Ministry of Agriculture

About Pesticides

General Information


Pesticides include all materials that are used to prevent, destroy, repel, attract or reduce pest organisms. Insecticides, herbicides, fungicides and rodenticides are some of the more well-known pesticides. Less well-known pesticides include growth regulators, plant defoliants, surface disinfectants and some swimming pool chemicals. Under federal legislation, all pesticides used in Canada must be registered by Health Canada.

Pesticide Names

Pesticides can be named in three ways: by trade or brand name, by common name or active ingredient, and by chemical name.

For example:

  • Roundup = trade name of a herbicide product
  • glyphosate = common name of the active ingredient in Roundup
  • N-(phosphonomethyl) glycine = chemical name of the active ingredient in Roundup

More information on pesticide names is located on the Pesticides Names page of this website.

Types of Pesticides

There are approximately 400 different pesticide active ingredients and approximately 7,600 pesticide products (Trade Names) registered for use in Canada. Each pesticide product contains one or more of the registered active ingredients.

Pesticide Groups/Classifications

Pesticides are grouped or classified according to the pests they control, their chemical structure, how/when they work, or their mode of action (site of action).

Classification by Target Pest Species

Most pesticides may be classified according to the pests they kill. The word ending or suffix -cide means to kill. The following types of pesticides are used to kill specific kinds of pests:

Pesticide    Target pest
algicide   algae
avicide   birds
bactericide   bacteria
fungicide   fungi
herbicide   weeds
insecticide   insects
miticide   mites
molluscicide   snails, slugs
nematicide   nematodes
piscicide   fish
rodenticide   rodents

Classification by Chemical Structure

Pesticides can be grouped according to chemical structure. Pesticides with similar structures have similar characteristics and usually have a similar mode of action. Most pesticide active ingredients are either inorganic or organic pesticides. From a scientific view, inorganic pesticides do not contain carbon and are usually derived from mineral ores extracted from the earth. Examples of inorganic pesticides include copper sulphate, ferrous sulphate, copper and sulphur. Organic pesticides contain carbon in their chemical structure. Most organic compounds are created from various compounds, but a few are extracted from plant material and are called 'botanicals'. Examples of organic pesticides include: captan, pyrethrin, and glyphosate. Organic pesticides with similar structures are grouped into families of chemicals.

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Grouped by How or When They Work 

Pesticides can also be classified according to how or when they work. Some groups that describe how or when pesticides work are:

  • Contact pesticides generally control a pest as a result of direct contact. Insects are killed when sprayed directly or when they crawl across surfaces treated with a residual contact insecticide. Weed foliage is killed when enough surface area is covered with a contact herbicide.
  • Systemic pesticides are pesticides which are absorbed by plants or animals and move to untreated tissues. Systemic or translocated herbicides move within the plant to untreated areas of leaves, stems or roots. They may kill weeds with only partial spray coverage. Systemic insecticides or fungicides move throughout treated plants and kill certain insects or fungi. Some systemic insecticides are applied to animals and move through the animal to control pests such as warble grubs, lice, or fleas. Some pesticides only move in one direction within the plant, either up or down. Knowing what direction the pesticide moves will help guide your decisions. For example some insecticides only move upwards in plants. If applied to the root zone, it will travel throughout the plant, but if applied to the leaves it will not move throughout the plant. Some pesticides are considered locally systemic. These will only move a short distance in a plant from the point of contact.
systemic fungicide.gif
  • Foliar pesticides are applied to plant leaves, stems and branches. Note, they may be either a contact pesticide or a systemic pesticide.
  • Soil-applied pesticides are applied to the soil. Some are taken up by roots and translocated inside the plant. Other soil-applied herbicides kill weed seedlings by contact with young shoots or leaves as they break through the soil.
  • Fumigants are chemicals that are applied as toxic gas or as a solid or liquid which forms a toxic gas. The gas will penetrate cracks and crevices of structures or soil or the spaces between products stored in containers.
  • Preplant herbicides are applied to the soil before seeding or transplanting.
  • Premergent herbicides are applied to the soil after planting but before emergence of the crop or weed. The pesticide label should indicate if a pesticide is preemergent to the crop or weed.
  • Postemergent herbicides are applied after the crop or weed has emerged.
  • Translocated herbicides enter the roots or above ground parts of plants and move within the plants. They are also called systemic herbicides.
  • Eradicant fungicides destroy fungi that have already invaded plants and begun to damage plant tissues. They inhibit metabolic processes of growing fungal organisms.
  • Protectant fungicides prevent fungal infections. They retard fungal growth or prevent the organisms from entering treated plants. They must be used before the fungi reach the infection stage. Once a plant s infected, the fungicide will normally not kill the fungi inside the plant.
  • Selective pesticides will only control certain pests.
  • Non-selective pesticides will control a wide range of pests.
  • Suffocating insecticides clog the breathing system of insects and may affect eggs.
  • Residual pesticides do not break down quickly and may control pests for a long time (i.e. several weeks or a year).
  • Non-residual pesticides are quickly made inactive after application and do not affect future crops.

