The research team, led by Omolara Jemimah Ojezele of the Federal College of Animal Health and Production Technology in Ibadan and Matthew Obaineh Ojezele of Delta State University, focused on Amaranthus cruentus, a leafy green vegetable that is a dietary staple across Nigeria and much of sub-Saharan Africa. Sampling was carried out at 30 sites spread across three major vegetable-producing settlements in Oyo State, yielding 240 matrix-season samples of water, sediment, soil, and vegetable tissue. After analytical duplicates were averaged, the dataset comprised 480 independent pesticide-specific sample-level observations. All samples were analysed using validated chromatographic methods, providing the analytical foundation for the layered statistical and risk assessments that followed.

The study’s first major finding concerns environmental partitioning, the tendency of a chemical to accumulate in particular compartments of an ecosystem. Glyphosate, a systemic herbicide that binds strongly to soil particles, predominated in soil and sediment samples, consistent with its known physicochemical behaviour. Cypermethrin, a synthetic pyrethroid insecticide, showed a different pattern, occurring at comparatively higher concentrations in the edible Amaranthus cruentus tissue itself. This divergence matters because it shapes the primary route of human exposure: while glyphosate residues largely remain locked in the ground, cypermethrin residues travel directly onto the plates of consumers through the vegetable crop, bypassing many of the natural attenuation processes that limit exposure to soil-bound chemicals.

To understand whether contamination was random or clustered, the researchers applied Moran’s I spatial autocorrelation analysis, a statistical technique that tests whether values measured at nearby locations are more similar than expected by chance. The results were striking for one compound: glyphosate in sediment displayed significant spatial autocorrelation, with a Moran’s I statistic of 0.783 and a p-value of 0.0003. In practical terms, this means that sites with high glyphosate contamination in sediment tended to sit near other highly contaminated sites, forming identifiable hotspots rather than a scattered pattern. Such clustering suggests that localised factors, such as application intensity, topography, and runoff pathways, drive glyphosate accumulation in sediments, information that could help regulators target interventions at specific zones rather than imposing blanket restrictions.

The team complemented the spatial analysis with hierarchical mixed-effects modelling and principal component analysis, statistical tools that allowed them to separate the influence of different environmental and seasonal variables on residue concentrations while accounting for the nested structure of the sampling design. Together with a structured survey of vegetable farmers, these methods revealed a troubling gap between residue levels in crops and the practices that produced them. The survey documented limited pesticide stewardship among growers, including short pre-harvest intervals, meaning farmers were applying pesticides and harvesting their crops with little time for residues to degrade. Substantial exceedances of selected European Union maximum residue limit benchmarks for spinach were recorded in the vegetable samples, underscoring the consequences of these practices.

The heart of the study lies in its dietary risk assessment, which the researchers conducted in two complementary ways. The first was a deterministic approach, which uses single point estimates of residue concentration and consumption to calculate a hazard quotient, the ratio of estimated exposure to a reference dose below which no adverse effects are expected. A hazard quotient above one signals a potential health concern. The deterministic results indicated acceptable dietary risk for adults for both pesticides, and acceptable risk for children for glyphosate. However, cypermethrin exceeded the hazard threshold in children, with a hazard quotient of 1.818, nearly double the level of concern for the youngest and most vulnerable consumers.

Because deterministic assessments rely on single values, they can obscure the true range of possible exposures. To address this, the researchers turned to Monte Carlo simulation, a probabilistic technique that runs thousands of virtual exposure scenarios by randomly drawing residue concentrations and consumption rates from their measured distributions. Each of the 10,000 iterations represents one plausible combination of real-world conditions, and the resulting spread of hazard quotients reveals how often risky exposures might actually occur. The simulation results sharpened the study’s central warning: hazard quotients above one appeared in 15.09 percent of adult cypermethrin exposure scenarios and a remarkable 70.47 percent of child exposure scenarios. For glyphosate, by contrast, no simulated exposure scenario for either group exceeded the threshold, suggesting the herbicide poses comparatively limited dietary risk under the conditions measured.

The contrast between the two pesticides carries important implications. Cypermethrin is prized by farmers for its effectiveness against the insect pests that devastate vegetable crops, but its persistence on leafy surfaces means that harvest timing is critical to food safety. The finding that roughly seven in ten simulated child exposure scenarios exceeded the hazard threshold points to a systemic problem rather than isolated lapses, one rooted in the short intervals between spraying and harvest documented in the farmer survey. Children are particularly sensitive in such assessments because their lower body weight means the same residue concentration in food delivers a higher dose per kilogram of body mass, and because developing systems may be more vulnerable to neurotoxic compounds such as pyrethroids.

The study’s authors argue that their findings support a coordinated response spanning pesticide stewardship, residue surveillance, farmer education, and regulatory oversight. In many smallholder farming systems across sub-Saharan Africa, extension services that once trained farmers in safe application practices have contracted, leaving growers to rely on agrochemical vendors and informal knowledge networks. The short pre-harvest intervals recorded in this study are a classic symptom of that gap, reflecting neither malice nor ignorance of risk so much as the absence of accessible, practical guidance. Simple interventions, such as clear labelling in local languages, community-level training on waiting periods, and routine market testing of leafy vegetables, could substantially reduce exposure without requiring farmers to abandon chemical pest control altogether.

