Insecticides to control grain insect pests

Insecticides are a powerful tool for controlling insect pests. Carefully read and follow the instructions on the label when using any insecticide. Labels for approved insecticides are available from Health Canada’s Pest Management Regulatory Agency (PMRA).

Insects may develop resistance to insecticides if the same chemical class is employed repeatedly. You can minimize the development of resistance by alternating the control methods you use.

Insecticides for structures

There are several insecticides available for treating cracks and crevices in buildings, empty bins, or other storage containers, including:

  • malathion
  • pyrethrins
  • cyfluthrin
  • diatomaceous earth
Photo shows a man spraying a chemical insecticide on the interior surface of a steel grain bin
Spraying a chemical insecticide on the interior surface of a steel grain bin

Insecticides for direct application to grain

Several insecticides can be applied directly to grain, including:

Diatomaceous earth

  • Causes death by desiccation through absorbing the waxy layer on the insect’s skin
  • Works best when applied as dry grain is augered into a bin during harvest
  • Needs a 6-week period of treatment at above 20°C for maximum efficacy
  • Has the potential to reduce test weight
  • Increases grain friction, so lower auger flow rates when applying


  • Incapacitates the insect’s central nervous system
  • Is best applied sprayed as grain flows through an auger or conveyer
  • Is intended for use on cereal grains and must not be used on oilseeds
  • Formulation must be registered for direct grain treatment; not all formulations meet this requirement
  • Treated grain should not be sold for 7 days

Aluminum phosphide (phosphine)

  • Can be used in 3 ways:
    • applied as pellets to bulk grain as it enters storage
    • placed into the grain with a probe after the grain is stored
    • contained in prepackaged devices (ropes) on grain surface
  • Must be applied in a well-sealed structure in order to be effective
  • Reacts with water in the air to produce phosphine gas
  • Treatment effectiveness is influenced by grain temperature and moisture
  • Should not be used if the temperature is less than 5°C or if the moisture content is less than 10%
  • Should be used according to the label to control all life stages of stored-grain insect pests
  • Is more effective against adults and larvae than eggs; eggs are the most resistant stage, requiring approximately 20 times higher doses to control than adults and larvae
  • Should be monitored during fumigation to ensure gas levels are sufficient
  • May cause corrosion of certain metals (copper, brass, silver and gold) at high temperatures and humidity; take precautions to remove or protect equipment containing these metals, such as electrical motors, wiring and electronic systems
  • Resistance has occurred in the United States and Australia; continuous or inappropriate use may result in resistance developing
Fumigant pellets are placed into bulk stored grain using a hollow probe
Fumigating stored grain using a probe

Magnesium phosphide (phosphine)

  • Reacts with water in the air to produce the gas phosphine
  • Generates phosphine faster than aluminum phosphide
  • Cannot come in contact with the commodities fumigated
  • Is applied contained in plates, pouches or strips
  • Is mainly used for fumigating empty structures or tarped commodities
  • Has issues with temperature, humidity and corrosion similar to aluminum phosphide
  • Must be applied in a well-sealed structure in order to be effective

Gaseous phosphine

  • Is compressed gas in a cylinder
  • Allows for more precise dosage and faster fumigation than metal phosphides
  • May be applied at temperatures as low as 0°C
  • Has similar issues with corrosion of metals as aluminum phosphide
  • Has 2 formulations:
    • ECO2FUME® ,ready for application
    • VAPORPH3OS®, needs onsite dilution

Carbon dioxide

  • Is applied to grain as a gas from cylinders
  • Must be applied in a well-sealed structure
  • Must be maintained at 60% for 4 days between 20°C and 25°C; refer to label for further dose information

Methyl bromide

  • It is prohibited for any person to use or sell methyl bromide, unless it was imported, and it is sold, for use as a quarantine application or a pre-shipment application to comply with foreign plant quarantine import requirements
  • The only quarantine insect on Canada’s list of regulated insect pests associated with grain is the Khapra beetle, Trogoderma granarium

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