Abstract: The present study was conducted to compare the effectiveness of different insecticides with reference to chickpea pod damage by the larvae of Helicoverpa armigera (Hubner) during Rabi season 2001-02. Four insecticides viz. cypermethrin (10 EC) @ 350 ml acre–1, endosulfan (35 EC) @ 1000 ml acre–1, lambdacyhalothrin (2.5 EC) @ 250 ml acre–1 and chlorpyrifos (40 EC) @ 800 ml acre–1 were tested twice. The screening of best insecticide was determined by comparing treated plots with untreated plots. Chlorpyrifos proved to be the best insecticide in reducing the pod damage and hence increased biomass and yield followed by endosulfan, lambdacyhalothrin, cypermethrin. However, all the insecticide treatments proved to be better in comparison with control in all the above mentioned aspects.
Introduction
Chickpea, Cicer arietinum L. is the world’s third most important pulse crop grown on about 10 million hectares annually (Rheenen and Van Rheenen, 1991). The crop is damaged extensively by gram pod borer, Helicoverpa armigera (Reed et al., 1980; Lal et al., 1985; Naresh and Malik, 1986; Deka et al., 1987) as it feeds on tender shoots and young pods (Lal, 1996). They make holes in pods and insert their half body inside the pods to eat the developing seeds (Kadam and Patel, 1960).
The damage may reach 10-30% in grain yield (Qadeer and Singh, 1989) or even up to 60 % (Vaishampayan and Veda, 1980). According to Joginder et al. (1990), damage to pods and seeds by pod borer varies from 13.58-84.28 and 3.15-84.28 % respectively. These losses to the crop can be reduced by the application of insecticides (Gohokar et al., 1987 and Biradar et al., 1999). The present study was executed to determine the most effective insecticide in reducing the pod damage.
Materials and Methods
The present study was conducted to test the efficacy of different insecticides in relation to chickpea pod damage. The experiment was laid in Randomized Complete Block Design comprising five treatments including a control and four replications at Ayub Agricultural Research Institute, Faisalabad during Rabi season 2001-02. The plot size was 7.00 m X 3.60 m. Four insecticides viz. cypermethrin (10 EC) @ 350 ml acre-1, endosulfan (35 EC) @ 1000 ml acre-1, lambdacyhalothrin (2.5 EC) @ 250 ml acre-1 and chlorpyrifos (40 EC) @ 800 ml acre-1 were applied twice, eight and nineteen days after the commencement of pod formation. The aforesaid insecticides were applied with the help of “Solo Knapsack Hand Sprayer”.
The pod damage was noted one day before and one, three, five, seven and nine days after the application of each spray. Healthy and damaged pods were counted on randomly selected five plants per plot and then percent pod damage was evaluated. The biomass and yield of one row from each plot of ripe crop was determined and then extrapolated for one acre. The data about percent pod damage was finally subjected to statistical analysis using analysis of variance and Duncan’s multiple range test.
Results
Pod damage: The percent pod damage inflicted by gram pod borer, Helicoverpa armigera recorded one day before the application of first spray revealed that the means of different treatments were statistically insignificant but after the application of spray significant differences were found among treatment means (Table 1). The least percent pod damage was observed in plots treated with chlorpyrifos and this situation remained as such in all the observed days after the application of sprays. The percent pod damage in the plots treated with cypermethrin, endosulfan and lambdacyhalothrin was also lower compared with control. The least effective insecticide was cypermethrin.
Biomass: Table 2 indicated that the plots treated with chlorpyrifos offered maximum biomass of 2261.93 kg acre-1 compared to control with biomass of 1192.74 kg acre-1. The biomass in plots treated with cypermethrin, endosulfan and lambdacyhalothrin were 1435.69, 1944.76 and 1868.88 kg acre-1, respectively.
| Table 1: | Percent pod damage inflicted by gram pod borer (Helicoverpa armigera) observed at different time intervals after the application of insecticides on chickpea during Rabi season 2001-02 |
| A. NS = Non Significant B. Treatment means marked by the same letter/letters are non-significant at α = 0.05 and vice versa. | |
| Table 2: | The biomass and grain yield per acre (kg) of chickpea after the application of different insecticides during Rabi season 2001-02. |
Yield: The extrapolated grain yield/acre (Table 2) showed that the chlorpyrifos was the most effective treatment (with grain yield of 570.10 kg acre-1) while cypermethrin was the least effective (having grain yield of 423.16 kg acre-1). However, all the insecticide treatments were proved to be better than control (294.68 kg acre-1).
Discussion
Chickpea crop is damaged extensively by Helicoverpa armigera which is a widely distributed pest (Reed et al., 1980). The population of H. armigera increased greatly during the pod formation stage (Deka et al., 1987; Lal, 1996; Patel and Koshiya, 1999) and caused serious damage to pods. In the present study different insecticides were tested to reduce the pod damage. A comparison of the present study with those of other entomologists was not possible in absolute terms because of the differences in combinations of insecticides employed by them.
The results of the present study i.e., chlorpyrifos be the best insecticide in reducing the pod damage and hence increased biomass and yield was in agreement with that observed by Balasubramanian et al. (2001). The results also revealed that all the insecticides reduce the pod damage to a considerable extent compared with control. These investigations are in accordance with those of Sinha et al. (1983), Gohokar et al. (1987), Rakesh et al. (1996), Khurana (1997), Subbarayudu (1997) and Biradar et al. (1999). These authors applied different insecticides against H. armigera on chickpea and concluded that the application of insecticides reduced the pod damage to a considerable extent and hence increased the yield in comparison with control.
Although, in the past, the best insecticide was considered to be the cypermethrin (Gohokar et al., 1987; Singh et al., 1987; Khan et al., 1993; Jadhav and Suryawanshi, 1998) and endosulfan (Chaudhary et al., 1980; Rizvi et al., 1986) but in the present study chlorpyrifos proved to be the best insecticide. This was due to the reason that H. armigera in certain localities have acquired resistance to these insecticides. High resistance to the cypermethrin (King and Sawicki, 1990) and to a lesser extent to the endosulfan and lambdacyhalothrin (Ahmed et al., 1997) was observed in H. armigera larvae. Phokela et al. (1990) also observed a tendency of increased resistance to cypermethrin in the population of H. armigera. The older larvae were more resistant to the insecticides than the younger ones (Khurana, 1997). Although the pest has developed resistance to the insecticides but still insecticide treatments were useful in reducing the pod damage and increasing the biomass and yield.