Diversity and relative abundance of insect visitors and pollinators in sunflower (Helianthus annuus L.) ecosystem

Introduction

Sunflower (Helianthus annuus L.), belonging to family Asteraceae, is a globally important oilseed crop grown for its high-quality edible oil and as a valuable component of crop diversification. Native to North America, it was first domesticated by indigenous tribes and later introduced into Europe, Asia and other parts of the world, and today ranks as the second most important oilseed crop globally after soybean, owing to its adaptability, short duration and relatively high oil yield. In India, sunflower is cultivated over an area of approximately 3.02 lakh hectares with a production of about 3.97 lakh tonnes and an average productivity of 1,314 kg/ha (DOD, 2023-24), and contributes significantly to the country's edible oil economy. Sunflower is primarily an entomophilous and cross-pollinated crop. Although its hermaphroditic florets permit a degree of self-pollination, optimal seed set, seed filling and oil accumulation largely depend on insectmediated cross-pollination, a process favoured by the large capitulum bearing numerous disc florets that facilitate frequent insect visits. Among insect pollinators, honey bees (Apis mellifera F. and Apis cerana indica F.), bumble bees and wild bees such as Xylocopa, Trigona and Andrena are reported to be the most effective and frequent visitors, enhancing pollination efficiency as well as the genetic diversity and resilience of sunflower crops. Insect-pollinated sunflower has been reported to record higher seed yield and oil content than self-or windpollinated crops (Dag et al., 2002; Mallinger and Prasifka, 2017) [1] , with open pollination further improving head diameter, seed number per head and 100-seed weight (Chandel et al., 2004) [2] . Similar yield gains attributed to insect pollination have been documented outside India, including a 53 per cent increase in seed yield under open pollination over pollinator-excluded plots in Kenya (Nderitu et al., 2008) [3] and comparable benefits reported from Pakistan, where four Apis species were recorded visiting sunflower capitula (Ali et al., 2015) [4] . In India, Jadhav et al. (2011) [5] documented the diversity of insect pollinators visiting sunflower capitula at Tirupati, Andhra Pradesh, recording 24 species across four orders, viz., Hymenoptera, Lepidoptera, Diptera and Coleoptera, with A. dorsata as the most abundant and effective pollinator followed by T. irridipenis and A. cerana indica.

Despite these gains, insect pollinator populations continue to face pressure from habitat loss, pesticide exposure and the intensification of monoculture cropping systems, making it essential to document pollinator diversity under local agro-climatic conditions before pollination benefits can be optimised. The present investigation was undertaken to document the diversity and relative abundance of insect visitors and pollinators on sunflower capitula at Rajendranagar, Hyderabad, during kharif 2025.

Materials and methods

Experimental site

The present investigation was carried out at the experimental farm of the ICAR-Indian Institute of Oilseeds Research (IIOR), Rajendranagar, Hyderabad, Telangana, during kharif 2025. The site falls under semi-arid tropical conditions with a hot and dry climate suitable for sunflower cultivation, and the soil of the experimental site was red sandy loam, low in available nitrogen, medium in phosphorus and high in potassium. Each plot measured 20 m 2 and the crop was spaced at 60 cm x 30 cm, with all recommended agronomic practices followed.

Plant material

Four sunflower genotypes differing in capitulum and floret morphology were evaluated:

Assessment of insect diversity and abundance

Insect visitors to the sunflower capitulum were recorded by direct visual observation at the peak blooming stage between 08.00 and 16.00 h. Observations were made at 10-minute intervals per plot, repeated three times daily (morning, noon and afternoon) throughout the flowering period. For every visit, the identity of the insect species together with its family and order, and the type of floral reward exploited (nectar and pollen), were recorded. Representative specimens were collected, preserved and identified using standard taxonomic keys, and identifications were verified by specialists at the Division of Entomology, ICAR-IIOR. The relative abundance (%) of each species was worked out as the proportion of its visits to the total number of insect visits recorded during the entire observation period.

