Impact of Chickpea Varieties and Sowing Dates on Pod Borer Helicoverpa armigera (Hubner)

Chickpea (Cicer arietinum L.) is one of the most important Rabi pulse crop of India and occupies first position among the pulses crops. Although all the pulses occupy a unique position in Indian agriculture as well as throughout the world, chickpea is considered as “King of Pulses”. It is a rich source of calcium, iron, niacin, vitamin B and C; and provides the valuable protein supplement to the diet of the predominately-vegetarian human population-besides-contributing to the national income. It is also considered to have medicinal value for blood purification and beneficial for diabetic patients. It is also widely used as fodder and green manure. It is one of the most important food legume crops in sustainable agriculture systems because of its low production cost, wider adaptation, ability to fix atmospheric nitrogen and fit in various crop rotations (Singh, 1997). It can be grown profitably on residual moisture in heavy soils, in rainfed rice fallow lands (RRFL) without or with minimum irrigation. In India, the main chickpea growing states are Madhya Pradesh, Uttar Pradesh, Rajasthan, Bihar, Haryana, Maharashtra and Punjab.
       
 Several biotic and abiotic constraints limit the production and productivity of chickpea. But, insect-pests are a major constraint to decrease the production and productivity of chickpea (Sharma et al., 2007; Yadav et al., 2006). Losses due to insect pest damage are likely to increase as a result of changes in cropping patterns and global warming. On chickpea, a number of insect-pests are observed such as aphid (Aphis craccivora Koch), jassids (Empoasca kerri Pruthi), pea aphids (Acrythosiphum pisum Harris), thrips (Megalurothrips usitatus (Bugnall), whitefly (Bemisia tabaci Gennadius), gram pod borer (Helicoverpa armigera Hubner), gram semilooper (Autographa nigrisigna (Walker)), termites (Odontotermes obesus Ramb. and Microtermes obesi Heomgr), cutworm (Agrotis ipsilon Rott), budworm (H. punctigera), leaf miner (Liriomyzaci trifolli Burgess) and pulse beetle (Callosobruchus chinensis Linnaeus) (Mosier et al., 2004; Anandhi et al., 2011; Sachanand Katti, 1994, Sharma et al., 2007; Ram et al., 2021). Among these gram pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is a major and prominent pest in different chickpea growing areas of the country, accounting for 21% of crop yield losses and 50-60% of crop pod losses (Kambrekar, 2012). The adult of pod borer is a light reddish-brown moth with a prominent dot near the middle of the forewing. The caterpillars have variable colours ranging from green, brown or yellow. The caterpillars feed on the leaves, floral parts, pods and developing grains in pods (Begum et al., 1992; Anonymous, 2021). It assumed a major pest status across number of crops because of its high fecundity, migratory behavior, high adaptation to various climatic conditions and development of resistance to a range of insecticides (Rheenen and Rheenen, 1991; Srivastava, 2003). Currently, the insect-pests control is dominated by synthetic chemical use based on pest scouting and pre-determined action levels. This has resulted in the overuse of these pesticides, leading to the killing of natural enemies and development of resistance (Magallona, 1989; Forget, 1993; Tudi et al., 2021).
               
A number of cultural practices like sowing dates, crop rotation, selection of resistant cultivars, judicious use of fertilizers and proper plant spacing (Matthews and Turnstall, 1994) can be used in place of synthetic pesticides. Many of these practices were overlooked in preference to the effective and easy-to-use pesticides. Now the Indian population is being more aware about health, which has opened doors for production of organic food and these points towards bright future for resistant varieties. The increased demand of residue free products will definitely motivate farmers to select resistant varieties for management of insect-pests.  Host plant resistance is a relationship between the plant feeding insects and their hosts. The resistance enables plants to avoid, tolerate or recover from the effects of insect-pests attack and has proved to be a successful tool against insects in many crops (Felkl et al., 2005). Plant genotypes, either due to environmental stress or genetic makeup, possess physiological and biochemical differences which alter the nutritional value (primary metabolites) for plant feeding insects (Alvim et al., 2004). Secondly management of the pest through agronomic manipulation was considered as a possible way, as most of the insects infest the plant/crop at particular growth stage under certain environmental conditions which may be manipulated by sowing the crop on different dates (Singh et al., 2002). Several researchers have studied the effect of different dates of sowing and the seasonal abundance of gram pod borer with the corresponding yield of chickpea in different parts of India. It is learnt from the past studies of Deka et al., (1989), Yadava et al., (1991) and Cumming and Jenkins (2011) where they stated that the date of sowing has a great impact on the incidence of the insect-pests which may be attributed to the difference in weather conditions. The objectives of present study hence were to: (1) establish optimum sowing dates for new gram varieties (PBG 7 and PBG 8) and (2) test the new varieties for susceptibility to infestation by gram pod borer. Therefore, the present investigation was formulated to determine the effect of different dates of sowing on the incidence of H. armigera with different varieties of chickpea.

