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.
During World War II, the U. S. chemical industry developed pesticides to eradicate malaria-infected mosquitoes and to increase crop production. At the war’s end, the industry expanded into new markets. Insecticides such as DDT became widely used in agriculture and households, and new herbicides helped to have weed-free lawns.
In the 1950s and ‘60s consumers believed that these pesticides affected only plants and insects and that they broke down quickly in the environment. It wasn’t until the publication of Rachel Carson’s Silent Spring in 1962 that awareness of the dangers of synthetic pesticides for humans and natural ecosystems began to grow.
The most familiar herbicide is glyphosate, the key ingredient in Roundup, the most widely used herbicide in the world. Another frequently used chemical is 2,4-D (dichlorophenoxyacetic acid), an ingredient in "weed and feed" products. 2,4-D: The Most Dangerous Pesticide You've Never Heard Of
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. Understanding Neonicotinoids
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.
Beyond Pesticides - comprehensive information
National Pesticide Information Center - a collaboration between Oregon State University and the Environmental Protection Agency
Northwest Center for Alternatives to Pesticides - a good pesticide fact sheet
Pesticide Action Network (PAN) - an international coalition of NGOs, citizens' groups, and individuals which opposes pesticide use and advocates what it presents as more ecologically sound alternatives
Xerces Society - excellent information about pollinators and other invertebrates