Insecticides to control grain insect pests

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

Malathion

• 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

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