Result and discussion

Diurnal insect visitors on sunflower capitulum

Observations on insect visitors to the sunflower capitulum during kharif 2025 revealed the occurrence of twelve species belonging to three orders and six families (Table 1.) Order Hymenoptera was the most diverse, represented by seven species under two families; family Apidae accounted for six species, viz., Tetragonula iridipennis Smith., Apis mellifera F., Apis florea F., Xylocopa fenestrata F., Xylocopa confusa L. and Heterotrigona sp., while family Vespidae was represented by a single species, Scolia sp. Order Lepidoptera comprised four species, one each from four families, namely Borbo cinnara Wallace (Hesperiidae), Hypolimnas misippus L. (Nymphalidae), Rapala manae Hewitson (Lycaenidae) and Thysanoplusia orichalcea F. (Noctuidae). Order Diptera was represented by a single species, Stomorhina xanthogaster Wiedemann, belonging to family Rhiniidae. With respect to the floral reward exploited, all six species of family Apidae and the dipteran visitor, S. xanthogaster, foraged on both nectar and pollen, whereas the wasp, Scolia sp., and all four lepidopteran visitors foraged on nectar alone Table 1. The findings of the present study align with Jadhav et al. (2011) [5] , who reported 88.85% abundance of the family Apidae on sunflowers at Tirupati. Similar findings were reported by Padhy et al. (2024) [6] , who recorded Apidae as the most speciose and most abundant family among the pollinators of sunflower in Odisha. The present findings align with Goswami et al. (2013) [7] and Basak et al. (2018) [8] , who reported a similar hymenopteran-dominated pollinator spectrum on sunflower in West Bengal.

Relative abundance of insect visitors on sunflower capitulum

The relative abundance of insect visitors on the sunflower capitulum is presented in Table 2. Among the twelve species recorded, order Hymenoptera accounted for 91.21% of the total insect visitors, comprising family Apidae (90.73%) and family Vespidae (0.48%). Within Apidae, the stingless bee, T. iridipennis was the single most dominant species, constituting 71.45 per cent of the total visitors, followed by X. fenestrata (5.38%), X. confusa (3.65%), A. mellifera (3.51%), A. florea (3.45%) and Heterotrigona sp. (3.29%). The wasp, Scolia sp. (family Vespidae) contributed only 0.48% to the total abundance. The remaining insect orders, Lepidoptera and Diptera, together constituted 8.79% of the total insect visitors. Among these, the dipteran nose fly, S. xanthogaster, recorded the highest abundance (4.24%), followed by the skipper, B. cinnara (3.38%). The remaining lepidopterans, H. misippus, T. orichalcea and R. manae, each contributed less than one per cent (0.54, 0.54 and 0.48%, respectively) to the total abundance. The present findings align with Piankra et al. (2019) [9] , who reported that T. iridipennis maintains strong and sustained foraging activity on sunflower throughout the flowering period, reinforcing its standing as an efficient and dependable pollinator of this crop wherever its colonies are locally abundant. Similar findings were reported by Gore et al. (2025) [10] , who reported low visitation rates for lepidopteran (P. demoleus, D. crysippus and R. manae) and dipteran (Ischiodon scutellaris) relative to the dominant hymenopteran foragers on sunflower in Maharashtra, reinforcing that these groups function mainly as occasional nectar foragers rather than as primary pollinators of the crop.

Stomorhina xanthogaster Wiedemann Conclusion

The present study revealed that the sunflower capitulum attracted a total of twelve insect species belonging to three orders and six families with Hymenoptera being the most diverse and abundant group. Unlike most previous reports from India, where Apis species dominate the pollinator spectrum of sunflower, the native stingless bee, T. iridipennis, emerged as the single most abundant floral visitor in the present study, underscoring its potential as an efficient and locally important pollinator of sunflower. Conservation of stingless bee colonies in the vicinity of sunflower fields, together with further correlation of insect visitation with seed set, seed yield and oil quality, is recommended to harness the full pollination benefits of this crop.

Acknowledgement

AcknowledgementI would like to thank Professor Jayashankar Telangana Agricultural University, Rajendranagar, Hyderabad, for providing support throughout this research. I would like to express my sincere gratitude to ICAR-Indian Institute of Oilseeds Research, officials, and staff for providing necessary research facilities, guidance, support and encouragement throughout my study term.

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12. How to cite this article: Swamy K, Boopathi T, Upendhar S, Yadav P. Diversity and relative abundance of insect visitors and pollinators in sunflower (Helianthus annuus L.) ecosystem. International Journal of Advanced Biochemistry Research. 2026;10(10):01-04. doi: https://www.doi.org/10.33545/2617469