Pesticides & Herbicides

Why Do Farmers Use Pesticides?

First, let’s define “pesticides”:

Pesticides are “chemical substances used to prevent, destroy, repel or mitigate any pest ranging from insects (i.e., insecticides), rodents (i.e., rodenticides) and weeds (herbicides) to microorganisms (i.e., algicides, fungicides or bactericides).”  (source)

Farmers can combat pests in many ways:

  • staggered harvest schedules with long-short intervals,
  • harvesting early in the pests’ lifecycle,
  • border strip harvesting (leaving uncut strips intermittently throughout field to focus pests and house beneficial insects),
  • minimizing wheel traffic and compaction on soil (i.e reducing number of passes by the tractor/swather/rake, etc.),
  • optimizing fall harvest time,
  • chemical pesticides and herbicides

The need to utilize pesticides/herbicides can vary by climate, environment, and geographical location so each farm poses different needs and requires different actions.


Pesticides are chemicals used to kill insect pests.  DDT is a well-known pesticide that was banned in North America in 1972.  For more information about the DDT Story (Pesticide Action Network), click here.  Other pesticides common today are atrazine, clothianidin,  Clothianidin is a neonicotinoid.

Neonicotinoids are a relatively new class of insecticides chemically related to nicotine. The name literally means “new nicotine-like insecticides”. Neonicotinoids, “neo-nics” for short, are neurotoxins that act on the central nervous system of the exposed insect.  Neonicotinoids infect a plant throughout its entire system, including the nectar and pollen.  In addition, neonicotinoid insecticides are persistent, meaning that they do not break down quickly in soil. They are water soluble and have the potential to easily run off into local watercourses, where they can potentially harm aquatic insects.  A growing body of scientific evidence shows that neonicotinoid insecticides are highly toxic to honey bees and other beneficial insects. Click here for a link to Ontario’s Neonicotinoid Regulations.


Herbicides are chemicals used to kill undesirable plants such as weeds or residual crop from the previous year.  Some crops, like corn for instance, compete poorly with other plants so farmers find it necessary to spray a herbicide to ensure successful crop growth.  Herbicides can also be used to dry down crop (“crop desiccant”) for a more consistent harvest. Herbicide drift occurs when the wind carries the herbicide into a non-target field.

Monsanto’s Roundup

Roundup is a herbicide with the primary ingredient being glyphosate. Glyphosate works by preventing plants from being able to make the proteins they need to survive. Since virtually all plants make these essential proteins the same way, glyphosate affects nearly all plants.  Currently corn, soy, canola, alfalfa, cotton, and sorghum, (wheat is under-development) are “Roundup ready”.  This means that the plants have been genetically modified to resist Roundup.  Thus these plants are unaffected when Roundup is applied, and the weeds alone are impacted.

However, it should be noted that some weeds are becoming Roundup tolerant (“superweeds”) so it is unclear how many more years glyphosate will be effective.

Additionally, since a large percentage of corn is “Roundup Ready” and corn is used extensively as animal feed, there are studies that indicate meat and dairy contain measurable amounts of glyphosate. (Article) There are also studies that have shown that there are already measurable amounts of glyphosate in human urine.  (Article)

Monsanto is working on a Roundup Ready alfalfa, but the wisdom is generally questioned because alfalfa is a perennial plant so it grows year after year. When a farmer wants to rotate his crops, Roundup won’t work to kill the regrowth of alfalfa so what herbicide will he use instead, and how strong will it have to be?


Runoff is water from rain or melted snow which is not absorbed and held by the soil, but runs over the ground and through loose soil. Agricultural runoff is water leaving farm fields because of rain, melted snow or irrigation. As runoff moves, it picks up and carries pesticides, herbicides, fertilizers and other pollution, which it can deposit into ponds, lakes, coastal waters and underground sources of drinking water.

Government of Ontario

Ministry of the Environment and Climate Change (MOECC) ) is responsible for regulating the sale, use, transportation, storage and disposal of pesticides in Ontario. Ontario regulates pesticides by placing appropriate education, licensing and/or permit requirements on their use, under the Pesticides Act and Regulation 63/09. All pesticides must be used in accordance with requirements under the law.

So Why Do Farmers Use Pesticides?

The Government of Ontario sets the rules for pesticide use.  For the most part, the “free” market comes down to doing what everyone else is doing to stay competitive.

Farmers are people too.  They are more aware than most of what is going into the food system, and they know what they want to feed their families.

Farmers make the best decisions they can, given the set of circumstances that they are in. Every farm is different. Each farmer is different.

So when there is a better, more efficient, cost-effective way, they will take it.  Today they use pesticides because they believe they must.

Tomorrow might tell a different story.


See also:

Industrial Agriculture

AWARE-Ontario Pollinator News

FAQs – #ProtectPrimeFarmland

FAQs – #ProtectOurWater