ml (1.35) (1.23) (1.29) (2.25) (1.68) (1.99) (12.58) (11.24) (11.93) Lufenuron 5.4 EC bc 1.00 bcde 1.17 bcd bc 1.33 cde 2.33 bcd cd 2.73 c 4.35 cd 68.1 ml (1.68) (1.18) (1.45) (1.93) (1.35) (1.68) (14.14) (9.51) (12.04) Novaluron 10 EC b 0.67 cde 1.84 bc bcdef 1.67 cde 2.00 bcd de 2.96 c 3.92 de 71.3 ml (1.86) (1.05) (1.52) (1.68) (1.46) (1.58) (12.74) (9.88) (11.40) Emamectin Benzoate bcd 0.67 cde 0.84 cde def 1.33 cde 1.33 de efg 1.30 d 2.85 f SG gm (1.23) (0.99) (1.13) (1.23) (1.35) (1.29) (12.12) (6.53) (9.72) Untreated Check a (4.16) a (4.02) a (4.12) e (2.63) 9.67 a (3.18) 8.17 a (2.93) a (23.56) a (19.96) a (21.69) -- CD (P=0.05) CV *Values in parentheses are square root x transformed values ** Values in parentheses are arcsine percentage transformed values 156

5 Table 2: Economics of insecticides for the control of lepidopteran caterpillar pests viz., Spodoptera exigua and Helicpa armigera in chickpea Treatments Seed Yield (Kg/ha) Dose /ha Mean Additional Yield control (Kg/ha) Increase in yield control Cost of additional yield (Rs) *Cost of plant protection (Rs/ha) Net profit (Rs/ha) Thiodicarb gm d c f :2.09 WP Indoxacarb ml ab c cde :3.19 EC Spinosad ml a a a :3.57 Chlorfenapyr ml bcd c ef :1.53 Thiacloprid ml d c f :1.99 Flubendiamide gm a b abc :4.08 WG Chlorantraniliprole 150 ml a b ab : Pyridalyl 10 EC 625 ml bcd c def :2.76 Lufenuron 5.4 EC 625 ml cd c ef :2.23 Novaluron 10 EC 500 ml bcd b de : gm abc b bcd :3.75 Emamectin Benzoate 5 SG Untreated Check e d g CD (P=0.05) CV Market Price of chickpea: Rs. 30/- per kg; Standard spray volume: 500 l/ha; *Labour and sprayer charges including for two sprays. C:B ratio 157

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