The research also demonstrates the value of methodological rigour in regions where pesticide monitoring data have historically been sparse. By pairing validated chromatographic analysis with spatial statistics, mixed-effects modelling, and Monte Carlo simulation, the study transforms a set of field measurements into a nuanced risk picture that distinguishes between compounds, environmental compartments, and consumer groups. The strong spatial clustering of glyphosate in sediment, for instance, would have been invisible to a conventional point-sampling survey, and the probabilistic approach revealed a child-specific risk that a deterministic calculation alone might have understated or overstated. As pesticide use intensifies across African agricultural landscapes to meet growing food demand, studies of this kind provide the evidence base that national regulators and international bodies such as the Joint FAO/WHO Meeting on Pesticide Residues need to set meaningful, locally calibrated safety standards. For now, the message from Oyo State is clear: the greens on the market stall are nutritious and affordable, but for the children eating them, the invisible residues of an everyday insecticide may be crossing a line that better farming practice could hold firmly in place.

Subject of Research: Pesticide residue occurrence and dietary health risk assessment in agricultural ecosystems of southwestern Nigeria

Article Title: Environmental occurrence, spatial distribution, and probabilistic dietary risk assessment of cypermethrin and glyphosate residues in agricultural ecosystems of southwestern Nigeria

Article References: Ojezele, O. J., & Ojezele, M. O. (2026). Environmental occurrence, spatial distribution, and probabilistic dietary risk assessment of cypermethrin and glyphosate residues in agricultural ecosystems of southwestern Nigeria. Environmental Monitoring and Assessment, 198(11), Article 1171. https://doi.org/10.1007/s10661-026-15973-z

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15973-z

Keywords: cypermethrin, glyphosate, pesticide residues, Amaranthus cruentus, food safety, dietary risk assessment, Monte Carlo simulation, spatial autocorrelation, Nigeria, vegetable farming, pesticide stewardship, environmental monitoring

The team, led by Andreas A. Kudom, began with a simple question: how do people actually manage weeds in Ghanaian cities? To find out, they surveyed 600 households across twelve urban towns in the country’s Central Region. The results were unambiguous. Herbicides have become the dominant method of weed control in residential areas, displacing hand weeding and other mechanical approaches. Glyphosate-based formulations, the same active ingredient found in the world’s best-selling weedkiller, and paraquat-based products, a fast-acting and highly toxic bipyridyl herbicide, were the most frequently reported choices. Haloxyfop-methyl, a selective herbicide targeting grasses, also appeared in the urban arsenal. This chemical reliance matters because residential spraying happens close to homes, gardens, and the wild plants that urban insects rely on, often with little regulation or protective equipment.

With the spraying patterns established, the researchers turned to the butterfly. Hypolimnas misippus, commonly known as the Danaid eggfly, is a widespread and visually arresting species in which females mimic the toxic monarch-like Danaid butterflies. Its caterpillars feed on Portulaca quadrifida, a low-growing succulent herb that thrives in disturbed urban soils, exactly the habitats where herbicide spraying is most intense. The team conducted laboratory no-choice bioassays in which butterfly eggs and larvae were exposed to glyphosate, paraquat, and haloxyfop-methyl at field-recommended concentrations, the doses a homeowner following the label would actually apply. This design choice is important: the study did not rely on exaggerated laboratory doses but tested the concentrations that urban spraying routinely delivers to non-target plants and insects.

The paraquat results were stark. Within 24 hours of exposure, every larva in the treatment group was dead, a complete mortality event that left no survivors to continue development. Eggs fared scarcely better, with mortality reaching 96 percent. Paraquat’s mechanism explains this ferocity: the compound acts as a redox cycler, generating reactive oxygen species inside cells that destroy membranes and tissues within hours. A caterpillar crawling across or feeding on freshly sprayed vegetation essentially ingests a molecule that dismantles its biochemistry on contact. For an urban butterfly population, a single spraying event on a patch of host plants could effectively wipe out the entire generation of eggs and young larvae occupying that patch.

Haloxyfop-methyl told a slower but equally troubling story. Rather than killing larvae outright within a day, the herbicide substantially reduced overall survival and, critically, slashed adult emergence. Mortality was distributed across both the larval and pupal stages, meaning individuals that survived early exposure often failed to complete metamorphosis or died before emerging as adults. In population terms, adult emergence is the metric that matters most, because only adults can disperse, mate, and found the next generation. A chemical that allows caterpillars to feed and pupate but prevents them from ever becoming flying adults functions as a demographic trap, luring females to lay eggs on plants that will produce no surviving offspring.

Glyphosate, by contrast, emerged as the least directly lethal of the three. Butterfly survival was not significantly affected at field-recommended concentrations, though exposed individuals took slightly longer to complete their development. This nuance is worth pausing on. Glyphosate’s reputation as relatively benign for animals has made it the default choice for urban weed control worldwide, and the study does not overturn that picture for direct contact. But the researchers’ second line of investigation reveals why direct toxicity assays alone can miss the real ecological damage. The herbicide that spares the caterpillar may still starve it, by degrading the plant it eats.

