Biology and morphometric characterization of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on field pea under laboratory conditions

Introduction

Field pea, Pisum sativum L. (Family: Leguminosae), is an important grain legume crop cultivated during the Rabi season throughout the world and is believed to have originated in Western Asia and Europe (Bijjur and Verma, 1997) [2] . Fresh green peas (100 g edible portion) contain 44 calories, 75.6% moisture, 6.2 g protein, 0.4 g fat, 16.9 g carbohydrates, 2.4 g fibre, 0.9 g ash, 32 mg calcium, 102 mg phosphorus, 1.2 mg iron, 6 mg sodium, 350 mg potassium, 405 μg beta-carotene equivalent, 0.28 mg thiamine, 0.11 mg riboflavin, 2.8 mg niacin and 27 mg ascorbic acid. In contrast, dried peas contain 10.9% moisture, 22.9% protein, 1.4% fat, 60.7% carbohydrates, 1.4% fibre and 2.7% ash per 100 g (Duke, 1981; Hulse, 1994) [8] . During 2024, field pea occupied about 7.72 lakh hectares in India, producing 10.67 lakh metric tonnes with an average productivity of 1.38 tonnes ha⁻¹ (FAO, 2024). In Haryana, the crop is grown over 4.1 thousand hectares with a production of 3.2 thousand tonnes and an average productivity of 780 kg ha⁻¹. Crop productivity is adversely affected by inadequate crop management practices as well as various abiotic and biotic stresses. Among the biotic factors, insect pests are considered one of the major causes of yield losses. Among them, Etiella zinckenella and Helicoverpa armigera attack the crop during flowering and pod development stages and are regarded as important constraints responsible for reduced productivity and deterioration in grain quality. The early instars of H. armigera initially feed on leaves and flowers and subsequently bore into the pods, feeding on developing seeds while keeping a part of their body outside the pod. A single larva is capable of damaging several pods during its development. Singh et al. (2004) [20] reported that pod damage caused by pod borers in field pea varied from 1.0 to 4.0 percent. Knowledge of biological parameters such as fecundity, egg hatchability, duration of larval stages, larval and pupal mortality, and adult emergence can help identify the most vulnerable stages of the insect and facilitate the adoption of timely and effective management strategies.

Materials and Methods

Laboratory Culture of H. armigera

Studies on different biological parameters of Helicoverpa armigera were conducted under laboratory conditions in the Department of Entomology at a temperature of 28±1 °C and relative humidity of 60-70 percent using field pea cv. HFP-1428. For establishing the culture, an adequate number of fully grown larvae of H. armigera were collected from field pea plots during January, 2024. Since the larvae exhibit cannibalistic behaviour, they were maintained individually in glass tubes of 7 × 2.5 cm dimensions. Tender leaves and pods of field pea cultivar HFP-1428 were provided as food to 100 individually reared larvae. The glass tubes were plugged with cotton and fresh, unsprayed leaves and pods collected from the field were supplied daily by replacing the old food material. The larvae completed their development and pupated inside the soil provided in the glass tubes. After adult emergence, male and female moths were paired and released into glass jars measuring 15 × 10 cm. The openings of the jars were covered with muslin cloth and fastened securely with rubber bands. Two folded paper strips were hung inside each jar to provide resting sites for the moths. Fresh twigs of field pea were placed inside the jars to encourage oviposition. To prevent desiccation and maintain leaf freshness, the cut ends of the twigs were wrapped with water-soaked cotton swabs. Cotton swabs dipped in 10 percent sugar solution were provided as food for the adults.

Females laid eggs on the leaves, muslin cloth and inner surface of the jars. The eggs were carefully collected with the help of a moist camel hair brush and transferred to Petri dishes for recording the incubation period and egg viability.

Egg

Ten pairs of freshly emerged male and female moths were maintained separately in specimen jars containing fresh field pea twigs for oviposition in order to record the preoviposition, oviposition and post-oviposition periods. The twigs were replaced every day. A cotton swab soaked in 10 percent honey solution was squeezed and suspended inside each specimen jar to serve as a food source for the moths, and fresh swabs were provided daily. The females used for recording the oviposition period were also observed to determine their total fecundity. For fecundity studies, leaves bearing eggs from the twigs were detached and the eggs present on them were counted. A field pea twig containing a known number of eggs was placed on blotting paper inside a Petri dish. A moist cotton swab was wrapped around the petiole of the leaf to maintain adequate humidity and to prevent desiccation of both the eggs and the leaf. Egg hatching was observed at 24-hour intervals in five such replicates. The number of eggs hatched each day was recorded and converted into percentage hatchability, and observations were continued until completion of hatching. The mean incubation period was calculated from these egg batches.

