University of Maryland Extension

Pollinators and Pesticides

bumblebee on yellow flower
Bumble bee.
Photo: David Cappert, Bugwood.org

Pollinator Protection Act of 2016

European honey bees, native bee species, and other pollinators in Maryland have suffered population losses in recent years. This has led to increased scrutiny of a widely used class of insecticides, known as neonicotinoids. Public concerns resulted in the passage of the Pollinator Protection Act of 2016 by the Maryland General Assembly. The law went into effect on January 1, 2018, and restricts the sales and use of neonicotinoid pesticides. Only farmers and certified pesticide applicators (or people working under their supervision) can apply neonicotinoid pesticides outdoors. So, while neonicotinoid products may appear on store shelves in Maryland, they cannot be applied outdoors by gardeners.

Key Points

  • Pesticides include a wide range of substances labeled herbicides, insecticides, rodenticides, and fungicides.
  • Neonicotinoids are a class of insecticides that are cited as a primary threat to pollinators and other beneficial insects.
  • Pollinators are essential for the reproduction of many native plant species and to the production of food crops on farms and in gardens.
  • You can help pollinators by avoiding pesticide use when possible and using alternative pest control.
  • If you must use pesticides, it is important to read and follow label instructions and avoid direct application of pesticides where pollinators frequently visit.
  • Some large chain stores are responding to public interest and demand by either phasing out or eliminating the sale of plants treated with neonicotinoids. Ask your local garden centers and nurseries about the pesticides that are used to produce the plants they sell.

 Pollinators and Neonicotinoid Insecticides

    • Mode of action: Kill insects by causing nervous system excitation, resulting in paralysis and death. The chemical structure is similar to nicotine.
    • Active ingredients of neonicotinoids: Include acetamiprid, clothianidin, cyantraniliprole, dinotefuran, imidacloprid, nitenpyram, sulfoxaflor, thiacloprid, thiamethoxam. (PDF) A list of product names can be found online through the Xerces Society 
    • Systemic action: Products may be applied to soil, seeds, and foliage, sprayed on bark, or injected into trees. Research shows that neonicotinoids can move into pollen, nectar, and fruits. The active ingredient is absorbed by leaves, stems, and roots and moves through the plant's vascular system They can persist in plants from months to multiple seasons depending on the active ingredient, application rate, plant species, and environmental conditions.
    • Risks: Low risks to people, mammals, and other vertebrates. Imidacloprid, clothianidin, dinotefuran, thiamethoxam are considered by the US EPA to be highly toxic to honey bees. Acetamiprid is the least toxic neonicotinoid for bees but is more toxic to mammals (it's on the US EPA's reduced risk list).
  • Pollinators can pick up neonicotinoids from treated plants by ingesting the following:
    • Nectar and pollen from flowers.
    • Honeydew excreted by aphids and other sucking insects feeding on plants.
    • Water droplets pushed out of plant leaves and stems at night (guttation).
  • The U.S. Environmental Protection Agency has taken steps to reduce the risk of negative effects of neonicotinoids on non-target organisms. These include changes to pesticide labels regarding the timing of pesticide applications and other actions that will protect pollinators.
  • To learn more: Understanding Neonicotinoid Insecticides Infographic from the Xerces Society.

Neonics and Colony Collapse

honey bee on purple flower
Honey bee. Photo: Joseph Berger, Bugwood.org

  • There is no evidence that neonicotinoids solely cause colony collapse disorder, and the role of neonicotinoids in high honey bee mortality is not clear. Researchers believe that neonicotinoids pose a greater threat to native bee species than to honey bees.
  • The consensus among researchers is that the interaction of multiple stressors and factors has contributed to honey bee and native bee population declines. These include parasites (especially varroa mite in honeybees), habitat loss, pesticides, climate change, and diseases.
  • Exposure to neonicotinoids can produce sub-lethal effects such as impaired foraging, navigation, and reproduction.

Pest Control Alternatives


An example of an alternative to using pesticides. When you visit your garden look for pests
and eggs. Video: Dr. Mike Raupp, University of Maryland, Entomologist 

Additional Methods of Alternative Pest Control Include:

  • Encourage insects that eat pest species, often called natural enemies, to visit your garden.
  • Regularly survey your garden to look for pests and their eggs. Manually eliminate pest adults, eggs, or pupae by putting them in soapy water or crushing them.
  • Use natural chemical control such as pheromones and hormones to disrupt the pest’s normal behavior and stop it from coming to your yard to mate or eat.
  • Most plant problems are caused by environmental and cultural factors, such as weather extremes, compacted soil, poor location or installation, crowding, winter injury, and over-mulching. Yet insects and diseases usually get the blame! Use our resources to learn how to diagnose and prevent problems, distinguish between beneficial and pest insects, and manage pest problems without pesticides.
  • First and foremost, select varieties of plants that are more naturally resistant to a pest. 

 If you Decide to Use a Pesticide, Follow These Tips to Reduce Risks to Beneficial Insects:

  • Select the least toxic product and avoid broad-spectrum pesticides that target a wide range of insects. (PDF)The Xerces Society provides a reference sheet  to help you determine the general toxicity level of common pesticides.
  • Select products listed by the Organic Manufacturers Research Institute (OMRI) or are on EPA’s Reduced Risk list whenever possible.
  • Carefully read and follow label directions.
  • Avoid spraying open flowers.
  • Spray in the evening when fewer pollinators are active.
  • Wear protective clothing and gloves.

Additional Resources 

 Sources

Rev. 2020 by Margaret Hartman, M.S. student, Department of Entomology, University of Maryland

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