To quantify that plant-mediated pathway, the team used laser-induced chlorophyll fluorescence, or LICF, a technique that measures how a leaf’s photosynthetic machinery responds to pulses of light. When chlorophyll molecules absorb light, a fraction of the energy is re-emitted as fluorescence, and the shape and speed of that fluorescence response act as a sensitive diagnostic of plant health. Healthy leaves show a rapid rise and fall in fluorescence when a saturating light flash follows a period of adaptation, and the ratio of the maximum fluorescence peak to the steady-state level, known as the vitality index or Rfd value, indicates how vigorously the leaf is photosynthesizing. Stressed leaves, whose photosystems are damaged or whose energy metabolism is disrupted, produce flattened, sluggish curves and depressed Rfd values.

The LICF measurements revealed pronounced reductions in two vitality indices, Rfd-685 and Rfd-740, in Portulaca quadrifida leaves following exposure to paraquat and haloxyfop-methyl. In plain terms, the sprayed host plants were photosynthetically impaired, their leaf vitality measurably diminished. For a specialist herbivore like the Danaid eggfly caterpillar, this matters in two ways. Stressed plants may have altered nutritional chemistry, producing tougher tissues, changed nitrogen levels, or defensive compounds that reduce caterpillar growth and survival. Stressed plants may also wilt, yellow, or die, removing the food resource entirely before larvae finish development. The study thus demonstrates that herbicides disrupt plant–insect interactions through two simultaneous channels: direct toxicity to the insect and physiological stress to its host plant, each compounding the other.

The broader implications extend well beyond a single butterfly species. Urban ecosystems are increasingly recognized as refuges and corridors for biodiversity, particularly in tropical regions where cities expand into species-rich landscapes. Butterflies are pollinators and prey, and their caterpillars are a critical food source for birds and other animals. If routine residential spraying converts urban green spaces into ecological traps, where attractive host plants lure egg-laying females into chemical kill zones, the cumulative effect across a city could erode urban biodiversity and the ecosystem functions that depend on it. The finding that herbicides are already the dominant weed control method across twelve Ghanaian towns suggests this is not a marginal or hypothetical risk but an ongoing, landscape-scale process.

The authors argue that ecological considerations must be integrated into urban weed management strategies, and the study points toward practical adjustments. Reducing blanket spraying in residential areas, timing applications to avoid butterfly breeding periods, leaving patches of host plants unsprayed, and favoring mechanical or manual weed removal near gardens could all blunt the damage. The research also highlights the value of pairing toxicity bioassays with plant physiology measurements, a combination that captures the full chain of herbicide effects from leaf to larva. For now, the image that lingers is a small one: a Danaid eggfly egg glued to the underside of a purslane leaf in a Ghanaian courtyard, an egg that in a single day of ordinary household weed control has a 96 percent chance of never hatching. The tidy gardens of the city, the study suggests, are being purchased at a price written in the lives of its smallest residents.

Subject of Research: Effects of urban herbicide use on the non-target butterfly Hypolimnas misippus and its host plant in Ghana

Article Title: Urban herbicide use threatens a non-target butterfly ( Hypolimnas misippus ) through direct toxicity and host plant stress in Ghana

Article References: Kudom, A. A., Bosompem, M., Adu, M. O., Afful, B., Anderson, B., Armah, F., Asare, P. A., Ayettey, J., Mensah, B. A., & Adueming, P. O.-W. (2026). Urban herbicide use threatens a non-target butterfly (Hypolimnas misippus) through direct toxicity and host plant stress in Ghana. PLOS Ecosystems, 1(1), e0000020. https://doi.org/10.1371/journal.pesy.0000020

Image Credits: AI Generated

DOI: 10.1371/journal.pesy.0000020

Keywords: herbicides, glyphosate, paraquat, Hypolimnas misippus, butterflies, urban ecology, Ghana, host plant stress, chlorophyll fluorescence, pesticide toxicity, biodiversity, plant-insect interactions

The research team, drawn from the University of Buenos Aires and Argentina’s National Scientific and Technical Research Council (CONICET), exposed the green microalga Scenedesmus vacuolatus to two different treatments over a 96-hour period. One treatment used the isopropylamine salt of glyphosate, or IPAG, which is the active ingredient in many glyphosate-based products, at concentrations of 150, 250, and 350 milligrams per liter. The other used a commercial glyphosate-based formulation, referred to in the study as CFG, at concentrations of 4, 6, and 8 milligrams of acid equivalent per liter. This paired design allowed the researchers to separate the toxicity of glyphosate itself from the toxicity of the so-called inert ingredients that manufacturers blend into commercial products to improve their performance in the field.

The headline finding is stark. The concentration that suppressed algal growth by 50 percent, a standard toxicological benchmark known as the IC50, was 326.11 milligrams per liter for the pure active ingredient but only 4.43 milligrams of acid equivalent per liter for the commercial formulation. In other words, the formulated product achieved the same level of growth inhibition at roughly one-seventieth of the glyphosate concentration required by the active ingredient alone. That enormous gap strongly suggests that the co-formulants, the surfactants and adjuvants that help the herbicide stick to leaves and penetrate plant tissue, are doing much of the biological damage once the product reaches the water.

