Bees can encounter pesticides in a few different ways, depending on where and how they live. This potential exposure can happen as pesticides are applied, or if bees come into contact with pesticide residues.
Exposure can happen when pesticides are applied to or drift into:
- An area where bees are actively foraging on flowers.
- An area where bees nest or have hives.
- Places where bees drink, such as puddles.
Some pesticides have residual activity, this means that the product can be active even after we have finished our application and left the area. This can open up other potential exposures.
- Pesticide residue is present on a plant that a bee uses to build its nest, exposing itself and its offspring.
- Pesticide residue is present on pollen bees feed on. This could expose multiple bees if the pollen is brought back to the hive.
General practices to protect pollinators from pesticides
Because bees live and move through many parts of the landscape, general practices aimed at reducing and targeting pesticide use help protect them from pesticide exposure. Some general practices include:
- Do not apply pesticides to flowers that are in bloom.
- Wait until all petals have fallen before applying to a crop.
- Mow flowering orchard floors before applying pesticides.
- When possible, use spot treatments in areas where active pest problems are present.
- Apply pesticides at dusk or in the evening when fewer bees are active.
What happens to bees after they encounter a pesticide?
What happens after a bee is exposed to a pesticide is influenced by a lot of factors. These include:
- The species of bee.
- The type of pesticide encountered.
- How pesticide is encountered.
- Amount of pesticide encountered.
- Health of the bee.
When scientists study the impacts of different pesticides on various types of bees, they categorize the effects they observe into two categories: lethal and sublethal effects.
Lethal effects
Lethal effects are those which kill the bee.
Sublethal effects
Sublethal effects are more varied. Sublethal effects refer to health impacts that don’t kill the bee, but instead cause a difference in health and behaviour. Common sublethal effects seen in research include negative impacts on:
- Flight
- Navigation
- Mobility
- Reproduction
- Learning
Synergistic impacts
Adding another level of complexity is that bees can be exposed to different types of pesticides. For some combinations of pesticides, when bees are exposed to both, you may see different lethal or sublethal effects that aren’t seen when bees are exposed to just one product. These impacts are called synergistic.
Pollinator protection information on pesticide labels
An essential source of information on pollinator protection is the label itself.
Using integrated pest management techniques and understanding if bees are attracted to our crops helps, but another place we must look is the label. The label is a legal document, and the information it provides regarding pollinator protection must be followed by law. This information isn’t always easy to find. Look for pollinator protection information on pesticide labels in these places:
For neonicotinoid products, look for the bee hazard symbol.
Neonicotinoids have the most obvious pollinator protection section of any pesticide label. This is due to the potential harm these products can cause to pollinators, due to the systemic action of these products, and what happens to pollinators that encounter them.
The product can remain present in flowers for weeks to months after an application is made, even if the initial application was not directly applied to the flowers themselves.
A systemic product applied to other plant parts, including the roots, will move to all parts of the plant.
Flowers that bloom after the application of a systemic product may also have pesticide incorporated into their nectar and pollen.
Use caution when using systemic products in crops that are actively blooming or are yet to bloom.
The Environmental Hazards section of the label provides information on how the pesticide may interact with the environment and non-target organisms. This is a place where information about bee protection often lives. Keywords to look for include toxic or highly toxic when discussing bees or pollinators.
Residual Toxicity information
If the product you are looking at mentions pollinators, you may encounter some common language. Some insecticides, such as neonicotinoids, specifically mention bees, but the majority refer to pollinators.
The terminology used refers to how long the pesticide remains active, and therefore the potential danger the product poses to pollinators. These terms include:
- Foraging
- Visiting
- Actively foraging
- Actively visiting
The terms foraging and visiting are found on the labels of products that remain toxic to pollinators for more than eight hours, and shouldn’t be applied to flowering plants. The terms actively foraging and actively visiting remain toxic for less than eight hours and should be applied in the evening when bees are less active.
All pesticide labels include information on drift mitigation. Following these instructions is not only legally required but also helps prevent products from drifting to areas where bees feed, nest, and drink.
More steps to protect pollinators
The types of information used when making a pesticide label don’t always capture what the research says about the safety of different active ingredients for every species of bee.
The testing of pesticide toxicity is conducted almost exclusively on honeybees. This means the measures detailed on the label only reflect the impacts of the product on one of Minnesota’s hundreds of bee species.
We must always follow the label's instructions, but growers may want to be more cautious about the products they use and when, based on newer research.
The Midwest Vegetable Production Guide integrates information from the University of California Davis' Bee Precaution Pesticide Ratings into its pesticide recommendations.
When generating a list of pesticides recommended for a pest problem, you can get more information on how to protect pollinators beyond label requirements when using the selected product, such as advice on application timing or tank mixes to avoid synergistic effects.
Buhl, K., & Miller, W. (n.d.). Pesticide labels – pollinators. Solve Pest Problems. https://solvepestproblems.oregonstate.edu/pesticide-information/labels/pollinators
Grinstead, A.; Lievers, R.; Morandin, L.; Redfield, P.; Wilson, C.; DiGiacomo, G.; Hutchison, W.; Illes, M.; Lee, K.; Schuh, M.; Wimmer, M.; Ziegler, B. (2025). Supporting pollinators in agricultural landscapes: a technical guide for specialty crop growers in the U.S. Midwest. Retrieved from the University Digital Conservancy.
Pollinator protection. National Pesticide Information Center. https://npic.orst.edu/envir/pollinator.html
Riedl, Helmut W., et al. “How to reduce bee poisoning from pesticides.” (2006).
Tosi, Simone, et al. “Lethal, sublethal, and combined effects of pesticides on bees: A meta-analysis and new risk assessment tools.” Science of The Total Environment 844 (2022): 156857.
- University of California IPM. (n.d.). Bee precaution pesticide ratings. bee-precaution-pesticide-ratings / University of California
- Statewide Integrated Pest Management Program (UC IPM). https://ipm.ucanr.edu/bee-precaution-pesticide-ratings
Reviewed in 2025