Fumigants act on all insect life stages. They reach these pests by diffusing through the spaces between grain kernels as well as into the kernels themselves. So fumigants are able to penetrate into places that are inaccessible to insecticide sprays or dusts.
All fumigants are poisons—highly toxic to humans and other warm-blooded animals, as well as to insects.
Currently, only three fumigants are labelled for use in stored grain: phosphine, chloropicrin, and methyl bromide. Each of these products has special limitations and restrictions governing its use.
Methyl Bromide (CH3Br) + Chloropicrin (MB 98%)
Chloropicrin is still registered for grain fumigation as well as empty bin fumigation to combat insect infestations. It is especially useful for the control of insects in the sub-floor aeration area of empty bins.
Methyl Bromide (CH3Br) – (MB100%)
Methyl bromide is an effective grain fumigant for the control of stored grain insects at all stages of development. It evolves into a gas at temperatures above 39° F and has virtually no odor or irritating qualities to indicate its presence.
Phosphine-producing materials have become the predominant fumigants used for the treatment of bulk-stored grain throughout the world. It is available in solid formulations of aluminum phosphide or magnesium phosphide. When exposed to heat and moisture the formulations release phosphine, a highly toxic gas. The time required for release of phosphine will vary with temperature, grain moisture, and formulation.
Before applying phosphine, level the grain surface and break up any encrusted areas. These areas are sometimes hidden from view just below the grain surface. Failure to locate and break up encrusted grain will result in uneven penetration of fumigants.
Seal the bin as well as possible before fumigation. A high degree of gas tightness is essential to achieve the required combination of gas concentration and exposure time necessary to kill insect grain pests. Roof ventilators and aeration ducts should be covered with plastic bags that are gathered at the base and taped in place. Doors should be sealed with a foam seal or tape. Also make sure that the roof-wall junction is sealed. All cracks and holes in the bin wall or ceiling must also be sealed.