Bio-efficacy of Insecticides against Helicoverpa armigera in Chickpea

Pulses are an important group among the food crops which occupy a unique position in agriculture by virtue of their high protein content. Chickpea (Cicer arietinum L.), commonly known as Bengal gram, gram or chana, originated from South Western Asia, is an important rabi pulse crop of India, which has been considered as king of Pulses (Bhatt and Patel, 2001). Chickpea was cultivated in an area of 135.4 lakh hectares with a production of 131.02 lakh tones and a productivity of 968 kg/ha in the world (Tiwari and Shivhare, 2016).
        
Chickpea was cultivated in an area of 73.7 lakh hectares with a production of 58.9 lakh tones and a productivity of 799.19 kg/ha in India. In north India, states like Uttar Pradesh, chickpea is cultivated in an area of 5.05 lakh hectares with a production of 3.78 lakh tones with a productivity of 7481.51 kg/ha (Anonymous, 2015).
        
Among biotic factors chickpea is infested by nearly 60 insects’ species in which cutworm, Agrotis ipsilon (Ratt.), gram pod borer, Helicoverpa armigera (Hub.), semilooper, Autographa nigrisigna (Walk.) and aphid, Aphis craccivora (Koch.) are the pests of major importance (Acharjee and Sharma, 2013). Among these, the major damage is caused by gram pod borer which is polyphagous in nature; Helicoverpa armigera is one of the serious pests of chickpea, which feeds more than 150 crops throughout the world (Vinutha et al., 2013). Gram pod borer is widely distributed and a serious pest of chickpea causing heavy crop losses (20-60%) throughout the India (Anonymous, 2013). Helicoverpa armigera is the major and most devastating pest of chickpea which can cause crop loss up to 80 per cent under congenial weather conditions. In terms of monetary value, the estimated annual loss due to this pest in chickpea is Rs.2030 million in India (Anonymous, 2013a). It is estimated that Helicoverpa armigera alone is responsible for losses over Rs. 3500 million annually in India, despite heavy application of pesticides inputs (Kumar and Kapur, 2003). Helicoverpa armigera alone accounts for the consumption of half of the total pesticides used in India for the protection of different crops (Suryavanshi et al., 2008).

The experiment was conducted at the Student’s Instructional Farm of the University, which was out by growing a popular variety ‘Udai’ in a randomized block design (RBD) having six treatments with four replications in the plot size of 5x3 m² with spacing of row to row and plant to plant 30x10 cm, respectively. The recommended agronomical practices were followed to raise the good crop. The detail of treatment for management of Helicoverpa armigera, are as follows:


 
Application of treatments
 
The incidence of H. armigera was recorded on regular basis to apply different treatments at appropriate time. The treatments were applied, as and when larval population was reached Economic Threshold Level i.e. 01 larvae m^-1 linear row length.
 
Determination of amount of insecticides
 
The required amounts of insecticides were calculated by using the formula as given below:

 

        
Insecticides were sprayed with the help of hand Sprayer. The care was taken to avoid drift of spray from one plot to another plot by surrounding the plots with polythene sheets at the time of spraying.
 
Observations recorded
Pre and post treatment observations
 
The pre and post treatment observations on larval population of  H. armigera were taken in each treatment at five places. The population of H. armigera was recorded one day before of spray as pre-treatment observation and post treatment observations were taken at 3, 7 and 10 days after spray. The percentage reduction of larval population was determined for each treatments using following formula.

  

 
Seed yield
 
Seed yield of chickpea was recorded on the basis of individual plot and expressed in kg plot^-1 and converted in to kg ha^-1. The increase in seed yield of chickpea over control was calculated for each treatment separately by using the following method given by Pradhan, (1964):

 

 
Determination of benefit: cost ratio
 
The benefit: cost ratio was determined for each treatment by using the following formula:

 
 

Statistical analysis
 
The data obtained from the experiments were statistically analyzed in appropriate programme.

