From Beachapedia

Pesticides are a group of chemicals used to kill or repel unwanted organisms. Insecticides target unwanted insects (and other invertebrates), herbicides are used on weeds and unwanted plants, fungicides are used on fungus and mildew, and rodenticides target mice and other rodents. Unfortunately, the toxic chemicals contained within pesticides can have unintended effects on many organisms that come in contact with them (non-target organisms), ultimately harming our local ecosystems and the health of our environment.

59 million pounds of pesticides are used in the U.S. every year in home and garden applications (28 million lbs of herbicides, 14 million lbs of pesticides, 2 million lbs of fungicides, and 15 million lbs other pesticides). [1] Additionally, 48 million lbs of pesticides are used in the U.S. every year in industrial, commercial, or government applications (26 million lbs of herbicides, 12 million lbs of pesticides, and 10 million lbs of fungicides).[1]

Pesticides are considered household hazardous waste and must be safely disposed of at proper household hazardous waste (HHW) facilities and collection events to avoid contamination of our environment.


Insecticides advertised to kill specific insects can also kill many species of ecologically beneficial pollinators, like bees and butterflies[2]. Many species of bees native to North America are critically important pollinators and help maintain biodiversity within plant communities and ecosystems.

Insecticides can also harm predatory insects that naturally regulate and control pest populations. The larvae of insects like ladybugs, lacewings, syrphid flies, and other insects naturally prey on common pests like aphids, mealybugs, and fungus gnats. Attracting the adults of these beneficial insects can result in adults laying eggs near pest infestations. Many larval stages of these insects feed voraciously on the pests, naturally lowering their populations. Planting native plants can attract beneficial predatory insects that are best adapted to your local environment and that support birds and wildlife throughout your local food webs.

Neonicotinoids are a group of insecticides[3] used widely on farms and in urban landscapes. Neonics are sprayed onto plants, coated onto seeds, injected into trunks, or directly drenched onto surrounding soil. They are absorbed systemically by plants and can be present in pollen and nectar, making them toxic to bees and other pollinators long after initial application.

Neonic-coated seeds have been shown to not increase crop yields in corn and soybeans, yet they are still used ubiquitously and can contaminate soil for years after application.[4] Because neonics are highly soluble in water, it is estimated that only 5% of neonic coatings on seeds are absorbed by the plant while 95% of the pesticide volume is washed into soil and groundwater[5]. At least one neonicotinoid insecticide was found in 53% of streams sampled by USGS.[6]

The EPA recently assessed that neonicotinoids would adversely affect over two thirds of the endangered and threatened species and over half of critical habitats it investigated, with severe effects jeopardizing survival and recovery in the wild of about 10% of those endangered species[7]. This includes many aquatic species that can be affected by neonic pesticides entering waterways through runoff and groundwater.

For target pests like mosquitos, “mosquito dunks” can be an environmentally friendly alternative to spraying insecticides near wet areas. They consist of bacteria that naturally live in soil, which kill mosquito larvae without affecting other beneficial insects like dragonflies. Most mosquito infestations can be prevented by dumping out any pools of standing water.

An important part of pest control within an Ocean Friendly Garden is reframing how much "damage" to plants we tolerate from caterpillars, grasshoppers, and other plant eating insects. "If nothing is eating your garden, it is not a part of the ecosystem" is one popular saying among habitat gardeners. Non-invasive insects that are feeding on plants native to your region are simply a part of nature and local ecology. These insects feed baby birds, lizards, and other wildlife that is vital to a healthy, resilient local foodweb.

More non-toxic solutions to controlling pests can be found on Our Water Our World.


Herbicides or “weed killers” have been widely used in agriculture and landscaping to avoid labor and costs associated with the manual removal of weeds.