Larva

To determine the number and duration of larval instars, twenty newly hatched larvae were reared individually in separate specimen tubes. Fresh field pea twigs bearing pods were provided regularly as food for the developing larvae. The duration of each larval instar was determined by observing the cast exuviae. The exuviae of the early instars were examined daily under a stereoscopic binocular microscope, whereas those of the later instars were detected either with the help of a hand lens or by naked eye observations.

Pupa

For studying the pupal period, five groups (replications) of pupae, each consisting of ten individuals, were maintained separately in Petri dishes and examined daily for adult emergence. The pupal duration was calculated based on the number of days taken for adult emergence from the pupae, and adult emergence was subsequently expressed as percentage.

Adult

Twenty newly emerged adults were paired individually (one male and one female) and each pair was maintained in a separate specimen jar. A cotton swab soaked in 10 percent honey solution was provided as food, along with fresh field pea twigs bearing pods. The adults were examined daily and their mortality was recorded to determine adult longevity.

For estimating the sex ratio, five batches of pupae, each comprising ten individuals, were maintained and observed for adult emergence. The emerged adults were killed in a killing bottle and sexed on the basis of their morphological characteristics. The total life cycle of H. armigera was determined by recording the time interval from egg laying to adult emergence. These observations were made in ten replications.

Morphometrics

The length and width of different developmental stages were recorded during the first generation using an ocular micrometer and a stage micrometer. Measurements were taken for ten individuals of each stage, including egg, first to sixth larval instars, pupa, and adult males and females, with the aid of a stereoscopic zoom binocular microscope.

Statistical Analysis

The data generated during the present investigation were subjected to statistical analysis. The observations recorded on various biological parameters of Helicoverpa armigera were analyzed by computing the mean and standard deviation for each parameter.

Results and Discussion

The data presented in Table 1 were examined to study the various biological parameters of Helicoverpa armigera, which are described below:

Pre-oviposition, Oviposition and Post oviposition Period

The data presented in Table 1 revealed that the preoviposition, oviposition and post-oviposition periods of H. armigera varied from 2 to 4 days (Mean ± SD 2.70±0.82 days), 5 to 6 days (Mean ± SD 5.50±0.53 days) and 1 to 2 days (Mean ± SD 1.50±0.53 days), respectively. The present findings are in close agreement with those reported by Singh et al. (2023) [21] , who observed pre-oviposition, oviposition and post-oviposition periods ranging from 2-3 days (average 2.46±0.29 days), 5-8 days (average 6.33±0.14 days) and 1-2 days (average 1.67±0.14 days), respectively. Similar results were also obtained by Sharma et al. (2019) [18] , who recorded mean durations of 2.56±0.50, 5.80±0.86 and 2.40±0.50 days for pre-oviposition, oviposition and postoviposition periods, respectively.

Fecundity and Adult Longevity of H. armigera

Observations on the eggs revealed that females deposited eggs on the muslin cloth, paper strips and also on the plant parts provided as food inside the cage. Eggs were generally laid singly, predominantly on pods, flowers and leaves of field pea. Freshly laid eggs of the gram pod borer were spherical and creamy white in colour, which gradually turned dark brown prior to hatching. A single female deposited 397 to 507 eggs during her lifetime, with an average fecundity of 456.00±43.28 eggs (Table 1). The present findings corroborate those of Shinde et al. (2022) [19] , who reported an average fecundity of 453.19 eggs per female. Similar results were obtained by Sharma et al.

(2019) [18] , who recorded an average of 490.20±77.87 eggs per female. Comparable observations were also reported by PuRabiya et al. (2024) [16] , who observed a fecundity ranging from 424 to 631 eggs with a mean of 544.85±63.89 eggs per female. The longevity of male and female moths ranged from 8 to 9 days (Mean ± SD 8.70±0.48 days) and 10 to 12 days (Mean ± SD 10.80±0.79 days), respectively, indicating that females survived longer than males (Table 1). These findings are in close conformity with those reported by Gadhiya (2014) [10] , who observed the longevity of mated male and female moths to range from 7 to 8 days (average 7.64±0.49 days) and 8 to 10 days (average 9.08±0.70 days), respectively. Similar observations were also made by PuRabiya et al.

