Honey bees, pesticides, and sustainable crop production: A comprehensive review

Introduction

Insect pollination is a crucial yet often unseen ecosystem service that supports global food production. Honey bees, along with wild bees, butterflies, flies, and other pollinators, enable the sexual reproduction of many flowering plant species, including numerous fruits, vegetables, oilseeds, nuts, and fibre crops vital for human diets and farm incomes. A comprehensive study covering over 200 countries by Klein et al., (2007) [12] found that the production of 87 major global food crops relies to some extent on animal pollination. While these crops constitute a minority by weight, they are essential for dietary diversity and quality. Potts et al., (2016) [24] estimated that animal pollination supports 35% of global crop production volume, with a market value between USD 235 billion and USD 577 billion, and highlighted ongoing declines in wild pollinator diversity and managed honey bee colonies worldwide.

As the role of pollinators in agriculture has become more clearly understood, evidence has shown that both managed and wild bee populations worldwide are under ongoing stress. In North America and Europe, beekeepers started reporting unusually severe and unexplained colony losses in the mid-2000s, a phenomenon now called colony collapse disorder (CCD). A comprehensive study comparing CCD-affected and unaffected colonies across the United States analysed 61 variables, including pathogen levels, bee physiology, and pesticide residues, and found no single factor consistently distinguished collapsed colonies, though CCD-affected colonies carried higher pathogen loads and more co-infections than healthy colonies (vanEngelsdorp et al., 2009) [33] . Around the same time, broader research on pollinator decline identified habitat loss, fragmentation, pesticide exposure, pathogens, parasites, competition from non-native species, and climate change as key interacting drivers that rarely act alone under field conditions (Potts et al., 2010) [23] .

Although no single cause fully explains these declines, a significant body of research points to agricultural pesticides, used both to protect crops from pests and within beekeeping to control mites and hive pests, as a central, modifiable factor acting alongside pathogens, parasites, habitat destruction, and nutritional stress. This review consolidates scientific research on the link between pesticide exposure and honey bee health, with a focus on Indian agricultural contexts, where native bee species, varied cropping systems, and a large smallholder farming sector present circumstances that differ significantly from the North American and European settings in which most early pesticide-pollinator research was conducted. The review is structured as follows: Section 2 details its scope and methodology; Section 3 discusses honey bees' role in sustainable farming; Section 4 reviews key pesticide classes and their mechanisms; Section 5 examines lethal and sub-lethal impacts on individual bees and colonies; Section 6 explores colony collapse disorder and multi-stressor effects; Section 7 examines pesticide residue data specific to India; Section 8 compares global regulatory responses; Section 9 considers mitigation strategies and integrated pest and pollinator management; Section 10 presents policy and extension initiatives for India; Section 11 identifies research gaps and future opportunities; and Section 12 offers concluding remarks.

Scope and review approach

This review draws on peer-reviewed research, government and intergovernmental reports, and reputable scientific and regulatory sources focused on honey bee biology, pesticide toxicology, pollination ecology, and agricultural policy, with particular emphasis on studies of native Indian honey bee species (Apis Cerana indica, Apis dorsata, Apis florea) alongside the internationally dominant literature on the introduced Western honey bee, Apis mellifera. Sources include laboratory toxicology studies, field and semi-field trials, residue-monitoring surveys, and synthesis reviews, spanning both acute lethal-dose research and the sub-lethal, behavioural, and colony-level literature that has become increasingly central to pollinator risk assessment over the past decade. Because pesticide-pollinator research is a fastmoving field, the review privileges recent primary literature while retaining foundational studies that continue to shape regulatory and scientific thinking.