Growth was only the beginning. When Iummato’s team looked at photosynthetic pigments, they found that both treatments reduced total chlorophyll content relative to untreated controls, indicating that the herbicide interferes with the alga’s photosynthetic machinery. The commercial formulation added a further twist: exposed cells increased in volume. Cell enlargement without proportional growth in cell number is a classic sign of disrupted cell division, a pattern that has been documented in other algae exposed to herbicides and that points to an arrest of the reproductive cycle while individual cells continue to expand. For a phytoplankton population, that combination means the community can no longer replace itself at the rate the ecosystem depends on.

To understand the biochemical mechanisms behind these visible effects, the researchers measured a battery of molecular biomarkers that reveal the state of the cell’s antioxidant defenses and the extent of oxidative damage. When organisms are exposed to chemical stressors, their metabolism generates reactive oxygen species, unstable molecules that attack proteins, lipids, and DNA. Cells respond by ramping up antioxidant enzymes such as superoxide dismutase (SOD), which converts superoxide radicals into hydrogen peroxide, and catalase (CAT), which breaks the hydrogen peroxide down into water and oxygen. A third enzyme, glutathione-S-transferase (GST), helps detoxify harmful compounds by conjugating them with glutathione, a versatile cellular antioxidant. The levels and activities of these molecules serve as an early-warning system, registering stress long before populations collapse.

The two treatments told strikingly different biochemical stories. Algae exposed to the pure active ingredient, IPAG, responded with a coordinated defensive effort: levels of oxidized proteins rose, the ratio of carotene to chlorophyll a increased, glutathione content climbed, and the activities of SOD, CAT, and GST all went up compared with controls. This is the signature of a cell that has detected the threat and mobilized its full antioxidant arsenal against it. The elevated carotene-to-chlorophyll ratio suggests the cells were also reinforcing their pigment shields, since carotenoids quench reactive oxygen species generated in the photosynthetic membranes and protect chlorophyll from photo-oxidative destruction.

The commercial formulation produced a more alarming pattern. Exposed algae showed increased thiobarbituric acid reactive substances, or TBARS, a widely used indicator of lipid peroxidation, meaning the herbicide was literally damaging the fatty membranes that enclose the cell and its organelles. Oxidized proteins accumulated, the carotene-to-chlorophyll ratio rose, glutathione and carotene levels increased, but here the antioxidant enzymes told the opposite story: SOD, CAT, and GST activities all decreased relative to controls. The combination of rising oxidative damage markers and falling antioxidant enzyme activity suggests that the formulation did not merely provoke a defensive response but overwhelmed or impaired it. When the enzymatic defenses falter while lipid peroxidation accelerates, the cell is losing the oxidative battle.

This contrast between the active ingredient and the formulated product is the study’s most consequential message for environmental regulation. Glyphosate risk assessments have traditionally focused on the active ingredient, treating co-formulants as biologically inert helpers. A growing body of ecotoxicological work, including comparative studies of pesticides on aquatic and soil organisms, has challenged that assumption, and the present findings add algal primary producers to the list of victims. Because algae sit at the foundation of freshwater food webs, suppressing their growth and photosynthesis can ripple upward to zooplankton, fish, and everything that depends on them. The finding that a commercial formulation can be toxic at concentrations tens of times lower than the active ingredient means that water quality criteria based on glyphosate alone may dramatically underestimate the ecological risk of real-world herbicide applications.

The study also carries geographic weight. Glyphosate use is intensive in the agricultural regions of Argentina, particularly the soy-growing Pampas, and monitoring programs have repeatedly detected the herbicide and its degradation product aminomethylphosphonic acid, or AMPA, in surface waters and groundwater across the region. Scenedesmus vacuolatus, the species used in these experiments, is a common freshwater chlorophyte and a standard test organism in algal growth inhibition assays conducted under international testing guidelines, which makes the results directly relevant to regulatory frameworks. The researchers note that both the formulation and the active ingredient negatively affected the alga, altering growth and metabolic parameters including oxidative stress markers, with the commercial formulation causing greater alterations at lower glyphosate concentrations.

What emerges from this multi-biomarker approach is a picture of glyphosate-based herbicides as more than simple weed killers acting on a single plant-specific enzyme. In these algal cells, exposure triggered cascades of oxidative stress, pigment remodeling, protein oxidation, and membrane damage, with the formulated product inflicting a heavier and less recoverable blow than its active ingredient alone. As debates over glyphosate’s environmental fate continue worldwide, this study adds a technically rigorous data point to the argument that the toxicity of a pesticide product cannot be judged by its active ingredient in isolation. The co-formulants that make the spray effective in the field may be the same compounds that quietly undermine the microscopic engines of aquatic ecosystems, and regulators, the authors’ findings imply, would do well to evaluate the products as they are actually sold and sprayed, not just the molecule on the label.

