Pesticides—What You Should Know

to protect yourself, your family and pets, your property,
and Islesboro's wildlife and water

What Are Pesticides?

Pesticides, both synthetic and organic, control unwanted plants (herbicides), insects and rodents (insecticides, rodenticides), and plant fungi (fungicides). PSI focuses on herbicides used for landscape and driveway care and insecticides used for tick control.

  • Synthetic. Following the end of World War II, the chemical industry developed pesticides from warfare agents. Some synthetics break down slowly in the environment, remaining in soil or water for long periods. Run-off can transport them to different parts of the environment (from a lawn to the bay, for instance). (source: Extension Toxicology Network).
    • Herbicides. The most familiar herbicide is glyphosate, the key ingredient in Roundup, the most widely used herbicide in the world. Another chemical commonly used in "weed and feed" products is 2,4-D (dichlorophenoxyacetic acid).
    • Insecticides. Synthetics used in insecticides include bifenthrin, fipronil, permethrin, among many others. They are found in sprays and granules that control mosquitoes and ticks. A class of chemicals called neonicotinoids is active in a wide range of insect control products found on local garden center shelves, including seeds that have been "treated” or "coated.” As the plant grows, the whole plant becomes capable of killing insects. The effects are systemic, for neonicotinoids have a propensity for run-off and groundwater infiltration. This tainted water is taken up by the roots of other plants. The chemicals can persist in the soil for years.
  • Organic. Usually made from natural substances, including botanical oils and biological substances such as bacteria and nematodes, organic pesticides break down rapidly in the environment and have lower risks of long-term toxicity.

Why Be Concerned?

Increasingly, scientific research is showing that synthetic chemicals can be harmful to human, pet, and wildlife health and to the environment.

  • Humans. Respected scientific research organizations such as the American Academy of Pediatricians and the National Cancer Institute have concluded that exposure to synthetic herbicides such as glyphosate and 2,4-D can be linked to reproductive disorders, birth defects, learning disabilities, neurological disease, endocrine disorders, and cancer (Carey Gillam, Whitewash, The Story of a Weed Killer, Cancer, and the Corruption of Science, 2017, pp. 237-238. A copy of this book is available at the Alice L. Pendleton Library).
  • Pets. Pets may be at risk if they come in contact with herbicides. Under certain circumstances, for instance, animals exposed to products with glyphosate may drool, vomit, have diarrhea, lose their appetite, or seem sleepy (source: National Pesticide Information Center). Exposure to permethrin when wet can be lethal to cats (source: International Cat Care).
  • Wildlife. Synthetic insecticides such as bifenthrin, fipronil, permethrin as well as the neonicotinoids are toxic to pollinators, birds, and to shellfish. This is specified (under Federal law) on labels of products that contain them.
    • Pollinators. Bees, hummingbirds, and some kinds of butterflies, flies, wasps, and spiders fertilize plants so that they produce flowers and seeds. The ecological service they provide is necessary for the reproduction of over 85% of the world’s flowering plants, including more than two-thirds of the world’s crop species (most fruits, vegetables, and nuts). The United States alone grows more than 100 crops that either need or benefit from pollinators, and the economic value of these native pollinators is estimated at $3 billion per year (source: Xerces Society).

      Yet pollinators world-wide are in trouble. In a report released in March 2017, the Center for Biological Diversity reports that more than half the bee species with sufficient data to assess are declining; nearly 1 in 4 is imperiled and at increasing risk of extinction (source: Center for Biological Diversity). Scientists have identified several possible causes of bee Colony Collapse Disorder (CCD), among them loss of habitat, climate change, parasites. Another suspect is exposure to synthetic insecticides, which adversely affect bees’ nervous systems. Very small amounts of neonicotinoids can cause bumble bee colonies to grow more slowly and produce fewer new queens. Exposure can impair honey bees’ ability to fly, navigate, and forage for food (source: Xerces Society).

      For use of organic pesticides in ways that are safe for pollinators, see this Organic-Approved Pesticides Fact Sheet.

    • Birds. Scientists believe that some insecticides may have high potential to affect avian reproduction. Chemicals can also contribute to declines in bird populations by reducing the numbers of insects upon which birds feed. Birds also eat seeds; studies have shown that a single seed coated with a neonicotinoids can kill a songbird within days (source:
    • Shellfish. In laboratory tests, synthetic chemicals such as bifenthrin and some forms of 2,4-D have proven to be highly toxic to fish and shellfish (source: NPIC Bifenthrin General Fact Sheet, NPIC 2,4-D General Fact Sheet).

      In the wild, synthetics accumulate in organisms. Filter feeders such as mussels and clams are on the front line of accumulation; fish and lobsters can also be affected. Mussel Watch, conducted by the National Oceanic and Atmospheric Administration (NOAA), has found a range of chemicals in mussels in the Penobscot Bay, including 2,4-D (source: NOAA's National Status and Trends, 2011 data).

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