The herbicide glyphosate, the active ingredient in the weed killer Roundup® and the most widely used herbicide in the U.S., was detected at least once in 66 of 70 U.S. streams and rivers tested by USGS[8]. Glyphosate is a chemical of increasing concern for human health, and has been associated with cancer. AMPA (aminomethylphosphonic acid), the chemical produced when soil microbes break down glyphosate, was detected even more frequently. AMPA is persistent in the environment with a half-life of 121 days, but little is known about its toxicity to the environment or to humans.[9]

Herbicides are often sprayed over entire local weed populations, and in agriculture or large-scale landscaping, the small percentage of surviving weeds is not physically removed or otherwise killed. This artificial selection pressure actually favors individuals within the local weed population that are resistant to the herbicide, fostering a weed population that is increasingly resistant to the herbicide over time.  220 species of agriculturally significant weeds have become resistant to herbicides as a result of widespread herbicide applications, impacting crop production and in some cases increasing quantities of herbicide application to compensate.[10]

Hand-pulling weeds, applying boiling water, vinegar solutions, salt, sheet mulching, and controlled burns can all be effective alternatives to toxic herbicides in residential and community scale landscaping. Learn more about alternatives to glyphosate.

Pesticides as water pollution

Pesticides can reach waterways through overspray carried in the air, runoff from irrigation and precipitation, groundwater transport, and direct application to aquatic environments to control algae and aquatic insects. When the pesticides applied to landscapes and hardscapes in our urban environments are washed off with rain, sprinklers, or hoses, they travel into storm drain systems as urban runoff, polluting our waterways, wetlands, and coasts.

Pesticide pollution is not limited to agricultural environments. While one or more pesticides were detected in 97% of stream water and 61% of shallow groundwater in agricultural areas, one or more pesticides were also found in 97% of stream water and 55% of shallow groundwater in urban areas.[11] The concentrations of these pesticides exceeded human health benchmarks in urban areas in 6.7% of stream water and 4.8% of shallow groundwater.[11]

Pesticides are often found as mixtures in aquatic environments. 90% of streams sampled in developed watersheds contained 2 or more pesticide compounds and 20% of streams tested contained 10 or more pesticide compounds[11]. These combined mixtures may contribute to higher overall toxicity and ecosystem disruption than a single high-concentration pesticide.

Pesticides are carried down the watershed and eventually reach our coastal and marine ecosystems. Estuarine environments, which connect rivers to the ocean, support many early stages of fish and aquatic wildlife, as well as migratory birds, plants, and pollinators. A study on a central Californian estuary frequently detected 3 fungicides (azoxystrobin, boscalid, and pyraclostrobin), one herbicide (propyzamide) and 2 organophosphate insecticides (chlorpyrifos and diazinon)[12]. Fungicides and insecticides were also detected in fish and invertebrates living within the estuary. Pesticides have been documented in open seas and even in remote marine regions like the Arctic[13].

Effects on Aquatic Wildlife

The toxic chemicals found in pesticides can harm fish, invertebrates, and other aquatic life. Approximately a thousand different pesticides are currently registered for use in the US. Of these, the US Environmental Protection Agency (EPA) has established aquatic life criteria (intended to protect 95% of non-target species) for fewer than 1%[14]. Most studies on pesticides address the persistence of legacy pesticides within the environment, and in contrast, limited information is available on the uptake, accumulation, and effects of current-use pesticides on non-target organisms[12]. Regulatory studies may prioritize the effects of pesticides on human health over prolonged environmental impacts to drive regulation decisions[15]. Due to a lack of information on what levels of pesticides are safe in aquatic environments, how long they persist, and how they transfer between organisms, we do not yet know the full scope of how pesticides are impacting our aquatic ecosystems.

Pesticide concentrations exceeded aquatic wildlife benchmarks in 83% of stream water and 70% of bed sediment in urban areas, mainly by the insecticides diazinon, chlorpyrifos, and malathion[11]. The toxicity of pesticides, their persistence in aquatic environments, and their effects on different levels of the food chain all contribute to the severity of ecological damage.