Subject of Research: Toxic effects of a glyphosate-based commercial formulation and its active ingredient on the green microalga Scenedesmus vacuolatus

Article Title: Multi-biomarker evaluation of the effects of a glyphosate-based commercial formulation and its active ingredient on the green microalga Scenedesmus vacuolatus

Article References: Iummato, M. M., Graziano, M., Ríos de Molina, M. D. C., & Juárez, Á. B. (2026). Multi-biomarker evaluation of the effects of a glyphosate-based commercial formulation and its active ingredient on the green microalga Scenedesmus vacuolatus. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38265-y

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38265-y

Keywords: glyphosate, herbicide, Scenedesmus vacuolatus, microalgae, ecotoxicology, oxidative stress, antioxidant enzymes, biomarkers, commercial formulation, co-formulants, freshwater, lipid peroxidation

The research, published in the Journal of Agriculture and Food Research, was led by Keisuke Soga and colleagues at Japan’s National Institute of Health Sciences and collaborating institutions. The team took soybean samples that had previously been analyzed for herbicide residues and subjected the very same material to a battery of event-specific real-time PCR tests. Their goal was exploratory but ambitious: to see whether the residue profile of glyphosate, glufosinate, and their metabolites could be matched to particular herbicide-tolerance traits in commercially distributed soybeans imported from the United States and Brazil.

The logic behind the approach rests on the biochemistry of herbicide tolerance. Glyphosate kills plants by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase, or EPSPS, an enzyme essential for synthesizing aromatic amino acids through the shikimate pathway. Glyphosate-tolerant soybeans evade this attack by carrying a modified epsps gene, such as the cp4 epsps gene borrowed from the soil bacterium Agrobacterium tumefaciens strain CP4, which produces an enzyme the herbicide cannot bind. Glufosinate works differently: it blocks glutamine synthetase, causing toxic ammonia to accumulate and shutting down photosynthesis. Soybeans tolerate glufosinate by carrying the pat or bar gene, which encodes phosphinothricin N-acetyltransferase, an enzyme that acetylates the herbicide into N-acetyl-glufosinate, an inactive compound that no longer threatens the plant.

These mechanisms create a chemical fingerprint. A soybean carrying a modified epsps gene can survive glyphosate spraying and may retain detectable glyphosate residues, but it cannot convert glufosinate into its acetylated form. Conversely, a soybean carrying pat can metabolize glufosinate into N-acetyl-glufosinate, so the presence of that metabolite hints at a pat-containing event. The Japanese team reasoned that detecting glyphosate or the acetylated glufosinate metabolite in a shipment should statistically correlate with the presence of the corresponding transgenes, and that the strength of the correlation might even reveal which specific events dominate cultivation in the exporting country.

The sample set consisted of fifteen soybean lots: one edible soybean sample grown in Japan, eight feed samples from the United States, three non-GM samples from the United States imported under identity-preserved handling, and three feed samples from Brazil. Identity-preserved systems segregate non-GM soybeans from GM ones through documentation and traceability, though they cannot guarantee the complete absence of unintended commingling. The researchers ground 100 grams of each sample in a cryogenic mill, extracted genomic DNA, and screened for eleven GM events using primers and probes drawn from the European Union’s GMOMETHODS database and Japanese official detection methods, with the soybean lectin gene serving as an endogenous reference.

The qualitative results were striking. In the non-GM samples, GM events were essentially undetectable, with only a faint signal for event DAS-44406 in one sample. In the American feed samples, the team detected RRS, MON89788, FG72, A2704-12, A5547-127, and DAS-44406, while Brazilian feed samples were dominated by RRS, MON89788, and DAS-81419. The edible Japanese sample contained none of the tested events. Crucially, the events found in the herbicide-positive samples matched the residue chemistry: glyphosate-containing lots carried high levels of epsps-harboring events, and lots containing N-acetyl-glufosinate carried high levels of pat-harboring events.

Quantification sharpened the picture considerably. In American feed samples where glyphosate was detected, MON89788 ranged from 8.7 to 50.7 percent commingling, and DAS-44406, a stacked event carrying 2mepsps, pat, and aad-12 transgenes, reached an extraordinary 41.3 to 71.6 percent. In Brazilian feed samples, MON89788 dominated at 62.6 to 102.6 percent, with the value above 100 percent attributed to inherent measurement uncertainty in event-specific quantitative PCR rather than an impossible true percentage. Meanwhile, the American feed sample in which neither glufosinate nor its metabolite was detected showed low commingling for the pat-containing events, at 0.4 percent for DAS-44406 and 1.1 percent for A5547-127, reinforcing the link between the metabolite and the trait.

The authors interpret these patterns through the lens of regional agricultural practice. In the United States, herbicide use on soybeans has diversified markedly as growers battle glyphosate-resistant weeds. Department of Agriculture surveys show that in 2006 more than 50 million soybean acres were treated exclusively with glyphosate, but by 2012 that area had shrunk by roughly 20 million acres as farmers adopted tank mixes. By 2023, glyphosate isopropylamine remained the most widely used herbicide at 46 percent of planted acres, but 2,4-D choline salt followed at 37 percent, with glufosinate-ammonium at 23 percent. This diversification aligns neatly with the prominence of DAS-44406, whose stacked transgenes confer tolerance to glyphosate, glufosinate, and 2,4-D simultaneously.

