Photo by J. Gardner, 2015

What are pesticides?


  • Are living organisms that occur where they are not wanted

  • Cause damage to crops, humans, or other animals

  • Include some insects, mice and other animals, unwanted plants (weeds), fungi, and microorganisms such as bacteria and viruses


  • Are substances or mixtures of substances that are intended to prevent, destroy, repel, or mitigate pests

  • Include insecticides, herbicides, fungicides, and various other substances used to control pests

  • Are also defined as substances intended for use as a plant regulator, defoliant, or desiccant

Many household products are considered to be pesticides including:

  • Insect repellents for personal use

  • Rat and other rodent poisons

  • Flea and tick sprays, powders, and pet collars

  • Kitchen, laundry, and bath disinfectants and sanitizers

  • Products that kill mold and mildew

  • Some lawn and garden products, such as weed killers

  • Some swimming pool chemicals

Why should I care?

When pesticides end up in our lakes and streams, they can threaten aquatic life and impact our drinking water quality. All pesticides are toxic at some level, but each type of pesticide varies in its toxicity to humans and other animal species. While some pesticides may not be harmful to humans, they may be fatal to fish and aquatic invertebrates in our lakes and streams.

How do pesticides enter our lakes and streams?

Pesticides can enter our waterways via stormwater runoff or outdoor water use. Runoff carries pesticides into our storm drains or directly into lakes and streams where it may result in serious impacts to fish and wildlife.

What can I do to help?

  • Use environmentally-friendly alternatives to pesticides

  • If you have to use pesticides, use them responsibly:

    • Make sure you have accurately identified the pest

    • Make sure the pesticide you have selected is effective against your pest but poses the least risk to human health and the environment

    • Apply pesticides in dry weather, not right before big storm events

    • Never allow pesticides to enter storm drains or creeks