SECTION 2

 THE EVOLUTION AND USE OF METHYL BROMIDE IN THE

 VEGETABLE AND CITRUS INDUSTRIES



 Methyl bromide is marketed as a broad spectrum pesticide that acts as an insecticide,

nematicide, herbicide, and fungicide when used in the fumigation of soils (Noling and Overman,

1988). The chemical plays an important role when used as a preplant fumigant which reduces

soilborne pest populations and enables continued cropping of the same land year after year. It

is also used as a fumigant in greenhouses, transplant beds, and potting soils. Methyl bromide

is also used as an acaricide and rodenticide in the treatment of nondwelling space and packaged

materials. The intended purpose for the chemical dictates which formulation of the compound

is used (refer to appendix A for examples of various formulations of methyl bromide, their

restricted uses, and their listed items of control). Methyl bromide is injected into soil as a

liquid, however, once in the soil the chemical converts to a gas moving through open soil pore

spaces (Noling, 1993b). This chemical is registered as a restricted use pesticide due to its acute

toxicity (refer to Table 2.1 for properties of methyl bromide).

 Methyl bromide is produced by both natural and man-made processes (IFAS-Chemically

Speaking, April, 1992). The ocean is reported to be the primary source of naturally-made

methyl bromide (Sze and Ko, 1991). Man-made methyl bromide is a product derived from the

treatment of brine, which is pumped from underground sources, such as natural brine or oil field

brines. Processing methods require that the brine be treated with chemicals or undergo heat

reaction to obtain bromine. Bromine is then used to produce methyl bromide (Kent, 1974).