Bees Can Learn to Avoid Contaminated Pollen – But at a Cost

(What new research on glyphosate and imidacloprid means for brood health and colony resilience)

Modern beekeeping takes place in landscapes where agrochemicals are a fact of life. While we know a great deal about how pesticides harm bees, a new study published in Scientific Reports (2026) asks a subtler and highly relevant question:

Can young honey bees recognise and avoid pesticide-contaminated pollen before it does serious damage?

The answer, according to this research, is yes – but it’s not a free win for the colony.

What the researchers did

The study focused on young worker bees (nurse-aged bees) – the individuals responsible for consuming pollen and producing brood food. These bees were given a choice between two different monofloral pollens. One pollen was then contaminated with field-realistic concentrations of either:

• Glyphosate (a widely used herbicide), or

• Imidacloprid (a neonicotinoid insecticide)

The researchers measured:

• How much pollen bees consumed

• Whether they changed preferences over time

• Whether avoidance persisted after contamination stopped

• Survival and total pollen intake

Key findings

1. Young bees can learn to avoid contaminated pollen

Bees did not immediately reject contaminated pollen. Instead, after repeated exposure, they reduced consumption by 10–23%, depending on dose and chemical.

This suggests bees are not “tasting” the pesticide directly. Rather, they are associating pollen cues (smell, taste, texture) with feeling unwell after eating it – a classic malaise-based learning response.

2. Avoidance persists even after contamination stops

When the contaminated pollen was replaced with clean pollen, bees continued to avoid it for at least 24 hours. In other words, bees form a short-term memory linking that pollen type to a bad experience.

This is important: it means pesticide exposure can reshape pollen use inside the hive even after the spray event is over.

3. Total pollen intake can drop

In some treatments (notably glyphosate with certain pollens), bees didn’t just shift preference – they ate less pollen overall.

While avoidance may reduce toxin exposure, reduced pollen intake can compromise nutrition, especially during brood rearing or early spring buildup.

4. Survival effects depend on context

• Glyphosate showed complex, pollen-dependent effects, sometimes with no clear survival penalty.

• Imidacloprid reduced survival in some groups, even as bees learned to avoid it.

Avoidance does not guarantee safety.

Why this matters to beekeepers

This study challenges a common assumption: “If bees don’t like it, they won’t eat it.”

In reality:

• Bees may consume contaminated pollen for hours or days before learning to avoid it.

• Once learned, avoidance may reduce brood food intake or skew pollen balance.

• Nurse bees are exposed inside the hive, via stored pollen and beebread – not just in the field.

For beekeepers, this means pesticide exposure can have hidden, delayed effects on:

• Brood nutrition

• Gland development in nurse bees

• Colony growth efficiency

• Resilience during stress periods

The bigger picture

The ability of bees to learn avoidance is impressive and adaptive. However, it is not a solution to pesticide exposure. Avoidance trades toxin intake for nutritional disruption, and colonies operate on narrow margins when pollen quality or quantity declines.

From a management and policy perspective, the study reinforces that:

• “Sub-lethal” does not mean “biologically insignificant”

• Pesticide residues in pollen matter just as much as residues in nectar

• Protecting clean pollen sources is critical for colony health

  
  

If you are a beekeeper who:

• Manages hives near cropping land

• Wonders why brood patterns falter without obvious disease

• Is interested in how bees actually cope with chemical stress

  
  

…this paper offers one of the clearest experimental demonstrations yet of how young bees respond to contaminated pollen – and why avoidance alone cannot protect the colony.

Understanding these subtle behavioural responses helps explain real-world outcomes we see in hives every season.

Hunkeler et al. (2026). “Young honey bees Apis mellifera learn to avoid pollen contaminated with glyphosate or imidacloprid.” Scientific Reports https://www.nature.com/articles/s41598-026-35416-6