Honey bees in sustainable crop production Pollination services and crop yield

Honey bees support crop production through both managed pollination, in which colonies are deliberately placed in or near flowering fields, and incidental pollination by wild and feral colonies. A comprehensive assessment of Indian crop production found that over half of the 211 crops and commodities examined depend partly on animal pollination, with direct insect pollination contributing an estimated ₹112,616 crores (about USD 22.5 billion) annually to Indian agriculture, roughly nine percent of total agricultural value (Chaudhary and Chand, 2017) [5] . Field trials across a range of pollinator-dependent crops show yield increases of 15 to 50 percent attributable to effective honey bee pollination (Partap, 2011) [20] , while crop-specific studies have documented pollination-driven improvements in fruit set, fruit weight, sugar content, and seed quality that translate directly into higher farm-gate value (Khalifa et al., 2021) [11] . Globally, these figures sit within a well-established literature: Gallai et al., (2009) [7] , in a widely cited bioeconomic valuation of 100 crops used directly for human food worldwide, estimated the total economic value of insect pollination at approximately €153 billion in 2005, roughly 9.5% of global food production value, and projected consumer-surplus losses of €190 to €310 billion under pollinator decline scenarios, identifying fruit, vegetable, and stimulant crops such as coffee and cocoa as the most economically vulnerable categories to pollinator loss, consistent with the nutrition-security concerns raised for India in Section 3.4.

Beekeeping as a livelihood and sustainability strategy

Beyond crop pollination, apiculture is a low-input, eco-friendly farming practice that boosts rural income through the sale of honey, beeswax, propolis, royal jelly, and other hive products. In India, the native Apis Cerana is particularly well suited to smallholder and rainfed farms because it does not require migration, tolerates a wide climatic range, and can be kept in simple, affordable box hives, making it accessible to small and marginal farmers. Migratory beekeeping with Apis mellifera, moved seasonally among flowering regions such as mustard, sunflower, and litchi, has created a rental-pollination market that benefits both crop yields and beekeeper incomes. Because beekeeping uses less land and fewer chemicals than most other farming activities, its promotion aligns closely with sustainability goals centred on input efficiency, biodiversity conservation, and income diversification.

Pollinators and agricultural biodiversity

Beyond their direct economic contribution, pollinators support the reproduction of wild flowering plants essential for agroecosystem biodiversity, including hedgerow and fieldmargin vegetation that supports natural pest enemies, stabilises soils, and sustains wildlife food webs. Protecting pollinators is therefore not merely an environmental concern but a structural component of sustainable, resilient agriculture.

Food security and nutritional dimensions

Crops that depend heavily on animal pollination fruits, vegetables, pulses, nuts, and oilseeds are vital sources of micronutrients such as vitamin A, vitamin C, folate, and essential fatty acids, in contrast to the wind-and self-pollinated cereal staples that mainly supply calories. A decline in pollination services therefore poses a smaller threat to caloric intake than to dietary diversity and quality, a distinction crucial to India's public health efforts to improve micronutrient consumption through agricultural diversification rather than staple-crop expansion alone. Because smallholder and marginal farmers in India often rely on pollinator-dependent horticultural crops for both nutrition and income, pollinator decline carries a compounding risk to both farm revenue and household nutritional security.

Pesticide classes and modes of action relevant to bee's neonicotinoids

Neonicotinoid insecticides such as imidacloprid, clothianidin, thiamethoxam, acetamiprid, and thiacloprid target the insect nicotinic acetylcholine receptor, disrupting neural signalling. Typically applied as seed coatings or soil drenches, they translocate through plant vascular tissue into pollen, nectar, and guttation fluid, creating a route of chronic, low-dose exposure throughout a crop's flowering period. By the early 2010s neonicotinoids accounted for roughly one-third of the global insecticide market, making them the most studied pesticide class in pollinator toxicology (Wood and Goulson, 2019) [35] . Several landmark field and semi-field experiments have confirmed laboratory concerns under real-world conditions. Whitehorn et al., (2012) [34] showed that bumble bee (Bombus terrestris) colonies exposed to realistic imidacloprid levels experienced slower growth and an 85% reduction in new queen production compared with untreated colonies. Rundlöf et al., (2015) [26] observed lower wild bee densities, decreased solitary bee nesting, and impaired bumble bee colony growth and reproduction on oilseed rape from clothianidin-coated seeds across sixteen Swedish landscapes, though managed honey bee colonies showed no comparable effect. A multi-country study in the UK, Germany, and Hungary linked neonicotinoid-treated oilseed rape to lower overwintering success and colony reproduction in both honey bees and wild bees, with outcomes varying by landscape quality and forage availability (Woodcock et al., 2017) [36] . In North America, honey bee colonies foraging near neonicotinoid-treated corn were exposed for three to four months, resulting in higher worker mortality, weakened social immunity, and increased queenlessness, effects intensified by fungicide co-application (Tsvetkov et al., 2017) [32] . A global survey of honey samples corroborates the scale of this exposure independent of any single field study: Mitchell et al., (2017) [16] , testing 198 honey samples collected worldwide, detected at least one neonicotinoid in 75% of samples and multiple neonicotinoids in 45%, indicating that neonicotinoid contamination of pollinator food resources is a near-global phenomenon. Taken together, these field studies demonstrate that laboratory-identified sub-lethal effects translate into measurable colony-level harm under real-world conditions, though the extent of damage depends on local landscape and forage factors.