Brazil tells a different story. No-tillage systems dominate Brazilian soybean production, and without plowing to control weeds, farmers lean heavily on herbicides; glyphosate was applied to roughly 95 percent of the soybean area by 2021. The insect-protected and glyphosate-tolerant stacked variety MON 87701 x MON 89788, introduced in the 2013/14 season, expanded from 1.2 million hectares to more than 30 million hectares, about 80 percent of national acreage by 2020/21. That near-total adoption explains why MON89788 commingling in Brazilian feed samples reached such extreme levels, while glufosinate-tolerant events remained scarce at 0.2 to 3.2 percent. The researchers note that as glyphosate-resistant weeds spread in Brazil, additional herbicide-tolerance traits may follow the American trajectory, making continued monitoring essential.

The study’s implications extend beyond curiosity. If herbicides or their metabolites appear in a product labeled non-GM, that could signal the presence of GM material and justify verification against labeling regulations, as illustrated by the glufosinate found in the identity-preserved American samples, which the authors attribute to cultivation practices, environmental sources, post-harvest handling, or commingling below the detection range of the genetic assays. Conversely, residue data can cross-check genetic findings, boosting overall reliability. The authors also point toward future work on 2,4-D and dicamba, whose tolerance events, DAS-44406 and MON87708 respectively, metabolize these auxin-mimicking herbicides into detectable signature compounds. Because the sample set was small, the team frames the work as exploratory rather than a quantitative correlation analysis, but the concept is clear: two regulatory silos, pesticide monitoring and GM surveillance, each hold half of a story that only makes full sense when the datasets are combined. Extending this integrated approach to maize and other crops could give food safety authorities a powerful, mutually validating tool for traceability and enforcement in global commodity chains.

Subject of Research: Association between herbicide residues and herbicide-tolerance GM soybean events in imported soybean samples

Article Title: Association between herbicide residues and herbicide tolerance-related genetically modified events in imported soybean samples

Article References: Soga, K., Yoshiba, S., Takabatake, R., Taguchi, T., Tsutsumi, T., Ito, R., Iwasaki, Y., Akiyama, H., & Shibata, N. (2026). Association between herbicide residues and herbicide tolerance-related genetically modified events in imported soybean samples. Journal of Agriculture and Food Research, 31, Article 103321. https://doi.org/10.1016/j.jafr.2026.103321

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103321

Keywords: glyphosate, glufosinate, genetically modified soybeans, herbicide tolerance, real-time PCR, food safety monitoring, maximum residue limits, MON89788, DAS-44406, identity preservation, Brazil soybean exports, United States soybean exports

The team installed pollen traps at two marked hives per apiary, pooling material into composite two-week samples across seven sampling periods each season, from early May to mid-August in 2025 and mid-May to late August in 2024. Samples were frozen at minus 18 degrees Celsius until analysis, and accredited laboratories in Berlin used validated multi-residue methods based on liquid and gas chromatography coupled with tandem mass spectrometry, with dedicated LC-MS/MS screening for the highly polar herbicide glyphosate and its breakdown product AMPA. Botanical composition was reconstructed under light microscopy, with more than 500 pollen grains identified per sample, allowing the researchers to link each residue detection to the plants the bees had actually visited.

In total, 15 active substances were detected in 2024 and 19 in 2025. Fungicides dominated the detection profile in both years, accounting for 51 percent of detections in 2024 and 54 percent in 2025, followed by herbicides and, trailing behind, insecticides. The most frequently recorded compounds included boscalid and azoxystrobin among the fungicides, glyphosate and clopyralid among the herbicides, and the neonicotinoid-class insecticide acetamiprid. Maximum concentrations were striking: glyphosate reached 840 micrograms per kilogram in 2024 and 327 in 2025, boscalid peaked at 610 micrograms per kilogram in 2024, and the herbicide fluazifop-P-butyl hit 660 and 1800 micrograms per kilogram across the two years, far exceeding the European Union recommended maximum residue level of 50 micrograms per kilogram for bee products.

The fluazifop-P-butyl findings stand out as among the most consequential for beekeepers and regulators. This grass-specific herbicide is not typically considered a bee-toxicity headline grabber, yet its concentrations in Latvian pollen exceeded most values reported elsewhere in Europe, though they remained below the extreme 6831 micrograms per kilogram documented in southern Germany by earlier researchers. Acetamiprid tells a different regulatory story. The European Union’s acceptable concentration in bee products was 50 micrograms per kilogram in 2024 but rose to 300 micrograms per kilogram in 2025, and individual Latvian samples exceeded the limits applicable at the time of sampling in both years, with maxima of 350 and 200 micrograms per kilogram respectively.

Perhaps the most unexpected detection was terbutryn, a herbicide banned for agricultural use in the EU, found once in 2025 exclusively at the urban-influenced Jelgava apiary. Because it appeared in no earlier sampling year, the researchers rule out current farming as the source. Terbutryn is known to leach from biocide-treated facade coatings and paints, and it is used for aquatic algae control; a wastewater treatment plant within the foraging radius of the Jelgava hives may represent a plausible contamination pathway. The finding is a reminder that pollinator pesticide exposure is not confined to fields, and that urban infrastructure can quietly contribute to the chemical loads carried back to the hive.

Seasonal patterns proved decisive. Residue concentrations and risk values rose mainly between mid-May and early July, coinciding with the flowering of oilseed rape and legumes and the associated pesticide applications. In 2024, the highest total residue load occurred in the second sampling period, when pollen from the crucifer family dominated the samples and bees were foraging intensively on winter oilseed rape. Elevated levels followed in early June, tied to legume crops such as field beans and peas, and again in late July when flowering weeds of the goosefoot family provided a late-summer pollen source. In 2025, detections were spread more evenly across the season, with peaks in late May and early June linked to crucifers and rose-family bloom such as apple, plum and pear, and renewed elevations in late July associated with summer oilseed rape.