(2024) [16] , who recorded adult longevity ranging from 8 to 10 days (average 9.04±0.78 days) for males and 9 to 12 days (average 10.54±0.99 days) for females.

Incubation Period and Hatchability of Eggs

The incubation period of H. armigera eggs ranged from 3.69 to 4.07 days, with an average duration of 3.91±0.16 days (Table 1). The present findings are in close agreement with those of Chauhan et al. (2018) [4] and Sharma et al.

(2019) [18] , who reported an incubation period varying from 3 to 5 days. Likewise, Shinde et al. (2022) [19] observed the maximum incubation period on soybean (3.20 days), followed by sunflower (3.10 days), maize (2.69 days) and sorghum (2.54 days). Egg hatchability varied from 78 to 86 percent, with a mean hatchability of 80.80±3.35 percent (Table 1). Similar results were reported by Chauhan et al.

(2018) [4] , who recorded 87.65 percent egg hatchability on chickpea. The present observations are also in close accordance with those of Shinde et al. (2022) [19] , who reported the highest hatchability on sunflower and maize (90.00%), followed by sorghum (89.00%) and soybean (87.00%).

Larval Period

The present investigation showed that H. armigera passed through six larval instars and completed the larval period in 19 to 26 days, with a mean duration of 22.50±2.28 days. Similar findings were reported by Shinde et al. (2022) [19] , who recorded a larval period of 22.20 days on soybean, followed by sunflower (20.54 days), sorghum (19.52 days) and maize (18.87 days). The duration of the first instar ranged from 2 to 3 days, with an average of 2.55±0.51 days. The second instar, which was reddish-brown in colour and possessed dark hairs, remained active for 3 to 4 days (average 3.40±0.50 days) before moulting. The third instar lasted for 3 to 4 days, with a mean duration of 3.55±0.51 days. The fourth instar persisted for 3 to 5 days and averaged 3.75±0.85 days. The fifth instar continued for 4 to 5 days, with an average duration of 4.40±0.50 days. The sixth and final instar remained active for 4 to 6 days and recorded a mean duration of 4.90±0.81 days before entering the pupal stage (Table 1). These findings are in close conformity with those of Chauhan et al. (2018) [4] , who reported that the durations of the first, second, third, fourth, fifth and sixth larval instars varied from 2-3 days (average 2.48±0.51 days), 2-4 days (average 2.76±0.72 days), 2-5 days (average 3.08±1.08 days), 2-5 days (average 2.92±0.90 days), 3-6 days (average 3.72±0.94 days) and 3-6 days (average 4.24±0.93 days), respectively, before moulting.

Pupal Period

Pupation was observed on the inner surface of the glass jars, soil, muslin cloth and tissue paper in all five observations. The pre-pupal period of H. armigera ranged from 1.70 to 2.10 days, with an average duration of 1.92±0.18 days (Table 1). Similar findings have been reported by several researchers. Ali et al. (2009) [1] observed a pre-pupal period of 1 to 3 days, with a mean duration of 2.15±0.16 days. Rabari et al. (2017) [17] recorded a pre-pupal period varying from 1 to 3 days with an average of 1.93±0.69 days, whereas Sharma et al. (2019) [18] reported duration of 1 to 2 days with a mean of 1.48±0.50 days. The pupal period varied from 8.30 to 11.60 days and averaged 10.04±1.23 days. These findings are in agreement with those of Ali et al. (2009) [1] , who reported a pupal duration ranging from 10 to 14 days with an average of 13.15±0.27 days. Similarly, Baikar and Naik (2016) [13] recorded a pupal period of 13 to 15 days with a mean duration of 13.8±0.84 days, while Sharma et al. (2019) [18] observed a pupal period ranging from 11 to 15 days with an average of 13.48±1.29 days.

Adult Emergence

Adult emergence ranged from 80 to 100 percent, with an average emergence of 88.00±8.37 percent (Table 1). The present findings are in close agreement with those of Goyal and Rathore (1988) [11] , who observed 100 percent adult emergence when H. armigera larvae were reared on gram leaves and pods under laboratory conditions at 30±1 °C. Similar results were reported by Srivastava and Srivastava (1990) [22] , who recorded adult emergence ranging from 80 to 90 percent on different chickpea genotypes under laboratory conditions.