Organophosphates, carbamates, and pyrethroids

Older insecticide classes remain widely used in Indian agriculture and pose their own risks to bees. Organophosphates and carbamates target acetylcholinesterase, causing acute neurotoxicity at sufficient doses, while synthetic pyrethroids act on voltage-gated sodium channels; both are acutely toxic to bees on contact, though generally less persistent in plant tissue than neonicotinoids. Surveys of Indian honey have repeatedly detected residues of organophosphates and pyrethroids such as monocrotophos, profenofos, ethion, chlorpyrifos, and cypermethrin, alongside legacy organochlorines such as DDT and HCH isomers that persist in soils despite restrictions on their use (Choudhary and Sharma, 2008; Kumar, Gill and Bedi, 2018) [6,14] .

Fungicides and herbicides

Fungicides were long assumed to pose little direct risk to bees because they target fungal rather than insect physiology; this assumption has not held up under closer study. Certain fungicide classes, notably demethylase-inhibitor (DMI) compounds, significantly potentiate the toxicity of co-applied neonicotinoids in laboratory trials, and fungicide residues are now recognised as near-ubiquitous contaminants of bee-collected pollen (Godfray et al., 2014) [8] . Herbicides act indirectly on bees primarily by eliminating the flowering weeds that provide forage between crop bloom periods, but glyphosate exposure also has direct experimental support for a more specific mechanism: Motta et al., (2018) [17] found that honey bees exposed to field-realistic glyphosate concentrations experienced measurable depletion of several core gut bacterial species, most notably Snodgrassella alvi, and that bees with glyphosate-perturbed gut communities suffered substantially higher mortality when subsequently challenged with the opportunistic pathogen Serratia marcescens than bees with an intact microbiota. Because these gut bacteria assist with nutrient processing and pathogen resistance, the study's authors argued that glyphosate's conventional classification as harmless to animals, based on the absence of its plant-specific molecular target in bee tissue, overlooks an indirect but biologically significant route of harm operating through the bee's associated microbial community.

Acaricides used in hive management

A pesticide category specific to beekeeping rather than crop protection is the class of acaricides applied directly within hives to control Varroa destructor and other mite pests. Compounds such as amitraz, coumaphos, and various synthetic pyrethroids are widely used for this purpose, and while formulated to be less toxic to adult bees than to mites, residues accumulate in beeswax comb over repeated seasons and have been detected alongside fieldapplied pesticides in Indian honey residue surveys (Tripathy et al., 2024) [31] . This makes in-hive chemical management an additional, often overlooked, contributor to the cumulative pesticide burden experienced by managed colonies, distinct from but compounding foraging-related exposure.