Field trial was conducted during rabi, 2014-15 and 2015-16 to evaluate the efficacy of insecticides against gram pod borer. In order to ascertain the time of application of treatments, population of gram pod borer, H. armigera was recorded at weekly interval and treatments were applied as and when mean larval population of H. armigera reached  ETL i.e. 1 larvae m^-1 row length during both the years. The trend of effectiveness of different insecticides has been presented below:
 
Efficacy of treatment (2014-15)
 
The data presented in (Table 1) reveals that all insecticides lowered down and reduced percentage of the population of gram pod borer in comparison to control. All the treatments were found effective and differed significantly from each other. Significantly lower surviving population of gram pod borer with mean of 0.20, 0.75 and 1.00 larvae per plant was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha) and maximum surviving larval population of gram pod borer with mean of 1.00, 1.16 and 2.00 larvae per plant was recorded in the treatment T₁ (HaNPV @ 250 LE/ha); whereas maximum reduction in larval population of gram pod borer with 89.84, 64.28 and 65.51 per cent was recorded in the treatmentT5 (Spinosad 45 EC @ 166 ml/ ha) and minimum  reduction in larval population of gram pod borer with 49.23, 44.76 and 31.03 percent was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 1^th spray, respectively during 2014-15.
        
The data presented in (Table 1) reveals that all the treatments were found significantly superior over control. Significantly lower surviving population of gram pod borer with mean of 1.05, 0.30 and 0.75 larvae per plant was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha) and maximum surviving larval population of gram pod borer with 1.05, 1.50 and 2.45 larvae per plant was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th  days after 2^nd spray, respectively during 2014-15; whereas maximum reduction in larval population of gram pod borer with 91.17, 80.26 and 76.69 per cent was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha)  and minimum  reduction in larval population of gram pod borer with 69.11, 60.52 and 41.66 percent was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 2^nd spray, respectively during 2014-15.
        
The data presented in (Table 2) reveals that all the treatments were effective and significantly superior to control. At this stage also Spinosad 45 EC @ 166 ml/ ha was found to enough to control H. armigera for entire crop season, in this treatment low survives 0.50, 0.52 and 0.58 larvae/ plant and highest survives 0.91, 0.94 and 0.96 larvae/ plant in treatment T₁ (HaNPV @ 250 LE/ha)  was recorded at 3^rd, 7^th and 10thdays after 3rd spray, respectively during 2014-15. The maximum reduction in larval population of gram pod borer with 47.36, 42.24 and 40.81 per cent was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha); whereas minimum reduction in larval population of gram pod borer with 4.21, 2.08 and 2.04 per cent was recorded in the treatment T1 (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 3^rd spray, respectively during 2014-15.
 
Efficacy of treatments (2015-16)
 
The data presented in (Table 2) reveals that all the insecticides lowered down and reduced percentage of the population of gram pod borer in comparison to control. All the treatments were found effective and differed significantly from each other. The data showed, significantly minimum surviving population of gram pod borer with 0.75, 1.00 and 1.10 larvae per plant were recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha) and maximum surviving larval population of gram pod borer 1.20, 1.40 and 1.80 per plant larvae were recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 1^st spray, respectively during 2015-16; whereas maximum reduction in larval population of gram pod borer with 77.94, 69.73 and 73.80 per cent was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha)  and minimum  reduction in larval population of gram pod borer with 64.70, 63.15 and 57.14 per cent was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 1^st spray, respectively during 2015-16.
        
The data presented in (Table 2) depicts all the treatments were found significantly superior over the control. Significantly lower surviving population of gram pod borer with 0.70, 0.98 and 1.00 larvae per plant were recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha) and maximum surviving larval population of gram pod borer with 1.10, 1.24 and 1.80 larvae per plant were recorded in the treatment T₁ (HaNPV @ 250 LE/ha at 3^rd, 7^th and 10^th days after 2nd spray, respectively during 2015-16; whereas maximum reduction in larval population of gram pod borer with 70.00, 67.33 and 71.42 per cent was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha)  and minimum  reduction in larval population of gram pod borer with 60.71, 58.66 and 48.57 percent was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th  days after 2^nd spray, respectively during 2015-16.
        
