Efficacy of New Generation Insecticides in Comparison with Biopesticides and their Economics against Chickpea Pod Borer (Helicoverpa armigera Hub.)

Chickpea (Cicer arietinum L.) is one of the most important pulse crops cultivated in 89.28 Lakh hectares with a production of 83.65 Lakh tonnes in Madhya Pradesh comprising the Rewa Division with, 0.64 Lakh ha area producing  0.64 lakh metric tonnes and productivity of 999 kg/ha (Anonymous 2015). Helicoverpa armigera [Hubner] is the most devastating chickpea pest responsible for substantial yield loss. Productivity losses by gram pod borer range from 20 to 90 percent depending upon the severity of insect attack (Akhtar et al., 2022).  Chickpea crop is damaged by a large number of insect species, both under field conditions and in storage (Clement et al., 2000). Among them Helicoverpa armigera Hub. is known to be the key pest due to high reproduction rates and short life cycle (Kumar and Singh, 2014). Pod borer, H. armigera is a noxious and polyphagous pest of global importance ravaging more than 200 cultivated and wild hosts (Yadav et al., 2011) which is the major factor for low yield of chickpea damaging the crop from vegetative to podding stage (Dhingra et al., 2003). Among the biotic factors responsible for low yield the, damage due to insect pests is the major limiting factor. Keeping the above facts in view, the present investigation was planned and carried out to establish a new generation molecules are comparatively safer to natural enemies, honeybees and other pollinators than old generation molecules play an important role in reducing the pest populations.

A field experiment was conducted at the Entomology Instructional Farm, JNKVV College of Agriculture Rewa during Rabi season 2018-19 on chickpea variety JG-16 in District Rewa. The field was prepared following the recommended package of practices with plant spacing of 30 x 10 cm with plot size 3 m x 2.7 m . The incidence of H. armigera was observed from five randomly selected plants from four middle rows of each plot at weekly interval. The spray of insecticides was applied as soon as the pest incidence is noted. The first spray was done by knapsac sprayer at 50% flowering stage of the crop and repeated after 15 days. Pre-treatment observation on pest population was undertaken one day before the application of the first spray by direct counting of H. armigera larvae per five randomly pre-selected plants in each plot. Similar procedure was followed for post-treatment observation which was recorded at 1, 3, 7, 10, 15 days after both the spray operations. The data were analyzed as per the experimental design to test the significant of the treatment by suitably transforming the larval population to square root ( x+0.5) for the statistical analysis. Pod damage and grain yield in different treatments recorded per plot.
 
Pod damage
 
Per cent pod damage was calculated under different treatments as per formula:

 

Benefit cost ratio
 
Gross return was calculated by multiplying total yield with the market price of the produce. Cost of cultivation and cost of treatment imposition was deducted from the gross returns, to find out net returns and cost benefit ratio by following formula:
 

                 

                                
Where, B:C = Benefit cost ratio.
 
Grain yield
 
Yield was calculated under different treatments as per formula:
 

Pod borer (H.  armigera) incidence
 
All insecticides were found very effective and significantly superior over untreated control. However, T₃ and T₆ (indoxacarb and emamectine benzoate) were the best among them (Table 1). Over all mean analysis indicated that all the insecticidal treatments were significantly effective in reducing the larval population of H. armigera as compared to untreated plots (1.56 larvae/plant). Indoxacarb was the most effective in controlling the incidence of gram pod borer (0.59 larva/plant) among all treatments. Whereas efficacy of rest of the treatments were in the order of Emamectin benzoate @ 10 g a.i./ha (0.75 larva/plant), chlorantraniliprole @ 37 g a.i./ha (0.79 larva/plant), spinosad @ 90 g a.i./ha (0.80 larvae/plant), Fipronil @ 50 g a.i./ha (0.83 larva/plant), Bt.K. @ 35 g a.i./ha (0.89 larvae/plant), novalurone @ 100 g a.i./ha (0.95 larvae/plant) and neem oil @ 4.5 g a.i./ha (0.97 larvae/plant). In chickpea two sprays of Indoxacarb 14.5 SC @ 72 gram ai/ha first at 50% flowering and pod formation stage and second spray after 15 days applied were effective to reduced the pod borer population (Kumar et al., 2013).