Legacy pesticides, such as DDT and other organochlorines, are currently banned from use but still persist in the environment. Water bodies such as San Pedro Basin still contain high concentrations of DDT[16] from chemical waste that was intentionally dumped into the ocean between 1947 to 1982 by a DDT manufacturer in Los Angeles. As of 2004, fish are still being sampled in Santa Monica and San Pedro Bay[17] with levels of DDT that are unsafe for human consumption[18]. DDT is known to affect human and ecosystem health, with connections to cancer, liver damage, and reproductive complications. It is also an example of how pollutants can accumulate and transfer throughout a food web in a process called biomagnification.

By affecting primary consumers like small aquatic invertebrates, pesticide pollution may also be impacting species of concern like Pacific Salmon[19]. Further research and monitoring are needed to fully understand how pesticide exposure is impacting the complex food webs and life histories of salmon and other aquatic species.

Resources for Chapters

Pesticide Free Pledge Printable Flyers

  1. 1.0 1.1 Atwood, D., & Paisley-Jones, C. (2017). Pesticides industry sales and usage: 2008–2012 market estimates. US Environmental Protection Agency, Washington, DC, 20460, 2017-01.
  2. Bargar, T. A., Hladik, M. L., & Daniels, J. C. (2020). Uptake and toxicity of clothianidin to monarch butterflies from milkweed consumption. PeerJ, 8, e8669.
  4. Grout, T. A., Koenig, P. A., Kapuvari, J. K., & McArt, S. H. (2020). Neonicotinoid Insecticides in New York State.
  5. Pietrzak, D., Kania, J., Kmiecik, E., Malina, G., & Wątor, K. (2020). Fate of selected neonicotinoid insecticides in soil–water systems: Current state of the art and knowledge gaps. Chemosphere, 255, 126981.
  6. Hladik, M. L., & Kolpin, D. W. (2015). First national-scale reconnaissance of neonicotinoid insecticides in streams across the USA. Environmental Chemistry, 13(1), 12-20.
  8. Medalie, L., Baker, N. T., Shoda, M. E., Stone, W. W., Meyer, M. T., Stets, E. G., & Wilson, M. (2020). Influence of land use and region on glyphosate and aminomethylphosphonic acid in streams in the USA. Science of the Total Environment, 707, 136008.
  9. Grandcoin, A., Piel, S., & Baurès, E. (2017). AminoMethylPhosphonic acid (AMPA) in natural waters: Its sources, behavior and environmental fate. Water Research, 117, 187-197.
  10. Heap, I. (2014). Global perspective of herbicide‐resistant weeds. Pest management science, 70(9), 1306-1315.
  11. 11.0 11.1 11.2 11.3 Gilliom, R. J. (2007). Pesticides in US streams and groundwater.
  12. 12.0 12.1 Smalling, K. L., Kuivila, K. M., Orlando, J. L., Phillips, B. M., Anderson, B. S., Siegler, K., ... & Hamilton, M. (2013). Environmental fate of fungicides and other current-use pesticides in a central California estuary. Marine pollution bulletin, 73(1), 144-153.
  13. Mai, C., Theobald, N., Lammel, G., & Hühnerfuss, H. (2013). Spatial, seasonal and vertical distributions of currently-used pesticides in the marine boundary layer of the North Sea. Atmospheric Environment, 75, 92-102.
  14. Macneale, K. H., Kiffney, P. M., & Scholz, N. L. (2010). Pesticides, aquatic food webs, and the conservation of Pacific salmon. Frontiers in Ecology and the Environment, 8(9), 475-482.
  15. Hendlin, Y. H., Arcuri, A., Lepenies, R., & Hüesker, F. (2020). Like oil and water: the politics of (not) assessing glyphosate concentrations in aquatic ecosystems. European Journal of Risk Regulation, 11(3), 539-564.
  17. NOAA. (2007). 2002-2004 Southern California Coastal Marine Fish Contaminants Survey.
  19. Macneale, K. H., Kiffney, P. M., & Scholz, N. L. (2010). Pesticides, aquatic food webs, and the conservation of Pacific salmon. Frontiers in Ecology and the Environment, 8(9), 475-482.