The data presented in (Table 2) reveals that all the treatments were effective and significantly superior to control. At this stage also Spinosad 45 EC @ 166 ml/ ha was found to give enough to control of H. armigera for entire crop season. In this treatment low survival 0.05, 0.10 and 0.22 larvae/ plant and highest survival 0.62, 0.56 and 0.90 larvae/ plant in treatment T₁ (HaNPV @ 250 LE/ha) was recorded, respectively.
        
The maximum reduction in larval population of gram pod borer with 90.00, 86.66 and 75.55 per cent was recorded in the treatment T₅ (Spinosad 45 EC @ 166 ml/ ha); whereas minimum reduction in larval population of gram pod borer with 34.00, 25.33 and 5.55 per cent was recorded in the treatment T₁ (HaNPV @ 250 LE/ha) at 3^rd, 7^th and 10^th days after 3rd spray, respectively during 2015-16.
 
Seed yield of chickpea and economics
 
The seed yield recorded both the rabi season during 2014-15 and 2015-16 is presented Tables 3 and 4. Significantly higher seed yield was obtained in case of (T5) Spinosad 45 SC (2550 kg ha^-1 in 1^st and 2680 kg ha^-1 in 2^nd year). The lower seed yield was obtained in (untreated) control (1350 kg ha^-1 in 1^st and 1480 kg ha^-1 in 2^nd year) but differed significantly from remaining treatments. All the treatments were found superior over control on the basis of grain yield during both seasons.
        
Based on benefit: cost ratio of different treatments, Spinosad 45 SC ha^-1 (T₅) was found to be the  most economic treatment insecticide, because it gave the maximum benefit (10.93 during 2014-15 and 11.68 during 2015-16) as compared with remaining treatments. The next profitable treatment was Indoxacarb 14.5 SC (T₄) (10.41 during 2014-15 and 10.88 during 2015-16). The minimum B:C ratio was obtained in HaNPV (T₁) (3.32 during 2014-15 and 2.43 during 2015-16) followed by NSKE 5% (T₄) as compared with remaining treatments (Tables 3 and 4).
               
The present result conform to the findings of Karabhantanal and Awaknavar, (2004), as they also reported Spinosad (30g a.i ha^-1) as most effective with maximum reduction in larval population of gram pod borer on chickpea. Similarly, Kumar et al., (2012) reported the application of Spinosad 45 SC @ 90g a.i ha^-1 was most effective treatment against H. armigera. Srinivasan and Durairaj, (2007) evaluated the bio-efficacy of certain newer insecticides against gram pod borer (H. armigera), the results indicated that the least Helicoverpa larval population (2.0 plant^-1) was recorded with use of spinosad 45 SC (73 g a.i. ha^-1) followed by indoxacarb 14.8 SC (2.4 plant^-1) as compared with untreated control (6.7 plant^-1). Earlier findings have also reported HaNPV least effective Kulhari et al., (2009). Singh and Singh, (2007) reported that NPV was less effective than Endosulfan. Kumar (2008) reported that highest yield of 21.25 q/ ha was recorded in Spinosad 45 SC @ 90 g a.i./ ha followed by Indoxacarb 15.5 EC @ 50 g a.i./ ha, Novaluron 10 EC @ 100 g a.i./ ha and Endosulfan 35 EC @ 700 g a.i./ ha i.e., 19.31, 18.75 and 17.5 q/ ha, respectively. Spinosad 45 SC when tested by Gowda et al., (2005) at different doses also recorded significantly lower pod damage and higher seed yield as compared to Endosulfan 35 EC @ 700 g a.i./ ha. Sherzad and Kumar (2014) reported that, highest cost benefit ratio was obtained in the treatment of Spinosad 45% EC @ 0.40% (1:11.19). Yadav and Singh (2016) also obtained the highest cost: benefit in Spinisad (1:2:12).