Field experiments were carried out during Rabi seasons of 2019-20 and 2020-21 at the PAU Regional Research Station, Gurdaspur located in North-West Province of Punjab.  The station is located at 75.24°E and 32.02°N and 265 metres  above sea level. It is in sub-mountainous region of Punjab and receives an average 1000 mm annual rainfall. In summer, average temperatures over 32°C (max.) and 24°C (min.) and a relative humidity of 92.5% and 83.5% in October and April, respectively.  The soil at, Gurdaspur (Punjab) India has been classified as fine loamy, non-calcareous, developed under hyperthermic regime (USDA: Typic Haplustalfs) (Soil Survey Staff, 2003) with silt loam texture- (41.0% sand, 39.0% silt, 20.0% clay). The experiments were laid out in a factorial randomized block design with two factors i.e. varieties and dates of sowing with four replications. Two chickpea varieties i.e. PBG 7 and PBG 8 were sown across four sowing dates viz. 25^th Oct, 05^th, 15^th and 25^th November in Rabi seasons during 2019-20 and 2020-21. The plot size of each treatment was kept as 10.0 m² and the buffers were maintained with 1.5 and 1.0 meter between replication and treatment plots, respectively. The seeds were sown in furrows in a depth of 3-4 cm with space of 30 x 15 cm. The experimental plots were maintained with margins at a large distance from the surrounding fields to make sure that the insecticides sprayed to other fields do not affect the study plots. The crop was raised by following all recommended package of practices for Rabi crops of Punjab Agricultural University, Ludhiana except plant protection measures which enabled the buildup of insect-pests in a pesticide free environment.
       
The data on larvae population were recorded at weekly interval from three central rows of each treatment of the field. The outermost rows were left as border rows and excluded from sampling. The crop monitoring was started and terminated at 30 and 140 days after sowing, respectively as suggested by Saini and Jaglan (1998) and Ahmed and Rai (2005). One day before harvesting, the healthy and infested pods from 10 randomly selected plants were counted and per cent infestation of pod borer was determined. The per cent pod damage was calculated by using formula given below,
                 
Harvesting and threshing was done separately of each plot and grain yield data recorded from each treatment for assessment of yield losses. Cumulative yield of each treatment was converted into quintal per hectare. Thus, the data recorded during the course of investigation were subjected to statistical analysis by using square root transformation (Sheoran, 1998).

Effect of chickpea varieties and sowing dates on
 
Larval population of pod borer, H. armigera
 
The data regarding mean larval population per three central rows for each treatment of gram pod borer were recorded during the year 2019-20 and 2020-21 and presented in Table 1. The results indicated that mean larval population had a significant and non-significant interaction between dates of sowing and varieties of chickpea, respectively during both the years. However, the larval population of H. armigera decreased with delay in sowing of chickpea crop. The significantly maximum (av. of two varieties) larval population per three rows was recorded 8.06 and 7.69 (Table 1) from chickpea crop that was sown at 25^th October and it was followed by the 05^th November sown crop with (mean of two vars.) larval population 7.42 and 7.19 during year 2019-20 and 2020-21, respectively while mean minimum larval population 5.29 and 5.28 recorded on the crop sown on 25^th November during year 2019-20 and 2020-21, respectively. The data on pooled mean larval population for two years was demonstrated in decreasing order with respect to date of sowing of both cultivars (PBG 7 and PBG 8) as 25^th October>5^th November>15^th November>25^th November with mean larval population 7.88>7.31>6.60>5.29 per three central rows. The more larval population at the early dates of sowing can be attributed to the fact that, during this period the vegetative growth of crop was more which resulted in higher larval population of pod borer.
 