Summary of pesticide classes and bee risk

Table 1: summarises the pesticide classes discussed above, their primary agricultural use, mode of action, and the nature of the risk each poses to honey bees, drawing together the mechanistic evidence reviewed in this section. [17] In-hive acaricides Amitraz, coumaphos Varroa mite control within managed colonies

Pesticide class

Residue accumulation in wax, additive chemical burden on managed bees

Lethal and sub-lethal effects on bees Acute toxicity Direct, high-dose exposure to insecticides through spray drift, contact with treated foliage, or ingestion of heavily contaminated nectar can kill foragers outright and, in severe cases, cause visible mass mortality events at hive entrances. Acute toxicity has historically dominated regulatory testing because it is straightforward to measure through standard LD50 assays, but a growing consensus in the literature holds that acute lethality alone substantially understates the risk pesticides pose to bee populations under realistic field conditions (Siviter et al., 2018) [28] . [29] . Working with several neonicotinoids side by side, Mustard et al., (2020) [18] found that honey bees fed thiamethoxam were completely unable to differentiate floral scents in a differential learning task, whereas bees fed imidacloprid, clothianidin, or dinotefuran learned more slowly but retained the ability to discriminate odours evidence that neonicotinoid effects on cognition are compound-specific rather than uniform across the class. Navigation has been examined directly: using RFID tags to track free-foraging bees, Henry et al., (2012) [10] found that a single field-realistic dose of thiamethoxam significantly increased homing failure, suggesting a pathway through which chronic low-dose exposure could destabilise colony forager populations; similarly, Schneider et al., (2012) [27] showed that clothianidin and imidacloprid exposure led to fewer foraging trips and longer time away from the colony per trip. These findings have faced methodological criticism, with some researchers arguing that the statistical treatment of control mortality may overstate the effects (Guez, 2013) [9] , underscoring the difficulty of translating small behavioural effects into confident colony-level risk assessments. Because foraging efficiency, waggle-dance communication, and homing accuracy are all central to a colony's ability to gather sufficient food, these behavioural impairments can threaten colony survival even without individual bee mortality.

Indian research on native Apis Cerana populations has produced parallel findings using different methodologies. Bees sampled from pesticide-intensive cropping landscapes in Odisha showed significantly reduced proboscis extension response, structural damage to antennal sensillae, and disrupted resting-state calcium signalling in the brain compared with bees from low-pesticide sites, effects reproduced under controlled laboratory exposure (Chakrabarti et al., 2015) [3] . Related studies documented elevated oxidative-stress biomarkers superoxide dismutase, catalase, and xanthine oxidase in Apis Cerana and Apis dorsata sampled along a pesticide-use gradient in West Bengal and Odisha (Chatterjee et al., 2014), while a follow-up study found heightened markers of oxidative damage and apoptosis in Apis Cerana exposed to multiple pesticides simultaneously, a scenario the authors note is closer to real farm conditions than single-compound laboratory tests (Kumar et al., 2022) [15] .

Colony-level consequences

Sub-lethal effects on individual foragers accumulate into observable colony-level impacts, including reduced brood production, smaller adult populations, lower honey yield, and reduced resilience during winter or dearth periods. Field evidence for this aggregation is direct, Woodcock et al., (2017) [36] found that neonicotinoid-treated oilseed rape reduced overwintering colony survival in a multi-country European trial, and Tsvetkov et al., (2017) [32] documented increased queenlessness in colonies chronically exposed near corn crops. Modelling incorporated into pollinator-risk assessments indicates that once forager death rates exceed a critical threshold, colonies can enter a self-reinforcing decline in which younger bees are recruited to forage prematurely, further accelerating collapse (Godfray et al., 2014) [8] . Because these effects often take weeks to manifest, beekeepers and researchers frequently find it difficult to directly link a specific pesticide application to eventual colony loss, contributing to historical underestimation of pesticide risk relative to more visible threats such as disease.