Grouped by Mode of Action (Site of Action) 

Pesticides can be grouped according to their mode of action or the way a pesticide destroys or controls the target pest. This is also referred to the primary site of action. For example, one insecticide may affect an insects nerves while another may affect moulting. One herbicide may mimic the plants growth regulators and another may affect the plants ability to convert light into food. One fungicide may affect cell division and another may slow the creation of an important compounds in the fungus. There are a limited number of different modes of action, but there are many pesticides. Some pesticides have the same mode of action. Scientists have grouped pesticides according to their mode of action or the target site of action.


Types of Pesticide Formulations

When a pesticide active ingredient (a.i.) is manufactured, it is not in a usable form. The a.i. may not mix will with water or may be unstable. Therefore the a.i. is mixed with other compounds to improve its effectiveness, safety, handling and storage. The other compounds can include solvents, mineral clays, stickers, wetting agents, or other adjuvants. This mixture of a.i. and inert (inactive) ingredients is called a pesticide formulation. Some formulations come ready to use while others must be mixed before use. One a.i. is often made into several different formulations. When choosing between formulations consider:
  • If it registered for the use (pest/crop)
  • Which will be most effective against the pest and current life stage
  • What formulation works best in your application equipment
  • Which will result in less drift or runoff
  • Whether the proper safety equipment available
  • Which is safest for workers, bystanders or nearby sensitive areas or organisms
  • The cost

The trade name of a pesticide may tell you about the formulation. It may include an abbreviation of the formulation. For example WP means wettable powder; E or EC means emulsifiable concentrate. Not all companies use the same abbreviations. Check the label if you do not understand the abbreviation. The exact name and amount of a.i. in the formulation is listed beside the guarantee.

Pesticide formulations can be divided into three main types: solids, liquids or gases. The most commonly used formulations are listed in the following table. The formulations abbreviation is shown below in parentheses.

Table of Common Pesticide Formulations

Name Description Advantages Disadvantages Typical Use
Solids
BaitMixture of a.i.  and food that attracts pests. Usually <5% a.i. Made as meal, pellets, or liquid; Most are solids.Easy to spottreat.
Easy to apply by hand. Usually, ready to use.
Children, pets, or wildlife could eat it. Baits for: insects (i.e. weevils, ants), rodents, birds, or slugs.
Dry flowable (DF) or Water Dispersible Granules (WDG)Mixture of a.i. and inert material made into small pellets or granules. Forms a suspension in water. Less dusty than WP. Easier to measure and mix than WP. Less inhalation hazard than WP. Spray mix requires constant agitation. Abrasive (increases wear on nozzles and pumps). Sprays for insect, disease, and weed control.
Dust
(D or DU)
Finely ground inert particles (i.e. talc, clay, volcanic ash) with a 1 10% a.i. Ready to use. No mixing Easily drifts. Visible on plants. Easily inhaled. Spot treatment. Animal powder.
Seed treatment.
Ear Tag / Vapour Strips Solid material with volatile or solid a.i. Slowly releases vapour or releases on skin contact.  Ready to use.  Animal ear tags.
Fly control
Granules
(G or GR)
Dry inert materials (i.e. clay, walnut shell, corn cob) combined with 2 to 25% a.i. Ready to use. No mixing. Minimal drift.Some dust produced.
May be eaten by birds.
May need incorporation.
Soil treatment for insect or weed control.
Impregnated Fertilizer A granular fertilizer containing a little pesticide (usually herbicides). One step application. Could clog equipment. Applicators usually need special equipment. Agricultural soil application
Pellets
(P)
Inert material containing a.i. Like granules, but has more uniform shape and weight.Easy to spot treat.
No mixing.
Ready to use.
Minimal drift.
Some dust produced during handling may be inhaled. Needs special application equipment. Baits to control rodents, slugs
Soluble powder
(SP)
Dry powder or granules which dissolve in water to make spray solution. Often > 50% a.i. Agitation not needed after mixing. Dust can be hazardous to applicator if inhaled. Mostly sprays for insect and weed control. Few SP formulations available.
Wettable powder
(WP or W)
Finely ground inert ingredients with usually 50+ % a.i. Forms a suspension in water. Less skin absorption than EC's. Hazardous if inhaled. Dusty. Needs pre-mixing and constant agitation. Abrasive so increases nozzle and pump wear. May clog screens and filters. Sprays for insect, disease, and weed control.
Liquids
Aerosol (A) Usually contain small amounts of a.i. and a petroleum solvent. Two main types:
1. Ready-to-use are under pressure, in small containers, and when nozzle is triggered fine droplets with pesticide are driven through a small hole
2. Fog generators are not under pressure, equipment breaks the liquid into fine mist or fog using spinning discs or heat.
Mixing not usually required.
Low concentration of a.i.
Inhalation hazard.
Pressurized containers hazardous if punctured.
Used mainly inside greenhouses or for mosquito control.
Emulsifiable concentrate
(EC or E)
Contains a.i., petroleum  solvent, and emulsifiers. Pesticide is suspended in spray which is milky coloured High concentration of a.i. so less product to store, purchase, or transport. Easily mixed. Non-abrasive. Amount of a.i. increases mixing hazard.
May cause leaf burn, be flammable or easily absorbed through skin.
Sprays for insect, disease, and weed control.
Flowable
(F)
Finely ground particles suspended in an inert liquid carrier. Forms suspension in spray mix like WP. No dust. Pre-mix not needed. Needs agitation before mixing as a.i. may settle out. Spray mix needs constant agitation. Abrasive, wears nozzles. Sprays for insect, disease and weed control.
GelSemi liquid emulsifiable concentrate Used with water soluble packaging.Cannot measure amounts smaller than package size. Herbicides and insecticides.
Micro-encapsulated Materials Consist of pesticide surrounded by a plastic coating. Mixed with water and sprayed. Breaks down slowly. Reduced hazard to applicator.
Easy to mix and apply.
Agitation needed Can be very hazardous to bees. Insecticide and pheromone sprays.
Solution
(SN)
A.i. comes dissolved in liquid. Forms a solution in spray mix. High concentration of a.i. means less product to store and transport. Easily mixed. Non-abrasive. Agitation not needed. High concentration of a.i. increases mixing hazard.Sprays for weed control.
Ultra low volume concentrate or sprayable concentrate
(ULV)
Liquid with very high concentration of a.i. Designed to be used as it is or slightly diluted in ULV equipment. Requires little or no mixing.
Few formulations available.
Needs special application equipment.Insecticide sprays inside greenhouses or for forestry.
Gases
Fumigants Volatile liquids or solids packaged to release a toxic gas. Toxic to many types and stages of pests. Good penetration of structures and soils under proper conditions. Highly toxic.
Treated area must be well sealed.
Greenhouses, mushroom houses, graineries. Pre-plant soil treatment for hard-to-control pests.
Packaging
Water-Soluble Packets Pre weighed amount of WP or SP formulation in a special plastic bag which dissolves in spray tank and releases contents. Low applicator exposure during mixing and loading Convenient for measuring. No container to dispose. All quantities are pre-measured and may not be the correct amount for a field. 