Sex Ratio

Male and female moths were distinguished on the basis of forewing colouration. The forewings of male moths were greenish-brown, whereas those of females were orangebrown. The percentage of male and female moths varied from 37.50 to 60.00 (Mean ± SD 47.28±8.38) and 40.00 to 62.50 (Mean ± SD 52.72±8.38), respectively. The sex ratio (female: male) ranged from 1.0:0.6 to 1.0:1.5, with an average of 1.0:0.94, indicating a slight predominance of females (Table 2). The present findings are in accordance with those reported by earlier workers. Dahegaonkar and Mohite (2014) [6] observed a sex ratio of 1:0.66 (F:M) in H. armigera. Similarly, Baikar and Naik (2016) [13] , Rabari et al. (2017) [17] , and PuRabiya et al. (2024) [16] reported sex ratios of 1:0.78 (F:M), 1:0.87 (F:M), and 1:0.76 (F:M), respectively.

Total Life Cycle

The data presented in Table 1 revealed that the total life cycle of H. armigera ranged from 40 to 51 days, with an average duration of 46.2±3.55 days. The present findings are in close agreement with those of Gadhiya (2014) [10] , who reported that the total life cycle of H. armigera varied from 40 to 61 days (average 49.40±5.21 days) in males and from 43 to 65 days (average 52.40±7.03 days) in females. Similar observations were made by Singh et al. (2023) [21] , who recorded the average total life span of male and female adults as 50.30±7.51 days and 53.50±7.93 days, respectively. Sex-ratio (Male:Female) 1.0:0.6-1.0:1.5 1.0 :0.94 13.

Total life cycle 40-51 46.2±3.55

Morphometrics of Various Developmental Stages Egg

Freshly deposited eggs of H. armigera were spherical in shape and creamy white in colour, which gradually changed to a darker shade before hatching. The egg length varied from 0.34 to 0.52 mm, with an average of 0.44±0.06 mm, whereas the width ranged from 0.41 to 0.62 mm, averaging 0.51±0.06 mm (Table 3). The present observations are in close agreement with those of Chavan et al. (2014) [5] , who reported the mean length and breadth of eggs as 0.48±0.07 mm and 0.50±0.07 mm, respectively. Similar findings were also recorded by Jat et al. (2020) [14] , who observed average egg dimensions of 0.51±0.06 mm × 0.46±0.37 mm on an artificial diet and 0.52±0.03 mm × 0.48±0.62 mm on a natural diet (pigeon pea), which are comparable with the present results.

Larva

The larval stage of H. armigera comprised six instars, with body dimensions increasing progressively after each moult. The first instar larvae were relatively small, measuring 1. 3). Similar findings were reported by Parmar (2006) [15] , who observed larval lengths and breadths of 1.74±0.12 and 0.30±0.01 mm, 4.85±0.42 and 0.49±0.02 mm, 8.46±0.47 and 1.01±0.17 mm, 17.42±0.75 and 2.21±0.10 mm, and 28.76±1.05 and 3.56±0.14 mm for the respective larval instars. These results are in conformity with the present findings.

Pupa

Based on morphological characteristics, freshly formed pupae were soft and pale brown to greenish in colour, which gradually changed to dark brown within a few hours. Sex differentiation at the pupal stage was carried out on the basis of the distance between the genital and anal openings. In male pupae, the genital opening was situated on the ninth abdominal segment, whereas in female pupae it was located on the eighth abdominal segment. In both sexes, the anal opening was present on the tenth abdominal segment. Consequently, the distance between the genital and anal openings was greater in female pupae than in male pupae. [14] , who recorded average dimensions of male pupae as 18.82±1.

Adult

The adults of H. armigera were stout-bodied moths possessing a broad thorax. Their antennae were filliform, non-sexually dimorphic and covered with fine hairs. Male and female moths could be easily distinguished by the colouration of their forewings. The forewings of males were greenish-brown, whereas those of females varied from orange-brown to dark brown. In both sexes, the hind wings were dull creamy in colour and possessed a broad darkbrown band at the apical margin, which was interrupted by a pale patch. 3). Similar observations were reported by Deepa and Srivastava (2010), who described male moths as greenish-grey in colour, while females were orange-brown. They also recorded pre-emergence periods of 9.25±0.19 days in males and 11.08±0.38 days in females. Comparable findings were documented by Herald and Tayde (2018) [12] , who observed an average body length of 17.94±0.52 mm and a wingspan of 36.22±0.94 mm in male moths, whereas female moths recorded an average body length of 19.38±0.73 mm and a wingspan of 40.26±0.87 mm. These observations are in close conformity with the present findings.