Colony collapse disorder and multi-stressor interactions

As Section 1 notes, no single factor has been shown to consistently distinguish CCD-affected from healthy colonies (vanEngelsdorp et al., 2009) [33] , and the weight of evidence points instead to interacting combinations of stressors (Potts et al., 2010) [23] . Among the specific interactions documented, the relationship between pesticide exposure and the parasitic mite Varroa destructor, together with the viruses it transmits most notably deformed wing virus has received particular attention. Pesticide-related immune suppression appears to weaken a colony's ability to control viral replication, turning normally lowlevel, covert infections into deadly outbreaks under additional stress (Nazzi and Pennacchio, 2018) [19] . Neonicotinoid exposure has similarly been linked to increased vulnerability to the gut pathogen Nosema, and to synergistic toxicity when combined with DMI fungicides or other insecticides in tank mixtures, a concern of growing relevance given that bees in intensively farmed landscapes are rarely exposed to a single compound in isolation (Godfray et al., 2014; Kumar et al., 2022) [8,15] . A recent study on a mixture of a neonicotinoid (acetamiprid) and a pyrethroid (deltamethrin) in the native Saudi Arabian honey bee subspecies Apis mellifera jemenitica found significantly higher mortality and impaired learning and memory in bees exposed to the mixture compared with either compound alone, reinforcing the case that risk assessments based on single-compound testing may understate real-world hazard (Abuagla et al., 2025) [1] . This multi-causal picture has also generated genuine scientific debate: some researchers argue that the timing of reported pollinator declines does not consistently coincide with neonicotinoid adoption patterns, and caution against attributing colony losses to any single chemical class without longer-term field data (Blacquière and van der Steen, 2017) [2] . This dissenting analysis reinforces, rather than undermines, the broader scientific consensus that bee health outcomes are shaped by multiple interacting factors, and that risk assessment frameworks need to account for those interactions. [3] . These findings are significant because they extend evidence largely established using the introduced Apis mellifera to India's native pollinator species, which differ in physiology, foraging behaviour, and ecological role, and cannot be assumed to respond identically to pesticide stress.

Pesticide-pollinator evidence from India Field and laboratory studies on native bees

Pesticide residues in Indian honey

Indian research has also investigated pesticide residues in honey as both an environmental-contamination indicator and a foodsafety concern. Kumar, Gill, Bedi and Kumar (2018) [14] surveyed 100 raw honey samples from northern India and detected residues in 19% of samples, with dichlorvos, monocrotophos, profenofos, permethrin, ethion, and lindane the most frequently identified compounds; honey from cotton, sunflower, and mustard fields showed significantly higher contamination (33.3%) than honey from natural or fruit-tree vegetation (13.5%

). An earlier study of honey from Himachal Pradesh identified HCH and DDT isomers as the most frequent residues, with malathion in some samples exceeding the maximum residue limit proposed for honey (Choudhary and Sharma, 2008) [6] . A related multiresidue survey of 150 market honey samples from northern India by the same research group detected pesticides, predominantly organophosphates, in 12% of samples, though the associated human health risk was assessed as low at the concentrations observed (Kumar, Gill and Bedi, 2018) [14] . Separately, a survey of honey from apiaries in Kerala using LC-MS/MS and GC-MS/MS screened for a broad panel of pesticide classes and found propoxur and deltamethrin exceeding the maximum residue limit set for honey exported to the European Union in two of twelve samples tested (Prasanth et al., 2022) [25] . More recent tandem mass spectrometry analyses screening over 400 pesticide compounds in honey collected across India have continued to detect acaricide, fungicide, and insecticide residues, some attributable to chemicals applied within hives to control Varroa mites rather than to field spraying alone (Tripathy et al., 2024) [31] . Collectively, these residue studies indicate that Indian honey bees are chronically exposed to a mixture of contemporary and legacy pesticides through their foraging environment, that exposure levels vary substantially by cropping system and region, and that contamination is generally, though not universally, higher in honey sourced from intensively sprayed field crops such as cotton and mustard than from mixed natural vegetation a pattern consistent with the mechanistic and physiological evidence of pesticide harm described in Section 5 and the global contamination pattern documented by Mitchell et al., (2017) [16] in Section 4.1.

Economic stakes for Indian agriculture

This evidence carries significant economic weight. Where pollinator decline reduces pollination services, yield losses in dependent crops have been estimated at 20 to 80 percent, with per-hectare income losses of ₹10,000 to ₹55,000 and potential aggregate national losses exceeding ₹1 lakh crore annually under severe decline scenarios (Swain et al., 2025). Many crops most reliant on pollination mustard, cotton, fruits, and vegetables are also among the most heavily insecticide-treated in Indian agriculture, meaning the regions that stand to benefit most from healthy pollinator populations are frequently those where pesticide exposure risk to bees is highest, underscoring the need for management strategies that reconcile the two.