To translate chemical concentrations into biological risk, the team applied the Pollen Hazard Quotient, a screening metric that divides the detected concentration in pollen by the acute oral or contact LD50 for honey bees, assuming a maximum daily intake of up to 9.5 milligrams of bee bread per nurse bee. Values below 50 are considered low risk, between 50 and 500 moderate, and above 500 high. Median PHQ values stayed safely under 50 in every sampling period of both years, indicating generally low colony-level toxicological pressure. But individual samples told a sharper story: several 2025 samples crossed the threshold, and one sample from Vecauce parish in the fifth period of 2025 reached a staggering PHQ of 1173.91, driven almost entirely by cypermethrin, a pyrethroid insecticide whose very low contact LD50 means even a moderate concentration translates into a high hazard score.

That cypermethrin result crystallises a central lesson of the study: toxicity, not abundance, determines risk. Frequently detected fungicides and herbicides contributed little to cumulative PHQ because their LD50 values are comparatively high, while compounds such as acetamiprid, flupyradifurone and cypermethrin punched far above their concentration weight. The researchers caution that PHQ is a screening tool with real limitations. It rests on acute endpoints only, ignoring chronic exposure, sublethal effects and the potential interactions within the pesticide mixtures that bees inevitably encounter simultaneously. Real-world exposure risk may therefore be underestimated, particularly when colonies face repeated pulses throughout a brood-rearing season.

What the study did not find may matter just as much. The team hypothesised that apiaries surrounded by more agricultural land, more nectar-producing crops, or crops under higher pesticide-use intensity would show higher cumulative PHQ values. Graphical comparisons across the six sites and two years found no consistent pattern. Platone parish, with the highest proportion of agricultural land, did not post the highest risk values, while some sites with little farmland still recorded measurable exposure. High proportions of crucifer, legume or rose pollen did not reliably track the mapped crop areas around each apiary, suggesting that bees forage selectively, that systemic pesticides move residues away from treated fields, and that broad landscape categories are simply too coarse to capture field-level application timing. Exposure, the authors conclude, is shaped by temporal dynamics, local management and bee behaviour rather than landscape composition alone.

The study builds on earlier Latvian work published in 2024 and offers the Baltic region some of its first long-term pollen monitoring data, filling a gap where oilseed rape covers 145,100 hectares and legume areas have grown 84 percent since 2020. For beekeepers, the practical message is that danger is concentrated in identifiable windows, chiefly mid-May through early July, when crop flowering and spraying overlap with intensive foraging and brood rearing. For regulators and researchers, the findings argue for monitoring designs that capture short-term exposure peaks and application timing rather than averaging the season into invisibility. Honey bee-collected pollen, the authors note, proved a suitable and temporally resolved tool for exactly this purpose, identifying precisely when and where agricultural environments turn most hazardous for their most industrious visitors.

Subject of Research: Pesticide residues and seasonal exposure risk in honey bee-collected pollen across Latvian agricultural landscapes

Article Title: Pesticide exposure risks and seasonal variation in honey bee-collected pollen across agricultural landscapes in Latvia

Article References: Pesticide exposure risks and seasonal variation in honey bee-collected pollen across agricultural landscapes in Latvia. (n.d.). https://doi.org/10.1007/s11356-026-38238-1

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38238-1

Keywords: honey bees, pesticide residues, pollen, pollinator health, glyphosate, cypermethrin, Pollen Hazard Quotient, agricultural landscapes, fungicides, Latvia, ecotoxicology, bioindicators

A research team led by Shruti Khanna of the California Department of Fish and Wildlife and the University of California, Davis, together with Jereme Gaeta, Krista Hoffmann, and remote sensing pioneer Susan Ustin, analyzed the Delta’s aquatic invasive plant control program across two five-year windows, 2004 to 2008 and 2014 to 2018. Their study, published in the journal Environmental Management, combined more than six hundred treated and reference sites with multi-year airborne hyperspectral imagery capable of mapping floating aquatic vegetation at the genus level. By fusing these vegetation maps with detailed herbicide application logs and boat path records, the team could ask questions that no small-scale field trial could answer: does the type of herbicide matter, does the dose matter, does the number of visits matter, and does any of it last?

The stakes are enormous. California spends more than 13 million US dollars each year treating invasive aquatic plants in the Delta, a 2,220-square-kilometer estuary formed by the confluence of the Sacramento and San Joaquin rivers. The main villains are water hyacinth (Pontederia crassipes), a Brazilian native that has plagued the Delta since 1904, and water primrose (Ludwigia hexapetala), present since 1949 and increasingly dominant since 2014. Two newer arrivals, spongeplant detected in 2008 and alligator weed in 2017, add to the threat. These plants form dense floating mats that darken water, deplete oxygen, block fish movement, and displace native communities, while their drifting fragments seed new infestations throughout the tidal system.