 
Pod damage due to gram pod borer, H. armigera
 
The data pertaining to per cent pod damage due to H. armigera  at different sowing dates and varieties during the year 2019-20 and 2020-21 are presented in Table 2. The data showed that the pod borer’s incidence did not differ significantly between tested chickpea varieties during both years. The data further revealed that per cent pod infestation (av. both cultivars) due to pod borer varied 42.29-64.44 and 42.25-61.49 during the year 2019-20 and 2020-21, respectively. The first date of sowing (25^th October), recorded highest pod borer’s incidence (64.44 and 61.49 %) and followed by second and third dates of sowing (05^th and 15^th November) which recorded mean infestation 59.32 and 57.50% during the year 2019-20 and 2020-21, respectively. The significantly lowest pod damage 42.29 and 42.25% was recorded from 04th dates (25^th November) of sowing of year 2019-20 and 2020-21, respectively. The pooled mean data on pod infestation for two years was demonstrated in decreasing order with respect to date of sowing of both chickpea varieties (PBG 7 and PBG 8) as 25^th October>5^th November>15^th November>25^th November with pod incidence 62.96>58.41>52.44>42.27 per cent. The higher pod infestation (%) at the early dates of sowing can be attributed to the fact that, advance sowing of crop has more vegetative growth which resulted in more larval population and more pod infestation. However, per cent pod incidence varied non-significantly between two tested varieties.
 

 
Grain yield of chickpea
 
The data on grain yield of chickpea was recorded after harvesting of the crop and it was significantly varied to the different sowing dates and varieties (Table 3). During both years (2019-20 and 2020-21), the maximum yield (16.97 and 17.93 q/ha) was recorded on third date of sowing i.e., 15^th November followed by 25^th November (15.86 and 17.01 q/ha), whereas minimum grain yield (15.09 and 14.74 q/ha) was obtained from crop sown on first date of sowing i.e., 25^th October (Table 3). Pooled data on grain yield per hectare (Table 3) showed non-significant interaction between sowing dates and gram varieties. But grain yield was increased as the crop sowing delayed up to 15^th November during study period.
 

       
Regarding the impact of chickpea varieties and dates of sowing for multiplication of pod borer, Helicoverpa armigera, the results are in accordance with Kumar et al., (1983), Borah (1998) and Patnaik (2004) who reported that sowing dates had a greater effect on pest population, their incidence and grain yield when sown in first week of November than second week of December. Kabir et al., (2009) were also observed maximum yield in November 22 sown chickpea crop followed by December 2 and December 12 sown crop. Singh et al., (2008) also recorded yield losses from different locations varied from 37 to 50% due to H. armigera. Present finding was corroborated with the results of Prasad and Singh (1997) and Singh et al., (2002) and it has been reported that the pod filling ability in chickpea varieties also varied with sowing dates and exhibited a definite trend on pod damage. Jamor and Jamir (2015) also recorded minimum population of H. armigera in late sown crop of pea. The H. armigera larval population was high in early sown crop (October 15^th to November 1^st) than in delayed sowing i.e. after first week of November (Anwar et al., 1994). Similar observations were also published by Rishi et al., (2016), Singh et al., (2005), Singh and Yadav, (2006) and Pavani et al., (2019).

The present study concluded that very early sown crop had more population and pod infestation of pod borer, Helicoverpa armigera. It was further indicated that higher grain yield could be obtained by sowing the crop during 2nd week November. However, interaction between dates of sowing and varieties clearly indicated non-significant effect on larval population, pod damage and grain yield. Therefore, high quantum in grain yield losses can be lowered by the adoption of improved technologies for its cultivation, which include the sowing of pest resistant/tolerant variety at optimum time supported with recommended agronomic manipulation. Hence, for ensuring the less insect-pest infestation, chickpea should be sown in second week of November.

We are highly thankful to Director, PAU Regional Research Station Gurdaspur and Incharge, Pulses Section, Department of Plant Breeding and Genetics for providing technical guidance and facilities to conduct the experiments.

None.