International and indian regulatory responses European union

In 2013, the European Union restricted outdoor use of three neonicotinoids clothianidin, imidacloprid, and thiamethoxam on bee-attractive crops following a European Food Safety Authority risk assessment, and moved to an almost complete outdoor ban in 2018 after further evidence, including the Woodcock et al., (2017) [36] field trial described in Section 4.1, confirmed unacceptable risk to bees. A retrospective review of this regulatory episode concluded that the risk-assessment protocols in place when neonicotinoids were first authorised in the 1990s were not designed to capture risks arising from high persistence, systemic movement through plant tissue, and environmental mobility, and argued for risk assessment grounded in the precautionary principle amid scientific uncertainty (Wood and Goulson, 2019) [35] . Post-moratorium monitoring substantiates this persistence concern directly: Woodcock et al., (2018) [37] , analysing 130 UK honey samples collected before and after the ban, found that neonicotinoids were present in about half of samples taken before the moratorium and still present in over a fifth of samples afterward, with residues correlated with the area of oilseed rape surrounding each apiary evidence that soil-persisting residues from previously treated fields continue to reach bees via subsequently planted, untreated crops.

United states

The United States Environmental Protection Agency has pursued a more incremental regulatory path, restricting neonicotinoid use during active bee foraging, expediting registration review of the neonicotinoid family, and temporarily pausing approval of new outdoor neonicotinoid product uses pending additional pollinator risk data. This approach has drawn criticism from some researchers and advocacy groups as insufficiently precautionary relative to the EU's restrictions, while others caution that abrupt restriction without adequate alternative pest-control options can impose significant costs on growers.

India

India's pesticide regulation, centred on the Insecticides Act, 1968, and its associated rules, has historically emphasised human toxicity, efficacy, and residue limits in food, with comparatively limited explicit attention to pollinator risk during registration. Some insecticide labels carry bee-hazard warnings, but enforcement of application-timing guidance and grower awareness of bee-safety practices remain inconsistent across states and crops. As Indian horticultural and oilseed production continues to expand and export markets increasingly scrutinise pesticide residues in honey and produce, there is a substantive case for more explicit integration of pollinator-risk data into pesticide registration, alongside strengthened extension messaging on application timing relative to crop flowering.

Mitigation strategies and integrated pest and pollinator management Integrated pest and pollinator management (IPPM) Integrated Pest and Pollinator Management extends conventional

Integrated Pest Management by explicitly incorporating pollinator health into pest-control decision-making, rather than treating pesticide use and pollinator conservation as separate concerns (Phan et al., 2025) [22] . Field research demonstrates that IPM regimes based on economic thresholds and targeted intervention can reduce insecticide applications very substantially: in a four-year, commercial-scale experiment integrating corn and watermelon production in the midwestern United States, Pecenka et al., (2021) [21] found that IPM reduced insecticide applications by approximately 95% relative to conventional calendar-based management while maintaining or even increasing watermelon yields, an effect mediated primarily through conservation of wild bee pollinator communities rather than managed honey bee colonies.

Application practices that reduce bee exposure

A set of affordable, widely applicable practices can significantly reduce pesticide exposure for foraging bees without eliminating pesticide use entirely. These include spraying insecticides late in the evening or at night when bees are not foraging; avoiding application to flowering crops, weeds, or field margins; choosing products with lower bee toxicity and shorter residual activity where efficacy permits; observing bee-hazard warnings and preharvest intervals on product labels; and informing nearby beekeepers of spray schedules so hives can be moved or closed during treatment.

Habitat and landscape-level measures

Because herbicide use and monoculture cropping reduce flowering forage outside the main crop's bloom period, preserving flowering field margins, hedgerows, and buffer strips gives bees alternative forage and reduces the concentration of foraging activity on treated crops at any given time. Such landscape diversification has been shown to support both wild pollinator abundance and biological pest control, complementing rather than competing with productive farmland, consistent with the wildbee-mediated yield benefits documented by Pecenka et al., (2021) [21] in Section 9.1. [31] . Judicious, rotation-based use of in-hive treatments, combined with non-chemical mite-control methods such as brood interruption and resistant stock selection, can reduce this additional exposure pathway.

