Methyl bromide is a potent biocide with insecticidal, fungicidal and herbicidal properties contained in 16 registered products. Products containing methyl bromide have been registered in Australia since the second world war. Methyl bromide is used as a soil fumigant in horticultural industries, as a pest control treatment on dry commodities such as stored grain or dried fruit, as well as quarantine and pre shipment (QPS) treatments for imports, exports and certain commodities transported interstate.

In accordance with the Montreal Protocol for ozone depleting substances the total phase-out of methyl bromide, except for Critical Use Exemptions and Quarantine and Pre-shipment uses, was to be completed by January 2005. Legislation to ensure that methyl bromide imported into Australia is only used for CUEs and QPS purposes is now in place and administered by the Department of the Environment and Heritage. This enables DEH  to track methyl bromide imported into Australia to ensure that none is diverted into other uses.

Use patterns

Methyl bromide, is classified as an alkyl bromide. It is a colorless and odorless gas at normal temperatures and pressures, but the liquefied gas can be handled as a liquid under moderate pressure. Methyl Bromide is a highly effective, broad-spectrum fumigant registered for use to control a number of pests including insects, rodents, weeds and disease-causing organisms in a wide range of agricultural and horticultural crops. Its primary uses are for soil fumigation, post-harvest protection and quarantine treatments.

More specifically, product labels permit the use of methyl bromide on:

• Flowers, bulbs, nursery and horticultural crops – control of fusarium and verticillium wilts, rhizoctonia, pythium, nematodes, weeds, weed seeds;

• Plant beds, turf, local areas, well-rotted compost, manure and topsoil, mulching straw or hay – control of nematodes, insects, weed seeds, nutgrass;

• Plant beds and other local areas, decomposed compost and manure – control of damping off fungi such as species of pythium, rhizoctonia and fusarium, soil borne fungi such as sclerotinia and verticillium;

• Buildings and other structures – rodents;

• Cereal grain, cereal products, dried fruits, pulse and pulse products (including field peas), timber and cane products, buildings and other structures, living plant material, nuts, chocolate products – control of stored product insect pests.

Other uses of methyl bromide include:

• fumigation before export—commodities such as wheat, rice, cut flowers and some fruit and vegetables are treated with methyl bromide before export in order to meet phytosanitary (pest-free) requirements of importing countries; and

• quarantine—methyl bromide is the recommended fumigant for a significant number of

imported commodities including fruits, vegetables, flowers, plant products, timber, bamboo and cane products, machinery, tyres, food processing equipment.                    

When used as a soil fumigant, methyl bromide gas is usually injected into the soil before a crop is planted. This effectively sterilizes the soil, killing the vast majority of soil organisms including soil-borne fungi, nematodes, bacteria and weed seeds. Immediately after the methyl bromide is injected, the soil is covered with plastic tarps, which slow the movement of methyl bromide from the soil to the atmosphere. Its use in soil underpins approximately $300 million worth of Australian horticulture. Horticultural uses of methyl bromide accounted for approximately 80% of Australia’s methyl bromide use in 1991. It provides a broad spectrum of control under a wide range of soil and climatic conditions. Pre-plant soil fumigation accounts for approximately 80% of world use of methyl bromide.

When used as a commodity treatment, methyl bromide gas is injected into a chamber or under a tarp containing the commodities. Commodities which use this material as part of a post-harvest pest control regime includes grapes, raisins, cherries, nuts, and imported materials. Some commodities are treated multiple times during both storage and shipment. Commodities may be treated with methyl bromide as part of a quarantine or phytosanitary requirement of an importing country (these uses are exempt from the phase out).

Structural pest control treatment with methyl bromide gas involves the fumigation of buildings and other structures for stored product insect pests and rodents. 

The Status of Methyl Bromide in Developed Countries:

Based on research findings and proposed alternative methods, the use of this substance in developed countries has been eliminated or significantly reduced by adopting suitable alternatives. However, in developing countries, due to certain limitations and a lack of appropriate technologies for substitution, more time is needed to reduce or eliminate its use.

Given the importance of the issue, the ozone layer protection program, supported by the United Nations under the Montreal Protocol, banned and enforced the mandatory elimination of methyl bromide use starting in 2005 for industrialized countries and by 2015 for developing countries.

This was approved through an international agreement by 160 countries, with several alternatives proposed for methyl bromide:

Phosphine or Hydrogen Phosphide (PH₃): An effective fumigant against pests in stored products. The main advantages of phosphine are its ease of use and rapid insecticidal action. It is a common method for treating stored food products and is effective against pests even at low doses.

A major drawback of phosphine is the required exposure time for food (3 to 5 days), which can have a corrosive effect on structures.

Heat Treatment:

The temperature is raised to a level that destroys most pests attacking dates. After 2 hours at 60–70°C, most insects present in the dates are eliminated. However, this method reduces the quality of processed fruit and can create a caramelized effect.

Microwave Treatment:

Research has shown that using microwave treatment for 55–90 seconds results in the death of all date moth larvae. According to reports, parameters such as color and weight of treated dates show no significant difference compared to untreated dates. However, there may be some damage to product quality during storage.

Gamma Radiation:

A successful method for preserving food without any adverse effects on treated products. However, the cost of this method and the chemical changes and free radicals created within the treated fruit limit its use.

Carbon Dioxide Treatment:

A biological alternative and one of the natural and effective techniques for controlling insects during date storage.