The control program itself has a long institutional history. Funded after 1982 legislation, it began as the Water Hyacinth Control Program and was renamed the Aquatic Invasive Plant Control Program in 2019, administered by California State Parks’ Division of Boating and Waterways. For most of its history it has relied on two systemic herbicides with remarkably long pedigrees: 2,4-dichlorophenoxyacetic acid, patented in 1945, which disrupts plant growth hormones and kills broadleaf dicots while sparing monocots, and glyphosate, patented by Monsanto in 1974, which blocks the shikimate pathway enzyme EPSPS essential to plant survival. The program straddled a major transition, relying mainly on 2,4-D in the early period and shifting to glyphosate in the later years, a natural experiment the researchers exploited to evaluate each chemical independently.

The analytical approach was rigorous. The team fitted mixed-effects logistic regression models, treating the probability of floating vegetation presence at each site as a function of herbicide application rate, spray frequency within a season, and consecutive years of treatment, with random intercepts for site and year to account for repeated observations. Separate models were built for each of the Delta’s three hydrologically distinct habitat types: fast-flowing tidal channels, slow shallow waters between remnant wetland patches, and flooded islands, lake-like expanses created by levee failures where water lingers and tidal action is weak.

The results were strikingly habitat-dependent. Both herbicides performed best in slow, shallow, open-water habitats and flooded islands, and worst in fast-flowing channels. Glyphosate was essentially ineffective in channels at any application rate, while 2,4-D showed significant impact there only at the highest rates used in the field. The likely explanation lies in the Delta’s relentless tidal dynamics. Previous work using GPS trackers showed that water hyacinth mats drift constantly in all directions with the tides, so treated plants in channels are quickly replaced by fresh propagules floating in from untreated areas. Flooded islands, isolated from these tidal conveyor belts, allow treatment effects to persist and become detectable months and even years later.

Perhaps the most actionable finding concerns dose and frequency. Across habitats and time periods, applying a higher concentration of herbicide in fewer visits consistently outperformed delivering the same total amount in smaller, more frequent doses. Low-dose applications were not merely ineffective; in some cases they were associated with a higher probability of floating vegetation than untreated reference sites. The authors point to two possible mechanisms. The first is hormesis, a well-documented phenomenon in which sublethal chemical stress actually stimulates plant growth and defense mechanisms, potentially triggering a post-treatment rebound. The second is herbicide resistance: sites treated with glyphosate for more than six consecutive years required noticeably higher application rates to achieve significant reductions than sites treated for only one or two years, a pattern consistent with resistance evolving under repeated sublethal selection pressure.

The legacy effects, meaning how long benefits persisted after spraying stopped, differed sharply between the two chemicals. Sites treated with 2,4-D showed no detectable reduction in floating vegetation one, two, or three years after treatment ended, in any habitat. Glyphosate, by contrast, left a measurable legacy in flooded islands, where the probability of floating vegetation remained significantly below reference levels even three years after the last application. In slow shallows, longer histories of glyphosate treatment, five to six consecutive years, produced stronger lasting suppression than shorter histories. In channels, neither herbicide left any lasting benefit, and longer treatment histories there appeared if anything counterproductive.

The study also revealed an unsettling background trend: floating vegetation cover and occurrence probability were higher across all habitats in 2014–2018 than in 2004–2008, suggesting the invasion problem has intensified even as treatment continued. Slow shallows consistently showed the highest occurrence, likely because their nutrient-rich, slow-moving waters combine continuous propagule input with ideal conditions for fragments and seedlings to take root.

For managers, the recommendations are concrete. Avoid sublethal doses that risk stimulating growth or breeding resistance; concentrate herbicide into fewer, higher-dose applications; match herbicide choice to habitat, favoring glyphosate’s longer-lasting action in stable flooded islands while recognizing that neither chemical offers much hope in fast channels; and rotate active ingredients, a strategy the Division of Boating and Waterways has begun testing with newer herbicides such as imazamox and penoxsulam in demonstration zones. Above all, the authors argue, chemical control must be embedded in a holistic program of monitoring, integrated methods, and native plant restoration. What this study demonstrates most powerfully is the value of scale: only by combining ten years of treatment records with a decade-spanning remote sensing archive could the true contours of herbicide efficacy in a tidal ecosystem come into focus, and only at that scale can the difference between money spent and money wasted finally be seen.

Subject of Research: Herbicide efficacy against invasive floating aquatic vegetation in the Sacramento–San Joaquin Delta

Article Title: Multi-Year Regional-Scale Efficacy Assessment of Two Herbicides for Treatment of Invasive Floating Aquatic Vegetation in a California Estuary

Article References: Khanna, S., Gaeta, J. W., Hoffmann, K., & Ustin, S. L. (2026). Multi-Year Regional-Scale Efficacy Assessment of Two Herbicides for Treatment of Invasive Floating Aquatic Vegetation in a California Estuary. Environmental Management, 76(10), Article 326. https://doi.org/10.1007/s00267-026-02625-8

Image Credits: AI Generated

DOI: 10.1007/s00267-026-02625-8

Keywords: glyphosate, 2,4-D, invasive species, water hyacinth, water primrose, Sacramento-San Joaquin Delta, remote sensing, estuary management, herbicide resistance, aquatic plants, tidal wetlands, environmental management