Policy and institutional support in India India's principal institutional response to the pollination and beekeeping challenge is the National Beekeeping and Honey Mission (NBHM), a Central Sector Scheme managed by the National Bee Board under the Ministry of Agriculture and Farmers' Welfare. Launched in 2020 under the Atmanirbhar Bharat initiative with an initial outlay of ₹500 crore, the mission has been extended through 2025-26 with a further ₹370 crore allocation, and operates through three Mini Missions addressing pollination-assisted productivity, post-harvest processing and marketing, and region-specific research. Programmes under the Khadi and Village Industries Commission provide subsidised credit for beekeeping equipment, support beekeeping clusters and Integrated Beekeeping Development Centres, and fund honeytesting laboratories intended to address adulteration and quality concerns identified in residue-monitoring research. Since 2020, India has risen from the ninth-to the second-largest global honey exporter. What remains comparatively underdeveloped is the explicit integration of pesticide regulation with pollinator and beekeeping policy: bee-hazard data are not yet a standard, enforced requirement of pesticide registration in India, and coordination between crop-protection and beekeeping extension services remains uneven. Strengthening this institutional linkage through mandatory bee-toxicity data at registration, coordinated advisories timed to regional flowering calendars, and routine residue monitoring in honey would help ensure that investment in beekeeping promotion is not undermined by pesticide practices in the same agricultural landscapes.

Research gaps and future directions

Several gaps in the current evidence base warrant attention. First, the great majority of sub-lethal toxicology research remains focused on Apis mellifera under temperate, single-crop conditions; comparable studies on Apis Cerana, Apis dorsata, Apis florea, and India's diverse wild bee fauna under mixedcropping, multi-pesticide conditions remain comparatively limited, though the Calcutta University studies discussed in this review represent an important start. Second, most toxicology testing continues to examine single compounds in isolation, even though field-realistic exposure typically involves mixtures of insecticides, fungicides, and herbicides; expanded mixture and synergy testing, of the kind illustrated by the neonicotinoidfungicide interaction in Tsvetkov et al., (2017) [32] and the neonicotinoid-pyrethroid binary study of Abuagla et al., (2025) [1] , is needed to better characterise real-world risk. Third, longterm, landscape-scale field monitoring linking pesticide-use intensity to colony survival, honey yield, and crop pollination outcomes over multiple seasons remains rare in the Indian context, limiting the ability to translate laboratory and short-term findings into confident policy recommendations. Fourth, economic research quantifying the return on investment of pollinator-protective pesticide practices for Indian farmers, as distinct from the value of pollination services generally, would strengthen the case for voluntary adoption of bee-safe practices, drawing on the yield-neutral or yield-positive outcomes documented for IPM adoption elsewhere (Pecenka et al., 2021) [21] . Finally, systematic residue monitoring of honey and pollen across a wider set of Indian agro-climatic zones and crop systems, extended over time, would help track whether policy and extension interventions are reducing pesticide burden on Indian pollinators.

Conclusion

This review supports three main conclusions. First, honey bees make a substantial and well-quantified contribution to the productivity, income, and dietary diversity of Indian and global agriculture, positioning pollinator health as a core rather than peripheral concern for sustainable crop production. Second, pesticide exposure, through both acute lethality and, more pervasively, sub-lethal impairment of learning, navigation, and immune function, is a significant and modifiable driver of pollinator stress that interacts synergistically with pathogens, parasites, and nutritional deficits to produce colony-level decline, and one for which India-specific field and residue evidence is now accumulating alongside the larger international literature. Third, meaningful mitigation is achievable without abandoning pesticide use altogether: Integrated Pest and Pollinator Management, beesafe application practices, habitat conservation, more pollinatorconscious pesticide regulation, and continued institutional investment through programmes such as the National Beekeeping and Honey Mission together constitute a realistic, evidence-based path forward. Realising that path will require closer coordination between toxicologists, agronomists, regulators, extension services, and the farmers and beekeepers whose livelihoods depend on both productive crops and healthy bees.

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