References

1. Ali A, Choudhury RA, Ahmad Z, Rahman F, Khan FR, Ahmad SK. Some biological characteristics of Helicoverpa armigera on chickpea. Tunisian Journal of Plant Protection. 2009;4:99-106.
2. Bijjur S, Verma S. Persistence and efficacy of insecticides against pest complex of pea crop. Pesticide Research Journal. 1997;9:25-31.
3. Baikar AA, Naik KV. Biology of fruit borer, Helicoverpa armigera (Hubner) on chilli under laboratory conditions. Plant Archives. 2016;16(2):761769.
4. Chauhan NN, Chaudhary FK, Patel HN, Kachhadiya NM. Biology of pearl millet earhead worm (Helicoverpa armigera) under laboratory conditions. International Journal of Current Microbiology and Applied Sciences. 2018;7:2958-2969.
5. Chavan AP, Patil SK, Tilekar VB, Deshmukh GP, Harer PN. Biology of Helicoverpa armigera (Hubner) on pigeonpea. Journal of Agricultural Research Technology. 2014;39:256-259.
6. Dahegaonkar JS, Mohite AS. Studies on the life stages and external morphology of gram pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae). International Journal of Research in Biosciences, Agriculture and Technology. 2014;2:226235.
7. Deepa M, Srivastava CP. Biological characteristics of Helicoverpa armigera. Annals of Plant Protection Sciences. 2010;18:370-372.
8. Duke JA. Handbook of Legumes of World Economic Importance. New York: Plenum Press; 1981. p. 199265.
9. FAO. FAOSTAT Statistical Database. Rome: Food and Agriculture Organization of the United Nations; 2024.
10. Gadhiya HA, Borad PK, Bhut JB. Bionomics and evaluation of different biopesticides against Helicoverpa armigera (Hubner) Hardwick infesting groundnut. The Bioscan. 2014;9:183-187.
11. Goyal SP, Rathore VS. Patterns of insect-plant relationship determining susceptibility of different hosts to Heliothis armigera (Hubner). Indian Journal of Entomology. 1988;50:193-201.
12. Herald KP, Tayde AR. Biology and morphology of tomato fruit borer, Helicoverpa armigera (Hubner) under Allahabad conditions. Journal of Entomology and Zoology Studies. 2018;6:1734-1737.
13. Hulse JH. Nature, composition and utilization of food legumes. In: Expanding the Production and Use of Cool Season Food Legumes. Current Plant Science and Biotechnology in Agriculture. Vol. 19. 1994. p. 77-97.
14. Jat BL, Dahiya KK, Rolania K, Yadav SS. Standardization of artificial diet for the mass rearing of Helicoverpa armigera. Indian Journal of Plant Protection. 2020;48:55-63.
15. Anand, Gujarat, India: Anand Agricultural University; 2006. p. 53-59.
16. Purabiya PN, Patel PB, Jena MK. Biology and morphometry of gram pod borer, Helicoverpa armigera (Hubner) infesting gram (Cicer arietinum L.). Journal of Advances in Biology and Biotechnology. 2024;27:13-28.
17. Rabari GN, Abhishek P, Patel BR. Comparative biology of Helicoverpa armigera (Hubner) reared on tomato during different seasons. Journal of Entomology and Zoology Studies. 2017;5:657-663.
18. Sharma VG, Kumar S, Srinivas G. Biology of Helicoverpa armigera (Hubner) on tomato in South Gujarat. Journal of Entomology and Zoology Studies. 2019;7:532-537.
19. Shinde VM, Dhormare AP, Somwanshi VL, Shetgar SS. Biology of Helicoverpa armigera (Hubner) on different host plants. The Pharma Innovation Journal. 2022;11:2362-2365.
20. Singh MK, Shrivastava CP, Agrawal N. Comparative performance of field pea, Pisum sativum genotypes against leaf miner, Chromatomyia horticola (Goureau) and pea pod borer, Etiella zinckenella (Treitschke). Journal of Entomological Research. 2004;28:345-349.
21. Singh RP, Singh R, Singh G, Singh DV, Singh G. Biology of fruit borer, Helicoverpa armigera (Hubner) on tomato under laboratory conditions. International Journal of Environment and Climate Change. 2023;13:2007-2016.
22. Srivastava CP, Srivastava RP. Antibiosis in chickpea (Cicer arietinum L.) to gram pod borer, Heliothis armigera (Hubner) (Lepidoptera: Noctuidae) in India. Entomon. 1990;15:89-93.