Adjuvants

leaf without and with adjuvants.gifAdjuvants are materials added to a pesticide formulation or tank mix to increase the effectiveness or change the properties of the pesticide in the spray mix. They may improve the effectiveness of a pesticide by:
  • Wetting the surface so the spray sticks better
  • Increasing or decreasing evaporation so it prevents the spray from drying too fast or help it dry quicker
  • Increasing absorption into the plant
  • Making the spray droplets more uniform to improve coverage

Adjuvants which directly improve the efficacy or enhance performance of a pesticide must be registered by Health Canada before they can be used. These are called Activators or spray modifiers. They either modify or enhance the physical or chemical characteristics of the pesticide. Adjuvants which are activators or spray modifiers include:

  • Surfactants which are used to improve the wetting, spreading, dispersing and emulsifying properties of pesticide mixtures
  • Wetting agents which help wettable powders and dry flowables mix with water and stick on surfaces
  • Spreaders which help pesticides form uniform coatings over treated surfaces
  • Ammonium and Sulfate Salts which enhance the uptake of some pesticides in hard water
  • Oil based adjuvants which affect leaf surfaces to allow better contact with the pesticide
  • Stickers which help pesticides resist being washed off by the rain

Adjuvants which do not directly improve efficacy but widen the conditions when a pesticide can be used or maintain the integrity of the spray solution do not need to be registered by Health Canada. These are called Utility modifiers. Adjuvants which are utility modifiers include:

  • Buffering agents which change the pH of the water to increase the dispersion or solubility of a pesticide.
  • Antifoam agents which decrease the amount of foam in a spray tank.
  • Compatibility agents which help pesticides mixed together in a tank blend uniformly. These are often used in herbicide/fertilizer tank mixes.
  • Drift retardants or thickeners which are used to increase the size of spray droplet

When to Use an Adjuvant Adjuvants are either incorporated into the formulation by the manufacturer or may be added to the spray by the pesticide applicator. When using adjuvants, always follow label directions. The label will state specifically what the adjuvant can be used for and what products it can be used with. The label will also have directions for use and may list special restrictions. Pesticide labels state the adjuvants that can or must be used with the product. Using an adjuvant that is not on a pesticide label or not according to label directions may:

  • Have no effect
  • Reduce pest control
  • Cause injury to the crop.

References

  • Adams, Robert W. 1995. Handbook for Pesticide Applicators and Dispensers. Fifth Edition, Victoria, B.C. BC Environment.
  • Pesticide Applicator Course for Agricultural Producers. 1992. Open Learning Agency, Richmond, B.C. Queen's Printers, B.C. Ministry of Environment, Lands & Parks.
  • The Safe and Effective Use of Pesticides. 2000. University of California
  • Certified Crop Protection Consultant. 1997. The University of Guelph and the University of Saskatchewan.
  • Registration Requirements for Adjuvant Products. 1993. Pest Management Regulatory Agency, Health Canada Regulatory Directive 93-15