In case of second spray of insecticides also, the indoxacarb was superior over th rest of the treatments and all insecticides were found to be very effective and significantly superior over control (Table 2). Over all mean analysis indicated that all the insecticidal treatments were significantly effective in reducing the larval population of H. armigera as compared to untreated plots (0.92 larva/plant) (Table 3). Indoxacarb was the most effective in controlling the incidence of gram pod borer (0.27 larva/plant) among all treatments, while the efficacy of rest of the treatments were in the order of Emamectin benzoate (0.44 larva/plant), chlorantraniliprole (0.47 larva/plant), spinosad (0.49 larva/plant), Fipronil (0.50 larva/plant), Bt.K. (0.52 larva/plant), novalurone (0.56 larva/plant) and neem oil (0.57 larva/ plant). In chickpea two sprays of Indoxacarb 14.5 SC @ 72 gram ai/ha first at 50% flowering and pod formation stage and second spray after 15 days applied were effective to reduced the pod borer population (Kumar et al., 2013).The highest grain yield was recorded with indoxacarb (1989.00 kg/ha) while the lowest grain yield was with neem oil (1414.00 kg/ha) which is accordance with the report of  Gowda et al. (2007) indicating that indoxacarb 14.5 SC @ 25 g a.i./ha. was found to be highly effective as compared to chlorpyriphos 20 EC @ 250 g a.i./ ha irrespective of spray equipment and offering maximum protection against pods which resulted in increased grain yield. Yogeeswarudu and Venkata Krishna (2014) also reported that indoxacarb 14.5 SC @ 0.5 ml/l was found the best treatment with the lowest population of  H. armigera, (recording 1.53, 0.46 and 0.73 larva/five plants) and 89.45, 97.01and 95.83 percent reduction over control at 3 , 5 and 7 days after first spraying, respectively and (0.00, 0.26 and 0.00 larva/five plants) with 100, 98.74 and 100 percent reduction over control, at 3, 5 and 7 after second spray, respectively. The effectiveness of Spinosad, Indoxacarb and Fipronil insecticides treatment was in reducing larval population, pod damage and recorded higher good yield in comparison to untreated plot (Nitharwal et al., 2017).

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Effect on grain yield and pod damage
 
The result on the yield per plot (Table 4 and Table 5) shows a significant deference among the treatments. The highest yield of 1989.00 kg/ha, was recorded in the plot treated with Indoxacarb as against in the untreated control the yield of 1240.00 kg/ha.

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The order of yield as influenced by insecticide was found in descending order Indoxacarb (1989.00 Kg/ha.) > Emamectin benzoate (1850.00 Kg/ha) > Chlorantraniliprole (1780.00 Kg/ha.) > Spinosad (1730.00 kg/ha) > Fipronil (1690.00 kg/ha) > Bt.K. (1642.00  kg/ha) > Novaluron (1530.00 kg/ha) > Neem oil (1414.00 kg/ha). Ghugal et al., (2013) reported that spinosad 45 SC @ 73 g a.i./ha was the most effective in controlling pod borer and resulting in the lowest pod damage (4.11%) and highest grain yield (2261.66 kg/ha) with CBR 1:7.37. Among biopesticides, Beauveria bassiana@ 1500 g/ha and NSKE 5% suffered 7.73 and 7.89 per cent pod damage producing 2011.66 kg/ha and 2001.66 kg/ha seed yield with CBR 1:12.6 and 1:5.78, respectively. Nitharwal et al. (2017) reported that effectiveness of Spinosad, Indoxacarb and Fipronil insecticides was in reducing larval population, pod damage and recorded higher good yield in comparison to untreated plot.

Differences in pod damage among insecticidal treatments were found significant CD value 0.573 and the pod damage ranged between 7.33 per cent in Indoxacarb to 26.74 per cent in untreated control.
 
The cost benefit ratio
 
The C:B ratio of various insecticide treatments was calculated and presented in Table 5 which divulge that maximum C:B ratio (1:12.3) was recorded from Indoxacarb treatment followed by Emamectin benzoate (1:10.83), Fipronil (1:6.9), Bt.K. (1:6.5), Novaluron (1:4.9), Chlorantraniliprole (1:4.1), Spinosad (1:2.6) and Neem oil (1:1.6). However, the minimum CB ratio was noted in the plot treated with The order of C:B ratio due to different insecticide treatments is given below.

Indoxacarb (T₃) > Emamectin benzoate (T₆) > Fipronil (T₂) > Bt.K. (T₈) > Novaluron (T₅) > Chlorantraniliprole (T₁) > Spinosad (T₄)  > Neem oil (T₇).

Highest cost: benefit ratio of 1:12.3 was observed in the treatment of Indoxacarb 15.8 EC @ 79 g a.i./ha, followed by the treatment of Emamectin benzoate 5 SG @ 10 g a.i./ha  with cost benefit ratio was 1:10.83.

As the chickpea pod borer was the key pest in the region demanding population suppression by insecticide which has eco-friendly impact on the agro-ecosystem, lower dose of indoxacarb 79 g a.i./ha was found to be effective by initiating the first spray at 50% flowering and second spraying after 15 could affect  desirable control of the pest. Following the indaxocarb, emamectin benzoate 5 SG @ 10 g a.i./ha were found superior pod borer management.

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